Nghiên Cứu Ảnh Hưởng Của Các Tải Trọng Tĩnh Và Động Tới Sức Chịu Tải Của Cọc Khu Vực Thành Phố Hồ Chí Minh

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIET NAM ACADEMY FOR WATER RESOURCES THE SOUTHERN INSTITUTE OF WATER RESOURCES RESEARCH NGUYEN MANH TUONG STUDY ON THE EFFECTS OF STATIC AND DYNAMIC LOADS ON BEARING CAPACITY OF THE PILE IN HO CHI MINH CITY SUMMARY OF THE DOCTORAL THESIS Major: Geotechnical Engineering Code: 58 02 11 HO CHI MINH CITY - 2022 The Thesis has been finished at THE SOUTHERN INSTITUTE OF WATER RESOURCES RESEARCH Scientific Advisers: Assoc Prof Dr CHAU NGOC AN Reviewer 1: Assoc Prof Dr TRAN TUAN ANH Reviewer 2: Assoc Prof Dr HOANG VIET HUNG Reviewer 3: Assoc Prof Dr VO NGOC HA The Doctoral Thesis was defended at the Assessment Committee at The Southern Institute of Water Resources Research, No 658 Vo Van Kiet Boulevard, Ward 1, District 5, HCMC At 8:30 a.m on Date 30 Month December Year 2022 The Thesis can be found at: - National Library of Vietnam - Library of The Southern Institute of Water Resources Research - Library of Vietnam Institute of Water Resources Research INTRODUCTION Reasons for choosing the topic HCMC(HCMC) area is located in a dynamic economic development area, focusing on many industrial civil construction site In HCMC, many places below the soft soil are fine sand layers of medium-tight state Building that use pile foundations, the pile tip is often resistant in this soil layer According to calculations this layer of sand bearing is quite good under the effect of static loads However, when subjected to dynamic load, the load capacity of this soil layer is significantly reduced, causing disadvantage to the pile system In industrial parks, export processing zones have factories that place machine foundations subject to dynamic loads of different frequencies, amplitudes and intensities The above loads from the building transmitted to the pile, or from the surrounding ground affect the pile causing the pile itself, the extreme deformation area around the pile different effects Therefore, the study of calculating the dynamic load bearing capacity of the pile to support the building as well as finding the reduction of load bearing capacity after the building is subjected to dynamic load is necessary Currently, the calculation of the effect of the dynamic load on the load capacity of piles has many methods Usually to add to the effect of the dynamic load on pile load bearing, one adds the coefficient to the result of static load bearing of piles The static compression experiment has the effect of dynamic load, initially clarifying the effect of dynamic parameters on pile load bearing The results of the experiment identified the correlations between pile deformation and frequency of dynamic load as well as force-resistance relationships These are the figures that serve as the basis for the design calculation, assessing the effect of the dynamic load on pile load capacity in the conditions of HCMC ground The purpose of the thesis Field static compression experiments and numerical simulations find the right model and select reasonable parameters for pile load bearing calculations Back analysis finds the model parameters of the ground to simulate the load bearing of the pile and the behavior of the pile - soil in the area has extreme plastic deformation around the pile Researching, building small-scale physical models, conducting experiments to load dynamics onto piles to determine the effect of dynamic loads on load bearing and deformation of piles Analyze the dynamic behavior of piles when subjected to the impact of dynamic loads with different frequencies Study the effects of the L/D ratio, the pile-soil effect, and consider the immediate load capacity when subjected to dynamic loads Establish the correlations of Force - Deformation, Force - tip Resistance, Force - Ratio of Side Resistance /Tip Resistance according to the frequencies and ratio of L/D in the pile bearing the dynamic load on the sand ground of HCMC Object and scope of the research The research object of the thesis is compression pile that is affected by the dynamic load The research pile is a hanging pile consisting of tip capacity and side bearing Scope of study: The study focused on the effect of dynamic load on piles in fine sandy soils in the tight state of fine sand in HCMC area This is a common soil layer and is rated as quite good bearing when subjected to static loads so it is necessary to consider the effects of dynamic loads on the resistance of piles in this soil layer on the load capacity The study focused on the type of single pile that carries load along the vertical axis The effect of the pile - the pile cap connect was omitted not surveyed in the study The ground to be studied is the fine sandy soil of a medium state The impact load on the pile is the circulatory load The frequency in the influence study is the frequency of stimulation that causes a mechanical response, not to the response frequency of the pilepile cap system The study dynamic load frequency ranges from to 10Hz Research content The study computational methods that affect static and dynamic load loads of piles according to laboratory, field, numerical simulation and other studies around the world Study the application of numerical methods in the analysis of pile load bearing calculation Select the model in accordance with the results of the field static compression experiment to simulate finding destructive load bearing Researching the fabrication of the ratio physics model, establishing the process of experimenting to increase the dynamic load for piles on the miniature experimental model determines the effect of the dynamic load on the load capacity of the pile The experiment determined the effect of dynamic load frequency on pile load bearing Surveying the mechanism of vertical force distribution in the pile body, the next stress change is mobilized between the pile wall and the soil by frequency Analyze the effect of dynamic load frequency on pile behavior, simulate numbers, establish stress correlations, deformation, frequency on pile types with L/D, smooth surfaces and different rough surfaces Research methods Statistical methods: Collect, analyze, and synthesize research results Statistical processing, analyzing experimental results, establishing correlations with modern data processing software Experimental methods: Experimental research to conduct experiments on physical models to serve as a basis for comparative analysis and comparison of results Numerical simulation method: Research on simulating static compression test using Plaxis software for comparative analysis Using data processing software to find results between numerical simulations and field experiments find out correlations in the ground model The new contributions of the thesis 1) Establish the dynamic loading experiment process for piles on the miniature experimental model, in order to study the effect of dynamic load frequency on the load bearing of single piles working in the sandy ground in HCMC 2) From the results of experiments on the miniature and numerical simulation model of single piles, establishing correlations in deformation – frequency of circulating dynamic load acting on piles with smooth surfaces and rough surfaces in the sandy ground in HCMC Scientific and practical significance The initial topic contributes to clarifying the effects of static and dynamic dynamic loads through static compression experiment simulations as well as small-scale physical model experiments Thereby proposing equations of correlation between frequency and deformation, force and strain, strength and resistance relationships The results of the study provide data to serve as the basis for the analysis of dynamic load impact in pile load bearing design taking into account the dynamic load effect that can appear in the current construction conditions of HCMC to help forecast pile load strength more accurately CHAPTER OVERVIEW OF THE EFFECT OF DYNAMIC LOADS ON PILE LOAD CAPACITY 1.1 Study the basic characteristics of the land in HCMC 1.2 Study the effect of dynamic loads on the ground 1.3 Characteristic shear strength under the influence of impulse loads 1.4 Intensity, deformation under the influence of instantaneous load Casagrande and Shannon experimented with impulse loads: tL= 0.2s Figure 1.10: Stress Deformation of soil in test with impulse load 1.5 Study of foundation oscillations with characteristics of movements from the foundation impacting to the ground 1.6 Research related to the research direction of the topic According to Han (2018) studied the model of driven pile field experiments to find load bearing and residual load in piles According to Naggar (2019), the study established a model of stress wave energy transmission in background Simulation results for piles are compared to control software for frequency effects with different physical influences 1.7 Study the calculation of load bearing by finite element method According to Wu (2020), Tolun (2020), Rajpoot (2020), Lin (2020) simulates a number of different models for piles to study the dynamic reaction of the back ground pile Ahmed (2015), Azizkandi (2018), Chaudhuri (2020), Zhang (2020), Lou(2020), Yan(2016), Liu(2020), Zhu (2020) studied dynamic load effects and found fairly reasonable results for the direction of digital simulation research 1.8 Study the test model of small scale of piles subject to dynamic loads Garala (2020) studied aluminum pile with centrifugal test Rui He (2019) studied the dynamic single pile model with frequencies Huang (2020), Mishra(2019), Li(2020), Subramanya(2019), Varghese(2020), Zhanf ang (2020), Yi (2017), Zhou (2019), researching the design of dynamic loadbearing models 1.9 Conclusion 1) The effect of the dynamic load besides the static load on the pile foundation in the area is something to be concerned when designing the construction of the foundation The formulas for determining foundation deformation not take into account all the parameters affecting roughness, L / D ratio, ground mechanical properties As the deformation rate increases: 𝑐𝑢(𝑑𝑦𝑛𝑎𝑚𝑖𝑐) /𝑐𝑢(𝑠𝑡𝑎𝑡𝑖𝑐) =1.5, reduce the angle of internal friction of the soil, ’ (dynamic) =’ (static) - 20 2) Braja M Das (2011) has added parameters: Frequency of dynamic load, Q circulating force, elastic hardness k of the foundation system Ahmed (2015) has not calculated the effect of damping versus the pile length in the soil When calculating the load capacity of piles from the load bearing of single piles taking into account the effect of dynamic loads, the provisions in Vietnam's construction standards not provide enough information necessary to apply 3) The effect of dynamic loads in works of different frequencies, amplitudes, intensities causes different responses to the pile - background system The load from the building transmitted to the pile, the surrounding ground affects the pile caused to the pile itself, the extreme deformation area around the pile in the specific area ground also needs further consideration The study by simulating the number of static compression experiments and the dynamic load-bearing pile model experiment can meet part of the requirements set out CHAPTER STUDY THE APPLICATION OF DIGITAL METHODS IN THE ANALYSIS OF PILE LOAD BEARING CALCULATION 2.1 Question Combining the semi-experimental formula of the foundation construction company, field experiments, numerical simulation is the research direction of scientific and practical value in calculating pile load bearing using Plaxis software with background models 2.2 Overview of load capacity by static compression test 2.3 Study on static compression test of pile on works in HCMC area 2.4 Calculate the load capacity based on the static compression test results S = ξ.Sgh S = ξ.Sgh = 0,2x80=16mm 2.5 Study on simulation of static test to determine the load capacity Figure 9: MCC model P-S chart with LoadTest 2.6 Analysis of results by model and static compression experiments The results of correlation of parameters in the MCC model: M-Kappa: M = 0.4073κ-0.219; Lambda-Kappa: κ = 729.62λ2 - 13.653λ + 0.0652 2.7 Study on simulation of destructive compression of 250% PTK 2.8 Conclusion 1) The right MCC model was developed for foundation computing software The analysis of the MCC model while using Plaxis software in combination with comparing the results of static compression experiments is the basis for accurate assessment of deformation stress in the ground floor 2) According to the experimental results, λ / κ = 13.12 / 5.41 = 2.4 (CK1) and λ / κ = 22.2 / 6.49 = 3.4 (CK2), λ/ κ ~3 correlation 3) M – Kappa correlation: M = 0.4073κ-0.219 4) Lambda - Kappa correlation: κ = 729.62λ2 - 13.653λ + 0.0652 CHAPTER STUDY THE APPLICATION OF THE PHYSICS MODEL TO DETERMINE THE EFFECT OF DYNAMIC LOADS TO THE LOAD CAPACITY OF THE PILE 3.1 Ask questions The research model looks at the effects of the load on Stress – Deformation throughout the length of the pile body and the pile tip, simulating custom changes to many factors affecting static and dynamic loads on pile 3.2 Dimension analysis According to studies and evidence, the frequency f has a decisive effect on the displacement of the pile: f = g(L; D; γ; φ; c; d) Transform Pi equation 𝐿 g {𝐷 ; 𝑑 ; 𝐷 φ; 𝑐.𝑓 𝛾 1/2 }=0 The research parameters range from independent quantities after the transformation of Pi to dependent quantities The dependence and relevance between quantities shows the degree and importance of quantities with the parameters of the dynamics due to the external dynamic load acting on affecting the deformation and displacement of the pile 3.3 Requirements on simulation model 3.4 Advantages and disadvantages of small-scale physical models 3.5 Steps to implement the material selection model and model ratio 3.6 Analysis of the limit load capacity of piles 3.7 Stress transmission mechanism 3.8 Equations for determining load bearing of piles 3.9 Study the distribution of forces along the results of field test 11 CHAPTER THE EXPERIMENT DETERMINED THE EFFECT OF THE DYNAMIC LOAD ON PILE LOAD CAPACITY 4.1 Results of static compression on piles with different L/D 4.2 Experiments to study the effects of loading dynamics on piles Dynamic parameters are loaded on speed control software Figure 9: Correlation of control frequency and measuring head 4.3 The results of dynamic test on the pile and the behavior of piles Figure 19: Chart of Deformation - Frequency - Resistance L50 Figure 26: L50 pile FFT frequency analysis results 12 4.4 Some experimental images 4.5 Conclusion 1) Deformation correlation - The ratio of unit friction force and tip resistance is uniform throughout the experiment The Fs0/Q_p ratio shows that the distribution of resistance on the side of the body near the pile head is very large With L/D>25, the appearance of bending torque causes local infestation and overall sabotage at the site of great internal force According to many studies, when long piles lead to oblique, bending, breaking, affecting deformation, load capacity 2) Piles with different L/D and roughness: The relationship of pile deformation corresponds to different frequencies, indicating that with the specific frequency the L/D ratio most pronounces the load bearing Frequencies ranging from 22Hz to 28Hz, distortions with a high absolute value describe behavior when subjected to oscillating frequencies 3) Rough L50 pile, S -  chart at the top of the large pile, compression deformation increases sharply Smooth L50 pile, Deformation - Tip resistance decreases and changes marks at 28Hz frequency Analysis of the peak acceleration smooth pile frequency spectrum increases very rapidly compared to rough piles CHAPTER ANALYSIS OF EXPERIMENTAL RESULTS OF RESEARCH MODEL APPLIED TO REALITY 5.1 The relationship of deformation of pile resistance to frequency 13 Figure 1: Frequency - Deformation - Tip resistance Q_p 5.2 Compare the results of experiments with different L/D piles 5.3 Comparison of test results of piles with different roughness 5.4 Study F- D of pile when subjected to destructive frequency 5.5 Analyze the mechanism of response of the ground floor when subjected to dynamic loads 5.6 Calculations applying research results to piles in practice Table 1: Correlation equation at actual destructive frequency FS1 F = -0.125P2 + 57.062P - 9.3687 Q_p F = 2.937P2 – 1221.18P + 200.56 Force - Lateral resistance ratio / Tip resistance Pile head section FS0/q_p = -0.125P2 + 63.56P - 11.608 Pile tip section FS1/q_p = 0.25P2 – 91.875P + 15.264 5.7 Application research FEM of small model experiments 5.8 Analysis of results 14 Figure 2: Frequency chart - Resistance on L/D piles Deformation – frequency of L40 pile starts from a frequency of 2025Hz piles with high deformation rate At 28Hz the whole system begins to have strong horizontal oscillations and the tendency to sabotage the pile head With L50 piles the tendency to respond to the frequency of slower piles from the frequency range of 22Hz L60 piles have the same effect as L50 piles 5.9 Compare the results of modeling experiments and numerical simulations: The Qp resistance of the piles responds to quite the same frequency from 0-10Hz According to analyses of the effect of the dynamic load on 15 the particle arrangement leads to an increase in tightness From the frequency of 10Hz onwards the tip resistance increases rapidly the greatest increase in tip load capacity When the background reaches the peak state, the angle of expansion ψ reach its maximum, the ground transitions to a sliding state Qp rapidly declines at the time of f = 22Hz However, the L60 pile has a slower mobilization Qp because the friction resistance is mainly concentrated in the Qs section The results are relatively consistent with the miniature model experiment L60 piles continue to increase Qp after a frequency of 22Hz, so the total Q resistance of the pile increases compared to piles L40, L50 Figure 25: Frequency comparison - Pile deformation From FEM results and experiments, the advantages of the FEM in geotechnical problems in general and the problem of simulating the loadbearing pile foundation in particular With numerical simulation experiments, the advantages of time conducted, speed of program processing, results are more reasonable The model test before simulating the number has the advantage of identifying the convergence of the program Simulation of the following number will reduce the stages of running the program with the defined frequency bands thereby significantly reducing the time of effort and reliable results As such, the frequency range has a dynamic response of piles 16 from 15-30Hz Tip resistance varies quite chaotically when the frequency of sabotage is reached and tends to decrease sharply The analysis of the dynamic response mechanism of the background - pile in the experiment and FEM can be satisfactorily explained on the basis of the stress roadmap The dynamic response of the pile body and the tip of the pile when subjected to stress waves transmitted down along the pile body and the mechanism of transmission from the pile to the extreme plastic deformation land around the pile can be explained by the PDA quite clearly 5.10 Study the application of results simulating the number of calculations of actual works Figure 5.30: Input dynamic parameters - dynamic module running process 5.11 Analysis of actual pile number model results The Chart of Frequency shows that at the time the frequency of about 5-6Hz begins to have strong nonlinear displacement, the load capacity is suddenly reduced With the L/D = 30 pile subsiding rapidly at the frequency of 6Hz, however the L/D = 20 pile and the L/D pile = 25 respond similarly and are jointly damaged at about 5Hz 17 Figure 3: Frequency chart - Deformation, Qs, Q_p on L/D piles Tip resistance Q_p have a fairly similar frequency response to piles With the L/D = 20 pile, the Q_p mobilized first and quickly declined at the time of f = 4Hz The results were relatively consistent with the miniature model experiment With the L/D = 20 pile, the tip resistance Q_p increase rapidly and at the frequency of 4- 6Hz fluctuates very strongly, causing the pile to be pulled continuously so the tip resistance increases suddenly This is the mechanism of damage to the pile head when the compression force coincides with the stress wave causing the compression to double at the pile head according to the PDA principle However, at the tip of the pile when there is a sharp vibration oscillation deformation will return to 0, the tip load capacity will be lost Table 2: Correlation Equation Frequency – deformation No Pile Type L/D Correlation equations L=8m 20 S = -56.735f2 + 183.85f - 67.524 18 L = 10m 25 S = -37.32f2 + 121.66f - 43.036 L = 12m 30 S = -50.819f2 + 222.03f - 110.32 Where: S is deformation (mm); f is the frequency (Hz) The total Q resistance of the L/D pile = 30, L = 12m grows rapidly, the mobilization resistance value is quite large compared to piles L /D = 20 and 25 With piles L/D =20 and 25, the total resistance is quite similar, Q increases slowly and tends to increase rapidly the rate of strength increase at the time of overlapping with the L/D pile = 30 when f = 6Hz Qs side resistance piles increase steadily in which the L/D = 30 pile has a strong increase rate at the frequency f = - 2Hz, the pile works in the elastic domain At the frequency f = - 5Hz, Qs decline with the frequency increases causing the pile to sink sharply From the frequency of - Hz when the strong deformation pile friction increases, Qs recover and reach its peak mainly due to the downward pile and the side friction is mobilized most strongly, the pile is damaged the tip load load load strength Analysis of the accelerometer recorded at the top of the pile with each different type of pile obtained remarkable results Figure 4: Chart of deformation by frequency spectrum at the top of the pile (L/D = 20, 25, 30) With long pile L/D = 30, at frequency f = - 4Hz, small vertical displacement, working pile in elastic domain At the frequency f = 6Hz, 19 the displacement is strong, the pile is subsided suddenly, the load capacity is sharply reduced At a frequency of f = 8Hz, the pile fluctuates sharply in the same way as the dynamic response of the pile in the miniature model At the frequency of 12 Hz, the sudden increase in deformation of the pile is completely damaged load capacity, Q_p returned to L/D pile = 25, at frequency f = - 4Hz, small vertical displacement, working pile in elastic domain At the frequency f = 6Hz, the displacement is strong, the pile is subsided suddenly, the load capacity is sharply reduced At 8Hz the pile frequency is damaged side friction and loss of tip load capacity With the L/D = 20 pile, the result is quite similar to the L/D = 25 pile At the frequency f = 6Hz, the start of strong displacement begins, the pile subsides suddenly, the load capacity is sharply reduced The frequency f = 8Hz pile is damaged side friction and loss of tip load capacity The results of the survey of the frequency of piles showed that the response of the pile to a reasonable frequency in accordance with reality and model experiments L/D piles =20 and 25 have similar responses and results of lateral resistance, tip resistance in accordance with the frequency spectrum measured above 5.12 Conclusions From small-scale modeling experiments to model theory studies and proportional law according to the above-mentioned analyses show: 1) The model pile shows the relationship of pile deformation corresponding to different frequencies; Deformation value - deformation; Deformation relationship - unit tip resistance - unit side friction; Deformation - The ratio of unit friction force and tip resistance according to the depth of piles shows that with the specific frequency, the L / D ratio will most pronounce the load resistance 20 2) The L40 pile, which starts the frequency of 26Hz, is worth the number of tip resistance Q_p is sharply impaired At a frequency of 28Hz responds to the pile head with a frequency that causes the tip resistance to increase suddenly The compression force coincides with the stress wave causing a strong increase in resistance according to the mechanism of damage to the pile head The L50 pile has a fairly stable Q_p and loses load capacity at deformation S = 5mm 3) Starting frequency 15Hz to 20Hz, deformation of straingages of pile body and pile head has small fluctuations, deformation at near the pile station with large value variation From a frequency of 22Hz to 28Hz, distortions have a high absolute value that describes behavior when subjected to fluctuating frequencies Shifting through the balance position of the pile increases rapidly leading to sabotage of side friction 4) Throughout the pile length, the analysis found forces-unit friction- tip resistance as well as force relationships - the ratio of FS1/tip resistance to the correlation equations established in chapter of the thesis 5) The pile has an L/D of 20 or more, with the D400mm prototype pile, a ratio of 1/25, a frequency of a ratio (1/25)-1/2 (ratio = 5) With a frequency range from 22Hz to 28Hz, an average of 25Hz, the pile with L/D > 20 internal forces reached dangerous value, the deformation increased rapidly, the load capacity of the pile ground load decreased sharply As such, it can be speculated in fact that frequencies above 5Hz can cause L/D piles = 20 to degrade strong load bearings, the pileheads and reinforced concrete pile joints near the pile head may be damaged due to the dynamic response of the pile to the destructive frequency 6) With the numerical simulation pile, at the actual frequency of 5Hz pile begins to reduce load capacity, the pile has L/D = 20 strong load resistance depletion and has a stronger deformation result than the L/D pile = 25 and L/D 21 = 30 At the time the pile reaches the destructive frequency, the side load capacity decreases steadily However, the tip load capacity Q_p suddenly declined sharply This is similar to the miniature model pile proving that the frequency plays a decisive role in the passive pile load capacity 7) The combination of numerical simulation and experiments shows the advantages of the FEM in Geotechnical problems in general and the problem of simulating dynamic pile foundations subject to load in particular With numerical simulation experiments, the advantages of time conducted, speed of program processing, results are more reasonable However, in order to be able to assess whether the numerical model reflects the actual dynamic response, the model experiment is necessary to observe the qualitative trend assessment and quantify the results The model test before simulating the number has the advantage of identifying the convergence of the program Simulation of the following number will reduce the stages of running the program with the defined frequency bands thereby significantly reducing the time of effort and reliable results 8) As such, the frequency range has a dynamic response of the pile from to 10Hz The tip resistance varies quite chaotically when the frequency of infestation is reached and tends to decrease sharply From the experiment showed that the fact that large L/D piles are prone to bending when subjected to dynamic loads, reducing tip resistance while the pile simulating the effect of vertical bending is quite small 9) The analysis of the dynamic response mechanism of the background - pile system in the experiment and the numerical simulation can be satisfactorily explained on the basis of the stress path of the soil around the pile The term around the pile can be explained in accordance with the PDA quite clearly 10) The input parameters of the D400mm pile actual number simulation have been analyzed backwards and are quite reasonable value to put into use the 22 numerical simulation the parameters are calculated according to model theory with the law of ratios that produce fairly reasonable results The results of the survey of the frequency of piles showed that the response of the pile with reasonable frequency in accordance with reality and the model experiment with a value of 5-10Hz 11) The effect of the layers of leveling soil and the clay layer above the sand layer placed the pile head is quite reasonable when meeting the pile head of the building is really reduced The frequency spectrum when comparing the two simulations and experiments showed that the effect of this value should meet the dynamics of the pile head when reaching the destructive frequency is quite clear through the pile resistance chart CONCLUSION - PETITION CONCLUSION The study of the effect of dynamic loads on vertical piles bearing vertical compression along the shaft in the sand environment in HCMC area identified the effect on load bearing and dynamic response of piles soil From the results obtained, the thesis has the following conclusions: 1) The dynamic loading experiment process for piles on the miniature experimental model is set up to study the effect of dynamic load frequency on the load bearing of single piles working in the sandy ground in HCMC The results of the experiment found parameters to take advantage of numerical simulation in the work calculation study 2) From the results of experiments on the miniature and numerical simulation model of single piles, establishing correlations in deformation – frequency of circulating dynamic load acting on piles with smooth surfaces and rough surfaces in the sandy ground in HCMC 3) Dynamic load experiments on miniature and numerical simulation models, the results obtained after comparative analyses: 23 a) The frequency of the circulating load determines the load capacity according to the ground of the pile b) The L/D slenderness of the pile greatly affects the dynamic load capacity of the pile 4) Simulation of the actual piles, the results obtained: a) With a circulating load frequency of about f > 5Hz, the pile with L/D > 20 internal forces reached dangerous value, the deformation increased rapidly, the load capacity of the pile ground load decreased sharply especially the head load capacity returned to b) Correlation between the deformation of the pile and the frequency of circulating dynamic load acting on the pile: - (L/D = 20) is S = -56,735f2 + 183.85f - 67,524 - (L/D = 25) is S = -37.32f2 + 121.66f - 43,036 - (L/D = 30) is S = -50.819f2 + 222.03f - 110.32 Scope of application: Circulating load-bearing piles have a frequency of 1-10Hz L/D slenderness of the L/D pile > 20 The roughness on the side of the pile from R = 2.5mm to R = 4.5mm The mechanical indicators of the area of sandy soil in HCMC PETITION 1) The results of the experimental study of piles with L/D changes showed that when designing piles with dynamic loads, attention should be paid to reducing the L/D ratio 2) The head of the pile needs to be strengthened when designing as well as when constructing need to pay attention when compressing to extreme load capacity 24 3) Studying the load bearing of pile types suggests that load bearing should be increased by extending the diameter or edge of piles rather than increasing the length, especially in piles bearing dynamic loads 4) The load capacity of the head when vandalizing returns to 0, so it is recommended to pay attention when calculating the load bearing capacity of the pile when bearing the dynamic load load NEXT RESEARCH DIRECTION The next direction of development of the thesis includes limited existences in the condition that the study has not been fully considered, so further research directions are needed 1) Researching experimental piles of full-scales at the site of different types of soils to make better contributions when applied in HCMC area 2) Study the effect of pile stations in the pile group and the group effect on the depletion of the load capacity of piles when subjected to dynamic loads Experiments in pile head conditions have the presence of piles considering whether the mounting condition reduces the load of the pile foundation or not 3) Study the effect of parameters such as horizontal load, tightness, saturation, initial hollow coefficient, Cc, Cs on the dynamic resistance of piles in the sand soil 4) The study builds an experimental model that includes the spatial and temporal factors after the dynamic load increase and the recovery of load bearing when the load stops working 5) Continue research for different types of soils in the area and multi-layered background for aggregate statistical results, in order to ensure more reliable accuracy of dynamic load effect on pile load strength 25 LIST OF PUBLISHED SCIENTIFIC WORKS Nguyen Manh Tuong (2013), "Analysis of the ground under the deep pile foundation according to the theory of elasticity - plasticity", Journal of Geotechnical Engineering Nguyen Manh Tuong (2019), "Analysis of dynamic response of piles under dynamic loads in HCMC area", Vietnam Journal of Construction Nguyen Manh Tuong (2019), "Analysis of the theoretical basis and calculation of pile load bearing through dynamic experiments on weak ground in the southern region", Vietnam Journal of Construction Chau Ngoc An, Nguyen Manh Tuong (2020), " Overview study of dynamic load and impact on different soils ", Collection of results for Science and Technology - Southern Institute of Water Resources Research Chau Ngoc An, Nguyen Manh Tuong (2020), " Physical geoengineering model model - study of physical model design to study the dynamic response of piles when subjecting to dynamic loads ", Collection of results for Science and Technology - Southern Institute of Water Resources Research