Soil-rock Mixture Research Articles

Shear failure analysis of slip zone soil with different coarse particle shapes: Visualized shear test and PIV technology

Coarse particle shape in slip zone soil influences the mesoscopic structure of the soil, which in turn affects soil shear strength and failure behavior. In order to investigate the effect of particle shape on the shear characteristics of coarse–fine-grained mixed slip zone soil, three types of coarse particles (spheroidal, rounded, and angular) were selected for mixing and matching, and a total of 10 sets of medium-scale shear tests were designed for this paper. To quantify the shear deformation and failure process of slip zone soils, particle image velocimetry (PIV) technology and the hanging hammer method were used to obtain mesoscopic data of the soil (displacement vector data of soil particles and elevation data of the shear failure surface), which were used to calculate shear band thickness, shear dilatation, and roughness coefficient of the shear failure surface. The results indicate that coarse particle shape can considerably affect the macroscopic mechanical properties (internal friction angle and shear strength) and mesoscopic deformation characteristics (shear band thickness, shear dilatation, and shear surface morphology) of soils. Angular coarse particles have higher interlocking strength than spheroidal and rounded coarse particles, allowing angular coarse-grained slip zone soils to develop large shear band thickness and rough shear failure surfaces. In addition, mesoscopic damage analysis suggests that the damage rate of slip zone soils decreases with increasing coarse particle shape complexity. These findings enhance comprehension of the failure characteristics of soil-rock mixture slopes and serve as a good reference for the stability analysis of similar slopes.

Cyclic shear behavior and BoBiLSTM-based model for soil-rock mixture-concrete interfaces

In order to study the impact of surface roughness on the cyclic shear characteristics of the Soil-Rock Mixture and concrete interface, a series of cyclic shear tests were conducted using a large indoor direct shear apparatus. The effects of three concrete surface roughness coefficients JRC (0.4, 9.5, 16.7), five rock content levels (0%, 25%, 50%, 75%, 100%), and three cyclic shear displacement amplitudes (1, 3, 6 mm) on interface cyclic shear stress and Soil-Rock Mixture shear deformation were analyzed. A Bidirectional Long Short-Term Memory (BoBiLSTM) model was proposed, utilizing Bayesian optimization and k-fold cross-validation for hyperparameter tuning to streamline the model parameter selection process and enhance the prediction accuracy of the stress-strain relationship under cyclic loading. The experimental results show that, under five rock content levels, as the concrete surface roughness coefficient and cyclic shear displacement amplitude increase, the interface average peak shear stress increases accordingly. The interface average peak shear stress of the sample with 75% rock content is the highest; in terms of vertical displacement, the sample with 50% rock content has the maximum displacement, while the sample with 25% rock content has the minimum. The two types of samples show different soil deformation patterns in the two shear directions during the cyclic shearing process; as the shear displacement amplitude increases from 1 mm to 3 mm and 6 mm, the greater the concrete surface roughness, the smaller the change in shear stiffness and damping ratio. Compared to traditional Long Short-Term Memory (LSTM) models, the BoBiLSTM model demonstrated improvements in the average metrics of R2, RMSE, and MAPE by 0.32%, 57.25%, and 72.32%, respectively.

Centrifuge model tests of h-type anti-slide pile reinforced slope under different rainfall duration

The h-type anti-slide pile (h-pile) plays a crucial role in mitigating soil-rock mixture slope (SRMS) instability. Despite its significance, the limited availability of research outcomes has constrained the practical application of h-piles for SRMS reinforcement. This study employs three centrifuge model tests to investigate the behavior and performance of h-pile-reinforced SRMS under rainfall conditions. We systematically describe the response of earth pressure on the pile side and behind the pile, bending moment along the pile, and pore water pressure at the slope toe and pile side. This elucidates the evolution of soil arching for h-piles under rainfall conditions. The results reveal that rainfall duration influences the distribution pattern of earth pressure on the pile side, while the distribution pattern of bending moment for the h-pile remains unaffected. Additionally, the soil arching pattern between piles demonstrates joint arching, involving the combined action of frictional arching and end-bearing arching. The evolution process of soil arching between piles under rainfall conditions gradually dissipates from bottom to top and from far to near.

Shear mechanical properties of the interface between soil-rock mixture and rough structural plane

Shear mechanical properties of the interface between soil-rock mixture and rough structural plane

Study on large deformation of soil–rock mixed slope based on GPU accelerated material point method

This study assesses the effect of stone content on the stability of soil–rock mixture slopes and the dynamics of ensuing large displacement landslides using a material point strength reduction method. This method evaluates structural stability by incrementally decreasing material strength parameters. The author created four distinct soil–rock mixture slope models with varying stone contents yet consistent stone size distributions through digital image processing. The initial conditions were established by linearly ramping up the gravity in fixed proportionate steps until the full value was attained. Stability was monitored until a sudden shift in displacement marked the onset of instability. Upon destabilization, the author employed the material point method to reconstruct the landslide dynamics. Due to the substantial computational requirements, the author developed a high-performance GPU-based framework for the material point method, prioritizing the parallelization of the MPM algorithm and the optimization of data structures and memory allocation to exploit GPU parallel processing capabilities. Our results demonstrate a clear positive correlation between stone content and slope stability; increasing stone content from 10 to 20% improved the safety factor from 1.9 to 2.4, and further increments to 30% and 40% ensured comprehensive stability. This study not only sheds light on slope stability and the mechanics of landslides but also underscores the effectiveness of GPU-accelerated methods in handling complex geotechnical simulations.

Effect of bench size on the strength and deformation properties of interphase between benched bedrock and soil-rock mixtures

Effect of bench size on the strength and deformation properties of interphase between benched bedrock and soil-rock mixtures

Study on large scale direct shear test on soil-rock mixture with multiple grain grades in high fill slope engineering

Soil-rock mixtures are multiphase natural geological materials composed of mineral particles of multiple grain sizes, and have significant natural characteristics of multiscale material groups. In order to investigate the shear strength characteristics and deformation failure characteristics of soil-rock mixtures with multiple grain sizes under in-situ conditions in fill engineering, samples of soil-rock mixtures with multiple grain sizes under in-situ conditions were prepared, and large-scale in-situ direct shear tests were conducted under natural and water-soaked conditions. The test results showed that the shear strength of soil-rock mixtures is relatively high, and after saturated by water immersion, its shear strength decreases significantly, mainly manifested in the decrease of internal friction angle while the cohesion remains basically unchanged. The cohesion of soil-rock mixtures with multiple grain sizes is mainly provided by the shear-breaking cohesion of coarse particles such as gravel in the soil-rock mixture, and its degree of exertion is controlled by the grading characteristics and particle morphology of the soil-rock mixture and affected by constraints. The reason for the significant decrease in shear strength of soil-rock mixtures with multiple grain sizes after water-soaked saturation can be explained as follows: the clay film covering the surface of coarse particles becomes soft after water immersion, resulting in a significant decrease in the sliding friction resistance between coarse particles and the clay film, as well as the occlusion friction resistance generated by the rotation transfer between coarse particles through the clay film interface.

A thermodynamically consistent constitutive model for soil-rock mixtures: A focus on initial fine content and particle crushing

The mechanical response of a soil-rock mixture (SRM) is crucial in railway, airport, highway, and dam engineering. However, existing studies of the SRM often fail to account for the effect of its components (e.g., fine content) and particle crushing. This paper aims to develop a thermodynamically consistent constitutive model that can simulate the mechanical behaviour of the SRM. Based on the initial fine content (FC0), we quantify the components of the SRM and explore the effect of FC0 on the mixture’s mechanical responses. The FC0-related energy dissipation due to particle crushing is highlighted in the proposed model. The model is validated by three experimental cases with different FC0, which shows that our model satisfactorily captures the complex SRM behaviours with only eight physically identifiable parameters. The model also confirms the experimental phenomenon that the FC0 has a substantial effect on both the shear strength and energy dissipative ratio of soil-rock mixtures.

A Study on Seismic Dynamic Response of Pile-Supported Tunnels in Deep Backfill Area of Soil–Rock Mixture Based on a Model Test

Aiming to address the problem of construction and environmental risks in tunnel construction through the soil–rock mixture backfill area, this paper carried out a seismic dynamic response model test of a pile-supported tunnel based on practical projects. Firstly, the stress–strain curves and failure characteristics of the soil–rock mixture in the study area were obtained through triaxial tests, and based on this, similar materials for the model test were developed. Then, a vibration table model test was devised to investigate the seismic dynamic response of the pile–tunnel structure. The findings revealed the following: when subjected to seismic waves, the soil–rock mixture stratum displayed a “skin effect” in its acceleration response, indicating that closer proximity to the surface led to heightened horizontal acceleration responses; the horizontal peak acceleration of the grouting mixture stratum in the vertical direction exhibited a “Zigzag” pattern; the peak values of strain response and bending moment in the tunnel lining cross-section exhibited an “X” shape and inverted “V” shape, respectively. The bending moment at the pile crown increased alongside the peak value of the input seismic wave acceleration. The maximum surface settlement in the model ranged from 0.5 to 1 cm, with the tunnel–pile structure effectively mitigating surface settlement.

Failure analysis of soil-rock mixture slopes using coupled MPM-DEM method

A 3-D concurrent MPM-DEM (material point method - discrete element method) scheme is proposed and developed in this paper to simulate soil-rock mixture slopes. The MPM and DEM are treated as two individual parts linked by the coupled contact force. Compared with MPM, the proposed MPM-DEM scheme provides a more realistic contact detection. Compared with DEM, the scheme can model such cases more efficiently and conveniently. Based on the characteristics of the soil-rock mixture, a CPU-GPU concurrent solving scheme is introduced, which can improve the efficiency and make full use of the computational resources of both GPU and CPU. The accuracy of the MPM-DEM scheme is validated by three benchmark examples, i.e., a block sliding on an inclined plane, granular flow impacting blocks, and collapse of hybrid granular columns. The failure mode and sliding distance of soil-rock mixture slopes are analyzed using the proposed MPM-DEM scheme and compared to a pure MPM. Influencing factors such as soil-rock friction and cohesion, rock content, and rock size are studied. The results indicate that this scheme can well capture the soil-rock interface and deal with complex interactions between soil and rock.

Study on meso‑mechanical properties and failure mechanism of soil-rock mixture based on SPH model

This study adopts the Smoothed Particle Hydrodynamics (SPH) technique to accurately and efficiently replicate and forecast the mesoscopic behavior of soil-rock mixtures (SRM). It introduces a novel approach for generating rock blocks within the SRM, utilizing a method that randomly selects angles and lengths. In addition, this research proposes a method for discretizing any shaped region into free particles with specific material attributes, named the regional medium particle discretization method. It incorporates the Drucker-Prager constitutive model to develop the SPH numerical model for SRM. Furthermore, it examines the effects of different rock sizes and rock contents on the SRM's failure characteristics and mechanical properties. The findings revealed that, for identical rock contents, smaller rock samples exhibit a more dispersed failure surface with numerous secondary shear bands, whereas larger rock samples display a smoother and more concentrated failure surface. As the rock content decreases, shear bands typically form in the sample's center and are relatively straight. However, as the rock content increases, the shear bands' configuration becomes more intricate, often featuring multiple shear bands. This method offers a fresh perspective for exploring the mechanical properties of heterogeneous materials.

Morphological characteristics of hysteretic curves of soil-rock mixture under stepped axial cyclic loading

Morphological characteristics of hysteretic curves of soil-rock mixture under stepped axial cyclic loading

Study on Characteristics of Hydro-Thermal Transfer andFreezing-Thawing of Soil-Rock Mixtures

Study on Characteristics of Hydro-Thermal Transfer andFreezing-Thawing of Soil-Rock Mixtures

Research on the Road Performance of Carbonaceous Mudstone Soil-Rock Mixtures under Multifactor Influence

To investigate the effects of compaction (K), rock content (RC), and wet-dry cycle (WD) on the road performance of carbonaceous mudstone soil-rock mixtures (CMSRM), orthogonal tests were designed to measure the unconfined compressive strength (UCS) and California bearing ratio (CBR). The correlation degree of K, RC, and WD with the UCS and CBR of CMSRM was investigated using orthogonal theory and grey correlation theory. Based on multivariate nonlinear regression analysis, mathematical models of the road performance of CMSRM were built. The results show that the UCS and CBR of CMSRM were positively correlated with K and negatively correlated with the WD. With increasing RC, UCS increased at first and then decreased, while CBR increased continuously. The failure modes of CMSRM change from tensile failure to shear failure as the K increases under uniaxial compression. The RC and WD affect the structural integrity of the failed samples. Combining the results of range analysis, variance analysis, and grey relational analysis, the most significant influence on the UCS is K, and the most significant influence on the CBR is RC. It is recommended to select 94%–96% for K and 40%–60% for RC in engineering.

Fractal Analysis on the Crushing Characteristics of Soil-Soft Rock Mixtures under Compaction

Soil-rock mixtures (SRM) are extensively utilized as filling materials in engineering slopes and roadbeds. A comprehensive understanding of the crushing characteristics of SRM during compaction is essential for precisely controlling its mechanical properties, particularly when dealing with SRM comprising soft rock blocks. This study conducted heavy compaction and screening tests to investigate the crushing and compaction behaviors of soil-soft rock mixture (SSRM) with varying coarse particle content (P5 content), the primary focus was primarily on analyzing the double fractal characteristics of coarse and fine particles. The research findings are as follows: with the increase of P5 content, the maximum dry density of SSRM initially rises and then declines, reaching its peak when P5 content is 70%. Soft rock blocks in SSRM exhibit extreme fragility during compaction, the crushing index of coarse particles exhibits a linear increase with the rise in P5 content, whereas the crushing index of fine particles displays a “double peak” characteristic. After compaction, a linear positive correlation is observed between the fractal dimension and the crushing index of coarse and fine particles. With the increase in P5 content, the slope of the relationship curve between the fractal dimension and the crushing index of coarse particles remains relatively constant, while the intercept gradually decreases. Moreover, the fractal dimension of fine particles effectively reflects the compaction characteristics of SSRM, and the relationship between the fractal dimension of fine particles and dry density aligns with the compaction curve of SSRM.

The Parameters Calibration of Additive Mass Method and Its Application in Compaction Density Measurement of Soil Rock Mixtures

The additive mass method (AMM) is applied to test the compaction density of soil–rock mixtures (S–RMs) due to its high efficiency, nondestructiveness and accuracy. However, there is no systematic research on influence factor of AMM. In this study, AMM test parameters were systematically calibrated first, and a calculation model for the compaction density of S–RM was established in the test area. After that, the AMM was applied in the on‐site detection of the compaction density of an earth–rockfill dam. After calibration test, the main geophone frequency was 40 Hz, the drop distance and offset distance were 20 and 70 cm, respectively, and set the ∆m of five levels as 38, 88, 138, 213, and 288 kg. The detection error of K–K/ρ model had a better precision than the ω−2−ω−2/ρ model through on‐site testing and verification. A new calculation model with lower accuracy based on vibration stiffness–vibration stiffness/density K−K/ρ) model was proposed according to the test error distribution. It was found that the test error of the K−K/ρ model was reduced to 0.9%. The results demonstrated that the AMM could accurately detect the compaction density of S–RM after the test parameters were reasonably determined.

Wetting deformation characteristics of soil–rock mixture considering the water-disintegration of red stratum soft rock

Wetting deformation characteristics of soil–rock mixture considering the water-disintegration of red stratum soft rock

Study of shear properties and shear model of soil-rock mixture

This study investigates the shear characteristics of soil-rock mixtures, a critical factor influencing slope stability in engineering construction. Soil-rock mixtures, often exhibit poor integrity and can easily soften in water due to geological influences. The YT1200 direct shear drawing friction system was employed to conduct shear tests, analyzing the effect of varying water content and fine particle mass fraction under different normal stresses. Utilizing fractional derivatives, we formulated a fractional derivative shear model. Test results illustrated a softening phenomenon post achieving peak shear stress in the soil-rock mixture. It was found that peak shear stress is directly proportional to the normal stress, and inversely proportional to both water content and fine particle mass fraction. Additionally, the cohesion and internal friction angle decrease according to a power function with increasing water content, and non-linearly decrease with the rise of fine particle mass fraction. The proposed shear model aptly simulates the entire shear failure process of the soil-rock mixture, effectively analyzing the influence of key factors on shear characteristics. These findings contribute to the strength prediction and numerical simulation of soil-rock mixtures, thereby aiding in the design of reinforcement schemes and slope stability analysis.

Study on strength damage model considering resistivity and failure characteristics of the frozen soil–rock mixture under different loading rates

The strength damage and deformation failure of frozen soil–rock mixture (FSRM) often restrict the safety of the major engineering construction in cold areas or the spatial development of urban underground water-rich rock and soil masses. To investigate the uniaxial strength damage evolution and failure characteristics of FSRM under different loading rates (0.3, 0.6, 3, 6, 30, and 60 mm·min−1) in the quasi-static range, resistivity monitoring and image recognition technology were used to study the time-stress-volumetric strain-resistivity changes. The results indicate that the peak stress, peak strain, initial yield modulus, and tangential modulus of FSRM increase rapidly before increasing slowly as the loading rate increases, and there are critical loading rates and post-peak failure phenomenon. Three distinct types of failure modes, bulge failure, oblique shear failure, and fragmentation failure were observed at low (0.3–0.6 mm·min−1), medium (3–6 mm·min−1), and high loading rates (30–60 mm·min−1), respectively. The macroscopic failure of the FSRM at different loading rates arises from a combination of strain rate hardening of the strength and damage softening of the structure. To predict the stress-strain characteristics at various loading rates, a damage prediction model with a damage variable correction factor considering residual strength was employed based on the improved Duncan–Chang model and damage theory of electrical resistivity, and the predicted results were in good agreement with the experimental data.

Shear Properties and Pore Characteristics of Soil-Rock Mixtures Under Dry-Wet Cycling

The mechanical properties of soil-rock mixture (S-RM) can deform significantly under the influence of dry-wet cycles, affecting the safety of high-fill projects. A drying device was developed to perform direct shear tests on S-RM. Large-scale direct shear tests were carried out under the action of dry-wet cycling to study the effect of dry-wet cycling on the mechanical properties of S-RM. The open-source ImageJ software was used to identify the number and area of pores in the binary image, and the pore characteristics of S-RM under dry-wet cycles were analyzed. The results show that the section of post-peak in the shear stress-strain curve softens under the natural state (no dry-wet cycles), but it plasticizes under the application of the dry-wet cycles. The cohesion of S-RM particles is affected by the dry-wet cycling. It decreases significantly under the first dry-wet cycle and then decreases gradually for each successive cycle, after which it stabilizes during the fifth dry-wet cycle. The internal friction angle is not affected to a large degree. The effect of a dry-wet cycle on pores with different areas is significantly different. The pores with initial sizes of 0.5–10 mm2 decrease, while pores with other initial sizes are hardly affected by the dry-wet cycling. This paper quantitatively analyzed the relationship between the surface two-dimensional porosity and S-RM's cohesion and peak strain.