Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.
MINISTRY OF EDUCATION AND TRAINING UNIVERSITY OF TRANSPORT AND COMMUNICATIONS THACH BICH NGUYEN EFFECT OF THE TUNNEL CONSTRUCTION PROCESS USING THE TUNNEL BORING MACHINE ON THE SETTLEMENT OF THE GROUND AND OTHER STRUCTURES IN HO CHI MINH CITY Branch Specialized Code : Traffic engineering construction : Construction of Tunnel Bridge : 9580205 SUMMARY OF DOCTOR OF THESIS Hanoi – 2022 The work was completed at: University of Transport and Communications Science Advisor 1: Assoc Prof Dr Nguyen Phuong Duy Science Advisor 2: Prof Dr Tran Duc Nhiem Review 1: Review 2: Review 3: The thesis will be defended in front of the School-level Evaluation Board for Doctoral thesis according to Decision No…/QD-ĐHGTVT …/…/ 2022 Meeting at: University of Transport and Communications At …/…/ 2022 Thesis can be found at: - The library of University of Transport and Communications; - National library INTRODUCTION Research problem One tab here the face of the situation of traffic overload in major cities, the development planning for urban transport has approved by the government, accordingly, Hanoi city is going to build a Metro system with lines and Ho Chi Minh city is going to build a Metro system with lines With the characteristics of these cities: The land reservation for traffic is very limited, population is crowded, traffic is always overloaded, buildings on the ground are numerous and diversified with complex foundation structures…, then TBM method is the most suitable consideration Even though tunnel construction is implemented by TBM method, surface settlement which is potentially dangerous for buildings on ground cannot avoid The main cause is radial volume loss and volume loss of tunnel face Two big cities like Hanoi and Ho Chi Minh City have inconsistent planning characteristics; land reservation for traffic system is limited; many ancient architectural buildings need to be conserved; population is crowded; traffic is overloaded; types of buildings on ground are diversified and abundant Therefore; the current issue with a special concern is the investigation of the influence of the tunnel construction for Metro system on the settlement and structural buildings on the ground, the behavior of the ground around the tunnel construction area, the factors affecting surface settlement, the influence boundary of settlement on structural buildings on the ground, and particularly, the estimation model for surface settlement should be developed when tunnel construction of Metro system by the TBM method is implemented in big cities in Vietnam The thesis would like to propose the selected research content as follows: “ Effect of the tunnel construction process using the Tunnel Boring Machine on the settlement of the ground and other structures in Ho Chi Minh city” Research object - The object of the investigation focuses on the phenomenon of surface settlement and the influence of settlement on buildings on the ground during the construction of metro tunnels in Ho Chi Minh city Research scope - The investigation focuses on the underground segment of Metro line from Ben Thanh Station to Ba Son Station in the construction project of Metro line No Ben Thanh - Suoi Tien, Ho Chi Minh city Research Methodology - The research methodology is the theoretical method based on the results of calculations according to the empirical formulas compared with the field monitoring results and comparison with results of the finite element analysis Objectives of the thesis - To develop a formula for calculation of Vloss in order to improve the finite element analysis method to analyze the influence of the Metro tunnel construction on settlement and buildings on the ground - To propose equations for calculation of surface settlement values by empirical methods reflecting the ground settlement rules during the construction of Metro tunnels by the TBM method in Ho Chi Minh city Scientific and practical significance of the topic The development of an empirical formula for calculation of the volume loss coefficient Vloss is considered a significant contribution in this field due to in previously published studies, although the problems of volume loss during construction the tunnel causing surface settlement were also mentioned, all were guidelines based on the field construction experiences without any published formula Simultaneously, with the calculated Vloss value, it will help to improve the finite element analysis method to evaluate the impact of Metro tunnel construction on buildings on the ground The investigation’s results for the surface settlement in the thesis have been compared with the results calculated by experimental formulas which were published by the authors and those of the actual monitoring data at the construction project of Metro line No Ben Thanh - Suoi Tien, from the Opera House station to the Ba Son station Based on that, formulas have been proposed to calculate surface settlement values by experimental methods reflecting the settlement rules of the ground during the construction of Metro tunnels by the TBMmethod in Ho Chi Minh City The research’s results of the thesis are of great scientific significance and practical relevance when in Vietnam, a series of Metro lines have been constructed in both Hanoi and Ho Chi Minh City The results of this study can be applied to the construction projects of the next Metro line in the planning in Viet Nam CHAPTER OVERVIEW OF THE ISSUES RELATED TO THE TOPIC 1.1 Metro construction situation in the world and Vietnam The first Metro line was built in England in 1863, so far about 80 cities around the world use the Metro system in public transport The largest Metro system in the world is in New York with a total length of 471km and 468 stations In Vietnam, the development planning for urban transport has approved by the government, accordingly, Hanoi is going to build a Metro system with lines and Ho Chi Minh City is going to build system with lines 1.2 Construction of metro tunnels using TBM technology and arising problems 1.2.1 The generation and development of TBM technology The Shield Tunneling Method is a mechanized construction method that uses shields to excavate underground tunnels A tunneling shield consists of a protective metal cylinder and trailing support mechanisms which can both support geostatic pressure and move ahead in stratum The tunnel boring machine complex (TBM) performs the entire tunnel construction cycle from excavating the tunnel, supporting, transporting soil and rock out and assembling the tunnel-ring unit The first idea of constructing by a shield was proposed by a French engineer, Brunel in 1818 derived from the image of the shell of the shipworm Between 1825 and 1843, Brunel used the tunneling shield to excavate the Thame Tunnel which is the first tunnel was constructed by this method with a total length of 458m So far from 1818, thousands of types of tunneling shields have been researched and manufactured in many countries and this method has also widely been applied in underground constructions in urban areas 1.2.2 Classification of TBM According to different excavation methods, tunneling shields can be divided into types: manual tunneling, semi-mechanized tunneling and fully mechanized tunneling Based on the rotational cutter head of tunneling shields: two types are available including open faced shield and closed shield Based on methods of groundwater drainage and stabilizing the tunnel face, shields are divided into types: manual groundwater lowering by needle well, mud and water compaction, non-pressurized soil pressure equalization, and manual type local compressed air, shield type using all compressed air, etc In practice, mechanized tunneling shields (MS), semi-mechanized tunneling shields (PMS) and non-mechanized tunneling shields (NMS) Mechanized tunneling shields are divided into earth pressure balance shields mining shields with equal pressure on the digging mirror and mining shields without equal pressure on the digging mirror (MS) The excavator shield has equal pressure on the digging mirror depending on the type of material creating pressure in the digging mirror, divided into types: with clay mortar solution (MS-S) (Bentonite Slurry Shield- BS Shield or Hydroshield), with excavated soil (MS-E) (Earth Pressure Baland Shield) (this type is divided into two: only MS-E soil and injected into the soil with clay solution or MS-ED powder), by compressed air ( MS-A) (Compressed Air Shield – CA Shield) and mixed type (MS-M) (Mixshield) 1.2.3 Arising Problems 1.2.3.1 Ground settlement during tunnel construction by TBM In tunnel construction by the tunneling shield method in soft and saturated clay stratums, deformation of the ground is generated along the tunnel axis In general, the deformation can be divided into phases: The ground pushes up and subsides in front of the shield, subsides during construction and subsides due to consolidation Figure 1.1: General deformation law of the ground 1.2.3.2 The settlement phenomenon caused by underground buildings has been recorded - Surface settlement of the ground during the construction of the city subway line München (Munich), Germany, 1994 - Tunnel collapse during subway tunnel construction in Taipei, Taiwan, 1994/1995 - Tunnel collapse of the subway tunnel (MRT) Singapore 2004 - Sinkhole formed in Tannery Road due to Bengaluru subway construction - Partial collapse of a highway during construction of a new subway line in Sao Paulo, Brazil, February 1, 2022 1.3 Investigations and evaluations of the influence from metro tunnel construction on the buildings on the ground 1.3.1 Influence of tunnel and Metro construction on buildings on the ground In general, the different types of structures will be affected by settlement troughs in different ways As experience, masonry structures will be affected the deformation equal to the deformation of the ground where they are erected The same occurrence to the majority of buildings placed on single foundations In contrast, the current advanced buildings made of reinforced concrete with strengthened stiffness will be affected smaller horizontal deformation than the deformation of the ground The bending stiffness of these structures is the reason of their reductive deformation compared to the deformation of the ground, especially, these cases usually occurs on buildings placed on strip foundations or raft foundations The greater the stiffness of the structure, the greater the shear resistance and this is reason of tilting deformation rather than warped deformation This feature depends on the height of the building (number of floors), the number of drilled holes and the type of buildings (concrete walls or beams or pillars, etc.) Figure 1.2: Types of influence of settlement funnel on buildings on the ground [01] In 1974, Burland & Wroth [02] showed that the signs to recognize and determine the deformation of the buildings are very abundant They have proposed parameters based on which the deformation of the structural buildings can be defined 1.3.2 Classification of failures on the adjacent buildings due to surface settlement The degree of failure on the structural buildings near the tunneling area, especially masonry structures, is often random rather than deterministic Therefore, the method used to investigate the failures of the structural buildings is introduction of limit thresholds When a certain feature of the building violates one of these thresholds, the engineer will rely on that and evaluate its damage level According to Burland et al (1977) [03], failures of structural buildings near the tunnel construction area can be classified into three main categories: Failure on architectural aspect can be observed by the naked eye; Function failures may lead to malfunctions in operation and use; Structural destructions can influence on the stability of the buildings Figure 1.3 Modeling a building as an elastic beam and defining relative deflections (Burland and Wroth, 1975) 1.3.3 Monitoring the displacement of the foundation of high-rise buildings during the construction of foundations and basements According to JGJ 120 - 99 [04], the monitoring content during the excavation process includes: monitoring the horizontal displacement of the supporting structures; deformation of underground pipelines and surrounding structural buildings; underground water level; internal forces in piles and walls; tension forces in the ground; longitudinal force in the strut; deformation of vertical columns; the settlement according to the depth of the soil layers and the emergence of the ground on the bottom of the foundation pit; horizontal pressure on the surface of the supporting structures 1.3.4 Analyzing and evaluating the monitoring data for displacement of foundations and basements of high-rise buildings In deformation monitoring of foundation and basement of high-rise building, the research orientation usually focuses on the increase of the accurate degree and reliability of the monitoring values and analyses monitoring data to control the potential troubles to internal and adjacent buildings P.Erik Mikkelsen (2003) investigated and analyzed the monitoring data to increase the accurate degree of the measurement of horizontal displacement by Inclinometer [05] On the basis of the monitoring data of 530 constructions, Christian Moormann (2004) proposed the warning and limit thresholds of horizontal displacements of walls and vertical displacements of the ground in the vicinity of excavated hole that these thresholds are applied to control and prevent possible failure on the buildings near excavated hole The actual construction incident of the deep foundation pit is analyzed based on the monitoring results predicted prior to the basement construction and promptly added during happening of the incident The incident control method is quite proactive based to the scientific analysis of information from monitoring [53] Richard N Hwang, Za-Chieh Moh and C H Wang (2007) have shown that fluctuations in the bottom point of Inclinometer tubes are inevitable, even when the bottom of the pipe is installed in a gravel bed In measuring the horizontal displacement by applying the bottom point of the tube as the reference point can be misleading Points at the top of the guide tube that need to be tracked for reading, can be calibrated accordingly [06] A.Rahman, M.Taha (2005), Inclinometers are good tools to measure and monitor the horizontal deformation of soil due to excavation and backfill However, the guide tube used must be deep enough to get reliable results For this reason Inclinometers guide pipes installed inside diaphragm walls must be installed at least to the end of the wall depth or even deeper It is recommended to install Inclinometers in order to perform more accurate analytical models of the displacement parameters of the soil outside of the retaining wall or for better design standards [04] 1.3.5 Domestic investigations in deformation and settlement of urban buildings around Metro construction area In 1985, there was standard TCVN 3972:1985 "Geodetic working in construction" [08] which mentioned the deformation monitoring of buildings Since then, there have been many scientific investigations at the whole levels, a number of research theses and dissertations on construction deformation monitoring to complete the working of construction monitoring to meet the monitoring requirements for the specific projects Investigation the method and regulation of deformation monitoring for buildings: The technological regulation of the deformation and displacement monitoring of the building was performed by Tran Khanh (1991) in the report of the branch project of the nation-level project 46A05-01 [09] Investigation the grid design and processing of construction deformation monitoring data In order to the deformation monitoring grid to meet the accuracy and time requirements, the monitoring grid system should have an optimal design As regard to optimal design for the monitoring grid, there was mentions in Quang Phuc Nguyen’s work (2006) This work fully presented the characteristics of the design of the construction deformation monitoring grid system and the research results on the optimal design of the construction deformation monitoring grid by computer The effectivity and simplicity for the optimal design of deformation monitoring grids by computers were also presented in many investigations [10] 1.4 Conclusion of chapter The tunnel construction for Metro lines by TBM method is suitable and effective in big cities with crowded population, complex and diversified architecture like Hanoi and Ho Chi Minh city Although the advanced construction technology has been applied, the negative influence on entity on the ground like surface deformation and settlement in construction is inevitable This significantly effects on the existing buildings on the ground Therefore, investigations for estimating, evaluating and controlling surface settlement due to tunnel construction of Metro lines are imperative issue which investors, contractors and managers should specially consider CHAPTER THEORETICAL BASIC TO ESTIMATE GROUND SETTLEMENT DURING TUNNEL CONSTRUCTION 2.1 Analysis and prediction of ground subsidence by theoretical methods Some authors develop analytical methods, extrapolate from semi-empirical formulas and combine all the factors to generalize the ground deformation calculation formula.: 2.1.1 Sagaseta (1987), Verruijt Booker (1996), Gonzalez Sagaseta (2001) Sagaseta (1987) [11] presents a generalized solution in unconsolidated, undrained, isotropic and homogeneous soils The soil is modeled as a linear elastic material with virtual image technology and the resulting semi-elastic space to calculate the surface soil displacement The volume of undrained soil loss at a finite depth of infinite space is estimated to be due to volume reduction when tunneling ignoring the action of the soil on the surface, provided that it is incompressible and transferred radial position has axial symmetry Verruijt and Booker (1996) [12] present an analytical method for tunneling in homogeneous elastic space, using the approximation method suggested by Sagaseta (1987) Verruijt and Booker (1996) [12] present an analytical method for tunneling in homogeneous elastic space, using the approximation method suggested by Sagaseta (1987) 2.1.2.Lee et al (1987), Rowe Lee (1992) Lo and Rowe (1982) and Rowe et al (1983) [13] introduced the gap factor causing volume loss with the strength and strain relationship between elastic and plastic states, which is the gap between hole diameter and tunnel cover This gap is corrected by Lee et al (1992) as follows.: 2.1.3.Loganathan Poulos (1998) Loganathan and Poulos (1998) [14] modified Veruijt and Booker's method by incorporating actual boundary conditions An oval was introduced at the top of the tunnel because volume loss occurs at different stages during tunneling 2.2 Analysis and assessment of settlement according to empirical and semi-empirical methods 2.2.1 Methods of empirical research Macklin and Field (1999): Macklin and Field (1999) [15] based on actual data with a 2.8 m diameter tunnel in London clay show the changing relationship between secondary earth pressure and surface settlement deformation with tunneling speed In this case, up to 70% of the ground surface settlement deformation at the perpendicular section occurred when the tail of the excavated shield was passed, during shell installation and grouting VL is determined as a percentage of the total tunnel cross-sectional area VL % V L 100% D / 2.2.2 Semi- empirical research method using stability coefficient: Macklin (1999) [16], Mair (1981) [17], and O'Reilly (1988) [18], combining historical and experimental results from centrifugation experiments suggested a method of loss prediction volume in both clay and vegetation This theory uses the concept of stability coefficient: Call the stability coefficient: N (the concept of Broms and Bennermark (1967)): [19] , 2.2.3 Semi- empirical research method of Schmidt-Peck (1969) The most common empirical method to predict surface settlement is based on the Gaussian distribution Peck (1969) [21], and Schmidt (1974) [22] assume that the shape of the settlement funnel is similar to that of the Gaussian normal distribution curve By statistical analysis based on actual observations, they have shown that this is a reasonable method to model the subsidence funnel shape caused by the tunneling process Basic Equation: S = Smax exp x2 2i In there: - S is the surface settlement according to theoretical calculation; - S max is the maximum surface settlement (above the tunnel axis); S max D VL ( ) 2 2,5.i - x is the horizontal distance from the center of the tunnel to the point to calculate settlement; - i is the standard deviation of the settlement curve (distance from the inflection point of the settlement chute to the center of the tunnel shaft), also known as the settlement width parameter Figure 2.1: Gaussian curve for horizontal settlement and soil loss Vl Then different authors have based on actual observed data to give formulas for calculating Smax in Table 2.1 The writer's name Peck (1969) Atkinson & Potts (1979) [24] New & O’Reilly (1982) Mair (1993) [25] Attewell (1977) [26] Clough & Schmidt (1981) [27] Formula for calculating Smax D VL ( )2 Smax 2,5.i D VL ( )2 Smax 2,5.i Based on actual observed data and model test results 2 VL D i S max S max 1.252 Note Based on actual observation data VL R i D VL ( )2 Smax 2,5.i D VL ( )2 Smax 2,5.i Based on actual tunnel monitoring data in the UK Based on actual observation data and centrifugation experiment Based on actual tunnel monitoring data in the UK Based on actual tunnel monitoring data in the US There are many authors, based on the results of field observations, have proposed formulas to determine the value of i in order to adjust Peck's original formula to suit each specific condition of the works The writer's name Peck (1969) Formula to calculate i n i ZO : R 2R Note Based on actual observation data n=0,8 ÷1,0 Atkinson & Potts (1979) i = 0,25(Z0 + R) for loose sandy soil Based on actual observed data and model test results New & O’Reilly (1982) i = 0,43Z0 + 1,1 for consolidated soil i = 0,28Z0 – 0,1 for unconsolidated soil Based on actual tunnel monitoring data in the UK i = 0,5Z0 Based on actual observation data and centrifugation experiment Mair (1993) n Attewell (1977) i Z O : R 2R α = n = 0,8 Based on actual tunnel monitoring data in the UK n Clough & Schmidt (1981) i Z O : R 2R α = n = 0,8 Based on actual tunnel monitoring data in the US 2.2.4 Chow's semi-empirical research method (1994) [30] This method investigates vertical settlement at a point located at the distance from the concentrated load position in an elastic semi-space (this concentrated load is modeled as a load line running along the tunnel center axis due to the process of digging earth blocks inside the tunnel) The land surface settlement displacement is then calculated according to the formula: S D Z 8.G.(x Z ) 2.2.5 Mair and Taylor's semi-empirical research method (1993) Mair and Taylor [32] studied to compare with the solutions of approximate formulas (empirical formulas) of the underlying deformation of the ground Specifically, the two men gave formulas for spherical and cylindrical pore shapes: su ( D )2 e(0.75N 1) and su ( D )2 e( N 1) * * D 2G r D 2G r Comment: The experimental and semi-empirical research direction provides numerical formulas that allow us to quickly and easily estimate the level of settlement influence caused by the tunneling construction process However, these methods not consider the interaction effects as well as the behavior characteristics of the soil A typical example of this method is Peck's publication in 1969 The scientists then continued to develop and refine Peck's formula based on actual monitoring data of works in different countries, in order to better suit the specific conditions of each country The empirical methods and empirical data are mostly based on the empty surface hypothesis “Green field”, in other words, the existence of construction works as well as its load influence affect the deformation behavior of the ground and surface settlement, displacement of ground structures caused during construction cellar is not considered 2.3 Analyze and evaluate surface settlement based on numerical model and using finite element method General concept of finite element method The finite element method is a numerical method for solving problems described by partial differential equations with specific boundary conditions Mathematically, the finite element method is used to approximate the problem of partial differential equations and integral equations The basis of this method is to discretize the complex continuous domains of problem Continuity domains are divided into several subdomains (elements) These domains are linked together at the nodes On this subdomain, the variant form is equivalent to the problem that is approximately solved based on approximation functions on each element, satisfying the boundary condition along with balance and continuity between the elements Comment: The problem of surface settlement during the construction of tunnels in the city, especially metro tunnels, is an extremely complex interaction problem and can be effectively solved with numerical methods The advantage of the mathematical method in modeling ground settlement analysis problems is that it is possible to consider the reciprocal impact between ground settlement caused by metro tunnel construction and existing works on the ground ground, can be analyzed according to the construction sequence of each project along with the development of commercial software makes the analysis of this problem by the method of mathematical analysis become more and more popular However, the results of the analytical problem by this method depend a lot on the input data Including the volume loss coefficient Vloss However, there are not many studies analyzing this quantity and most of them assume this value according to construction experience 2.4 Conclusion of chapter Through an overview study of methods to assess surface settlement due to tunnel construction by TBM, we have summarized three main research directions: Theoretical research, experimental and semi-empirical research, and numerical model and using finite element method The direction of finite element research applies the development of science and technology to model and consider more related factors such as interaction effects, or construction technical factors 11 With the comparison results from 30 typical cross-sections we studied, the error between the calculated results and the observed data is shown in Table 3.6 Table 3.6: Average error of maximum settlement between calculated and observed results Theory Average error (%) Error ( Peck1) Error ( Peck2) Error ( Peck3) Error ( New OReilly1) Error ( New Oreilly2) Error ( Mair) Error (Attewell) Error ( Clough) Error (Atkinson) (%) (%) (%) (%) (%) (%) (%) (%) (%) 39.9 28,7 13,8 16,1 98,5 13,6 13,8 39,0 90,0 3.4.2 Comparison of settlement curve calculated according to theories with observation results After applying theoretical formulas to specific conditions in the survey area, the section of the space from Ba Son Station to Opera House Station, of Metro line No Ben Thanh - Suoi Tien, the thesis has shown the theoretical settlement curves and compare with the observed values in the field The results are presented in Figure 3.13 of settlement curves at the survey sections below and in Appendix Figure 3.5 Graphs comparing surface settlement between observation and theoretical calculation 3.5 Conclusion of chapter After comparing the results of field observations with the results of theoretical calculations as proposed by Peck 1969 and the next proposals of the above authors, through settlement charts on 30 cross-sections we see that the settlement curves calculated according to the theories have not really followed the observed data It can be seen that these theories not really reflect the subsidence rule at the Metro Line project, Ben Thanh Suoi Tien, Ho Chi Minh city Since then, it is necessary to have studies to propose adjustments to Peck's formula to be more suitable for specific conditions in Vietnam CHAPTER DEVELOPMENT OF RESEARCH GROUND SETLEMENT AND ESTABLISHMENT OF EXPERIENCE FORMULATIONS 4.1 Proposed formula for calculating volume loss coefficient Vloss 4.1.1 Concept of volume loss coefficient VL VL is the volume loss coefficient: This factor considers the volume loss when installing the tunnel shell compared to the excavation process using the TBM technology Specifically, these losses include - Volume loss of excavated mirror surface (Vf), - Volume loss of around digging shield (Vs), - Volume loss at the tail of the shield (Vt) However, this coefficient even Peck's formula does not suggest any specific calculation formula Therefore, this coefficient is often estimated in the calculations And the subsequent studies also only adjusted the coefficients i or Smax without studying and proposing the exact formula for calculating VL The above studies have not mentioned the technical factors in construction and the geological conditions that the tunnel will go through 4.1.2 Analysis of correlations between Vloss volume loss coefficient and characteristic factors 4.1.2.1 Investigate the influence of volume loss coefficient on pumped grout pressure 12 4.1.2.2 Correlation analysis between volume loss coefficient VL with grouting pressure and changing depth Zo 4.1.2.3 Correlation analysis between volume loss coefficient VL and (ϬZ-pa) 4.1.2.4 Correlation analysis between volume loss coefficient VL and (ps-Ko.ϬZ) 4.1.2.5 Correlation analysis between volume loss coefficient VL and pumped mortar volume V 4.1.3 Proposing the formula for calculating Vloss 4.1.3.1 Proposing a general form formula for calculating Vloss With those studies, along with the correlation analysis between Vloss and the above related quantities, the thesis proposes a general formula for calculating volume loss as follows:: 1 2 1 VL K. p K Z s Z pa V 3 4.1.3.2 Building the experimental formula Vloss The logarithm of the above expression is a linear multivariable function log(VL ) log( K ) 1.log p K Z s 1 2 log 3.log p V a Z To calculate the coefficient K and the exponents β1, β2 β3 use the linear multivariable regression function with , , known ps K Z Z p a V Apply linear regression function Regression Statistics in Microsoft excel to build regression equation The results of calculating the coefficients K, β1, β2 β3 instead of the proposed formula, we have 31, 6.10 3 (3.4) VL 2.3 0.78 ps K Z Z pa V 0.7 Where: VL: Volume loss coefficient (%) ps: grouting pressure in front of the excavated mirror (Mpa) pa: Mortar injection pressure in the z direction (Mpa) Ko: Coefficient of earth pressure σZ: earth pressure in Z direction of geology (Mpa) V: volume of grout pumped (m3) 4.1.4 Apply VL formula in theoretical calculation and compare with field observation results 4.1.4.1 Applying VL formula in theoretical calculations The thesis research applies the above formula to the case of East tunnel construction (the lower and left tunnel on the Saigon river side viewed from the direction from Ba Son Station to Opera House Station.) The geological condition that the East tunnel passes through is the AS2 and AS1 geological layers shown in Table 4.3 and Appendix During the tunnel construction by TBM, the survey process has collected data on the volume of pumped mortar and the actual pumped grout pressure at the cross-sections Substituting all into the proposed Vloss formula (3.4) We get the result Table 4.5 Result of volume loss coefficient VL calculated according to the proposed formula Secti ons 1483 1462 1420 1400 1380 Tunnel depth Zo (Ps) (Ps) (V) (γ) (m) Mpa Mpa m3 MN/m3 -15.43 -15.98 -17.08 -17.6 -18.47 0.24 0.22 0.23 0.23 0.22 0.25 0.25 0.27 0.27 0.3 2.9 2.9 3.2 3.2 0.02 0.02 0.02 0.02 0.02 (φ) độ 31 31 31 33 33 E VL Mpa (%) 40 40 40 40 55 0.12 0.16 0.14 0.11 0.18 Note 13 1360 1325 1304 1284 1264 1243 1203 1183 1163 -19.34 -20.86 -21.77 -21.87 -21.97 -22.08 -22.28 -22.44 -22.61 0.3 0.27 0.27 0.3 0.32 0.3 0.27 0.27 0.22 0.31 0.31 0.3 0.33 0.34 0.33 0.33 0.33 0.29 2.9 2.9 2.9 2.9 2.9 2.9 2.90 2.90 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 33 33 33 33 33 33 33 33 33 55 55 55 55 55 55 55 55 55 0.05 0.07 0.06 0.05 0.04 0.05 0.08 0.07 0.16 1123 -22.94 0.23 0.33 2.90 0.02 33 55 0.16 1063 -23.43 0.25 0.34 2.90 0.02 33 55 0.11 1043 -23.59 0.25 0.34 2.90 0.02 33 55 0.11 1003 -23.92 0.24 0.30 3.00 0.02 33 55 0.11 980 -24.23 0.23 0.30 3.00 0.02 33 55 0.15 965 -24.44 0.22 0.25 2.80 0.02 33 55 0.16 945 -24.71 0.24 0.30 2.90 0.02 33 55 0.12 925 -24.98 0.24 0.30 2.90 0.02 33 55 0.12 900 -25.32 0.24 0.30 2.90 0.02 33 55 0.12 890 -25.39 0.21 0.27 4.50 0.02 33 55 0.21 860 -25.60 0.27 0.34 4.50 0.02 33 55 0.05 842 -25.37 0.28 0.35 4.50 0.02 33 55 0.05 828 -25.19 0.28 0.35 4.50 0.02 33 55 0.05 815 -25.02 0.24 0.35 4.50 0.02 33 55 0.11 4.1.4.2 Comparison with calculation results with field monitoring results NCS compares the results of Vloss calculated by the proposed formula above with the results of Vloss according to field monitoring data at cross-sections along the section of Ben Thanh - Ba Son Station Results show pictures Figure 4.1: Chart comparing calculated Vloss with Observable Vloss Compare the results of calculating the volume loss coefficient Vloss by the proposed formula with the result of calculating the volume loss coefficient using the actual observation data at the field with a small error of 4.75% It can be seen that the Vloss formula proposed by the thesis partly reflects the volume loss during the construction of metro tunnels at Metro project No Ben Thanh - Suoi Tien, Ho Chi Minh City 4.1.4.3 Comments on the proposed Vloss formula The comparison results show that compared with the observed Vloss values in the field, the error with the average Vloss when calculated according to the proposed formula is 4.75%, this is an acceptable small error The results of calculating Vloss according to the formula proposed by the thesis to create cross-sections with values from 0.05% to 0.22% are also completely consistent with the suggested Vloss values of Peck's assumption from 0.05 to 0.5% It shows that the proposed Vloss formula reflects the settlement rule in this project and is also consistent with previous studies With this Vloss calculation, it can be used as an input database for the numerical simulation problem analyzed by to further improve the finite word part problem in this research area 14 4.2 Proposing the formula to calculate the maximum settlement Smax 4.2.1 Proposing the formula Smax With the approach to actual monitoring data and similar research methods, the thesis proposes the formula to calculate the maximum settlement Smax at the center of the tunnel as follows: 1.65 S max VL 0.96 D.P Z 1.7 E In there: Smax: Maximum settlement at the center of the tunnel (mm) D: Diameter of tunnel pipe (m) VL: Volume loss coefficient (%) Z: Depth of tunnel heart (m) : Geological specific gravity that the tunnel passes through (KN/m3) E: Elastic modulus of geology through which the tunnel passes (Mpa) P: Value of loading on the surface (KN/m) 4.2.2 Apply the Smax formula in theoretical calculations and compare the calculation results with the results of field observations Applying the formula Smax and Vloss proposed above for the case of WEST tunnel construction with a diameter of 6.65m is the tunnel below and located on the left side of the Saigon River from the direction of Ba Son Station to the Opera House Station With the assumption on the surface with an additional load of P= 10 KN/m (Based on the survey results of buildings along the Ben Thanh - Suoi Tien section presented in chapter of the thesis) The results are calculated on the data of all aspects of the project Table 4.11 Maximum settlement Smax calculated according to the proposed formula Sectio n 1483 1462 1420 1400 1380 1360 1325 1304 1284 1264 1243 1203 1183 1163 1123 1063 1043 1003 980 965 945 925 900 890 860 842 828 815 Tunnel depth Zo (m) -15.43 -15.98 -17.08 -17.60 -18.47 -19.34 -20.86 -21.77 -21.87 -21.97 -22.08 -22.28 -22.44 -22.61 -22.94 -23.43 -23.59 -23.92 -24.23 -24.44 -24.71 -24.98 -25.32 -25.39 -25.60 -25.37 -25.19 -25.02 (P) (D) (VL) (γ) (φ) E Smax (KN/m) 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 (m) 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 6.65 (%) 0.12 0.16 0.14 0.11 0.18 0.05 0.07 0.06 0.05 0.04 0.12 0.16 0.14 0.11 0.18 0.05 0.07 0.06 0.05 0.04 0.05 0.08 0.08 0.17 0.17 0.11 0.11 0.11 KN/m3 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 độ 31 31 31 31 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 Mpa 40 40 40 40 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 (mm) -4.86 -6.04 -4.70 -3.65 -6.29 -2.00 -2.66 -2.51 -1.96 -1.59 -1.90 -2.86 -2.81 -6.10 -5.28 -3.90 -3.86 -3.78 -4.77 -6.51 -3.82 -3.82 -3.82 -6.28 -1.76 -1.50 -1.58 -3.52 Note 4.2.3 Compare with field monitoring results Compare the results of calculating the maximum settlement with the field observation data for the results shown in Fig 4.24 15 Độ lún Smaxx (mm) 0.00 800 900 1000 1100 1200 1300 1400 1500 -2.00 -4.00 Smax ( đề xuất) -6.00 Smax ( quan trắc) -8.00 Figure 4.2 Comparison of surface settlement results between observed and calculated data according to the proposed Smax formula Comment: By comparing the results of Smax calculated according to the proposed formula with the actual observed values in the field, it shows that the calculated results are very close to the measurement results, with an average error of about -2.99%, the error is at each cross-section are less than 10% It proves that the proposed Smax and Vloss formulas have quite accurately reflected the actual maximum settlement according to tunnel construction conditions in Ho Chi Minh city according to the TBM technology 4.2.4 Comparison with results calculated by other theories Table 4.13 Average error of maximum settlement between calculation results Error ( Peck2) Error ( Peck3) Error ( New OReilly1 Error ( New Oreilly2) Theory Error ( Peck1) Error ( Mair) Error (Attewell) (%) (%) (%) (%) (%) (%) (%) Average error (%) 39.9 28,7 13,8 16,1 98,5 13,6 13,8 Error (Atkinson) Error Smax Offer (%) (%) (%) 39,0 90,0 -2.99 Error ( Clough) 4.2.3.4 Comment on the proposed formula Smax The results of calculating Smax and Vloss according to the proposed formula of the thesis give very close results to the actual monitoring data on the cross sections along the route from Ba Son Station to Opera House Station From there, it can be concluded that the formula proposed by the thesis is suitable to predict the largest settlement when constructing Metro tunnels by the TBM technology according to construction and geological conditions in Ho Chi Minh city 4.3 Proposing formula to calculate settlement coefficient i 4.3.1 Proposing formula to calculate settlement coefficient i With the approach to actual monitoring data and similar research methods, the thesis proposes the formula for calculating settlement coefficient I as follows: 0.8 Z i P 0.52 D In there: i: Coefficient of subsidence trough Z: Depth of tunnel heart (m) D: Diameter of tunnel pipe (m) P: Load evenly distributed on the surface (KN/m) 4.3.4 Apply formula i in theoretical calculation and compare the calculation results with the results of field observations Compare the settlement curve calculated by the proposed formula Smax, VL and i and the settlement curve calculated by other theoretical formulas on the survey cross-sections and compare with the observed settlement curve at these cross-sections The results show that the proposed settlement curve is closer to the actual settlement values than all other theoretical settlement curves Specific results are presented in Figure 4.27 and Appendix 16 The results of calculating the settlement in the horizontal direction of the tunnel at each crosssection show that the settlement curve according to the Peck formula using the coefficients Smax and Vloss and the proposed settlement coefficient i, closely follows the settlement monitoring values At the measurement points, it shows that the proposed formula has correctly reflected the settlement law in this project From here, it can be confirmed that the formulas Smax, Vloss, and settlement coefficient i proposed by the thesis are reliable and suitable for construction and geological conditions in Ho Chi Minh city Predictive formulas for a similar project in Ho Chi Minh city 4.4 Conclusion of chapter From all the above results, it can be concluded that the formulas Smax, Vloss, and settlement coefficient i proposed by the thesis have practical significance and are valuable contributions in predicting surface settlement when constructing Metro lines in Vietnam Simultaneously with the formula for calculating Vloss, it will also contribute to a more complete method of equivalence in analyzing the influence of metro tunnel construction on ground settlement as well as existing works on the ground CHAPTER RESEARCH THE EFFECT OF TUNNEL CONSTRUCTION PROCESS BY TBM TECHNOLOGY ON EXISTING STRUCTURES ON THE GROUND BY THE NUMERICAL SIMULATION METHOD 5.1 Propose an an improved numerical simulation model to calculate surface settlement and assess the impact on structures on the ground 5.1.1 Propose an improved numerical simulation model Chapter of the thesis has proposed and proved that the VL formula proposed in the thesis is completely feasible Chapter will use the VL coefficient calculated according to the formula in Chapter to put into improved numerical simulation model to analyze the interaction effects between types of foundation works on the surface to surface settlement due to Metro construction by TBM technology Here, NCS will improve the numerical simulation model to study the interaction between ground settlement and foundation types on the surface as follows: Bảng 5.1 improved finite element problem model to calculate surface settlement and assess the impact on structures on the ground Traditional Improved numerical simulation model numerical simulation model Step Simulate background environment size Simulate background environment size Step Simulate geological conditions according to Mohr Coulomb or Harden soil Simulate geological conditions according to Mohr Coulomb or Harden soil Step Set the initial stress state of the ground and structure on surface Set the initial stress state of the ground and structure on surface Step Simulation of the construction of the first tunnel Simulation of the construction of the first tunnel Step Activation of cellar shell concrete elements Activation of cellar shell concrete elements 17 Step Activate the assumed volume loss factor Vloss according to construction experience Activation of the volume loss factor Vloss is calculated according to the formula proposed in chapter Step Repeat the above steps with the second tunnel Repeat the above steps with the second tunnel 5.1.2 Compare the results of analysis by the improved numerical simulation model with the observed data 5.1.2.1 Compare the results of ground settlement by the improved numerical simulation model with the observed data Figure 5.2 shows the comparison of calculation results and surface settlement monitoring results at the site where two parallel tunnels have the same elevation The results show that the settlement curve calculated by improved numerical simulation method is close to the actual observed values in the field It can be concluded that the improved numerical simulation model with the value of Vloss calculated according to the formula proposed in chapter is suitable and reflects the ground settlement law at Metro No Ben Thanh - Suoi Tien construction project 5.1.2.2 Compare the results of calculation of footing bottom displacement by the improved numerical simulation model with observation data Figure 5.3 shows the calculation results and the monitoring results of the building foundation displacement at the site where there are two parallel tunnels with the same elevation The results show that the field monitoring measurement points give the foundation displacement value approximately the calculated value That can confirm that the improved numerical simulation model proposed by the thesis is completely suitable and reflects the law of foundation bottom displacement on the ground Figure 5.1- 5.2 Comparison of ground settlement and Comparison of footing bottom displacement calculation results 5.2 Applying an improved numerical simulation method to evaluate the impact of tunnel construction on foundations of works on the ground 5.2.1 Problem model by improved numerical simulation method Applying the above-mentioned the improved numerical simulation method to the specific problem at some typical cross-sections at the construction project of Metro No Ben Thanh - Suoi Tien, Ho Chi Minh City The model was analyzed using Plaxis software Figures 5.4, 5.5 show the problem model assumed for the cross-section with two parallel tunnels, with an outer diameter of 6.65m, the distance between the two tunnels is 16.0m respectively The two tunnels are located on the same elevation, at a depth of -17.0m from the natural ground This case corresponds to the cross-section of the section located near Ba Son station In the digital model, the tunnel on the left, located further from the bottom edge of the assumed foundation, is pre-constructed The second tunnel on the right is to be constructed after the completion of the first tunnel This construction sequence is relatively consistent with the actual construction of the route between the two stations of Ba Son to the Opera House 18 Figure 5.3- 5.4 Mathematical model of the shallow foundation problem and and pile foundation Table 5.2 Input parameters for soil layers layer (Đất Đắp) Background pattern MC Thickness 1,1 Dry weight 17 Natural weight 18 Permeability (horizontal) 8,6.10-2 Permeability (vertical) 8,6.10-2 Young modulus of the ground 1,8.103 Adhesive force 8,5 Internal friction angle 28 Poisson's coefficient 0,35 Parameter Layer (Ac2) Layer (As1) Layer (As2) Layer (Dc) Layer (Dc) MC 1,7 15,3 16 8,6.10-5 8,6.10-5 1,8.103 14 15 0,48 MC 14 18 19,5 4,3.10-5 4,3.10-5 4,2.103 31 0,33 MC 17 18,6 19,5 4,3.10-5 4,3.10-5 13,9.103 1,1 31 0,33 MC 16 19,8 21 8,6.10-6 8,6.10-6 20,5.103 22 17 0,35 MC 19,5 21 8,64.10-2 8,64.10-2 20,5.103 3,5 34 0,31 unit m kN/m3 kN/m3 m/ngày m/ngày kN/m2 kN/m2 o - Table 5.3 Characteristics of tunnel shell material and ground structure foundation Material Parameter Lining Concrete shallow foundation Brick foundation Young modulus E ( kN/m2 ) 2944.104 2944.104 1944.104 unit weight of soils Poisson's coefficient γ ( kN/m3 ) υ 25 0,3 25 0,3 17 0,3 Size (m) 0,3 2,0 1,0 5.2.2.Analyze the results of the construction problem of two parallel tunnels 5.2.2.1 Analysis of results of calculation of ground settlement in case of shallow foundation Figure 5.5-5.6 Surface settlement curve after construction of left tunnel and construction of both tunnels However, the surface settlement curve (Figure 5.9) appears a turning point corresponding to the limit point of the foundation structure Besides, the simulation results also show that the influence of the shallow foundation structural stiffness on the settlement curve is small when the settlement curves of the two cases are almost identical This is extremely important in surveying and assessing risks for existing structures under the impact of tunneling work 5.2.2.2 Displacement of foundation bottom in case of farm foundation Figure 5.7-5.8 Vertical displacement and bottom rotation angle of shallow foundation due to left tunnel construction 19 Figure 5.9-5.10 Vertical displacement and bottom rotation angle of shallow foundation due to construction of two tunnels Comment: The results of shallow foundation bottom displacement when tunneling in the vicinity of the shallow foundation bottom will cause displacements for the foundation including vertical displacement and rotation angle displacement However, the effect of nail stiffness does not seem to be very pronounced Brick foundation with lower stiffness will have larger deformations under the effect of ground displacement due to excavation, but not really different from the case of concrete foundation with higher stiffness It should also be emphasized that the model is limited to small displacements and does not consider the incompleteness and fracture of the brick foundation under the effect of deflection settlement 5.2.2.3 Analysis of surface settlement calculation results in case of pile foundation Figure 5.11 - 5.12 Ground settlement curve with pile foundation when constructing one tunnel and two tunnels 5.2.2.4 Displacement of foundation bottom in case of pile foundation Figure 5.13 Vertical displacement and bottom rotation angle of pile foundation during construction of left tunnel Figure 5.14 Vertical displacement and bottom rotation angle of pile foundation when constructing two tunnels The thesis has applied this improved modeling method to analyze the problem of calculating ground settlement and foundation bottom displacement on the surface with specific data at the typical cross-section of the Ben Thanh - Suoi Tien Metro project, Following are some of the comments: When constructing a Metro tunnel in an area with urban constructions on the surface, the largest ground settlement will be reduced compared to the case on the surface without existing works However, the stiffness of the shallow foundation does not affect this change much, but the 20 type of short pile foundation or long pile foundation will have different effects on this maximum settlement change Smax The ground settlement curve will appear a turning point (fracture) at the position corresponding to the foundation edge of urban works on the surface This is especially important in studying the impact of Metro construction on urban works on the ground because it is this diversion point that will cause the foundation on the ground to appear translational and rotational displacement is dangerous for the foundation of the building When the foundation of urban works on the ground has a far enough distance from the center of the construction tunnel (>3.5D), it seems that the construction of the metro tunnel does not have much impact on the displacement of the foundation on the surface When the foundation is located in the vicinity of Metro construction, there is a mutual impact between the urban foundation and the ground settlement Specifically, the foundation works appear vertical displacements and rotational displacements However, in the case of a shallow foundation, the stiffness of the foundation does not affect these displacements much, and the pile foundation type is affected differently between the short pile foundation types or the long pile foundation types 5.3 Studying the influence of metro tunnel construction on urban works on the surface 5.3.1 Proposing a technology diagram for tunnel construction by TBM to control the impact to urban works on the ground In order to ensure the safety of urban works on the ground, the PhD student proposes a technological scheme to build tunnels by TBM in order to control the impact of urban works on the ground in the period before the organization construction and during construction Figure 5.15 Technological diagram before organizing tunnel construction by Metro 21 Figure 5.16 Technological diagram while organizing tunnel construction by Metro 5.3.2 Surveying and data collection Site survey and data collection, risk analysis must be carried out on all aboveground constructions that are likely to be affected by the construction of underground stations and Metro lines Normally, a corridor will be established on both sides of the tunnel along the tunnel and all works located in that corridor must be surveyed and analyzed The research corridor is defined as follows: •All works are located within a distance of 50m from the longitudinal axis of the tunnel center • A distance of at least 30m or 2Zo (Zo is the tunneling depth) with open excavations from the outer edge of the excavation perimeter • All historical and cultural works are located within a distance of 200m from the heart of the tunnel Observational quantities In tunnel construction by tunneling machine, monitoring TBM is an effective aid used for the following purposes: • Monitoring and predicting geomechanical conditions in the area where the tunnel will be excavated; • Monitoring the deformation, durability of the tunnel shell structure; • Monitoring and evaluating the mechanical reaction of the soil mass around the tunnel after excavation; • Monitoring ground movement and surface structure damage caused by tunnel construction Observation and measurement objects include: • Tunnel shell structure; • Soil mass around the tunnel shell and on the surface; • Works affected by the construction process 5.3.3 Effects of surface settlement on adjacent structures When a structure is built near the tunnel construction site, one of the following types of displacement may occur: • Uniform subsidence; 22 • Uneven settlement between bearings; • Full rotation or uneven rotation; • Full traverse; • Uneven lateral displacement under compression and tension Vertical displacement, rotation angle displacement and horizontal displacement of the building 5.3.4 Limits of damage to structures Table 5.8 Limits on destruction of buildings due to ground deformation HIGH SENSITIVE BUILDINGS NORMAL BUILDINGS Permissible degree of damage Damage level Damage level Total subsidence Smax ≤ 5mm Smax ≤ 15mm Uneven subsidence ΔSmax ≤ 2mm ΔSmax ≤ 5mm Tilt β ≤ 1/1000 β ≤ 1/500 Deformation ε ≤ 0.025 ε ≤ 0.075 Table 5.9 Classification of superficial damage on walls (Burland & Wroth, 1975) Damage level Danger level Trivial Very light Light Normal Serious Very serious Typical failure description Hairline crack, width less than 0.1mm Typical cracks have a width of approximately 1mm Typical cracks have a width of approximately 5mm Typical cracks with an extension of 5mm to 15mm or dense cracks with an opening greater than 3mm Typical cracks range from 15mm to 25mm wide, but it depends on the number of cracks Typical cracks have openings greater than 25mm but depends on the number of cracks Table 5.10 Relationship between failure type and ultimate tensile strain (Boscardin & Cording, 1989 and Burland (1995) Damage type Degree of damage Limit tensile strain (%) Damage is almost negligible Very slight damage 0,05-0,075 Slight damage 0,075-0,15 Medium damage to Serious to very serious damage 0-0,05 0,15-0,3 >0,3 5.3.5 Measures to minimize impacts of neighboring buildings when building Metro tunnels in urban areas • Increase the load capacity of the building • Dramatically reduces the risk of subsidence caused during tunneling • Thoroughly reduce the possibility of excavating volume difference • Settlement compensation 5.4 Conclusion of chapter The improved numerical simulation model with Vloss coefficient calculated according to chapter formula has scientific and practical significance It can be proposed to use this model in calculating calculation problems and analyzing the influence of the process of constructing Metro tunnels by TBM on ground settlement and existing works on the surface The thesis has also 23 initially applied this improved numerical simulation model to analyze the influence of the Metro tunnel construction process on settlement and some types of existing foundation structures on the surface at the construction project of Metro line No Citadel - Suoi Tien, Ho Chi Minh City Chapter of the thesis has proposed a technological diagram of metro tunnel construction by TBM to control the impacts affecting urban works on the ground including: Technological diagram before construction organization and Schematic diagram technology during construction With this TBM construction technology diagram, it allows us to control and restrain the impacts affecting urban works on the ground before the construction and even during the construction stage of the Metro tunnel by TBM CONCLUSIONS AND RECOMMENDATIONS KL1 Summarize the process, content and research results of the thesis The thesis compares the results observed at the site of the construction project of Metro line No Ben Thanh - Suoi Tien, Ho Chi Minh City with the results calculated according to the theoretical formulas published by the authors previously and there are certain errors Since then, it is necessary to have studies to adjust Peck's formula to be more suitable for specific conditions in Vietnam The research thesis proposes the formula for calculating VL The results show that the calculated Vloss data is quite close to the measured value at the survey sections and the average error of this calculation result with the actual observed data is only 4.75% This error shows that the Vloss formula proposed by the thesis is reliable and has practical significance The thesis has continued to research and propose the formula for calculating Smax, The results are compared with the observed data in the field, showing that the error between the calculated results and the average observed value is only 2.99 %, much smaller than the average value much higher than the error that the formulas of the above authors have announced It can be confirmed that the Smax formula proposed by the thesis has more accurately and more realistically reflected the surface settlement behavior at the construction project of the Ben Thanh Suoi Tien Metro line in Ho Chi Minh city This is a significant contribution in this field The thesis continues to research and propose to adjust the formula for settlement coefficient i Peck's settlement curve which is adjusted by the coefficients Smax, Vloss, i reflects the law of surface deformation when constructing underground Metro line in Ho Chi Minh city And these are scientific contributions in this field that are valuable to apply to the construction conditions of the underground Metro line section in Ho Chi Minh city The thesis has more perfected the numerical simulation method for calculating ground settlement and bottom displacement of the existing foundations on the surface by using the Vloss coefficient calculated according to the formula proposed in chapter of the thesis instead of data input is assumed based on construction experience like previous models The improved numerical simulation model with Vloss coefficient calculated according to chapter formula has scientific and practical significance It can be proposed to use this model in calculating the ground settlement and foundation bottom displacement problems when constructing Metro tunnels by TBM The thesis proposes a technological diagram of metro tunnel construction by TBM to control the impacts affecting urban works on the ground including: Technology diagram before construction organization and Technology diagram in construction process With this TBM construction technology diagram, it allows us to control and restrain the impacts affecting urban works on the ground before the construction and even during the construction stage of the Metro tunnel by TBM 24 KL2 New contributions of the thesis KL2.1 Research and propose the formula for calculating Vloss VL 31, 6.103 2.3 ps K Z Z pa 1.65 KL2.2 Research and propose a formula for calculating Smax S max VL 0.96 KL2.3 Research and propose a formula to calculate settlement coefficient I D.P Z 0.78 V 0.7 1.7 E 0.8 Z i P0.52 D KL2.4 The thesis has more perfected the numerical simulation method for calculating ground settlement and bottom displacement of the existing foundations on the surface by using the Vloss coefficient calculated according to the formula proposed in chapter of the thesis instead of data input is assumed based on construction experience like previous models KL3 Shortcomings and directions for further research Some shortcomings of the thesis are new research based on survey and observation data at a project in Vietnam The initial ambition was to be able to use the monitoring data of two projects, namely the Metro Line Ben Thanh Suoi Tien project in Ho Chi Minh city and the Nhon Line project Hanoi Railway Station, Hanoi However, due to the slow progress of the Nhon Ga Hanoi project, the thesis cannot access this data in its research Proposing the next research direction of the thesis will continue to wait for the Nhon Ga Hanoi project, the construction will approach and collect monitoring data at the project to continue to improve its formula to increase the reliability reliable in predicting surface settlement when constructing underground metro lines in Vietnam The new thesis focuses a lot on surface settlement, there is not enough time to survey the specific building structure running along the Metro line and survey and monitor the deformations of these buildings The next research direction is to continue researching and surveying buildings running along the Ben Thanh - Ba Son route to build hazard prediction formulas for different types of buildings KL4 Some recommendations - Proposing units related to metro design and construction in Vietnam to refer to the model and empirical formula that the thesis has proposed to predict surface settlement during the construction of the next Metro lines followed in Hanoi and Ho Chi Minh City - It is recommended to continue researching to evaluate other influencing factors of the ground soil to surface settlement when constructing Metro tunnels using TBM technology - Recommend experimental studies to evaluate the influence of different TBM system's physical quantities on the problem model LIST OF SCIENTIFIC WORKS OF STUDENTS Thach Bich Nguyen, Xuan Nam Ho (2016), Analysis of factors affecting the surface subsidence due to shield tunnel construction at the ICSCE International Conference held at the University of Transport and Communication Thach Bich Nguyen, Phuong Duy Nguyen (2016), Numerical analysis of ground surface settlement due to volume loss during the tunnel construction by TBM at the ICSCE International Conference held at the University of Transport and Communication Nguyễn Thạch Bích, Nguyễn Phương Duy, Lê Thành Lê (9/2017), Study on the influence of Metro Station construction on surface settlement, Journal of Transport Thach Bich Nguyen, Phuong Duy Nguyen (2018), Ground movement analysis during the construction by numerical method of the Opera House underground station, Ho Chi Minh city at the ICSCE International Conference held at the University of Transport and Communication Thach Bich Nguyen, Phuong Duy Nguyen, Thanh Le Le (12/2019), Studying the interaction effects of shallow foundations on the ground to surface settlement due to tunnel construction by TBM technology, Journal of Transport Thach Bich Nguyen, Thanh Le Le, and Phuong Duy Nguyen (2020), Numerical Analysis of the Influence of Shield-Gap Pressure on the Volume Loss and Surface Settlement of the TBM Tunneling, Lecture Notes in Civil Engineering, ISSN 2366-2557, https://doi.org/10.1007/978-981-16-0053-1 Thach Bich Nguyen, Phuong Duy Nguyen, Ngoc Thanh Nguyen (11/2021), The coefficient of volume loss caused by tunnel construction using TBM technology to balance soil pressure, results of monitoring and numerical analysis by the numerical simulation method, Journal of Transport Thach Bich Nguyen, Duc Nhiem Tran, Phuong Duy Nguyen (08/2022), Survey of volume loss coefficient on the basis of monitoring data during tunnel construction by TBM at Metro Line 1, Ho Chi Minh City, Journal of Transport ... Thanh - Suoi Tien Route: Ben Thanh (at Quach Thi Trang Square) – Le Loi – Nguyen Sieu – Ngo Van Nam – Ton Duc Thang – Ba Son – Nguyen Huu Canh – Van Thanh – Dien Bien Phu – Saigon Bridge – Hanoi... (2.6 km underground and 17.1 km overhead) Number of stations: 14 (3 underground stations and 11 elevated stations) The connection between the Opera House station and Ba Son station is 02 single... 5.7-5.8 Vertical displacement and bottom rotation angle of shallow foundation due to left tunnel construction 19 Figure 5.9-5.10 Vertical displacement and bottom rotation angle of shallow foundation