Acta Geotechnica最新文献

In soft soil formations, grouting or surcharge loading can easily induce surrounding soil displacement, which in turn imposes additional passive loads on pile foundations. Accurately determining the deformation response of piles is crucial for assessing their safety. This study proposes a method for calculating passive loads on piles based on soil displacement. The method considers the soil between the inclinometer and the pile as the research object and employs the hardening soil (HS) model to characterize stress–strain behavior. The lateral soil resistance is represented using a nonlinear p-y curve to capture the differences in resistance between soft clay and sand layers. The calculated results from the proposed method show a high degree of agreement with measured values in both trend and magnitude. Additionally, iterative updates of the soil modulus using the HS model yield more accurate results compared to using a constant modulus, demonstrating the effectiveness of the proposed calculation approach. These findings provide a practical tool for estimating pile deformation based on surrounding soil displacement and improving the deformation assessment of piles under complex ground conditions.

Large diameter steel pipe piles are widely used in the construction of offshore wind farms. Pile running may take place during the dynamic driving of pile due to its enormous weight. Pile running can cause unsafe construction or even grave losses of life and property, so it is of practical significance to investigate the pile running behavior for the construction of offshore wind farms. In this paper, model tests of dynamic driving of steel pipe piles into soft marine clay were carried out. The vertical displacement and axial strain of the model pile, the skin friction and normal soil pressure on the pile surface, and the pore water pressure around the pile were investigated, based on which the mechanism for pile running was ascertained. It was found that the skin friction and normal soil pressure on the pile surface normally increased accordantly with the driving depth, while the vertical displacement of the model pile by each single hammer blow decreased successively throughout the dynamic driving process. However, in the case of pile running, the vertical displacement by the hammer blow which triggered the pile running was greater than that by the former blow, accompanied by a decrease in the unit skin friction to the pile surface and a continuous increase in the pore water pressure in the soil surrounding the model pile.

The frequent occurrence of strong mining-induced earthquakes has seriously threatened the safe and efficient production of deep coal mines. Hard rock strata is one of the main factors inducing strong mining-induced earthquakes. Taking the mining under hard rock strata of Dongtan coal mine as a background, combining the microseismic monitoring and theoretical analysis methods, we propose the method of collaborative control of the far- and near-field hard rock strata by ground hydraulic fracturing and underground deep-hole blasting. We investigated the mechanism and control effect of weakening the far- and near-field hard rock strata, which is verified by field experiments. Results show that after field experiment, the far- and near-field rock strata have been effectively weakened or broken, resulting in the loss or partial loss of its bearing capacity, releasing the elastic energy accumulated in the rock strata. The percentage of strong mining-induced earthquakes reduces by 54.4%, and the average depth of the epicentre decreased from 187.5 to 151.9 m. The problem of frequent occurrence of strong mining-induced earthquakes has been effectively solved, which ensures the safe mining of the subsequent coal seams. The implementation of field experiment could reduce or eliminate the occurrence of hazardous mining-induced earthquakes with large energy, and the frequency of strong mining-induced earthquakes is significantly reduced. It provides a certain reference for solving the control of strong mining-induced earthquakes caused by similar hard rock strata fracture.

Landslides occurring on the banks of reservoirs pose significant threats to the safety of hydropower stations, nearby infrastructure, and human lives. It is challenging to accurately predict the displacement of landslides due to the complex geological conditions and the coupling effects of rainfall and reservoir level fluctuations. This study proposes a deep-learning-based model for spatiotemporal prediction of landslide displacement by introducing the spatiotemporal heterogeneity of landslide response to rainfall and reservoir level fluctuations. Utilizing InSAR time-series data and the maximum information coefficient, we reveal and quantify the spatiotemporally heterogeneous responses of the Cheyiping landslide to triggering factors. A data fusion unit is designed to integrate the response characteristics of the landslide into the spatiotemporal prediction framework. The spatiotemporal heterogeneity analysis indicates that the tension cracks caused by reservoir water level fluctuations are responsible for larger and faster displacements in the lower and middle parts of the landslide. We also observe a previously overlooked area with significant response and suggest increased attention should be given during the period of reservoir water level variations. Furthermore, the proposed model outperforms other models in predicting the entire displacement field of the landslide and remains robust under different geological conditions. This study elucidates the spatiotemporal patterns of landslide response, offering a predictive framework that contributes to the precise localization and prevention of landslide hazards.

The microstructure of unsaturated soils plays a vital role in their hydromechanical behaviour. The study investigates the changes in tensile strength with microstructure for a clayey soil upon drying. Five compaction water contents (12.5%, 14.5%, 16.5%, 18.5%, and 20.5%) defining different initial soil microstructures were considered. Tensile strength was directly measured at various degrees of drying, along with the determinations of water content, degree of saturation and suction. Microstructure characteristics at as-compacted and dried states were analysed by mercury intrusion porosimetry. The results indicate that soil specimens on the dry side and at the optimum water content exhibit a bimodal pore size distribution, characterized by macropore and micropore populations, while soil specimens on the wet side have a unimodal distribution with one micropore population. After drying, the frequency of micropores decreases, while the frequency of macropores remains unchanged (on the dry side and at the optimum) or slightly increases due to shrinkage cracking (on the wet side). Upon drying, tensile strength increases with decreasing water content or degree of saturation due to suction effects. Soil specimens with both micropores and macropores develop lower suction than those with only micropores and are prone to tensile failure at the macropores (between aggregates). Consequently, when subjected to the same degree of saturation or suction, wet-side specimens exhibit significantly higher tensile strength compared to dry-side specimens. A theoretical model accounting for the microstructural differences was developed to describe the tensile strength of unsaturated soil. This model was validated against experimental data.

Understanding and accurately identifying the morphological characteristics of granite residual soil (GRS) particles are crucial for conducting in-depth research on the simulation of soil structures. In this research, the GRS particle samples are directly prepared and subjected to computer tomography scanning to quantify and simulate their morphological characteristics. Additionally, the simulation based on the coupled computational fluid dynamics-discrete element method evaluates the influence of different mesh face counts on the morphological changes of particles during their descent in water. The findings of this study indicate that direct scanning of the GRS particle samples improves scanning efficiency and accurately captures the morphological characteristics. Moreover, three-dimensional analysis shows that the particles present a rough surface, predominantly characterized by prolate and compact shapes. In numerical simulations, decreasing the number of mesh faces on the surface of the particles has a certain impact on the parameters used to evaluate morphological characteristics. Nevertheless, the evaluation parameters based on the geometric positions of the starting and ending points reveal no significant changes. Furthermore, simulation results for particles falling in water simplified to 50 mesh faces retain properties closely aligned with those of the original mesh count. This investigation provides a technical foundation for implementing simplified particle models in numerical simulations, as well as enriching the understanding of the microstructure of GRS.

A new technique, steel pile-large geotextile cofferdam, is employed for the cofferdam on soft clay as a cost-effective and structurally stable solution for construction projects. This study delves into the failure mechanisms and stability quantification of steel pile-large geotextile cofferdam constructed on typical soft-over-stiff soil profiles through comprehensive numerical simulations. The simulations have been rigorously validated against existing data, demonstrating a high level of accuracy. A detailed parametric analysis was carried out to investigate the key factors affecting the cofferdam’s failure mechanism, including soil properties, steel pile dimensions, and geotextile bag dimensions, further quantifying the critical fill height and overall stability during both construction and operational phases under seepage load. The results indicate a significant positive influence of steel piles on cofferdam stability. A novel formula with a high degree of accuracy (R² = 0.85) is developed to predict the stability of cofferdam under seepage conditions, offering valuable insights for the design and construction of this innovative cofferdam technology.

A hypoplastic model is proposed to simulate the mechanical properties of hydrate-bearing sand during dissociation by incorporating relative breakage ratio, hydrate bonding force, and degradation solid hardness. The relative breakage ratio and an internal tensor are introduced to describe the effect of grain breakage and hydrate bonding force of hydrate-bearing sand. Moreover, the evolution of the solid hardness is used for the creep behavior of the hydrate-bearing sand. The validation of model performance is conducted by simulating different types of laboratory experiments, including triaxial compression and dissociation tests of hydrate-bearing sand.

The issue of suffusion caused by damage to underground pipelines is becoming increasingly severe. Simultaneously, the cyclic load near the damaged pipeline further exacerbates the degradation of the strength and resilient modulus of the surrounding soil. However, the cyclic degradation characteristics of soil subjected to suffusion under cyclic loading have not been well understood, especially at the micro-level. In this paper, the coupled computational fluid dynamics and discrete element method are used to conduct the suffusion test of gap-graded sand, and the cyclic degradation characteristics of the specimens before and after suffusion are investigated through cyclic triaxial test. The effects of hydraulic gradient, confining pressure and initial fine particle content on the cyclic degradation of eroded specimen are analyzed in detail. The macroscopic differences of cumulative strain and resilient modulus before and after suffusion caused by initial fine particle content are discussed. The mechanism of the cyclic degradation is revealed from a micro-perspective, including mechanical coordination number, cumulative contact contribution and strong contact force chain. The results indicate that suffusion significantly alters the microstructure of gap-graded sand, reducing its resilient modulus and exacerbating cyclic degradation. The loss of fine particles destabilizes the coarse-grained skeleton, leading to increased axial strain and changes in mechanical coordination numbers and contact force distributions. Moreover, higher initial fine particle content induces more pronounced microstructural changes before and after suffusion.

Particle crushing, occurring in crushable materials under high-stress conditions exceeding their crushing strength, leads to particle breakdown and reduction in peak shear strength. The presence of water further diminishes crushing strength. Additionally, particle crushing significantly alters the soil–water characteristic curve (SWCC). The combined effects of particle crushing and the degree of saturation changes induce excessive deformation and weaken the soil. While existing models can predict the behavior of unsaturated soil and particle crushing effects individually, a comprehensive model for unsaturated crushable soils is necessary. This study proposes a constitutive model for unsaturated crushable soils, integrating the effect of the degree of saturation on crushing strength by developing the crushing surface. It incorporates variations in the grading state index and the degree of saturation, affecting soil strength via state boundary surface movement. Validation is achieved through past experimental evidence. The model effectively captures key features of unsaturated crushable soils, including the reduction in crushing strength with increased degree of saturation, the evolution of SWCC due to particle crushing, and additional particle crushing during wetting. Furthermore, a parametric study offers insights into unsaturated crushable soil behavior, highlighting the combined effects of particle crushing and variations in the degree of saturation. When significant particle crushing occurs, increased volumetric compression due to particle crushing leads to a higher degree of saturation and further strength reduction, amplifying soil deformation. Understanding these interactions is crucial for predicting the behavior of unsaturated crushable soils, emphasizing the significance of this study.