High-moisture dredger fill sites with significant clay content are prone to substantial deformation during operation due to the combined effects of large strain consolidation and creep, posing critical risks to engineering safety. This study focuses on the mechanical behavior of high-moisture dredger fill under these conditions. Through comprehensive laboratory testing, the large strain consolidation and creep characteristics of the soil were analyzed. A finite element equation for large strain consolidation was developed, and a creep constitutive model based on fractional derivatives was established. A finite element model was constructed to capture the overlying effects of both large strain consolidation and creep deformation. Validation through model box experiments demonstrated the accuracy of the numerical simulations, which were employed to analyze the impact of these combined effects on surface settlement under applied loads. The results indicate that the strain-time curve during large strain consolidation shows significant attenuation, with creep deformation becoming increasingly pronounced in the later stages. The creep behavior of the dredger fill soil is distinctly nonlinear, with the nonlinear viscoplastic deformation phase accounting for approximately 59% of the total creep deformation. As consolidation time progresses, drainage volume and surface settlement initially increase rapidly before reaching a stable phase. The numerical model successfully captures the coupled effects of large strain consolidation and creep, with simulation results closely matching the experimental observations. This research provides valuable technical insight for the rational design and safe management of high-moisture dredger fill projects.

In order to elucidate the expansion mechanism of spherical cavity in undrained unsaturated soils, based on the modified Cam Clay model considering suction hardening and a liquid phase equation, and by incorporating the associated flow rule, the logarithmic large-deformation geometric relation, and the equilibrium equation, the incremental governing equations of stress, matric suction, and void ratio in the cavity plastic zone with respect to an auxiliary variable were established. A novel plastic solution for spherical cavity expansion in undrained unsaturated soils was then iteratively obtained using the boundary condition at the elastic- plastic interface. The rationality of this solution, its radial variations, and the factors influencing the cavity expansion pressure were subsequently discussed. The results reveal that the novel solution not only reasonably accounts for cavity expansion ratio, suction hardening, and compactness, but also does not simplify the deviator stress and average stress. Its parameters have clear physical meanings, and its rationality is verified by comparison with both the undrained semi-analytical solution for spherical cavity expansion in saturated soils and the undrained similarity solution for spherical cavity expansion in unsaturated soils available in the literature. Consequently, it has theoretical significance and broad application prospects. In the plastic zone of the spherical cavity, the radial effective stress and circumferential effective stress decrease continuously, while the matric suction increases gradually, and the void ratio first increases approximately linearly and then slowly. In dense soils, volumetric dilatation occurs, and the void ratio of dense soils first increases and then decreases. The cavity radius ratio, initial suction, and initial void ratio all significantly affect the cavity expansion pressure, and the cavity expansion pressure curves are parallel to each other for different initial suctions or initial void ratios.

The main cause of underground disasters in coal mines is the stress concentration and high-intensity unloading of surrounding rock caused by man-made mining and the extraction of coal resources. Especially when the surrounding rock is affected by confined water, it is easy to lose stability and damage, which leads to the occurrence of disasters. Accordingly, the experimental study on the mechanical properties and energy evolution law of sandstone under the coupling of seepage and mining stress was carried out by means of Rock Top multi-field coupling tester. The test results show that : (1) The total stress-strain curve of sandstone can be divided into five stages. After the sandstone begins to unload, it changes from axial deformation to circumferential deformation. (2) The peak stress of sandstone increases with the increase of unloading level. With the increase of osmotic pressure difference, the peak stress of sandstone is not obvious due to the superposition of surrounding rock and water pressure. (3) The higher the unloading level of sandstone is, the larger the axial strain value at the peak stress is, and the axial deformation of sandstone is more obvious under high unloading level. The evolution law of dilatancy angle curve of sandstone roughly follows the law of ' increase—ecrease—increase—decrease ', and the expansion behavior of sandstone is more significant under low unloading level. (4) With the increase of initial unloading level, the elastic strain energy density of sandstone increases as a whole. The energy distribution coefficient of elastic strain energy density increases first and then decreases with the increase of axial strain of rock sample. (5) The instantaneous energy distribution coefficient of elastic strain energy of sandstone presents the change rule of 'increase—decrease—increase 'with the increase of axial strain of rock sample. The energy storage capacity of sandstone elastic strain energy reaches its peak after entering the elastic deformation stage, and its energy release capacity reaches its peak before entering the residual stress stage.

To compensate for the lack of prediction models for rock creep failure time under conventional triaxial compression conditions and their low accuracy, based on the Norton creep constitutive relationship, a new rock creep failure time prediction model under conventional triaxial compression conditions is established by replacing the creep stress of Kachanov rock creep failure time function with a constant creep rate function. A method for determining the model parameters is proposed and its influencing factors are analyzed. The conventional triaxial compression creep test of sandy mudstone was carried out, and the creep failure time test data of five different types of rock were statistically analyzed to verify the rationality and accuracy of the new model. The results show that under the conventional triaxial compression conditions, the logarithm of the constant creep rate of rocks is linearly related to the logarithm of their creep failure time. The new model can weaken the adverse effects of heterogeneity between samples on the prediction results, and its applicability is more extensive compared to the prediction model established from the perspective of creep stress. The creep test results of six different types of rock are basically consistent with the prediction results of the new model, which verifies its accuracy and rationality.

Structural instability caused by the fracture and coalescence of rock bridges within rock masses under external loads is a common issue in slope and mining engineering. Quantifying and revealing the precursory characteristics of rock mass fracture is crucial for ensuring the stability of surrounding rock and preventing fracture instability. In order to investigate the precursory characteristics and failure mechanism of fractured sandstone during deformation and failure, a series of uniaxial compression tests was conducted on fractured sandstone specimens with six different ligament angles. The mechanical strength parameters, fracture modes, and multifractal characteristics of acoustic emission (AE) parameters were analyzed, and the time intervals between different AE parameter variances and key fracture points were discussed. The precursor identification and early - warning time based on the time function of AE hit rates and the variance of AE parameters were obtained. The results show that when the ligament angle increases from 0° to 150°, the elastic modulus and peak stress of fractured sandstone exhibit an inverted Gaussian - like trend, decreasing first and then increasing, and reaching the minimum values at a ligament angle of 60°. The failure mode transitions from indirect coalescence dominated by compression - shear cracks to direct coalescence dominated by tension - shear cracks. The spectrum width (∆) exhibits an evolutionary trend of decreasing first and then increasing. The time function of AE hit rates and the variance of AE parameters can effectively identify early - warning points, sub - critical fracture points, unstable fracture points, and final failure points during the deformation and failure process. By comparing the warning times for the three key fracture feature points, it was found that the warning time of the method based on AE energy variance is the shortest, while that of the method based on AE rise time variance is the longest. Further comparisons indicate that the variance of AE energy, as a precursor factor, is more sensitive than the variances of AE count and AE rise time in identifying critical fracture points of rocks.

Nanomaterial modification can significantly enhance the mechanical properties and durability of engineering materials. However, its impact on the basic properties of geopolymer cutoff wall materials and their durability under freeze-thaw cycles remains unclear. In this study, fly ash-based geopolymer was modified with nano-silica (NS) and graphene oxide (GO). The slump, heat of hydration, hydraulic conductivity, and compressive strength of the materials were systematically tested to assess the effects of nanomaterial type and content on the basic properties of cutoff wall materials. Furthermore, freeze-thaw cycling test was conducted to evaluate the durability of geopolymer. Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) were used to explore the modification mechanisms. Results showed that the addition of nanomaterials resulted in an increase in hydraulic conductivity compared to unmodified samples. As NS content increased, the nanomaterial filled the pores, reducing hydraulic conductivity. GO addition, on the other hand, accelerated geopolymerization, further lowering the permeability. NS improved freeze-thaw resistance by refining the pore structure through micro-aggregate effect and inducing secondary hydration products that filled cracks, thus slowing down material degradation during freeze-thaw cycles. However, GO addition caused exfoliation of nanosheets and associated geopolymer gels during freeze-thaw cycles, resulting in localized structural damage and reducing freeze-thaw durability and impermeability.

In order to explore the failure process of deep-buried limestone under different confining pressures, limestone samples were taken from the 1104 level of a mine in Huize, Yunnan Province, and subjected to triaxial compression tests under six confining pressure conditions (10, 20, 30, 40, 50 and 60 MPa), with the entire process being monitored synchronously using acoustic emission technology. Analyses were conducted on the stress-strain relationships, ringing counts, cumulative ringing counts, energy counts, cumulative energy counts, and failure modes of the limestone under different confining pressures. The results show that under different confining pressure conditions, the limestone experiences four sequential stages when subjected to axial pressure: elastic deformation, yielding, plastic development, and brittle failure. The AE energy changes and the fluctuations in the ringing count curve resulting from the development of internal fractures in the limestone under different confining pressures exhibit similar patterns, and the peak values of both gradually decrease as the confining pressure increases. The failure mode of the limestone is mainly shear failure. It exhibits 'Y'-shaped cracks when failing at a confining pressure of 10 MPa and 'I'-shaped cracks when failing at other confining pressures. Under high confining pressures, the fragmentation degree of the limestone decreases, the development of secondary cracks slows down, the limestone becomes more resistant to damage, and its compressive strength increases. The integrity of the crushed limestone increases as the confining pressure rises.

In the analysis of the stability of rocky slopes, determining the mechanical parameters of large-scale fractured rock masses is a critical challenge that needs to be addressed. This thesis utilizes unmanned aerial vehicle (UAV) photogrammetry technology to obtain centimeter-level three-dimensional real scene models of slopes. A software called Slope RMI was developed on the VS+C# platform using the OpenGL 3D graphics engine, which identifies rock mass structural features through line and surface interactions, achieving efficient recognition and statistical analysis of structural plane characteristics based on a high-precision 3D model of the study area. Additionally, a synthetic rock mass technique with target rock quality designation as a constraint was proposed, generating a large-scale rock slope calculation model that directly integrates three elements: the mechanical properties of rock, the mechanical properties of structural planes, and the geometric morphology of structural planes. This approach circumvents the difficulties associated with obtaining mechanical parameters of large-scale rock masses and provides a reliable pathway for detailed analysis of the stability of large-scale rocky slopes. The research method has been successfully applied in slope engineering, demonstrating its significant practical value in engineering applications.

Calcium clay layers are widely distributed in the Huainan-Huaibei mining area, with the characteristics of low freezing point, strong frost heave, easy disintegration upon contact with water, and low strength, posing a severe challenge to construction using freezing methods. To investigate the mechanical response of frozen calcareous clay under complex stress paths, true triaxial compression tests were performed on the ZSZ-2000 frozen soil true triaxial test platform, varying confining pressures, temperatures, moisture contents, and intermediate principal stress ratios. The strength and deformation characteristics of frozen calcareous clay under these varying conditions were analyzed. The test results indicate that the strength of frozen calcareous clay has a good quadratic relationship with the intermediate principal stress coefficient b and confining pressure, is negatively correlated with temperature, and positively correlated with moisture content. Furthermore, the rate of increase in the failure strength of frozen calcareous clay decreases as the moisture content rises. The failure strength is significantly influenced by the intermediate principal stress and confining pressure, showing both strengthening and weakening effects. A critical intermediate principal stress coefficient of b_c =0.75 and a critical confining pressure of σ_3c=3 MPa were identified. As the confining pressure rises, the volumetric strain gradually shifts from initial shear contraction followed by shear dilation to pure shear contraction. Moreover, as the b value increases, the peak volumetric strain of the samples also increases. Based on the experimental results, an improved Duncan-Chang model was developed, taking into account the effects of temperature, moisture content, and intermediate principal stress coefficient, and its reliability was verified. The research findings provide a theoretical foundation for optimizing frozen wall design and deep shaft excavation using freezing methods.

China’s water conservancy projects are constructed under complex environmental conditions, including strong earthquakes and thick overburden layers, which exacerbate the challenges in assessing liquefaction of deep-buried sandy soils. Current SPT (standard penetration test) -based liquefaction assessment methods have limited depth applicability, failing to meet engineering demands. This study analyzed the differences between domestic and international SPT-based liquefaction assessment methods, summarized three primary factors influencing sand liquefaction: site environmental conditions, soil intrinsic properties, and dynamic loading characteristics, and investigated their impacts on calculation results. Under ideal site conditions, critical SPT blow count curves for deep-buried sandy soils were calculated using various methods. The results reveal that discrepancies exist in critical SPT blow counts among different methods at identical burial depths due to variations in parameter calculation algorithms. The critical blow count curves demonstrate distinct evolution patterns with increasing fines content or clay content. Under equivalent conditions, the critical blow counts exhibit positive correlations with both seismic magnitude and peak ground acceleration. Existing SPT-based liquefaction evaluation methods show varying applicable depth ranges in international practice. The influence of critical depth or critical effective overburden stress on liquefaction potential assessment for deeply buried sand deposits requires further investigation.

Numerous experimental studies indicate that particle breakage alters the grain size distribution curve of calcareous sand, thereby affecting its mechanical behaviors. Consequently, investigating the particle breakage characteristics of calcareous sand and establishing a corresponding breakage evolution model are of critical importance. First, a series of isotropic consolidation and triaxial compression tests were conducted under various loading paths, confining pressures, and axial strains to systematically explore the influence of these factors on particle breakage in calcareous sand. Next, the intrinsic relationships among particle breakage, mean effective stress, and stress ratio were analyzed to quantitatively assess their combined influence on particle breakage within a unified theoretical framework. Finally, a novel particle breakage evolution model was proposed by integrating the experimental findings with an analysis of the Hardin model’s strengths and limitations. The model includes the derivation of the breakage equipotential surface. The model comprises only three parameters, facilitating straightforward calibration and ensuring clear physical interpretations. Furthermore, the model's validity and robustness were rigorously validated through triaxial tests on calcareous sand and other crushable granular materials.

Heterogeneous structural planes are extensively developed in nature, making it significant to study their shear characteristics, especially regarding anchored heterogeneous planes, for the stability analysis of engineering rock masses. The study selected sandstone and limestone heterogeneous structural planes with different wall rock strengths to conduct shear tests before and after anchoring, with their corresponding homogeneous structural planes serving as controls. Combining acoustic emission parameters and waveform frequency spectrum characteristics, the study analyzed the shear stress-shear displacement relationship of anchored heterogeneous structural planes, the shear failure mechanisms of joint planes, and the deformation and failure characteristics of bolts. The results indicate that the shear strength of the heterogeneous structural plane lies between that of the corresponding homogeneous planes and is closer to the one with lower strength. The variation in joint wall rock strength results in distinct shear failure mechanisms in heterogeneous and homogeneous structural planes: homogeneous sandstone planes demonstrate sliding type failure, primarily characterized by extensive friction and wear; homogeneous limestone planes exhibit shear failure dominated by the brittle fracture of asperities. While heterogeneous structural planes tend to exhibit a mixed failure mode characterized by the interaction between both types of failure. The deformation characteristics and failure modes of the bolts are influenced by the strength and roughness of the wall rock on both sides of the structural plane, with variations in wall rock strength resulting in asymmetric bending deformation of the bolts. There is a strong correlation between acoustic emission characteristic parameters and shear mechanical properties, with different ringing counts, energy peaks, and peak frequencies effectively reflecting various joint shear failure mechanisms.

Natural gas hydrate is widely recognized as one of the most promising clean energy alternatives with the potential to replace coal, petroleum and conventional natural gas in the 21st century. However, it still remains a major challenge to accurately analyze multi-physical field evolutions in the entire exploitation process. In this study, based on the time-updating approach, a semi-analytical model is developed within a multi-physical coupling framework. This model comprehensively considers the entire exploitation process, including both the drilling and support phases. Specifically, the proposed model is capable of analyzing the interactions between hydraulic flow, heat transfer, mechanical properties and hydrate saturations. Meanwhile, more actual mechanical properties of hydrate are incorporated in this model, such as shear expansion and strain-softening post-failure behaviours. As a verification step, a good agreement is observed between the results obtained by numerical predictions and those derived from the developed semi-analytical model. In parametric analyses, it is found that appropriately reducing the depressurization rate is beneficial for increasing gas production, while appropriately increasing the depressurization rate can enhance extraction safety. Interestingly, compared to the classical elastic-perfectly-plastic or elasto-brittle-plastic models, the developed strain-softening model can significantly improve the predicting ability to assess the safety performance during the extraction process.

When cement-based alkaline materials are extensively utilized in peat foundation soils, the subsurface alkaline environment resulting from alkalization may adversely affect the peat soil, which is critical for evaluating its engineering performance. A systematic experimental study was conducted to investigate these damaging effects by simulating typical engineering alkaline environments (Ca(OH)₂ and cement-hydration systems) and analyzing environmental alkalinity, specimen morphology, compressive strength, solid phase composition, and microstructure. Results indicate that humic acid dissolution constitutes the primary mechanism for soil structural degradation in both alkaline environments. Accompanied by varying degrees of humic acid leaching, specimens exhibited apparent morphological deterioration, significant reduction in strength, continuous loss of solid phase components, pore enlargement with interconnected network formation, and progressive loosening of the soil skeleton. These cumulative effects resulted in severe structural damage to the peat matrix. Furthermore, while Ca²⁺ infiltration occurred in Ca(OH)₂ environments and hydration products accumulated in cement systems，providing partial structural compensation，these beneficial effects were insufficient to offset the alkaline-induced degradation. The structural compensation effect was consistently outweighed by the corrosion and porosity-increasing impacts of the alkaline environments. These findings offer new perspectives for mitigating alkaline damage and enhancing the engineering performance of peat soils in underground construction applications.

The true three-dimensional stress state of coral sand in actual engineering can be realized by using true triaxial test, but the influence of coefficient of intermediate principal stress b on the mechanics of coral sand in the existing true triaxial test is not considered deep enough. In this paper, true triaxial experiments of coral sand with different average principal stresses p and the coefficients of intermediate principle stress b were carried out to study the effects of coefficient of intermediate principal stress and average principal stress on particle breakage, strength and deformation of coral sand particles. The results show that the increase of b will reduce the shear stress, shear strain and volumetric strain of coral sand, while the increase of p will have the opposite effect on the stress-strain curve of coral sand. The critical state theory is applicable to coral sand in the true triaxial state. The effects of b and p on the particle breakage, the deviator stress in critical state and the friction angle of coral sand are different. According to the relationship between particle breakage, strength and deformation, the empirical formula of strength considering the influence of particle breakage was fitted, and the dilatation equation of coral sand considering particle breakage under true triaxial conditions was derived. The research results can provide theoretical support for the construction of coastal engineering in coral sand foundations.

Based on the basic characteristics of the sand-free air-boosted vacuum preloading, a radial seepage calculation unit model centered on the booster pipe, which is a non-ideal well, is established, taking into account the spatiotemporal nonlinear characteristics of the well resistance of drainage plates and the relationship between the booster load and its pipe length. The nonhomogeneous partial differential control equations are consequently derived. According to the Sturm-Liouville eigentheory, the analytical solution to the excessive pore water pressure is obtained using the eigenfunction expansion method. Further, analytical expressions for calculating the excessive pore water pressure and the average consolidation degree of the foundation are provided under three typical practical pressurization modes, including constant pressurization loading, constant pressurization loading in the later stage, and intermittent pressurization in the later stage, respectively. Some examples show that the excessive pore water pressure increases as the length of the pressurized pipe increases, and always shows a nonlinear distribution that gradually increases with depth. After the pressurization is initiated, the excessive pore water pressure increases instantaneously, with a more pronounced increase in the middle and lower parts of the foundation, and subsequently, its dissipation rate also increases. The total pressurization duration has a significant impact on the consolidation degree of the foundation. When the pressurization loads are 20 kPa and 40 kPa, the consolidation degrees increase by approximately 8% and 9%, respectively, for a total pressurization duration of 100 d compared to 50 d.

Tunnel engineering is a linear-type project. It is a common working condition for shield tunneling to successively penetrate sandy cobble strata and sandy strata. To clarify the influence of soil properties on the ground response during the construction of shallow-buried shield tunnels, shield tunneling model tests were sequentially conducted in sandy cobble strata and sandy strata. Then, from the perspectives of shield tunneling mechanical parameters, ground settlement curves, and face stability, the similarities and differences in the ground response during tunneling in these two types of strata were analyzed. The results show that soil properties have a significant impact on the ground response during the construction of shallow - buried shield tunnels. The shield tunneling mechanical parameters in sandy cobble strata are all greater than those in sandy strata. Moreover, both the cutterhead torque and the screw conveyor torque are negatively correlated with the rotation speed of the screw conveyor. The symmetry axes of the ground surface settlement curves in both strata deviate from the tunnel centerline. When the shield cutterhead rotates clockwise, the symmetry axis is located on the left side of the tunnel centerline, and the deviation in sandy cobble strata is significantly larger than that in sandy strata. In sandy cobble strata, the amount of excavated soil from the tunnel face shows a two - stage change pattern of "linear increase - constant" over time, and the soil in the stratum exhibits a local instability failure mode. In sandy strata, the amount of excavated soil from the tunnel face shows a continuous linear increase over time, and the soil in the stratum presents an overall instability failure mode. Additionally, the center of the ground surface collapse is located in the left - front area of the shield cutterhead.

The sliding-zone soil plays an important role in controlling the deformation evolution of landslides, making the study of its creep characteristics under seepage-mechanical coupling significant for understanding the evolution of reservoir landslides. This research focuses on the sliding-zone soil from the Majiagou landslide in the Three Gorges Reservoir area, conducting pore pressure tests and triaxial creep experiments under cyclic seepage-mechanical coupling. The study analyzes the dynamic effects of cyclic seepage pressure, the transmission and distribution of pore water pressure of sliding-zone soil samples, and the response of sliding-zone soil creep to seepage pressure under different stress levels. The results indicate that cyclic seepage pressure affects the deformation of the sliding-zone soil by influencing the transmission and dissipation of pore water pressure within the sample. As the number of cycles increases, the pore water pressure within the sample tends to stabilize and exhibits a parabolic distribution. Under the influence of cyclic seepage pressure, the sliding-zone soil exhibits "stick-slip creep" behavior; when the deviatoric stress is low, the creep of the sliding-zone soil shows significant fluctuations in response to cyclic seepage pressure. However, when the deviatoric stress exceeds 900 kPa, the response of the sliding-zone soil to seepage pressure becomes less pronounced.

The automatic identification of microseismic signals is an urgent issue to be addressed in microseismic monitoring technology, and its performance determines the accuracy and timeliness of early warning. Although machine learning methods have been extensively utilized in the identification of microseismic signals, they exhibit notable limitations in identifying original signals with low signal - to - noise ratios. Both feature sets and algorithmic models jointly determine signal recognition accuracy in machine learning approaches. However, the construction of feature sets is yet to be standardized uniformly. To address this issue, the automatic identification of microseismic signals in a metal mine was investigated based on the improved multi - criterion fusion feature selection algorithm. Firstly, a dynamic signal feature library was established, which categorizes validated recognition features into three domains. Subsequently, an improved multi - criterion fusion feature selection algorithm was applied to quantitatively score the features, through which an optimal feature subset was selected. Finally, this subset was utilized as input parameters for the particle swarm optimization-support vector machine (PSO - SVM) recognition algorithm to identify signals automatically. The results indicate that the optimal subset constructed using the improved multi - criterion fusion feature selection algorithm includes 32 features. Compared to the feature sets constructed by using traditional methods, the optimal subset contains a richer variety of feature categories. When used as signal input with few training samples, the recognition accuracy of the training and test sets is 100% and 99.23%, respectively. Feature contribution analysis revealed that time - frequency domain features have a better performance compared to time - domain and frequency - domain features. This study establishes a new paradigm for the identification of microseismic signals. It holds substantial significance in propelling the extensive utilization of microseismic monitoring techniques in engineering applications.

This paper presents an optimized clustering method based on the mixed Fisher model to tackle several critical challenges, including inadequate characterization of orientation features, inconsistent evaluation standards, and poor integration with engineering applications. In this model, discontinuity orientations are treated as random variables that follow a Fisher distribution. The minimum message length (MML) criterion is employed for model selection and parameter estimation, balancing model complexity and data fit. Moreover, cuckoo search algorithm is utilized to optimize model parameters, enhancing global search capability, and preventing local optima. We compare the performance of the optimized clustering model with a control algorithm that does not utilize the MML criterion or the cuckoo search strategy, calculating the minimum objective function value over 50 iterations on synthetic datasets. The results demonstrate that the proposed clustering model exhibits superior accuracy and stability. To address the specific needs of high-level radioactive waste disposal, we combine the optimized clustering model with pole isodensity maps to determine the number of dominant sets for outcrop joints and borehole fractures. Furthermore, we generate synthetic data based on the clustering parameters of the model, providing a solid foundation for the subsequent reconstruction of the three-dimensional fracture network in the disposal rock mass.

The determination of the axial bearing capacity of large-diameter steel pipe piles is a crucial aspect of the design of pile foundations. However, the existing methods for calculating the axial bearing capacity of pile foundations are mostly based on the test results of closed-ended piles or small-diameter steel pipe piles, and these methods are not applicable to large-diameter steel pipe piles. Based on the existing pile foundation bearing capacity calculation methods based on cone penetration tests, a modified method is proposed. By comprehensively considering the Poisson's effect, soil plugging effect, and side resistance degradation, an expression for the pile side friction resistance is derived. Meanwhile, the base resistance is divided into two parts: annular resistance and inner shaft resistance, and the proportional relationship between cone-tip resistance and these two resistances is established. The modified method is used to calculate the axial bearing capacity of large-diameter steel pipe piles in an actual offshore engineering project, and the results are compared with those obtained using six commonly used existing methods. The results show that compared with the existing methods, the modified method is more accurate, especially in terms of the prediction accuracy of pile side friction resistance. Additionally, sensitivity analyses of key parameters, including pile diameter, pile length, plug length ratio, and cone tip resistance, demonstrate that the soil plug effect significantly influences the calculation of the vertical bearing capacity of large-diameter steel pipe piles in both non-cohesive and cohesive soils. The research results can provide theoretical guidance for the calculation of the axial bearing capacity of large-diameter steel pipe piles.

Based on the scattering field theory, the forward algorithm of the horizontal-to-vertical spectral ratio (HVSR) establishes a connection between the surface HVSR and the properties of the site’s soil layers. By combining this with ground motion observations at the surface, the inversion of the velocity structure of the site’s soil layers can be achieved. However, most current HVSR inversions employ traditional deterministic inversion methods, which lead to significant non-uniqueness in the inversion results and make it difficult to assess their uncertainties. This study proposes a Bayesian inversion method for soil layer velocity structures to enable the assessment of uncertainties in the inversion parameters. This method combines Bayesian principles with the forward algorithm of the earthquake horizontal-to-vertical spectral ratio (EHV), using the S-wave components of strong ground motion observations as the data source to achieve the inversion of the site’s soil layer structure. The effectiveness and applicability of the proposed method are verified through numerical examples. The results indicate that the proposed Bayesian inversion method can effectively identify the velocity structure of the site’s soil layers and comprehensively assess the uncertainties of the parameters in the inversion model.

The discontinuities of natural rock mass possess specific mechanical properties that can define the vulnerable parts of the rock mass. These properties play a decisive role in the structure, strength and stability of various rock engineering projects, such as tunnel support, classification of surrounding rock mass, and slope reinforcement. Therefore, it is of crucial importance to recognize the single discontinuity and the dominant groups with relatively developed conditions. In proposed method, the automatic identification steps of dominant groups of discontinuities are divided into three parts, point clouds normal vectors calculation, single discontinuity segmentation and dominant groups clustering: 1) Calculate normal vectors based on Robust Randomized Hough Transform; 2) An improved region-growing algorithm is proposed to segment a number of discontinuities. In terms of seed points selection and region-growing conditions, curvature, planarity and roughness are considered, and dynamic outlier detection is added. In addition, the relationship between the thresholds and the number of discontinuities is used to qualitatively judge the extreme segmentation situation, and the optimal threshold range is screened out; 3) Finally, S-K-means clustering algorithm is proposed to recognize dominant groups clustering. The accuracy of the algorithm is verified by a rock slope. The results demonstrate that the inclination angle error ranges from 0.7° to 2.5°, and the average inclination angle error is 1.8° and 1.7° respectively. This method shifts from directly clustering point clouds to identify dominant groups to first segmenting several single discontinuity before clustering. This refinement enhances the robustness and accuracy of discontinuities clustering computation, increases computational speed, and maintains applicability across various discontinuities datasets. Consequently, this provides a more precise and rapid method for the intelligent identification of discontinuities.

The intense geological structure and complex rock mass conditions in western China pose significant challenges to the construction of large underground cavern groups, including sudden changes in surrounding rock deformation and diverse failure modes. To address this issue, this study focuses on the underground cavern group of the Yingliangbao hydropower station in the Dadu River Basin, summarizing the typical stress-structure type failure modes of underground cavern groups under medium to high stress conditions, analyzing the impact of the September 5, 2022 Luding earthquake on the stability of the surrounding rock, and proposing engineering control strategies for stress-structure type rock mass failure. The study reveals that: 1) after excavation, 90% of the monitoring points showed surrounding rock deformation values less than 100 mm, with the deformation following a log-normal distribution; 2) under excavation unloading, the surrounding rock deformation curve of the Yingliangbao underground cavern generally exhibits a gentle step-like growth pattern, but rock mass deterioration can lead to a sudden increase in deformation, with a daily deformation exceeding 90 mm, highlighting the hard, brittle, and heterogeneous deformation characteristics of the Yingliangbao granite; 3) the overall anchorage load exhibits a normal distribution, with areas of higher anchorage load corresponding to areas of greater deformation; 4) the September 5 Luding earthquake had a relatively minor overall impact on the three major caverns, but may have adverse effects on the support structures near stress concentration zones or discontinuities; 5) the excavation of underground caverns faces challenges such as frequent shallow failures and high costs for addressing deep failures, with failure modes including stress-type, structure-type, and stress-structure type failures, dominated by stress-structure type failures. To address the surrounding rock failure issues at the Yingliangbao underground cavern group, this study proposes the “pressure maintenance-reinforcement” principle for underground cavern support, and verifies the effectiveness of “precision blasting + rapid shotcrete + timely pre-stressed anchors” in inhibiting shallow rock mass deterioration and “fine layering + high-tonnage pre-stressed anchors” in inhibiting mid-deep rock mass deterioration, providing a reference for the construction of large underground caverns in western China.

Drainage is one of the most cost-effective and important seepage control measures in high-dam engineering. The multiple levels of drainage tunnels and the upwards- and downwards-drilled drainage holes constitute the 3D cross-connected drain system, but accurately modeling the drains has been one of the difficulties in the seepage analysis in hydraulic engineering. Long-term studies have shown that drains function by presenting discharge boundaries, which can be characterized by water head, no-flux, unilateral or mixed water head-unilateral boundary condition. However, it may result in erroneous modeling of the drains and the seepage field when the drain boundary conditions are incorrectly prescribed, or there lacks reliable transition algorithm for drain boundary conditions. Based on a proposed 200-m roller compacted concrete gravity dam, the control mechanism of the 3D cross-connected drain system on the seepage field is summarized, the self-equilibrated relationship of flow rate characterized by the water head-unilateral boundary condition is clarified, and the automatic transition algorithm of the boundary conditions for downwards-drilled drainage holes is presented. The simulation results of the transient seepage flow in the dam foundation show that, the core of accurately modeling the 3D cross-connected drain system is to locate the downwards-drilled drainage holes that characterized by the water head-unilateral boundary condition. When these boreholes are erroneously prescribed with no-flux boundary condition (i.e., recognized as failed), the phreatic surface is overestimated by 1.7−10.6 m; when they are erroneously prescribed with water head boundary condition (i.e., overflow occurs through their upper ends), the phreatic surface is overestimated by up to 29.4−94.5 m. Different from previous studies, the boreholes still perform well in lowering the groundwater level and pore water pressure in the dam foundation by their own self-equilibrated relationship of flow rate, where the seeped water is collected and discharged to lower boreholes, even no overflow occurs. Besides, the optimization analysis of the drain spacing implies that a drain spacing of 3 m commonly used in engineering practices is suitable, but a larger spacing of drainage holes could be suggested for those drilled downwards from the longitudinal drainage tunnel at elevation 2 928 m on the right bank. The research results are of great significance for the design and seepage safety evaluation of seepage control system of high dams.

On the basis of classical peridynamics, the nonlocal force density is re-derived using deformation equivalence. Combined with the theory of nonlocal differential operators, this approach reduces the calculation error at the boundary. A stress-strain solution model is constructed to address the limitations of traditional theories in stress analysis. Meanwhile, the strain energy density stiffness reduction theory is introduced to establish the correlation between the mechanical parameters of the medium at the crack and the residual strain energy. The proposed method is used to simulate the stress distribution in layered rock mass with prefabricated interval fractures. The results are compared with previous findings to verify its effectiveness and applicability. Furthermore, the evolution process of strip interval fractures in the middle weak layer of complete layered rock mass is studied. The results show that the ratio of crack spacing to thickness significantly affects the mechanical state of the layered rock mass. As the ratio increases, the stress between existing cracks transitions from compressive to tensile stress. The equidistant fracture phenomenon in the weak layer includes processes such as microcrack propagation, the formation of interval fractures, and gradual crack saturation. Continuous loading causes damage between the weak layer and the base layer, as well as overall failure of the rock formation. This method effectively describes the interval fracture process of layered rock mass and demonstrates good application prospects.

The Martian soil, serving as the primary support medium for the landing of Mars rovers, is of paramount importance for the success of exploration missions owing to its unique engineering and geological properties. By focusing on the latest advancements in Mars in-situ exploration technology, this study summarizes the physical and mechanical properties of Martian soil in potential landing areas and delves into the potential, limitations, and specific applications of various methods in Martian soil research, including penetration testing, robotic arm sampling, drilling techniques, geophysical exploration, and space remote sensing technologies. Furthermore, the potential application of piezocone penetration test (CPTU) technology in future Martian soil exploration is prospected. Given CPTU's efficient capability in assessing soil mechanical properties in terrestrial engineering, it exhibits significant potential for Martian soil exploration. This advanced technology is anticipated to provide more precise and comprehensive data support for deep space exploration activities such as site selection for Mars landing missions, construction of scientific research stations, and resource extraction plans. However, given the marked differences between Mars and Earth in terms of material composition, structural characteristics, and environmental conditions, the adaptive development and modification of CPTU equipment represent crucial scientific and technical challenges. Moving forward, with the continual advancement of deep space exploration technology, extensive research in this field will undoubtedly lay a solid foundation for Mars exploration and even more ambitious missions beyond.