To explore the environmental durability of heavy metal contaminated soil remediated by enzyme induced carbonate precipitation (EICP) technology, acid soaking, freeze-thaw tests, and rainfall tests were carried out on the zinc and lead contaminated soil after EICP remediation, respectively. The durability and influence of the zinc and lead contaminated soil remediated by EICP technique under different environmental conditions and the corresponding influence regularity were discussed in this paper. The results showed that under different concentrations and types of acid solutions, the leaching amount of heavy metal ions in exchangeable and carbonate bound forms in the zinc and lead contaminated soil after EICP remediation decreased with pH value, with the content of ions in carbonate bound forms decreasing and the content of ions in exchangeable forms gradually increasing. It was also found that the stability in sulfuric acid solution was greater than that in nitric acid solution. As the number of freeze-thaw cycles increased, the leaching amount of exchangeable ions in the zinc and lead contaminated soil remediated by EICP technique increased, while the content of ions in the carbonate bound form reduced. Under the condition of heavy rain, Zn²⁺ and Pb²⁺ were mainly released within the first 20 minutes and migrated from top to bottom. All the results demonstrate that the heavy metal contaminated soil remediated by EICP technology has a good durability under acid soaking, freeze-thaw cycles, and heavy rain.

Fluidized solidified mud can be used in foundation trench, road base and other casting projects, its mobility is an important factor to ensure the construction quality, but the lack of systematic research on the mobility of freshly mixed solidified muds with different liquid limits, it is of great practical significance to carry out the relevant research. In this study, flowability and viscosity tests were conducted on muds and freshly mixed fluidized solidified muds with six different liquid limits (w_L = 27.2%-62.0%), revealing the influence of curing material content, water content, and liquid limit on the rheological properties of muds and freshly mixed fluidized solidified muds, and methods for calculating the flowability and viscous shear force were developed. The study shows that: the adding of curing materials makes the fluidity of freshly mixed solidified mud decrease obviously, but the decrease slows down after the dosage exceeds 5%, and the fluidity basically stays unchanged after exceeding 10%; the larger the initial water content is, the better the fluidity of freshly mixed solidified mud is; the less change in fluidity were observed in the solidified mud when the water content is near w_L, and the fluidity of the solidified mud increases obviously after exceeding a certain number of times of w_L; the smaller the w_L is, the larger the value is; but when the water content exceeds a threshold, the growth rate of flowability slows down, and the flowability is positively correlated with the w_L. On this basis, a power function relationship between the flowability of mud/freshly-mixed solidified mud and w_L was proposed, and a hyperbolic model for computing shear force of freshly mixed solidified mud with different w_L was established. The results can provide a reference for the design and construction of freshly mixed solidified mud.

Microbially induced calcite precipitation (MICP) has been widely applied for soil reinforcement, but its applications in rock mass permeability reduction have been rarely reported. To explore the plugging mechanism of rock joints using MICP, artificial rock joint specimens made of transparent resin were prepared, and laboratory MICP plugging experiments under six various conditions considering MICP reaction influence factors were performed. Through the plugging experiments, evolution laws of rock joint transmissivity and hydraulic aperture, accompanied with corresponding CaCO₃ distribution images, during plugging processes were obtained. The experimental results showed that the hydraulic aperture of rock joint approximately decreases linearly with grouting cycles during MICP plugging process, and the decreasing rate is closely related to the CaCO₃ distribution that is significantly affected by grouting rate, injection time of fixation, bacterial, and reaction solutions, and standing time. Among the six experimental conditions, both the plugging efficiency and effect are optimal under the fourth experimental condition, where the grouting rate is high and the grouting and standing time is the longest. After only two grouting cycles under the fourth experimental condition, the rock joint transmissivity decreases from 40.51×10^–6 m²/s to 0.52×10^–6 m²/s with a decrease rate of 98.72%, and the hydraulic aperture decreases from 0.367 mm to 0.086 mm with a decrease rate of 76.6%. Furthermore, the CaCO₃ distribution on the upper and lower surfaces of rock joint specimens were observed, and CaCO₃ in rock joints produced by MICP reaction was found to bring cementation strength in a short time, which helps improve mechanical properties of rock joints while reducing rock joint permeability.

The variation of shear strength indices of unsaturated soil with the degree of saturation S_r is complicated. In order to describe the experimental phenomena, the existing literature on the variations of cohesion, internal friction angle and dilation angle with S_r is analyzed. The results show that: (1) When S_r decreases and the pore water gradually transits from capillary water to adsorbed water, the friction angle increases. The turning point can be defined as critical degree of saturation S_rc. When S_r is greater than S_rc, the value of the friction angle is constant; when S_r is less than S_rc, the friction angle increases linearly with the decreasing S_r, and the extended Mohr-Coulomb criterion is no longer applicable. (2) The “peak effect” exists in the process of cohesion changing with S_r, i.e. the cohesion first increases exponentially with the decrease of S_r and reaches its maximum when S_r reaches S_rv corresponding to the peak unsaturated strength, and then decreases, which is the main reason for the “peak effect”. (3) A linear model can describe how the dilation angle increases with the decrease of S_r and vertical load. In addition, an unsaturated shear strength model over a wide S_r range is proposed. The proposed model is verified by the comparisons between the published experimental data and the predicted results of the proposed and existing equations, which illustrate the superiority of the proposed model.

Expansive soil has strong swelling-shrinkage behavior. It swells and softens after absorbing water, and shrinks and cracks after losing water. These swelling-shrinkage behavior will seriously threaten engineering structures. In this study, the expansive soil was stabilized by rice husk ash (RHA) and ground granulated blast-furnace slag (GGBS). Through compaction test, unconfined compressive strength test, direct shear test, California bearing ratio (CBR) test, swelling test, scanning electron microscope test and X-ray diffraction (XRD) test, the mechanical strength, expansion characteristics and microscopic mechanism of solidified expansive soil were studied. Testing results show that the unconfined compressive strength of the stabilized soil with a ratio of RHA to GGBS of 6:4 and a 10% curing agent dosage is the highest among all stabilized soils. The mixture of rice husk ash-ground granulated blast furnace slag (RG) can reduce axial deformation and improve shear strength. With the increase of curing agent content, the cohesion of stabilized soil increases first and then decreases, and the internal friction angle increases gradually. Compared with the untreated expansive soil, the CBR value of the stabilized soil with RG can be increased to 7.9 times, and the mechanical strength of the soil has been significantly improved. RG can significantly reduce the swelling rate of expansive soil and the swelling force. The free swelling rate can be reduced from 11.4% to 0.5%, and the swelling rate with loading can be reduced from 1.1% to 0%. Additionally, the swelling force decreases between 12.1% and 62.8%. RG can promote the formation of flocculation, amorphous hydration products and a very small amount of ettringite (AFt), which are distributed on the surface of the soil and fill the pores so as to improve the strength of the soil and reduce the expansion of the soil. Meanwhile, RG can significantly diminish the hydrophilic minerals such as montmorillonite and illite in the soil and thus enhance the cementation between particles, thereby improving the strength and downgrading the swelling behavior of the expansive soil.

There are many in-situ remediation technologies for the total petroleum hydrocarbon (TPH) contaminated soils, investigation of potential effects of three remediation technologies on the engineering properties of petroleum hydrocarbon-contaminated silty sand is however limited. Laboratory tests have been conducted to examine variations of physical and mechanical properties of the contaminated soils before and after remediation. The test results show that the engineering properties of the contaminated soils have been largely improved after a thermal desorption remediation, with water content and compressibility decreasing as well as average pore size and shear strength and permeability increasing. After chemical oxidation remediation, the engineering characteristics of the soil become relatively poor, and the impact of thermal desorption coupled with chemical oxidation on the engineering characteristics of the soil is between the two. It is also found that the mechanical properties of the contaminated soils are well correlated with its concentration of residual petroleum hydrocarbon and water content, and it is not affected by remediation technologies. Based on the test results, normalized equations are proposed to estimate the mechanical properties of the contaminated soils before and after remediation. The findings are expected to be useful to choose a reasonable remediation technology as well as foundation design.

In the area of deep soft soil, there are a large number of deep foundation pits conforming to the following characteristics: (1) insertion ratio of retaining wall is between 1:2.0 and 1:2.2; (2) excavation process goes smoothly; (3) basal heave stability does not meet the requirements of relevant standards. In order to reduce the inconsistency between theory and practice, based on the calculation formula of the existed foundation bearing capacity model, a basal heave stability analysis method for foundation pit considering soil stress state and shear capacity was developed by introducing the virtual foundation width. The critical width was defined as the virtual foundation width with the minimal basal heave stability in mathematics. In addition to the critical width, the width of the foundation pit and the thickness of the soft soil layer should also be considered in the selection of the virtual foundation width. A completed engineering example was given to compare the basal heave stabilities of the existed different analysis methods, and to analyze the influence of soft soil layer structure and internal friction angle on stability. The analysis results were closer to the actual situation, and showed that the influence of soil shear capacity was limited when the critical width was used as the virtual foundation width.

The soft clay with low strength and high compressibility is widely distributed in the coastal area of China. The engineering characteristics evaluation of soft clay is crucial for engineering construction. Piezocone penetration test (CPTU) is one of the most commonly used in-situ testing methods, which has slight disturbance on soil. However, the mechanical properties of the soil requires interpretation of CPTU test results, which is site-specific. This paper presents a study conducted in the Taizhou coastal area to investigate the strength characteristics of deep soft clay through CPTU and laboratory tests. Based on the direct shear test (consolidated quick shear) results of reconsolidated Taizhou soft clay, the relationship between the normalized strength and overconsolidation ratio (OCR) of Taizhou soft clay was obtained, where the empirical coefficients a and b of the stress history and normalized soil engineering properties (SHANSEP) method were determined to be 0.226 and 0.761, respectively. The cone factor N _kt of Taizhou soft clay were calibrated from 10.23 to 16.88, with a total mean value of 14.08. Utilizing the SHANSEP formula and the undrained shear strength s_u obtained by N _kt method, a continuous section of the in-situ OCR of Taizhou soft clay was derived. The interpretation empirical coefficient k of different strata OCR were calibrated from 0.315 to 0.570, a value of k = 0.33 was recommended for interpreting the OCR of Taizhou soft clay.

This study aims to further reveal the deterioration mechanism of subgrade soil performance under the coupling of multiple factors. On the basis of previous work, CT scanning technology is adopted to analyze the mesoscopic structural characteristics of compacted silty clay under wetting-drying cycles sequentially coupled with dynamic loadings. By examining influences of the coupling effect on the three-dimensional spatial pore distribution, the statistical distribution of pore volume, and the statistical indicators of image grayscale, the relationship between the macroscopic performance and the mesoscopic structural characteristics of specimens is revealed. Results indicate that more large pores and through-cracks would be induced by wetting-drying cycles, while part of pores or cracks caused by wetting-drying cycles can be closed by dynamic loadings. With the sequential coupling of wetting-drying cycles and dynamic loadings, the number of small pores in the specimen tends to increase. Increasing of total pore volume can be caused by wetting-drying cycles, and decreasing of total pore volume can be caused by sequential dynamic loadings. The mesoscopic structural parameters can be used to explain the evolution of macroscopic performance of specimens.

To investigate the effect of clogging of aquifers around well on the flow dynamics in the well vicinity during the constant-rate recharge using a partially penetrating injection well, an analytical model for well hydraulics was proposed with special consideration of the clogging-related permeability reduction, which was assumed to reduce exponentially with time. By means of the variable substitution and the Laplace and finite Fourier cosine transforms, the solutions for the hydraulic head increment in the Laplace domain were derived and then the solutions in the real-time domain were obtained using the Stehfest numerical inversion method. A parametric study indicates that: a smaller asymptotic hydraulic conductivity K_r,∞ can not only increase the hydraulic head increment and the injection pressure during the recharge process but also accelerate the flow dynamics of the recharged aquifer at the quasi-steady state, whereas a larger permeability reduction exponent λ only result in larger hydraulic head increment and the injection pressure during the recharge process but doesn’t affect the flow dynamics at the quasi-steady state. The hydraulic head difference distribution due to various K_r,∞ and λ values reaches its maximum value in the wellbore and then decreases gradually with the radial distance. The findings of this study can offer theoretical reference for the estimation and prediction of the clogging in the aquifer around well during the constant-rate injection test.

The development of cracks is important to the damage and failure of soil. In order to study the evolution of meso-cracks in granite residual soil with complex geotechnical engineering properties, a series of reconstructed volume images was obtained by using CT to scan the process of the triaxial compression test. The crack volume overlap rate is introduced to improve the crack classification method proposed by the author, and the accuracy of judging the connectivity of the two cracks before and after deformation is improved. The results reveal that the change of crack volume overlap rate has a slight effect on the obsolete and brand-new cracks, while the greater sample deformation leads to the greater influence on other types of cracks, and the optimal crack volume overlap rate is 0.05. The volume content of obsolete and brand-new cracks increases with the increase of axial strain, and the volume content of brand-new cracks increases faster, while the volume content of compound cracks decreases, and the volume content of the other cracks is small. The change of fractal dimension of cracks is similar to that of volume content. Among them, obsolete, brand-new, and combined cracks show an increasing trend, and the fractal dimension of brand-new cracks increases the fastest, indicating that brand-new cracks can better reflect the shear failure process of samples. The results will provide theoretical and technical support for the fracture damage analysis of geomaterial.

The one-dimensional shear beam model method is unsuitable for determining the stress-strain relationship in the earth-rockfill dam foundation because of the constrained ground surface and the effects of the lateral normal stress. A centrifugal shaking table test was conducted on an earth-rockfill dam with overburden saturated sand foundation to analyze the soil acceleration response in the non-dam-covered area of the foundation, middle and toe of the dam under different input seismic loads. This test also obtained the variation characteristics of the horizontal dynamic earth pressure in the upper and middle layers of the dam foundation. An inverse calculation method was proposed to obtain shear stress-strain in the dam foundation soil, considering the influence of horizontal dynamic earth pressure. Comparing it with the stress-strain hysteretic loop inversed through the ideal one-dimensional shear beam model, the effect was analyzed about dynamic soil pressure on the dynamic shear modulus of the dam foundation soil. The test results show that the amplification effect of acceleration increases linearly from the bottom of the dam foundation to the top dam, and the variation of horizontal earth pressure cannot be ignored in the inverse analysis of shear stress-strain. Besides, the soil shear modulus decreases after considering the effect of horizontal dynamic earth pressure. As the depth increases, the effect of dynamic earth pressure on the shear modulus in the middle of the dam foundation is greater than that of the upper sand layer. Moreover, the relative calculation error increases with the increase of depth and peak acceleration of the input seismic wave.

To investigate the effect of coal stress on drilling energy during coal drilling, the coal rock drilling experiment was carried out by using the self-made drilling experimental device with constant drilling pressure, the drilling parameters were measured, and the relationship between drilling energy and coal stress was studied. The surface energy of drill cuttings was calculated by using drill cuttings parameters, and the relationship between coal stress and surface energy was examined. By comparing the drilling energy and the surface energy of drill cuttings, the energy conversion during drilling was analyzed. It was shown that the torque work accounted for more than 95% of drilling energy, and the drilling energy increased with the increase of coal stress, which is approximately in linear correlation with coal stress. The amount of drill cuttings and the surface energy of drill cuttings were both increased with increasing of coal stress. There was 8%−33% energy loss during the conversion of drilling energy to the surface energy of drill cuttings. Energy loss was mainly contributed by acoustical energy and frictional heat loss.

To investigate the mechanical behavior, infrared radiation, and fracture evolution characteristics of coal with different degrees of damage, simultaneous infrared radiation detection tests were carried out during uniaxial compression to analyze the mechanical behavior and infrared radiation response characteristics of different specimens after loading. And then based on the macroscopic mechanical properties of the specimens, particle flow software PFC^2D was used to simulate the uniaxial compression of the specimens to analyze the fracture evolution characteristics of the specimens on a meso-scale. The results show that the degree of damage affects the strength and deformation characteristics of the specimens. With the increase of the degree of damage, the specimens show weak brittleness and strong plasticity characteristics; the specimens with different degrees of damage all show time-varying characteristics of temperature increase; the temperature of Class I and Class II specimens show a precursor of a sudden increase before rupture, with a sudden increase of temperature up to about 1.7 ℃, while Class III specimens show the characteristics of a sudden drop followed by a rapid increase, with a temperature increase of 0.93 ℃. The thermal infrared images show divergent characteristics during the loading process, with the high or low-temperature anomalies corresponding to the spatial location of the damage to the coal rock specimens. The damaged area of the specimens is approximately the same as the anomalous area of the infrared radiation, and there is a close correlation between the internal damage (fracture development) and the surface damage (infrared radiation). The results of the study can provide a reference for the early warning of dynamic hazards during the mining process of coal bodies with different degrees of damage.

Suffusion refers to the phenomenon that the movable fine particles in internally unstable soil migrate through the pore channels under seepage flow. The constitutive model, which describes the transition of the deposited fine particles to the fluidized fine particles in the pore fluid, determines the reliability of numerical analysis results. Currently, there are many constitutive models for suffusion based on constant hydraulic conditions, but the models considering the effect of hydraulic fluctuation are still lacking. First, the meso-mechanism of fine particle migration under different hydraulic conditions was summarized, and the particularity of the fine particle migration mechanism under fluctuating hydraulic conditions was highlighted. Then, based on the meso-mechanism, a constitutive model for suffusion was developed by using the volumetric exchange rate of deposited fine particles to fluidized fine particles. The model can consider the combined effect of the interstitial flow velocity, the variation rate of interstitial flow velocity, as well as the hydraulic action time. Based on a set of parameters, the model well reproduced the fine particle erosion process under various hydraulic loading paths in the existing experimental studies, demonstrating the effectiveness of the model.

Calcareous sand is a geotechnical material formed after the death of marine calcareous organisms with abundant internal pores, low strength, irregular shape and easy fragility. In this study, the mechanical and deformation characteristics of calcareous sand under different stress paths were investigated through five tests of isotropic compression, conventional triaxial compression, triaxial compression with constant average principal stress, triaxial compression with reduced compression, and constant stress ratio loading on calcareous sand. The results indicated that the stress path notably affected the shear strength and deformation characteristics of calcareous sand. Calcareous sand had obvious anisotropic properties under isotropic compression. In the conventional triaxial compression test, dense calcareous sand presented the deformation characteristics of low-pressure dilatancy and high-pressure contraction, and there existed a power function relationship between the peak strength and the initial consolidation pressure. Increasing deviatoric stress could cause a volumetric strain of the specimen under the triaxial compression condition with constant average principal stress. Unlike the conventional triaxial compression test, the stress-strain relationship curves in the triaxial compression test with reduced compression presented strain softening. In the constant stress ratio loading test, the specimen was basically in the elastic state, and the relationship between the axial stress and the axial strain was a power function. The experimental results also indicated that the tangential Poisson’s ratio of calcareous sand was not only dependent on the deformation and stress state of calcareous sand, but also influenced by the stress path. The order of magnitude in the peak stress ratio and the maximum volumetric strain under different stress path tests were not affected by the initial consolidation pressure. The peak internal friction angle of calcareous sand decreased with the increase of the initial consolidation pressure, roughly as a linear function of the logarithm of the initial consolidation pressure.

To explore the improvement effect of adding silt on expansive soil, the swelling-shrinkage characteristics, road performance and microstructure of expansive soil with different proportions of silt were tested. The results show that the incorporation of silt changes the composition and structure of soil particles, and inhibits the expansion and contraction potential of expansive soil. With the increase of silt particles, the compactness and unconfined compressive strength of expansive soil increase first and then decrease. The maximum dry density reaches 1.889 g/cm³ when the proportion of silt is 40%, and the unconfined compressive strength reaches the maximum when the proportion of silt is 10%. The California bearing ratio (CBR) value continues to increase significantly, and the rebound modulus shows a downward trend. All of these indexes meet the requirements of the specification. The feasibility of using silt to improve expansive soil is verified, and the optimum dosing ratio of silt is determined to be 40%. In order to facilitate onsite construction and consider the uniformity of onsite mixing, 3% low-dosage lime is first added to causes the performance of expansive soil to tend towards those of sandy soil so as to reduce the viscosity of the expansive soil and break it. On this basis, the expansive soil is applied to highway embankment filling after improved with 40% silt content, and onsite compaction degree, CBR value, deflection and other tests are carried out. The field test results show that the overall compaction quality of the experimental section improved by silt and lime and the control section treated by the single lime are controlled well, but the compaction degree of the test section is reduced due to the influence of the uniformity of the silt. The CBR value and subgrade deflection of the test section are comparable to those of the control section, and the silt improvement effectively compensates for the strength provided by the 2% lime reduced relative to the control section.

Salt rock is an ideal medium for storing fossil energy and highly radioactive nuclear waste, and the study of creep mechanical properties of salt rock holds great significance for the safe operation of underground storage in salt caverns. In this study, a creep constitutive model for salt rock considering damage and hardening effects was developed, based on the component combination model and fractional calculus theory, so as to reasonably reflect the two mechanisms of damage and hardening existing in the creep process of salt rocks. The elastic element considering time-dependent damage was used to describe the damage deformation of salt rock in the initial loading stage in this model, and the fractional Murayama body was used to describe the viscoelastic plasticity creep mechanical behavior of salt rocks in transient creep stage. Meanwhile, a hardening function, which describes the strengthening characteristics with time of the yield strength of salt rocks, was introduced to reflect the hardening mechanism of salt rocks, and a transient plastic element was available to depict unrecoverable transient deformation. A nonlinear dashpot element with strain-triggering was constructed based on Kachanov creep damage law and Lemaitre strain equivalence principle. The dashpot better characterized the nonlinear deformation of salt rock in the accelerating creep stage. One-dimensional and three-dimensional creep equations for salt rock considering hardening and damage effects were derived based on the combination model theory. With the characteristics analysis of the isochronous stress-strain curves of the existing uniaxial and triaxial salt rock creep tests, the start-up stress threshold of Murayama body was determined. The parameters in the model were identified by combining isochronous stress-strain curves and creep tests data. The results show that the established creep constitutive model can describe the creep mechanical properties of salt rock in different stress states using only one set of parameters, which can provide a certain theoretical basis for predicting the creep deformation characteristics of salt rock.

Geogrids are often used in the aggregate cushion of the composite foundation to limit the lateral displacement and reduce the differential deformation. It depends on the interaction between geogrids and aggregate particles. In this study, a series of large-size pull-out tests was performed on bi-axial and tri-axial geogrids embedded in aggregates with three particle-size gradations. The test results showed that higher normal stress, better gradation and more suitable aggregate particle sizes yielded the increase of the pull-out resistance. The classic punching-shear failure model was proven to be valid for explaining the shear effect between transverse ribs of bi-axial geogrids and the aggregate layer during the pull-out process. The bearing resistance of oblique ribs of tri-axial geogrids can also be calculated based on this theory, as long as the effective length of the oblique rib is calculated in a reasonable manner. Furthermore, an empirical method was proposed to calculate the peak pull-out resistance of the extruded geogrid embedded in the aggregate considering the sizes of apertures and aggregates, and interlock effect. The concept of key particles was proposed in this paper to measure how well the apertures of geogrids match the size of the particles. This may help designers choose the type of geogrids and improve the reinforcement effect.

The investigation of earthquake damage shows that the pile foundation in liquefiable soils has been severely damaged in many destructive earthquakes. In view of the prominent problem of pile foundation disaster induced by soil liquefaction, many scholars have adopted multiple research methods to explore the earthquake damage mechanism of pile foundation in liquefiable soils, aiming to meet the urgent need of aseismic design of pile foundation in liquefiable soils. And they have obtained fruitful and important research results, revealing the failure modes of pile foundation in liquefiable soils, such as bending failure, buckling failure and settlement failure. This study surveys and analyzes the typical cases of pile foundation earthquake damage in liquefiable soils, and summarizes the manifestations and failure types of pile foundation earthquake damage. On this basis, the paper dissects progress of different earthquake failure mechanisms of pile foundation, and points out the key and difficult points in the current research. Finally, the insufficiency and challenges of seismic research on pile foundation in liquefiable soils are revealed, and the further research directions are given. This work can provide some useful reference for the researchers, and it is beneficial to the development and perfection of seismic theory of pile foundation in liquefiable soils.

This paper proposes a physics and information dual-driven intelligent diagnostic method for the longitudinal mechanical behavior of shield tunnels, aiming to address the current bottlenecks in its safety diagnosis. By embedding the physical equations that characterize the longitudinal mechanical behavior of the tunnel into physical neurons, and integrating the measured data as information neurons, a physics and information dual-driven neural network model called physics-informed neural networks (PINNs) is constructed. This model enables real-time updating and inversion of the structural parameters of shield tunnels, surrounding geological parameters, and load distribution patterns, thereby forward solving the longitudinal structural mechanics state of the tunnel. The inverted parameters obtained are further utilized to analyze the longitudinal mechanical behavior of other tunnel sections, so as to realize the diagnosis of the longitudinal long-distance shield tunnels. Case studies and engineering applications show that the proposed PINNs model can effectively solve the longitudinal structural problems in tunnels. Furthermore, compared to the traditional purely data-driven deep neural network (DNN) models, the PINNs model exhibits significant generalization capability and robustness, presenting promising prospects for engineering applications.

Severe ground pressure problem during shallowly buried fully mechanized mining under thick loose bed and thin base rock is increasingly prominent, which has seriously threatened safety and efficient production in coal mine. This study took 22614 working face in Shendong mining field as engineering background, adopted the combination research method of field monitoring, similar experiment and mechanical modeling to analyze the characteristics of its strong ground pressure, to reveal cause of mining-induced roof broken and instability, to build mechanical model of roof broken structure, to determine working resistance of hydraulic support in working face, and finally to perform field example application. The study results showed that: based on field monitoring, the average roof broken length of 22614 working face was 11.2 m; the average working resistance of hydraulic support was 8 450.1 kN, and the maximum working resistance was 11 857 kN. In similar materials simulation experiment, the average caving length was 12.5 m, and roof sheared and broke as short suspension beams, crack extended to surface, which led to the whole sheared roof falling behind coal wall. As well plane mechanical model of sheared and fallen roof structure was established, then the structure instability criterion was put forward, the positive correlation between instability coefficient and roof sheared and fallen angle, bearing capacity of hydraulic support was pointed out. Certainly, working resistance calculation formula of hydraulic support in working face was given and calculated average bearing capacity of hydraulic support was 8 364.22 kN, which is in good agreement with the field monitoring results. The results provided important theoretical basis for support selection and roof control of shallowly buried fully mechanized mining under thick loose bed and thin base rock in China.

The consolidation coefficient C_v of soft soil is an important parameter in geotechnical engineering. The artificial neural network (ANN) model is improved with the biogeography-based optimization algorithm (BBO). And the artificial neural network with biogeography-based optimization (ANN-BBO) model, trained and tested by using the subgrade soft soil data of the reconstruction and expansion project of Lianyungang–Huai’an expressway, has been adopted to calculate the soft soil consolidation coefficient. Using the correlation coefficient matrix and principal component analysis, eleven physical and mechanical parameters were statistically analyzed, seven of which were identified as input parameters of calculation model which was then trained and tested. The model was tested by correlation coefficient, root mean square error, and variance ratio, whose robustness was analyzed by using Monte Carlo simulation. The results show that the ANN-BBO model can be used to calculate the consolidation coefficient of soft soil, the correlation coefficient R ² = 0.947 1, the root mean square error RMSE = 0.165 7×10⁻³ cm²/s, and the variance ratio VAF = 94.54%. The ANN–BBO model has significantly higher prediction accuracy and better robustness, compared with the ANN model.

The sand liquefaction evaluation formulae based on the standard penetration test (SPT) blow count in China’s seismic design code are the most widely used and authoritative liquefaction evaluation formula proposed by Chinese scientists, which are suitable for China’s national conditions. The basic principle of this formula is to use the groundwater level of the site and the burial depth of the saturated sand layer to correct the reference value of SPT blow count to obtain the critical blow count. The SPT reference blow counts in this formulae depend on liquefaction data. However, the database used to construct the evaluation formulae in the codes mainly comes from post earthquake survey and testing data as well as earthquake damage experience of several earthquakes that occurred in China in the 1960s and 1970s, but the data has not been systematically updated. By adding liquefaction data from recent earthquakes in China, the number of liquefaction data is significantly increased. Drawing on the theoretical framework of liquefaction discrimination methods in China’s codes, this paper gives the benchmark values of SPT blow counts under different intensities through data analysis, and constructs a new liquefaction discrimination formula. To verify the formulae, back-judgement on the data were performed, and the results indicate the success rates of the new formulae are fairly satisfactory and keep balance between liquefaction data and non-liquefaction data. The analytical results presented herein can be helpful for revising liquefaction evaluation methods in seismic design codes.

The hydraulic performance of geosynthetic clay liners (GCL) is closely related to the swelling characteristics of the bentonite particles and the resulting porous medium. However, there currently needs to be more analysis at the mesoscopic level to understand the permeating mechanisms. A numerical model using COMSOL was developed to study the effects of particle swelling on the effective porosity, tortuosity, and hydraulic conductivity of GCL under deionized water actions. The results demonstrate that the swelling of bentonite particles is a crucial factor influencing the effective porosity, tortuosity, and hydraulic conductivity of GCL. Particle swelling significantly affects the width and number of flow paths. When the hydraulic conductivity of GCL approaches the order of 10⁻¹¹ m/s, a distinct main flow path exists. With an initial porosity increasing from 0.5 to 0.6, the effective porosity after particle swelling rises from 0.07 to 0.11. The width of the minor flow path is approximately 0.001 mm, which is about 2 500 times the size of a water molecule. As the bentonite particles swell, the tortuosity of the main flow paths within the GCL gradually increases. For an initial particle size of 0.1 mm and an initial porosity rising from 0.5 to 0.6, the tortuosity of the main flow path ranges from 1.2 to 1.4. However, the variation in tortuosity for all initial porosities is around 0.07. Meanwhile, when the hydraulic conductivity of GCLs approaches the order of 10⁻¹¹ m/s, the bentonite particle swelling significantly affects the permeability of GCL. After the pore’s swelling ratio exceeds 0.96, a 0.01 increment in the pore’s swelling ratio results in a rapid decrease in the hydraulic conductivity of GCLs by one order of magnitude. These findings shed light on the mesoscopic behavior of GCL hydraulic performance, particularly the influence of bentonite particle swelling on the effective porosity, tortuosity, and hydraulic conductivity of GCL.

Based on the ideal fluid wave theory and Biot’s theory, an undersea tunnel model with imperfect interface is established by considering the imperfect contact relationship between the undersea tunnel and the surrounding seabed soil in engineering reality. The model also considers the dynamic interaction of seawater-seabed soil-undersea tunnel. The analytical solution of the imperfect contact interface effect between the undersea tunnel and the surrounding seabed soil under P₁ waves incidence is derived using the Hankel function integral transformation method and the wave function expansion method. Based on the analytical solution, the effects of imperfect contact conditions on the seismic dynamic response of the undersea tunnel are analyzed by numerical calculations. The calculation results show that the imperfect contact condition has a significant effect on the displacement response and stress response of the undersea tunnel; the displacement response and stress response of the undersea tunnel considering the imperfect contact condition at the tunnel-seabed soil interface are significantly higher than those at the interface with perfect conditions.

Underwater two-way vacuum preloading not only reduces more excess pore water pressure comparing to conventional vacuum preloading with vacuum acting only on the top face, but also has the advantage of utilizing the effective load from the overlying water. However, two-way vacuum preloading is currently only applied in the treatment of dredged soil, thus the mechanism and performance of consolidation of two-way vacuum preloading are hardly studied. To explore the consolidation characteristics and efficiency of underwater two-way vacuum preloading, centrifuge modelling has been performed to simulate soft soil subjected to underwater two-way vacuum preloading in collaboration with group sand drains and single sand drain. The finite element method is also used to analyze and compare the results with those from centrifuge modelling test. Variation of pore water pressure and development of deformation are compared. Meanwhile, changes in total head of pore water and stress path of soil element, as well as degree of consolidation are discussed and evaluated. It is found that more effective load can be obtained from underwater two-way vacuum preloading comparing to conventional vacuum preloading, and the rate of consolidation is larger and the ultimate settlement can be reduced in group sand drains zone comparing with single sand drain zone. The stresses for soil in the center of treated zone follow a path close to K₀ line. Under the combination effects of vacuum and gravity, the reduction of pore water pressure at the bottom layer is larger than that at the top layer, and it is found that a lower water head exists at the bottom at final consolidation stage in this experiment. These findings may enhance the understanding and practical application for two-way vacuum preloading.