Research on using rock tunnelling quality index (q system) to estimate the proper support in tunnel

MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF MINING AND GEOLOGY VAN DIEP DINH RESEARCH ON USING ROCK TUNNELLING QUALITY INDEX (Q-SYSTEM) TO ESTIMATE THE PROPER SUPPORT IN TUNNEL SCIENTIFIC MASTER THESIS HA NOI - 2018 MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF MINING AND GEOLOGY VAN DIEP DINH RESEARCH ON USING ROCK TUNNELLING QUALITY INDEX (Q-SYSTEM) TO ESTIMATE THE PROPER SUPPORT IN TUNNEL Major: Underground Construction Engineering No: 8580204 SCIENTIFIC MASTER THESIS Supervisor Dr Ngoc Anh Do HA NOI - 2018 i DECLARATION I hereby declare that this thesis is my own performance work and the contains of this thesis are original and have not been submitted in whole or in part for consideration for any other degree or qualification in this, or any other university Hanoi, October 2018 Van Diep Dinh ii SOCIAL REPUCLIC OF VIETNAM Independence - Freedom - Happiness REPORT ON ADDITION AND EDITDING MASTER THESIS ACCORDING TO MINUTES OF EVALUATING COUNCIL Dear: - Hanoi University of Mining and Geology - Postgraduate Office Full name: Van Diep Dinh Master thesis title: “Research on using Rock Tunnelling Quality Index (Q-system) to estimate the proper support in tunnel” Major: Underground Construction Engineering No: 8580204 Supervisor: Dr Ngoc Anh Do After defending master thesis, master student edited and added some parts of thesis according to Minutes of Evaluating Council The details of edition and addition following as: Correcting grammar errors in page (Part 1.1, Chapter 1), page 11 (Part 1.2.2, Chapter 1), page 20 (Part 2.1, Chapter 2) and page 42 (Part 2.5, Chapter 2); Editing figures in pages 24, 25, 26, 27 and 28 (Part 2.2.2, Chapter 2); Correcting equations in page 30 (Part 2.2.3.1, Chapter 2), page 31 (Part 2.2.3.2, Chapter 2) and page 55 (Part 3.5, Chapter 3); Clearing Figure 3.4, Figure 3.5 and Figure 3.6 (Part 3.5, Chapter 3) Hanoi, Nov 20, 2018 SUPPRERVISOR MASTER STUDENT PRESIDENT OF EVALUATING COUNCIL iii SUMMARY Among rock mass quality classification systems, Rock Tunnelling Quality Index, Q-system (Barton et al 1974) was one in typical systems that was frequently used Q-system not only classified the rock mass quality but also gave a lot of recommend about supports for user during excavations Realistically, using the Qsystem was still based on looking for referencing tables and graphs by hands and did not optimally use the plenty of information in Q-system for tunnelling Hence, it is necessary to constitute a calculated tool in computer that make much convenient and professional To tackle this problem above, the author applied the Excel software and interpolation linearly algorithms to digitalize Q-system on the paper to Q*-system by the functions and restrict conditions in Excel After being digitalizing, Q-system will be tracked in Excel by calculated sheets that allow users to easily adjust the parameters of Q-system and show up the support parameters promptly Q*-system could be used with a great number of segments in tunnel so it is easy to control and record during excavations In addition, the performance research about tunnel stability was estimated by the radial displacement at some vital points on the tunnel boundary that facilitated designer and constructor to predict tunnel stability after supporting The analysis results by using RS2 software also showed the radial displacement at the top of crown and the middle of road were greater times than top of wall This thesis included four main calculated sheets to determine Q values and the support parameters based on Q-system The support parameters could be varied by users and after that the obtained results will be summarized and compared iv TABLE OF CONTENTS DECLARATION i SUMMARY iii TABLE OF CONTENTS iv LIST OF FIGURES vi LIST OF TABLES viii GENERAL INTRODUCTION CHAPTER ROCK TUNNELLING QUALITY INDEX, Q-SYSTEM OVERVIEW IN ROCK SUPPORT ESTIMATION FOR TUNNELS 1.1 Introduction 1.2 Determine the Q value for rock masses during Tunnelling .5 1.2.1 Estimate RQD value 1.2.2 Joint set number (Jn) 10 1.2.3 Joint roughness number (Jr) 11 1.2.4 Joint alteration number (Ja) .13 1.2.5 Joint water reduction (Jw) 16 1.2.6 Stress Reduction Factor (SRF) 16 CHAPTER DIGITALIZING Q-SYSTEM BY EXCEL SHEETS .20 2.1 Tunnel and Rock support parameters for tunnel in Excel sheets 20 2.2 Digitalizing Q-system 21 2.2.1 Remark important points 21 2.2.2 Digitalizing line graphs 22 2.2.3 Convert co-ordinate system 28 2.2.4 Determine reinforcement categories .31 2.2.5 Determine bolt spacing in shotcreted area (Sbs) 34 2.2.6 Determine bolt spacing in unshotcreted area (Sbus) .35 2.2.7 Determine bolt length (Lb) 35 2.2.8 Determine shotcrete thickness (Ts) 36 2.3 Calculated sheet in Excel .36 v 2.4 Estimate the precise degree 41 2.5 Discussion 42 CHAPTER ESTIMATING THE RADIAL DISPLACEMENT ON THE TUNNEL BOUNDARY WITHIN EFFICIENT WORKING AREA OF QSYSTEM 45 3.1 Introduction 45 3.2 Efficient working area of Q-system .46 3.3 Case study and Model parameters 47 3.4 Evaluation of rock mass and rock support parameters 51 3.5 Results 52 3.6 Discussion 55 CONCLUSIONS .57 REFERENCES 59 vi LIST OF FIGURES Figure 1.1 Procedure for measurement and calculation of RQD [9] Figure 1.2 Types of joint patterns given in stereo diagram .11 Figure 1.3 Joint wall surface with various Jr value 12 Figure 1.4 Joint with and without rock-wall contact .15 Figure 2.1 Types of supporting 1) Only roof; 2) Roof and a half of wall; 3) Roof and wall 20 Figure 2.2 Remarked points on Q graph [3] 22 Figure 2.3 Line graph - in Q*-system 24 Figure 2.4 Line graph - in Q*-system 24 Figure 2.5 Line graph - in Q*-system 25 Figure 2.6 Line graph - in Q*-system 25 Figure 2.7 Line graph - in Q*-system 26 Figure 2.8 Line graph 10 - 11 in Q*-system 26 Figure Line graph 12 - 13 in Q*-system 27 Figure 2.10 Line graph 14 - 15 in Q*-system 27 Figure 2.11 Line graph 16 - 17 in Q*-system 28 Figure 2.12 Line graph 18 - 19 in Q*-system 28 Figure 2.13 Q*- system 29 Figure 2.14 The relationship between Q value and xR coordinate 30 Figure 2.15 The relationship between B/ESR ratio and yR coordinate 31 Figure 2.16 Divided fields in Q-system 32 Figure 2.17 Determine reinforcement categories .33 Figure 2.18 Determine shotcrete thickness (Ts) .36 Figure 2.19 The interface of Q-system sheet 37 Figure 2.20 Estimating Q value sheet 38 Figure 2.21 Geometrical Input sheet 39 Figure 2.22 Temporary Rock Support Parameters sheet 40 Figure 2.23 The precise degree of points and functions in Q*-system 42 vii Figure 3.1 Limitation of Q-system for rock support Outside this area supplementary methods/evaluations/calculations should be applied (reproduced from Palmstrom and Broch, 2006) [1] 47 Figure 3.2 Adopted case studies .48 Figure 3.3 Layout of numerical model and monitored points (1), (2) and (3) was determined by the vertical displacement at point (1), (3) and horizontal displacement at point (2) 50 Figure 3.4 Vertical displacement at Point .53 Figure 3.5 Vertical displacement at Point .53 Figure 3.6 Horizontal Displacement at Point 54 Figure 3.7 Radial displacement at Point 1, Point and Point .55 viii LIST OF TABLES Table 1.1 Rock mass quality group and RQD value respectively .8 Table 1.2 An example of histogram presentation of Q-parameters from a tunnel section Table 1.3 Jn values 10 Table 1.4 Jr values 13 Table 1.5 Ja values 14 Table 1.6 Jw values 16 Table 1.7 RSF values .18 Table 2.1 Coordinates of points in Q-system and Q*-system 23 Table 3.1 Parameters of case study 48 Table 3.2 Rock support Parameters 52 46 useful guide on the basis of Q-system In other words, the deformation modulus was chosen according to the relationship with Q value This modulus is required the numerical research related the distribution of stress and displacement surrounding tunnels However, these results just illustrated the deformations modulus without mentioning the stability of tunnels in efficient working area of Q-system This study aims to estimate the stability of rock mass in efficient working area of Q-system based on radial displacement of tunnel boundary obtained from numerical model The performance research would significantly contribute to Qsystem application in tunnelling, especially in predicting the stability of tunnel 3.2 Efficient working area of Q-system Q-system was constituted by the plenty of data that was collected from tunnels in Norway and other countries before Based on Q-system, the parameters about rock supports as bolts and shotcrete were determined by Rock mass quality in terms of Q value and (Span or Height)/ESR ratio (Equivalent Dimension, De) Palmstrom and Broch (2006) conducted elaborately a survey about Q-system and showed that actually the Q-system worked best within a certain range of parameters [1] This range was illustrated by a rectangle in Figure 3.1 The best working area of Q-system fluctuated between 0.1 and 40 in Q value corresponding to the (Span or Height)/ESR ratio varied from 2.5 to 35 If the data was outside this area, it was necessary to use other supplementary calculated methods Those methods will enhance the reliability for determining the proper rock supports in tunnelling 47 Figure 3.1 Limitation of Q-system for rock support Outside this area supplementary methods/evaluations/calculations should be applied (reproduced from Palmstrom and Broch, 2006) [1] One of the requirements of rock support has to ensure the stability of tunnel after supported Although rock support was framed followed instructions by empirical methods of Q-system, the weakness of Q-system has not quantified the stability of tunnel In other words, the radial displacement degree on the tunnel boundary within efficient working area of Q-system has not taken into account adequately To handle this problem, the author conducted a numerical investigation using RS2 software (Rocscience) to determine the stability of tunnel in terms of radial displacement measured at three points on the tunnel boundary, which are (1) crown of tunnel; (2) top of tunnel wall and (3) tunnel floor (see Figure 3.3) 3.3 Case study and Model parameters On the basis of efficient working area of Q-system proposed by Palmstrom and Broch (2006) [1], adopted cases of rock mass quality and support structure used in this study have been selected on the mutual boundary between categories as seen in Figure 3.2 48 Figure 3.2 Adopted case studies Each case in Figure 3.2 was located by two parameters of Q value and (Span or Height)/ESR ratio There were totally 28 numerical calculations conducted in this study The parameters of all cases are indicated in Table 3.1 Table 3.1 Parameters of case study Bolt spacing Bolt Thickness of Case Q value GSI B/ESR 0.1 30 25 1.3 5.7 0.246 0.3 37 35 1.4 7.4 0.237 0.1 30 10 1.3 3.0 0.147 0.3 37 20 1.4 5.0 0.150 0.55 41 35 1.6 7.4 0.168 0.1 30 4.5 1.3 2.3 0.115 0.4 39 14 1.5 3.8 0.124 45 25 1.7 5.7 0.122 50 35 1.8 7.4 0.122 10 0.1 30 2.5 1.3 1.7 0.091 (m) length (m) shotcrete (m) 49 11 0.4 39 1.5 2.4 0.087 12 45 10 1.7 3.0 0.090 13 52 20 2.0 5.0 0.090 14 57 35 2.7 7.4 0.088 15 0.5 40 2.5 1.5 1.7 0.052 16 45 1.7 2.1 0.049 17 3.5 53 10 2.0 3.0 0.052 18 57 16 2.2 4.2 0.050 19 10 60 25 2.3 5.7 0.055 20 17 63 35 2.3 7.4 0.066 21 45 2.5 1.7 1.7 0.047 22 54 1.6 2.1 0.000 23 10 60 10 2.3 3.0 0.040 24 30 67 20 2.4 6.5 0.049 25 40 69 25 2.5 5.7 0.040 26 10 60 2.0 2.4 0.000 27 40 69 19 2.5 4.8 0.000 28 40 69 9.5 2.5 2.9 0.000 In reality, tunnelling is a complicate three-dimensional (3D) issue depending on the advancing process of the tunnel face However, the tunnel considered in this study has the length which is much larger than the dimensions in cross-section of the tunnel For the sake of simplicity, it could therefore be use two-dimensional (2D) models instead of 3D models [10] The 2D model has dimensions of 160 m in both the height and width These dimensions of 2D model were selected through a parametric analysis to eliminate the effect of the boundary condition on the numerical calculation results 50 The surveyed tunnels in this numerical model is D shape with the measurement was respectively determined for each survey case (see Figure 3.2) in which the height of tunnel (H) equals the width (B) The ESR was set as (categories D) for Power stations, major road and railway tunnel, civil defense chambers, porta intersections according to suggestions of Barton et al (1974) [5] Point Point Point Figure 3.3 Layout of numerical model and monitored points (1), (2) and (3) was determined by the vertical displacement at point (1), (3) and horizontal displacement at point (2) The numerical model was discretized and meshed into finite elements The elements in model was formed as triangles with nodes Since the model size was enough large to eliminate the effect of model size on the stress and displacement in the rock mass surrounding the tunnel The external boundary of the model was restricted by x and y directions respectively (see Figure 3.3) The simulated initial tress in rock mass was taken into consideration the effect of gravity on the model The parameters of gravity include the vertical stress based on unit weight of rock mass above the model (γ), depth of tunnel (H) and lateral earth pressure (K0) In this study, it was assumed that the depth of tunnel is 100 m, rock's unit weight (γ) equals 0.026 MN/m3 and lateral earth pressure (K0) was set as 0.5 for whole cases 51 3.4 Evaluation of rock mass and rock support parameters The constitutive model using Hoek-Brown failure criterion has been adopted for the rock mass surrounding tunnel [11] The deformation modulus of intact rock Ei was evaluated as follows [12] Ei = MR σci (3.1) Where: MR - Modulus ratio, MR = 500; σci - Uniaxial compressive strength, σci = 50 MPa The deformation modulus of rock mass (Erm) was calculated on the basis of the following relationship: Erm = Ei (0.02 + − D ⁄2 + e((60+15D−GSI)⁄11) ) (3.2) Where: D - Disturbance factor, assumed D = 0; GSI - Geological Strength Index The reduced value of material constant (mb) was calculated based on the Hoek - Brown failure criterion [11] mb = mi exp ( GSI − 100 ) 28 − 14D (3.3) Where: mi - Material constant For each case in Figure 3.2 just has produced Q value Consequently, Q value and Rock Mass Rating (RMR) value of rock mass was transferred by the relationship [6] GSI = RMR 89 − (3.4) In addition, the relationship between Q value and RMR value was determined by a logarithmic function as following [2] 𝑅𝑀𝑅 = 15 log 𝑄 + 50 (3.5) Therefore, GSI value can be calculated as: 𝐺𝑆𝐼 = 15 log 𝑄 + 45 (3.6) Bolts and shotcrete were used as rock support for tunnels applied Q-system The parameters of rock support in Q-system include bolt spacing, bolt length, 52 thickness of shotcrete These parameters were determined according to cases study in Table 3.1 respectively Moreover, the other parameters of bolts and shotcrete used in models were illustrated in Table 3.2 Table 3.2 Rock support Parameters Properties Unit Value Bolt Diameter mm 20 Bolt Modulus (E) MPa 200000 Tensile Capacity MN 0.5 Residual Tensile Capacity MN 0.5 Pre-Tensioning Force MN 60 MPa 45000 - 0.25 Fully Bonded Bolts Shotcrete Young's Modulus Poisson's Ratio 3.5 Results After simulating 28 cases study, the radial displacement on the boundary at points as (1) top of crown; (2) top of wall and (3) middle of road by using RS2 software (Rocscience) was illustrated in Figure 3.4, Figure 3.5 and Figure 3.6 53 Figure 3.4 Vertical displacement at Point Figure 3.5 Vertical displacement at Point 54 Figure 3.6 Horizontal Displacement at Point The results about radial displacement at points (1), (2) and (3) in the efficient working area of Q-system presented that the radial displacement degree had a descending trend gradually when Q value is ascending and (Span or Height)/ESR ratio is decreasing simultaneously In other words, the supported tunnels by bolts and shotcrete following suggestions of Q-system is more stability when rock mass quality is increasing and span of tunnels is decreasing Figure 3.4 showed that the radial displacement (vertical displacement) at point when Q value is 0.1 and B/ESR is 25, equals 4.4 cm whereas if Q value is 0.3 and B/ESR is 20, the radial displacement drops to cm The results in Figure 3.5 pointed out the radial displacement at point has a greater value than other points many times When the Q value was 0.3 and (Span or Height)/ESR ratio was 20, the radial displacement at point (the middle of road) was 7.2 cm, whereas the radial displacement at point and were 3.0 cm and 1.4 cm respectively Figure 3.7 illustrated the effect of Q/De ratio on Radial Displacement induced at Point 1, Point and Point on the tunnel boundary Generally, there was a downward trend in the Radial Displacement at three different points when the 55 Q/De ratio increased following exponential function The dependency of Radial Displacement in 28 cases for each point on Q/De ratio was formed in exponential curves in Figure 3.7 Obviously, the dependency degree of Radial Displacement at Point had a substantial higher in comparison with Radial Displacement at other points Figure 3.7 Radial displacement at Point 1, Point and Point It could be demonstrated that the road of tunnel was not support by any structures so the rock mass could move into tunnel space freely without any restriction Whereas, at Point and 2, the rock mass also had the radial movement but the displacement magnitude is smaller than at Point owing to the support of the number of bolts and shotcrete layer on tunnel boundary 3.6 Discussion In this literature, the number of numerical investigates has been conducted to estimate the Radial Displacement on the Tunnel boundary within working efficient area of Rock Tunnelling Quality Index (Q-system) Some conclusions could be derived from the performance study as follows: - It is undeniable that Q-system exists an efficient working area that has more reliable due to the large number of practical measurements Beyond this area of Q- 56 system, it demands a lot of supplemental methods to estimate the proper rock supports in designing rock supports for tunnelling - The Radial Displacement at Point is always greater than the Radial Displacement at other points in mutual conditions In other words, the magnitude Radial Displacement at Point 2, Point and Point are in ascending order - The Radial Displacement at Point depends significantly on the Q/De ratio compared dependency degree of Radial Displacement at others points 57 CONCLUSIONS The thesis concentrated on researching the proper rock support for tunnel when applying Q-system by creating calculated sheets and estimating the radial displacement on the tunnel boundary that was framed in efficient working area of Q-system To utilize Q-system efficiently, the author built calculated sheets in Excel those allowed users to trace Q-system visually, promptly and flexibly to vary input parameters In addition, the parameters of proper rock support in this thesis were determined by digitalizing Q-system in paper to function approximations and converting the coordinate system between Q-system and Q*-system Thus, it allowed users to apply this system in practice conveniently The rock supports in Q*-system* were also considered in three different cases (only roof, roof and wall, roof and a half of wall) After that, the calculating results were collected and summarized automatically according to each segment and whole length of tunnels Using Q*-system in Excel will help contractor and owner get more convenience during estimation rock mass and support Moreover, Q*-system will also aid students tracking Q-system quickly during study and research Furthermore, the proper rock supports in efficient working area of Q-system were also relied on the tunnel stability through radial displacements on the tunnel boundary These analysis results pointed out that there was a significant difference in term of radial displacements among monitored points, but the Radial Displacement at Point is always greater than the Radial Displacement at other points in mutual conditions Thus, considering proper rock supports for tunnel applied Q-system, it is necessary to take tunnel stability into account to meet whole stability requirement during excavations The results about radial displacements of tunnels framed by proper rock supports in efficient working area, was estimated through functions governed by Q/De ratio The dependency degree of radial 58 displacements at three different points on Q/De had a great difference, but the radial displacement at Point was governed more than other points It notices that the work performance in the thesis was restricted by D shape cross section, the proper rock support was only determined on the whole tunnel stability In practice, tunnels could be excavated with various cross sections to meet use requirements; considering proper supports was also relied on time and cost during excavations In addition, excavated tunnels in rock mass was impacted by the myriad elements as the adjacent tunnels that was existed before, reducing rock mass quality during excavations as well the various geology conditions Those are the orientation research of the thesis in the future 59 REFERENCES Arild Palmstrom, Einar Broch (2006) Use and misuse of Rock mass classification systems with particular reference to the Q-system Tunnels and Underground Space Technology, 575-593 Barton, N (2002) Some newQ-value correlations to assist insite characterisation and tunnel design International Journal of Rock Mechanics & Mining Sciences , 185–216 Barton, N (2007) Rock mass classification Retrieved from Rocscience: https://www.rocscience.com/ Barton, N L (1974) Engineering classification of rock masses for the Design of Tunnel support Rock Mech, 189-239 Barton, N., R Lien and J Lunde (1974) Engineering classifcation of rock masses for Rock Mechanics and Rock Engineering Bieniawski, Z (1989) Engineering Rock Mass Classifications: A Complete Manual for Engineers and Geologists in Mining, Civil and Petroleum Engineering New York: A Wiley-Interscience publication Bieniawski, Z T (1974) Estimating the strength of rock materials Journal of South African Instutute of Mining and Metallurgy David Chapman, N M (2010) Introduction to Tunnel Construction Canada: Taylor & Francis Deere, D (1989) Rock quality designation (RQD) after 20 years Vicksburg: U.S Army Corps Engrs Contract Report GL-89-1 10 Do Ngoc Anh, D D.-M (2014) 2D Tunnel Numerical Investigation - The Influence of the Simplified Excavation Method on Tunnel Behaviour Geotechnical and Geological Engineering, 43-58 11 E Hoek, C C.-T (2002) Hoek-Brown Failure Criterion - 2002 Edition Proc NARMS-TAC Conference, (pp 267-273) Toronto 12 E Hoek, M D (2006) Empirical estimation of rock mass modulus International Journal of Rock Mechanics & Mining Sciences, 203–215 60 13 Grimstad, E K (2002) Rock mass quality Q used in designing reinforced ribs of sprayed concrete and energy absorption International Symposium on Sprayed Concrete, (p 8) Davos 14 Grimstad, E., Barton, N (1993) Updating of the Q-system for NMT International Symposium on Sprayed Concrete, (p 22) Fagernes 15 N Barton, F R (1981) Application Of Q-System In Design Decisions Concerning Dimensions And Appropriate Support For Underground Installations Norwegian Geotechnical Institute 16 Norwegian Tunnelling Society (2010) Rock support in Norwegian Tunnelling Publication No 19 17 Norwegian Tunnelling Society (2011) Rock mass Grouting in Norwegian Tunnelling Oslo, Norway 18 Norwegian Tunnelling Society (2015) Health, Safety and Environment in Norwegian Tunnelling Oslo, Norway 19 NGI (2015) Using the Q-system Oslo, Norway: Norwegian Geotechnical Institute 20 Palmstrom A., B O (2002) The Q-system - possibilities and limitations (in Norwegian) Norwegian National Conference on Tunnelling (pp 41.1 – 41.43) Norwegian: Norwegian Tunnelling Association 21 Palmstrom, A (2005) Measurements of and Correlations between Block Size and Rock Quality Designation (RQD) Tunnel and Underground Space Technology, 362-377 22 Palmström, A (2009, February) Combining the RMR, Q and RMi Classification Systems www.rockmass.net Oslo Norway ...MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF MINING AND GEOLOGY VAN DIEP DINH RESEARCH ON USING ROCK TUNNELLING QUALITY INDEX (Q- SYSTEM) TO ESTIMATE THE PROPER SUPPORT IN TUNNEL. .. name: Van Diep Dinh Master thesis title: ? ?Research on using Rock Tunnelling Quality Index (Q- system) to estimate the proper support in tunnel? ?? Major: Underground Construction Engineering No: 8580204... and conveniently during supporting Objectives Determining types and parameters of proper rock support depended on using Rock Tunnelling Quality Index, Q-system for tunnels in rock masses Research