Site conditions have a serious impact on ground motion and earthquake damage. In this article, the authors briefly review the research history of the impact of site conditions on ground motion and earthquake damage, and summarize the research progress in this field. They focus on the impact of topography and landforms, rock and soil types, overburden thickness, soil layer structure, groundwater, rock and soil dynamic properties, and physical and geological phenomena on ground motion and earthquake damage, and achieve several consistent understandings in the current research on the impact of site conditions on earthquake damage and ground motion. On this basis, the authors put forward the issues that should be further studied in this field, including seismic field data survey, local terrain geometric scale, site classification, safety thickness limit of overburden, near-fault ground motion parameter distribution law, active fault avoidance distance, and the accumulation of strong earthquake data.

The wave function expansion method as well as the Graf addition theorem, combined with the continuous boundary conditions of displacements and stresses between the piles and the soil, are addressed to obtain the analytical full-space solutions of the cylindrical SH waves scattering by a single row of piles, and the time-domain solutions are gained by the inverse Fourier transform. In this method, the influence of the curvature of the incident waves is taken into account. In the frequency domain, the spectrum laws of the scattering wave fields due to piles under cylindrical SH waves incidence are analyzed. In the time domain, the contour maps of displacements near the piles due to the scattered cylindrical SH waves are given, and the influence of the number of piles and the distance between the piles on the scattering by the piles are discussed. The results show that:1) The isolation effects of the piles on the low-frequency band (η=0-1.0) of the cylindrical SH waves are significant when the vibration source is close to the pile (d/a=10), while those on each frequency band are significant when the vibration source is far from the piles; 2) When the pile spacing is fixed, the first-appearing maximum displacement behind the row of piles decreases with increasing the number of piles, as well as the range of influence of the scattering of the row of piles increases accordingly; 3) In order to improve the efficiency of isolation and save cost at the same time, the relative position of the vibration source to the piles and to the gap between the piles should also be considered; 4) When the row piles distribution width is fixed, the first-appearing maximum displacement behind the row of piles may be amplified with the reduction of pile spacing, due to the effect of incident wave curvature on the scattering of the row pile, so that a reasonable pile spacing should be used to block the cylindrical SH waves.

In order to improve the prediction ability of machine learning in ground settlement of deep foundation pit, in this study,the authors proposed a ground settlement prediction method based on multi-model combination under Stacking framework. Taking a deep foundation pit in Shenzhen as an example, the Spearman correlation coefficient was used to screen the influencing factors of foundation pit ground settlement,and the eight influencing factors were used to establish the prediction model of ground settlement of deep foundation pit, so as to verify the applicability of this method. The mean absolute error, mean absolute error percentage, and root mean square error of the Stacking prediction model are 0.34, 2.22%, and 0.13, respectively. Compared with conventional base models (random forest, support vector machines, and artificial neural networks),the mean absolute error, mean absolute error percentage and root mean square error values of the Stacking prediction model are minimum.

There are different opinions on the influence of tensile strength on the stability of homogeneous slopes, especially for slopes with different inclinations. Based on the composite tension-shear Mohr-Coulomb criterion provided by the finite difference program FLAC^3D, a series of numerical calculations were carried out for several typical homogeneous slopes by using the strength reduction method. The influence of soil tensile strength on the stability of slopes with different inclinations was studied. The results show that the steeper the slope is, the greater the influence of soil tensile strength on the safety factor of the slope. The value of soil tensile strength has great influence on the safety factor, deformation, and failure characteristics of vertical slopes. The influence on 45° inclined and gentler slopes is relatively small; while for the steep slope inclined over 60°, the variation range of the slope safety factor caused by different soil tensile strength can reach more than 10%. Therefore, special attention should be paid to the soil tensile strength in the stability analysis of steep slopes, so as to avoid the calculation results being too dangerous or too conservative because the selected value of soil tensile strength is too large or too small.

Instability of loess slopes induced by rainfall is severely destructive. In order to study the cracking characteristics of loess steep slopes under intensive rainfall, the field artificially simulated moderate rain and heave rain tests of loess steep slopes were carried out in Wuqi, northern Shaanxi Province. The water content and earth pressure of slopes were analyzed, along with their cracking characteristics and cracking patterns. The engineering effects of geotextile isolation grooves were summarized. The results showed that the rise of water content and earth pressure of the loess steep slope was little after 24 h moderate rain; While a thicker adjacent saturated zone was formed on the surface after 144 h heave rain, and the earth pressure increased significantly. The main failure sequence of the loess steep slope under the condition of 144 h heavy rain was top cracking, surface bulging, and local sliding in. The top crack of the slope is a precursor, and the failure mode of the slope is a shallow failure from the top to the surface of the slope.

The strength-reduction method (SRM) is widely applied in slope engineering projects, and FLAC^3D has become the main tool for 3D slope stability analysis. Although FLAC^3D has SRM intrinsic modular to complete this task, the computing process is complicated and time-consuming, hence the bisectional method is then involved to simplify the process by some researchers, which, however,is defactive in some aspects. An optimized bisectional method is supplied in this paper based on Python, including in-situ stress field reloading and selection of the upper limit of time-steps, which obviously improves computing efficiency. By using this optimized method, a fill slope in road engineering project was analyzed, showing that the strength reduced factor is consistent with those of the other methods and with much higher computing efficiency (ca. 50% and 300% higher than the other improved methods and the intrinsic modular, respectively).

Conventional physical and mechanical indicators can well reflect the engineering properties of soil. Through collecting relevant monographs, scientific papers, and seismic safety evaluation reports on soft soil, loess and red soil national widely, the statistics of the range, average value, and coefficient of variation of various physical and mechanical indicators of the three special soils were obtained. Based on the correlation analysis between the indicators, the engineering characteristics of the three special soils were studied. The comparison results show that the coefficient of variation of the physical properties of the three special soils is generally small and relatively stable, while the coefficient of variation of the mechanical properties varies greatly and discretely; There is a correlation between the physical and mechanical properties of the three special soils, either in a linear, or a belt-like change; The correlation coefficients of similar indicators of soft soil and red soil are higher than that of loess. The fitting formula of|r|∈[0.5, 1.0] is given by the regression fitting method used to test the precision and accuracy of the formula based on the linear relationship test. The results show that the F values of the fitting formula given in this paper are all greater than F_0.05,it can be seen that the regression effect is more obvious, which is convenient for engineering application.

At present, the commonly used methods to determine the dynamic shear modulus of soil include the standard method, the Kumar method and the autocorrelation function method. The methods to determine the corresponding damping ratio include the standard method, the Das and Luo method, the Kokusho method, the Kumar method, and the cross-correlation function method. So far, the understanding of the differences caused by the different methods is not deep enough, and there is a lack of quantitative comparative analysis. In this study, the Fujian standard sand (particle size 0.5-1.0 mm) was used as the research object, and the undrained stress-controlled dynamic triaxial test was used to discuss the differences of the different methods so as to determine the dynamic shear modulus and damping ratio of the sand, and then to recommend the method to use. The results show that:1) The dynamic shear modulus determined by the three methods has a certain difference. The difference gradually increases with the increase of the shear strain, but the difference decreases with the increase of the effective confining pressure. When the shear strain is 4×10^-3 and the effective confining pressure is 100 kPa, the difference between the three methods is the most significant, and the maximum relative error is close to 20%. 2) The damping ratios of the five methods have significant differences. The relative errors of the five methods for determining the damping ratio decrease rapidly with the increase of the shear strain; When the effective confining pressure is 100 kPa, the damping ratio only by the standard method has a smaller increasing trend. Among them, the damping ratio determined by the Kumar method is closest to the average damping ratio, the damping ratio by the cross-correlation function method is much higher than the average damping ratio, and the damping ratio determined by the Das and Luo method and the Kokusho method is basically the same but lower than the average damping ratio. So, it is recommended that in future engineering applications, when the loading method is stress control, the correlation function method can be used to determine the dynamic shear modulus and the Kumar method to determine the damping ratio.

To explore the mechanical properties of soil interfacial layers and their change law, the silt, silty clay, and gravel soil were taken as the experimental material, and the normal stress, soil type, interface treatment, load type, and effective time of dynamic load were taken as test variable factors. By using the orthogonal experimental design method, the indoor direct shear test of different undisturbed and remolded soil samples were carried out, and the shear force-displacement constitutive curves of soil interfacial layers were obtained. The bond coefficient of the interfacial layer was calculated according to the peak shear strength in these curves, which is related to the ability of resisting distruction. The experimental results show that the bond coefficient of silt is smaller than that of silty clay, and the strength of the soil interfacial layer is related to the combination type of the upper and lower soil layers;The greater the roughness of the interfacial layer and the more adequate the soil contact, the better the mechanical properties of the interfacial layer;With the increase of the acting time of the dynamic load, the strength of the soil interfacial layer decreases;The mechnanical properties of the interfacial layer are connected with the properties of the upper and lower soil layers.

In order to reveal and master the ground motion characteristics of marine soft soil site, to provide scientific and reliable design response spectrum as the basis for seismic design of marine engineering, better serve the engineering anti-seismic design, in this study, a centrifugal model of marine saturated soft soil site covered with water was designed and constructed. Five sets of shaking table tests were carried out under a 100g centrifugal environment, and the acceleration results at the seabed surface under different seismic input conditions were obtained; Three commonly used design spectrum fitting calibration methods were used to fit and regress the acceleration response spectrum, and the fitting parameters obtained by different methods were compared and analyzed. The results show that:There is a big difference between the design spectrum and the test response spectrum of the current building seismic code in my country, the characteristic period value of the calibrated design spectrum is obviously small, so there is a design risk for the seismic resistance of long-period projects; While the design spectrum and test response spectrum based on the U.S. seismic code have good consistency, the characteristic period of the calibrated design spectrum is relatively reasonable, but the design spectrum platform value is obviously too small, therefore the engineering is unsafe either. In contrast, the calibration results of design spectrum calibration proposed by Bo Jingshan research team are more reasonable, and the characteristic period of design spectrum is in good agreement with the test response spectrum.

The CFD-DEM coupling method has been widely used in the modelling of fluid-solid interactions in geotechnical engineering. The accuracy of the CFD-DEM modelling is strongly influenced by the precision of the drag force models used to deal with particle-fluid interactions. In this study, the sedimentation of a single particle in water was modeled by using the CFD-DEM method, three typical drag force models and various particle sizes were considered in the simulations, the terminal sedimentation velocities of particles were obtained in the simulations and then compared with those predicted by a popular empirical model, and the influence of the particle Reynolds number (Re_p) on the accuracy of the drag force models was analyzed. The results show that the accuracies of both the Ergun, Wen and Yu model and the Di Felice model decrease, while the accuracy of the Hill and Koch model firstly increases and then decreases with the increasing of Re_p. Generally, when Re_p ≤ 14 and Re_p>72, the relative magnitudes of the accuracy of the three drag force models are as follows:Ergun, Wen and Yu model>Di Felice model>Hill and Koch model; However, when 14<Re_p ≤ 40, Hill and Koch model has the highest accuracy, while the Di Felice model has the lowest accuracy; When 40<Re_p ≤ 72, the relative magnitudes of the accuracy of the three drag force models are Ergun, Wen and Yu model > Hill and Koch model > Di Felice model.

Normality assumption is one of the fundamental prerequisites of geotechnical risk assessment. Currently the Kolmogorov-Smirnov (KS) test is mainly applied to assess the normality of geotechnical parameters in geotechnical literatures;However, many studies demonstrated that the power of the KS test might be the lowest among the common formal normality tests for a small sample size. With the piezocone penetration test data collected from the floodplain silts of abandoned Yellow River, the performance of four formal normality tests was assessed, including Shapiro-Wilk (SW) test, KS test, Lilliefors (LF) test, and Anderson-Darling (AD) test. The ANOVA test was utilized to identify the samples of the same population. The normality tests were performed on different sample volume. When the sample size is sufficient,the results show that:Among the four formal normality tests, the KS test provides the least conservative assessment on rejecting normality assumption, the SW test is the strictest, while the strictness of LF test and AD test is between the two; For conventional geotechnical engineering design, the KS test result can meet the stability analysis requirements, while for complex geotechnical engineering design, the SW test is used to test the normality of the design parameters to reduce the design uncertainty.

Reinforced soil retaining wall with wrapped face is a kind of flexible panel retaining wall, which is widely used in many fields such as transportation, municipal, and water conservancy because of its good foundation adaptability and seismic safety. In this paper, the seismic performance of the reinforced soil retaining wall with wrapped face is investigated by using FLAC^3D numerical simulation program to study the slope of the wall, geotechnical bag filler, and reinforcement strength. The results show that when the slope of the wall is less than 1:0.30, the distribution of soil pressure behind the wall is uniform and small, approximately vertical straight line; When the slope of the wall is greater than or equal to 1:0.30, the distribution of soil pressure behind the wall is consistent and in accordance with Rankine earth pressure theory. Therefore, when the wall slope is less than 1:0.30, the structure should be designed according to the reinforced soil slope; When the wall slope is greater than or equal to 1:0.30, the reinforced soil structure should be designed according to the reinforced soil retaining wall. The type of geotechnical bag filler has almost no effect on the seismic dynamic response of the reinforced soil retaining wall with wrapped face, so its effect on the retaining wall can be disregarded in the seismic design. The higher the strength of reinforcement, the better the seismic performance of the reinforced soil retaining wall, however the strength of reinforcement is not proportional to the seismic performance of the retaining wall, so, to greatly increase the strength of reinforcement will not greatly improve the seismic performance of the retaining wall due to the phenomenon of "saturation of reinforcement effect" of reinforced soil structure; Therefore, it is necessary to pay attention to the economical efficiency of the project under the premise that the strength of reinforcement meets the standard.

The Xing'an-Baikal type permafrost, as the southern boundary of the high-latitude permafrost in Eurasia, is more sensitive to climate change and human activities. It is of positive significance to expatiate on the change of permafrost and predict the future development through the study of the interaction between permafrost and environment. In this study,the authors expounded the influence of zonal factors (latitude, altitude, longitude) and non-zonal factors (temperature, vegetation, precipitation, snow cover, etc.) on the distribution and development of permafrost, and analyzed the development trend of the Xing'an-Baikal type permafrost. The environmental factors such as air temperature, vegetation, precipitation, snow cover, have jointly changed the hydrothermal condition of the soil layer, leading to significant degradation of permafrost in a large area of the region. There are regional differences in the degree of degradation, which is the most significant near the southern boundary. Based on the particularity of the Xing'an-Baikal permafrost, the authors propose some suggestions for the study of Xing'an-Beikal type permafrost, such as the establishment of permafrost and cold region environmental monitoring mechanism in permafrost and cold regions, and the timely adaptive and remedial measures to protect and repair the regional environment.

In this paper, for a deep foundation pit of an underground station in Changchun, the instability crisis and its mechanism in the ventilation shaft section during the excavation of the foundation pit are studied in depth. Through the analysis of the horizontal displacement of the pile body, the horizontal displacement of the pile top, the support axial force of the bracing, and the settlement difference of the shoulders on both sides of the railway track, the major causes of the excessive deformation of the foundation pit in the ventilation shaft section are discussed. Then, the construction process of the foundation pit is simulated using ABAQUS finite element software, and the instability mechanism of the foundation pit in the ventilation shaft section is analyzed. The results demonstrate that the excessive deformation of the foundation pit in the ventilation shaft section is caused by the coupling of the excessive stress release of strata and the spatial effect of the foundation pit deformation. The spatial effect of the foundation pit deformation in the ventilation shaft section is remarkable due to the existence of positive corner in the ventilation shaft and the absence of diagonal bracing during construction, and the pit wall produces torsional deformation pointing to the inside of the ventilation shaft. The excessive excavation and unsuitable support installation lead to the excessive stress release in strata, which causes the excessive deformation of retaining piles and deteriorates the stability of the foundation pit.

In view of the increasing number of parallel and overlapping cases of underground tunnels and the unknown ground vibration law under the coupled load of subway and high-speed railway trains, the authors established a three-dimensional numerical analysis model of a large diameter shield tunnel under passing a double-line subway tunnel, and brought in a rigid train model and a track model based on the existing operating train parameters. The Hertz contact was used to simulate the contact between a moving train wheelset and a rail, the nonlinear contact between tunnel and surrounding rock was simulated by penalty contact and hard contact, and the infinite half space was simulated by using an infinite artificial boundary. By using the time domain explicit global analysis method, the operation of the running train in the tunnel was simulated and compared with the measured ground acceleration results, and the time-frequency characteristics of the vertical acceleration under the operation of single-line subway train and single-line high-speed train, as well as the distribution law of the surface acceleration under complex operating conditions were analyzed. The results show that the numerical model established in this study can better reflect the vibration response of the ground when the subway train is running.

In order to study the effect of ground motion characteristics on seismic performance of pile-supported wharf in liquefiable ground, a numerical model for seismic response analysis of pile-supported wharf with all-straight piles was established. The key dynamic response characteristics of pile-supported wharf under earthquakes were systematically analyzed, and the seismic performance demand indexes of pile-supported wharf were determined. The influence law of ground motion characteristics on seismic performance demand index was revealed. The results show that the weakness of bending, shear, and compression of pile foundation of pile-supported wharf occur at the junction of bearing layer and upper soil layer, bank elevation, and sand layer and upper soil layer, respectively. The peak acceleration, spectrum characteristics, and input direction of ground motion significantly affect the seismic demand of various performance indexes of pile-supported wharf. The flexural, shear, and compressive performance demand of pile-supported wharf are controlled by the bending moment at the top of the pile closest to the land side, the shear force of each weak link and the axial force at the junction of sand layer and upper soil layer, respectively. The seismic ductility demand is determined by the displacement demand at the top of the pile closest to the sea.

In order to study the influencing factors of the deformation of the water-stable base, a systematic experimental study was carried out on the cement content, variety, and gradation design. The dry shrinkage test and temperature shrinkage test were conducted through skeleton dense cement stabilized crushed stone, suspended dense cement stabilized crushed stone, and skeleton void cement stabilized crushed stone. Using the Origin to perform regression fitting on the test data, the deformation law of the semi-rigid base material was obtained, thereby improving the durability of the asphalt pavement. The results showed that:1) The dry shrinkage coefficient of the skeleton void structure increased by two times in 0-7 days, and the increase of the dry shrinkage coefficient was moderated. The dry shrinkage degree of the skeleton void structure was the lowest at the same cement content, that is, the skeleton void structure cement could effectively reduce the cracking of the water-stabilized base. 2) In cement stabilized gravel, the temperature shrinkage deformation of each temperature section increased gradually with the increase of the cement content, the temperature shrinkage deformation was the largest in the high temperature zone at 50-60℃, and the deformation became smaller as the temperature decreased; In the range of 0-10℃, the temperature shrinkage deformation of the section was the smallest, so the cement stabilized crushed stone is more suitable for the low temperature area in the north. 3) For the same cement content and cement grade, the average temperature shrinkage coefficient of the skeleton void is the smallest, the suspended dense type is the largest, and the skeleton dense type is in the middle. Therefore, the skeleton void structure cement can effectively reduce the cracking of the water-stable base. Through a large number of experimental studies, the skeletal void structure has the best temperature shrinkage resistance, cement 42.5 has better dry shrinkage resistance, and cement 32.5 has better temperature shrinkage resistance.

The dynamic stress-dynamic strain relationship is an important parameter reflecting the dynamic characteristics of subgrade filling soil, and the experimental study of its influencing factors can provide a reference for the engineering characteristics of subgrade filling soil. In this paper, the authors use the dynamic triaxial test method to study the influence factors of gravel-like soil, adopt the stress-controlled loading method to load, analyze five conditions such as test pressure, soil sample moisture content, soil sample compressibility, load frequency,and initial static deviatoric stresses of gravel-like soil, and also summarize the dynamic stress-strain relationship change law of gravel-like soil. The research results show that:1) When the pressure of the dynamic triaxial test is 30 kPa, the compaction of the soil sample is 96%, and the optimal moisture content is 7.5%. The dynamic stress-dynamic strain relationship curve is closer to the stress axis, and the dynamic strength of gravel-like soil is great; 2) When the load frequency changes between 1 and 2 Hz, the initial static deviator stress (less than 10 kPa) has little effect on the dynamic stress-strain relationship of gravel-like soil; 3) The fitting correlation coefficients of the dynamic stress-dynamic strain relationship curve to the hyperbolic model used are all greater than 0.96, indicating that the model can effectively fit the relationship curve; 4) Based on the test model, the greater the pressure in the test, the smaller the values of the parameters a and b; similarly, the greater the compression of the soil sample, the smaller the values of a and b.

Due to the remodeling of the soil around the pile after the settlement of the static pressure pile, the bearing capacity of the static pressure pile shows the characteristic of increasing with the growth of the resting period. From the perspective of the dissipation and consolidation of pore water in the soil around the pile after the pile sinking, in this paper, the authors summarize the theoretical and experimental studies on the time effect of the bearing capacity of the static pressure pile. For the existing shortcomings, it is recommended to fully consider the initial excess pore water pressure of the soil around the pile and its distribution characteristics, to conduct in-depth research on the time effect of the bearing capacity of the static pressure pile combined with the pore water dissipation path and consolidation model, and to explore through experiments the influence of different geology and pile types on the bearing capacity of static pressure piles during the rest period so as to further improve the empirical formula based on the measured data. This research helps to predict the safety of buildings, thereby optimizing the design of the static pressure pile, and bringing good economic benefits to the construction party and the designer. The stress field and displacement field solutions based on different constitutive relationship models and the solution of pore water pressure dissipation after pile sinking are summarized, the theoretical formula of ultimate bearing capacity of pile foundation through effective stress principle is established, and under the condition of cohesive soil and sand with considering the influence of over-consolidation ratio and undrained shear strength and plasticity index ratio on coefficient A, the empirical formula for ultimate bearing capacity of pile foundation is improved. It is recommended that multiple parameters should be set on the basis of the empirical formula to improve the accuracy of the empirical formula and the parameter solutions for different piles and soil types, and by using the BP neural network and importing the relevant parameters of the static pressure pile bearing capacity to obtain the optimal solution for the bearing capacity of different geological conditions, pile types, and resting periods.

The cavity expansion theory of semi-infinite soil is adopted to obtain the displacement field of soil caused by the new pile driving, and then it is applied to the existing pile based on the two-stage method to analyze the deformation and internal force changes of the existing pile. The constraint condition of the existing pile bottom, the rigidity of the pile body, and the soil modulus on the response of the existing pile was studied, meanwhile, the theoretical method was verified by using the numerical analysis, and also the influence of the distance between the new and used piles and the radius of the new piles was analyzed. The results show that the constraint of the pile tip only affects the deformation of the pile body near the pile tip:With the increase of the distance between the new and old piles, the deformation and internal force of the existing piles decrease significantly; The deformation and internal force of the existing pile increase gradually with the increase of the new pile diameter. The measures to stay away from existing piles and using long and thin piles are proposed to reduce the impact of new pile construction on existing piles.

Aiming to investigate the ground surface vibration during pile driving with resonance-free technology, a continuous vibratory pile driving model was established by using the finite difference program FLAC^3D. The density scaling method was introduced to eliminate the effect of time consuming due to the excessive elastic modulus of the model pile. The numerical results were compared to the field test data in literature, and then the influence of exciting force amplitude and vibrating frequency on ground surface vibration, was investigated. The results show that:The density scaling method can effectively increase the simulation efficiency, in which the calculation time for penetrating simulated 7.0 times pile diameter (4.9 m) is around 12.0 h, and there is an acceptable agreement between the numerical result and the field measurement; Additionally, the ground surface vibrations are influenced by the exciting force amplitude and the vibrating frequency mainly in the near field (horizontal distance less than 5.0 times pile diameter); Corresponding to the peak ground surface vibration, the critical penetration depth increases first with the horizontal distance and then tends to almost a steady value; Compared to the exciting force amplitude, the vibrating frequency can influence the critical penetration depth in the far field.

The rapid development of international trade speeds up the construction of port projects,and puts forward higher requirements for the seismic performance of port engineering. Pile-supported wharf, as one of the most common types of port engineering, has been widely used in port engineering construction. At present, there are few studies on the simplified method for seismic analysis of pile-supported wharf and the influence of pile foundation characteristics on its seismic response. In this study, a simplified analysis model of the pile-supported wharf was provided, and the influence of the characteristic parameters of the pile foundation on the seismic response was analyzed by using open-source OpenSees computational platform. The computed results show that:1) The elastic modulus of reinforcement has a little influence on the seismic response of the pile foundation; 2) The reinforcement stage of the steel bar plays an important role in the bending moment bearing capacity after the section reaches the yield curvature; 3) The increase of concrete compressive strength can reduce the peak displacement of the wharf; 4) Larger or smaller concrete compressive strength and steel bar yield strength are not conducive to the dissipation of seismic energy of the wharf structures.

In order to reveal the changes of the earth pressure at the pile-soil interface during the penetration of the jacked pile in the cohesive soils, based on a pile project in Dongying, Shandong Province, a full-scale field test was carried out. The variation law of the earth pressure on the side of the pile with the penetration depth during the process of jacked pile sinking was obtained. The distribution characteristics of the earth pressure on the side of piles in different soil layers were analyzed. It is clear that the earth pressure on the pile sides has obvious degradation effect in the process of pile sinking. The relationship between the soil pressure at the pile sides and the overburden soil weight at the pile-soil interface was discussed. The results show that the earth pressure at the pile-soil interface is closely related to the soil properties. As the penetration depth of the sensor increases, the soil pressure on the side of the pile increases gradually, and the increase rate varies with different soil layers. At the same depth, the earth pressure at the pile-soil interface degrades obviously, and the degradation rate in silt soil is less than that in silty clay. In the same soil layer, the ratio of the earth pressure on the pile-soil interface to the soil weight on the pile-soil interface is constant, and the ratio in silt soil is obviously greater than that in silty clay.

In freezing-thawing cycles, soil moisture changes dramatically, which leads to the change of bearing capacity of expansive soil. In this study, the unconsolidated and undrained triaxial shear tests were carried out on unsaturated expansive soil with different initial water content,and the strength variation mechanism of expansive soil in freezing-thawing cycles was analyzed on the basis of experiments. The influence of initial water content on the deviatoric stress-strain relationship and shear characteristics of expansive soil under freeze-thaw cycle was discussed. The results showed that:1) The form of deviatoric stress-strain curve of the unsaturated expansive soil changed gradually from strain softening to strain hardening with the increase of water content, while the peak deviatoric stress decreased with the increase of water content; 2) The shear strength of the unsaturated expansive soil decreased linearly with the increase of initial water content; 3) After the first freezing-thawing cycle, the deviator stress and shear strength of the unsaturated expansive soil decreased significantly, and reached stability after 3 to 7 freezing-thawing cycles. This study provides a powerful basis for the engineering design of expansive soil in a seasonal frozen zone.

In order to study the distribution of pore water pressure at the pile-soil interface in the process of static pressure pile sinking in a layered clay, based on a pile foundation project in Dongying, Shandong Province, a full scale static pressure pile test was carried out. The variation law of pore water pressure at the pile-soil interface was analyzed, the distribution characteristics of excess pore water pressure at the pile-soil interface were discussed, and the dissipation characteristics of pore water pressure and excess pore water pressure at the pile-soil interface were clarified. Combined with the theory of hydraulic fracturing and the theory of hole expansion, the distribution pattern of excess pore water pressure at the pile-soil interface along the direction of pile length during the process of pile sinking was revealed. The experimental results show that pore water pressure and excess pore water pressure are closely related to soil layer properties. Both of them increase slowly in the silt soil layer and faster in the silty clay layer. At the same depth, both of them are obviously dissipated, and the degree of dissipation in silty soil is obviously greater than that in silty clay. The variation law of excess pore water pressure along the direction of pile length calculated by hydraulic fracturing theory combined with hole expansion theory is consistent with the test value. The greater the penetration depth of pile, the closer the theoretical calculation value of excess pore water pressure is to the field measured value.

During coastal blowing and filling of sandy soil foundation, high water table levels and soft interlayers are often encountered, which results in the difficulty to reinforce the ground. In order to study the reinforcement effect of high energy dynamic compaction on this type of soil, a field test of high energy dynamic compaction with 6 000 kN·m and 8 000 kN·m energy levels on a blow-filled sandy soil along the coast of Shandong was conducted. After the test, standard penetration test,static cone penetration test and plate loading test were used for on-site inspection. Through analyzing, the number of SPT strokes and the tip resistance of CPT were significantly increased in the depth range required by the design before and after the dynamic compaction, indicating that high energy dynamic compaction is very effective in eliminating the liquefaction potential of saturated sand and saturated chalk soil. Through the PLT p-s curve and the relationship formula of the tip resistance standard value and the bearing capacity characteristic value, the bearing capacity characteristic value ≥ 120 kPa after dynamic compaction was obtained, proved the feasibility of the high energy dynamic scheme. The impacts of the position of the soft soil interlayer and the height of the water table were studied; And it was found that the soft soil layer impeded the transfer of the dynamic energy and reduced the effective reinforcement depth of dynamic compaction, and the different position of the soft soil layer had different influence on the effect of dynamic compaction:When there was a soft soil layer at the critical area affected by dynamic compaction, the effective reinforcement depth was at the top of the soft soil layer. In the field test of high energy dynamic compaction with 4 000 kN·m energy level, the effective reinforcement depth reached 5 m after dynamic compaction without precipitation; However, with the precipitation of 3 m below ground level, after dynamic compaction the effective reinforcement depth reached 7 m. On the basis of high energy level dynamic research,a high energy level ramming was carried out in a large area of 750 000 square meters, and it was found that the treated foundation met the requirements of the construction site.

In order to study the anchoring performance and optimal anchoring length of the FAST-1 new high strength anchoring agent, the bonding performance of the reinforced slurry rock system based on the FAST-1 new high strength anchoring agent was studied from many aspects through the ultimate pull-out test under continuous load. The continuous curve model with good fitting effect was selected to calculate the relative slip, which can effectively reflect the bonding properties of different interfaces, and the effective calculation method of reinforcement slurry length was optimized. It is found that when the water material ratio is in a certain range (0.22-0.31), and it affectes the failure mode of the anchor structure in the drawing process. The smaller the water material ratio, the greater the bond strength, but the worse the fluidity; The bonding performance of the anchoring agent to the rock stratum is greater than that of the anchor cable; Increasing the contact area between the anchor cable and the slurry consolidation body can effectively improve the anchoring performance. It is concluded that the new anchoring agent has the characteristics of high early strength, and the design strength can be reached with 24 h; The anchorage length is related to the length of the anchor body. It is suggested that the anchorage length is 10.0d-15.0d(d is the diameter of the anchor cable).

In order to solve the problem of failure criterion of concrete shafts in thick loose strata, the numerical limit strain method is used to analyze the change of shaft strain value,that is, when the strain of element circumferential connection reaches the limit strain value in the shaft, the calculation of non-convergence is taken as the criterion for the overall failure criterion of the shaft. In this study, two numerical calculation models of wellbore with and without pressure relief grooves were established respectively, as the stress-relief groove has a vertical pressure relief function. The calculations show that the soil around the shaft was destroyed before the shaft at 181-183 m. The shaft without stress-relief groove failed at 181-182 m when the groundwater level dropped by 27 m; While the shaft with stress-relief groove failed at 182-183 m when the groundwater level dropped by 38 m. At present, the groundwater level has dropped by 20 m, so the shaft is safe. The numerical ultimate calculation result is consistent with the actual monitoring value.

China has a large area of frozen soil, and the long-term stability of the expansive soil slopes in the seasonal frozen area can be guaranteed by controlling the deterioration of the slopes in freezing and melting cycles. In order to determine the role of geogrid in the stability of the expansive soil slopes during the freeze-thaw cycle, the model test of the expansive soil slope is carried out in this paper. The results show that:1) The geogrid can restrain the freeze-thaw cracks of expansive soil, make the crack development more uniform, and reduce the slope displacement; 2) The reinforced material can inhibit the water migration and heat conduction of the slope and reduce the change of soil pressure; 3) The reinforced treatment of expansive soil slope can significantly reduce the fluctuation of water content, so as to reduce the swelling and shrinking of expansive soil caused by the change of water content; 4) Different from ordinary clay, the expansive soil slopes show the characteristics of freeze shrinkage and thaw expansion in the freeze-thaw cycle, and the slope reinforcement can effectively improve the freeze-thaw stability of expansive soil slopes in frozen soil areas, which has engineering application value.

In the current geotechnical engineering, manual identification methods are usually used to distinguish the types of rock samples, which are highly specialized, time-consuming,and susceptible to subjective factors, resulting in low accuracy. With the development of computer technology, machine learning is gradually applied to the automatic lithology identification, which opens up a new path for rock sample classification. Based on this, the authors took the meso-images of the four typical rock samples (mudstone, sandy mudstone, argillaceous sandstone, and sandstone) in the main urban area of Chongqing as the research object. Based on the Inception V3 convolutional network model and migration learning algorithm, a deep learning model of rock sample mesoscopic images was eatablished, and training and learning were completed. The results show that after 1 000 times training, the classification accuracy rate in the training set reaches 92.77%, and the classification accuracy rate in the verification set is 76.31%. Among them, the sandstone recognition accuracy rate is 97.28%, the mudstone recognition accuracy rate in the verification set is 81.85%, the argillaceous sandstone recognition accuracy rate is 72.59%, and the sandy mudstone recognition accuracy rate is 72.35%. Compared with the existing machine learning methods, this recognition model can automatically recognize the rock samples with very similar lithology, and has higher recognition accuracy, robustness, and generalization ability.

In order to accurately simulate the spatial distribution of rock joints to evaluate the stability of surrounding rock in high level radioactive waste geological disposal repository, at first the probability statistics theory was introduced to simulate the geometric characteristics of joints through the investigation of outcrop joint data, then by using the Monte-Carlo method the spatial distribution characteristics of the joints of the granite rocks in the Tianhu district in Xinjiang were simulated, which is a preliminary area for the disposal of high-level radioactive waste. The authors studied the different depth of joint geometrical characteristics through borehole TV, circled the homogeneous areas, proposed statistical methods and calculation formulas for borehole joint occurrence, density, and size, and finally established a joint 3D network model. The results show that:1) Using the chi-square test of the list table and the overlapping window method, the rock mass of the Tianhu borehole is divided into 0-90,120-240,270-360, and 390-600 m homogeneous zones; 2) Using SPSS software and based on the quantitative relationship between joint diameter, joint trace length, and gap width, the joint occurrence and diameter were in normal and negative exponential distribution respectively; 3) The difference between the model statistics and the field measured joint occurrence is within ±3°, the average diameter is within ±1 m, and the surface density is within ±0.01 m^-2 through data comparison, which verifies the accuracy of the 3D network simulation of the joint established by the Monte-Carlo method.