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In recent years, landslides induced by underground mining have attracted much attention as they cause great harm and early warning signals are difficult to detect. The key work of the early warning of a mining landslide is to clarify its initiation mechanism and evolution process. Due to the complexity of the deformation and failure of the goaf overburden and the lack of monitoring of the slope evolution process, the deformation and failure law and evolution characteristics of mining landslides have always been difficult to analyze. In this paper, a typical mining landslide, the Madaling landslide, was selected as the study object. The soft-hard interlayer structure of the slope was generalized and explored by centrifuge model tests and a 3D discrete element model. The results showed that the evolution of the Madaling landslide are divided into four stages: (I) the bending and collapse of the goaf overburden, the slope settlement and the formation of tensile cracks at the trailing edge; (II) the upwards extension of the subsidence cracks of the rock mass; (III) the occurrence of shear cracks in the rock mass, with gradual slope deformation as a whole; and (IV) the connection of shear cracks, with the initiation of landslides. The long-term gravity creep of soft rock and the extension of trailing edge tensile cracks cause the internal rock mass of the slope to become the key block controlling slope stability. The slope surface displacement (S)-time (t) curve of mining landslides is divided into the settlement stage, rock mass crack development stage and landslide evolution stage. The formation time of shear cracks in the rock mass crack development stage is a sign of the transformation of subsidence into a landslide. The relationship between the horizontal displacement and the depth of the rock mass effectively reflects the development stage of shear cracks. The horizontal and vertical displacement of the deep rock mass can serve as the early warning criterion for mining landslides.

Toppling deformation is a unique geological form in rock slopes, with complex geomechanical behavior and engineering properties. A large number of deep-seated toppling deformation slopes are developed in the deep incised valleys in Southwest China. By summarizing these typical slope cases, it is found that there are certain differences in the rock mass strength, stratigraphic lithology, thickness and dip angle of rock strata. However, the slope angle of these slopes is relatively close. This finding shows that the free surface conditions are the key factors for the formation of deep-seated toppling deformation slopes. To further verify this preliminary conclusion, taking the toppling deformation body before the dam of the Lancang River Gushui hydropower station in Southwest China as a research object, this paper analyzes the basic characteristics of deep-seated toppling deformation of rock slopes. By analyzing the formation conditions, combined with the indoor centrifuge model test, the evolution process of the deep-seated toppling deformation of the anti-dip rock slope under hydropower engineering excavation conditions was simulated. The influence law of varied the free-face conditions on the deep-seated toppling deformation of slope was revealed. The results demonstrate that the free-face conditions of the slope have a significant impact on the deep-seated toppling deformation. The study area was subject to the continuous and rapid downcutting of the Lancang River, which led to the formation of the free face on both banks of the rock mass and further triggered the deep-seated toppling deformation of the slope under the condition of gravity. According to the three excavation tests of centrifuge model, it can be found that the catastrophic process of deep-seated toppling and deformation of the anti-dip rock slope can be summarized as follows: rock strata are toppling and bending—cracks appear in the rock mass—cracks are connected to form bending zones—multi-level bending zones are formed—the rock body is sheared and destabilized along a certain level of bending zones. Centrifuge model test has good applicability for the study of the deformation evolution process of rock slope.

The Jiangdingya (JDY) ancient landslide is a large-scale landslide located in the Bailongjiang River fault zone, Zhouqu County, Gansu Province. Affected by fault activities, rainfall, river erosion, and human engineering activities, the JDY landslide has been repeatedly reactivated and blocked the Bailongjiang River, causing great disasters. To study the reactivation mechanism of the JDY ancient landslide, based on field geological survey, the centrifuge simulation tests of the landslide body under 10%, 15%, and 20% water content conditions are carried out. The tests show that when the water content is 10%, only a few cracks are generated in the middle and rear parts of the slope by the end of the test, but the landslide is still in a stable state overall. However, when the water content is 15% and 20%, the landslide body is damaged, and the centrifugal acceleration required for slope instability is 100 g and 50 g, respectively. The test analysis shows that the JDY ancient landslide demonstrates composite retrogressive sliding. The deformation starts from the middle and rear parts of the slope, and cracks are generated. Then, the cracks gradually expand to the front edge. Under the river erosion influence of the slope toe, the cracks finally penetrate and cause landslide damage. The deformation process of the landslide body is mainly divided into four stages: ① consolidation; ② deformation initiation (crack formation stage); ③ deformation acceleration (crack acceleration development stage); and ④ instability. The centrifugal simulation tests suggest that the factors for JDY ancient landslide reactivation are mainly affected by rainfall and pore water pressure, as well as the coupling of sliding caused by the erosion of the river front with the movement of the middle and rear parts of the landslide caused by rainfall. At present, the JDY ancient landslide is still in a state of creeping deformation. It is necessary to pay close attention to the development of the cracks at the rear edge of the landslide and strengthen the prevention measures for landslide deformation instability and river blocking disasters.

The rigid pile composite foundation is widely used in highway projects in soft soil area as it can effectively increase the bearing capacity and stability of the foundation. While the research on the behavior and failure mode of rigid pile composite foundation under embankment is not enough, instability failure of rigid pile composite foundation often occurs in practical projects. This paper presents a centrifuge model test to investigate the load transfer mechanism, settlement characteristic and failure mode of rigid pile composite foundation under embankment. The test results show that: the soil displacement of different region in rigid pile composite foundation was different, obvious vertical displacement occurred in the soil under the center of embankment and the horizontal displacement was very small in this region; both vertical and horizontal displacement occurred in the soil under the shoulder of embankment; and obvious horizontal displacement occurred in the soil under the slope toe of embankment; moreover, ground heave also occurred near the slope toe of embankment. The soil displacement in rigid pile composite foundation had a large influence on the stress characteristic and failure mode of rigid piles, the compressive failure and bending failure would probably occur for the piles under the center and shoulder of the embankment, respectively, and the tension-bending failure would probably occur for the piles under the slope toe of embankment. The different failure modes of piles at different regions should be considered in the design of rigid pile composite foundation under embankment. The test results can be used to improve the design method for rigid pile composite foundation under embankment in practical projects.

Concrete columns are used to support embankments built on soft soils. Use of three groups of centrifuge model tests, this study exhibited the global performance of embankments supported by plain concrete columns and reinforced concrete columns. The objective of the centrifuge tests was to reveal the failure mechanism and the contribution of the reinforced concrete columns to embankment stability. In comparison with plain concrete columns, use of reinforced concrete columns alleviated the release and transfer of stress in the ruptured concrete matrix, thereby avoiding continuous failure, which improved the overall stability of the embankment. Based on parametric analysis, Pareto multi-objective optimization method was proposed to determine the optimal column configuration design. The optimization results showed that placing reinforced concrete columns from the toe to the shoulder, combined with the installation of plain concrete columns near the embankment’s centerline, not only satisfies the stability requirement of the embankment, but also minimizes construction costs and resource usage. Reinforced concrete columns which positioned of Rows 1–4 was suggested in this study.

Loess area is the region that geohazards happened most frequently, accounting for 1/3 of the geohazards in China. Cutting slope has become the most prominent products in human engineering activities and slope failure induced by rainfall has become the main form in recent years. Well-instrumented centrifuge model tests have been introduced to investigate the failure process and failure pattern, including pore water pressure, progressive deformation-failure process and characteristic of the high cutting slope by rainfall. The results show that rainfall induced loess slope failure is characterized by shallow slide to flow and two deeper creepage sliding-tension surfaces. All the sliding faces are characterized by planar surfaces parallel to slope surface. The planar sliding surface differs a lot to the circular sliding surface in the gravitational soil landslide. The accumulative deformation especially the abrupt displacement before failure induced the excess pore water pressure, after which flow failure with high-speed happened. The pore-water transducers on both sides of the shallow sliding surface have distinct response to slope deformation. The quantitative monitoring data indicates that the liquefaction is not the reason but the result of the deformation accumulation and big transient def o rmation.

Earthquake ground motion records often show that soil sites typically exhibit nonlinear amplification characteristics during strong seismic motions. The surface ground motion amplification effects are typically affected by site conditions and topographic features; however, the ground motion and site response of sea-based soil sites have not been extensively investigated due in part to the scarcity of available strong seismic records from few geotechnical observation arrays in the sea areas. In the present study physical centrifuge models are explored to simulate the ground motion response of land-based and sea-based soil sites and site response analysis is conducted to assess the free-field response of both deposits to earthquake motion. Both sites exhibit multiple modes of vibration; the first-order mode dominates in both the land-based and the sea-based soil sites with strongest amplification effect. The second-order mode occurs in both sites and the amplification effect is far more modest than the first-order mode. The amplification effects in the sea-based site are somewhat weaker than those in the land-based site. The third-order mode is found only in the response of sea-based site and the distribution of the amplification factor across the depth appears more complex without a clear pattern than in the lower order modes.

Toppling failure is one of the primary instability modes of layered anti-dip rock slopes. The presence of geological structures, such as synclines, can further complicate the instability modes of these slopes. To investigate the influence of synclinal structures on the deformation and failure of soft-hard interbedded anti-dip rock slopes, similar materials (artificial rock slabs and synclinal structures) were fabricated from quartz sand, cement, barite powder, gypsum, and water. The mechanical properties of these similar materials were measured, followed by large-scale centrifuge model tests and numerical simulations. The experimental results indicated that the slope model experienced toppling deformation and failure at the crest, whereas the synclinal structure underwent compressive deformation and slight rotation, with no significant deformation observed at the toe. Numerous bending and tensile fractures formed within the slope, resulting in a continuous bending tensile failure surface. The vertical displacement curves, corresponding to changes in the centrifugal acceleration, could be divided into six stages. The cumulative vertical displacements at the monitoring points S1 (crest), S2 (midslope), and S3 (toe) were 81.1 mm, 10 mm, and 8.3 mm, respectively. The simulation results closely matched the experimental observations, showing that the deformation and failure of the slope model could be divided into three stages: fissure compaction, toppling deformation, and instability failure. The soft-hard interbedded strata caused non-coordinated deformation within the slope, with the compressive deformation of the synclinal structure acting as a buffer, reducing the damage of the upper rock mass to the slope toe and leading to a top-down, deep-seated, non-coordinated toppling failure of the slope.

In this study, centrifuge model tests were carried out to investigate the lateral response of single pile in coral sand foundation. The load–displacement relationships, pile deflections, bending moments, the changes in horizontal soil pressure, the predicted particle crushing behaviors, and p-y curves were compared and discussed in detail to study the influence of pile diameter and vertical load. Test results show that increasing diameter is the most direct and effective method to improve the horizontal bearing capacity of pile; the presence of vertical load would lead to an increase of bending moment and lateral displacement of the pile due to P -Δ effect and an improvement in soil resistance due to the vertical compression effect; the influence of particle breakage behavior of coral sand was not significant. In addition, the applicability of the existing p-y models for the coral sand foundation was systematically evaluated. According to the comprehensive analysis of the stress state of sand around pile, the evolution of soil resistance with depth was determined, which can be simulated by a power function. Based on the centrifuge test results, a modified p-y model for coral sand was proposed, and its rationality and applicability in predicting pile–soil responses were validated systematically.

An unconnected pile foundation allows separation between the lower pile and the pile cap, and it has been proposed as an effective foundation type for reducing the seismic load during strong earthquakes. However, previous quantitative evaluations of unconnected piles with various foundation types and earthquake intensities are inadequate. In this study, the influence of base shaking level and the material of the interposed layer between pile and pile cap on the seismic behaviour of unconnected piles were evaluated using a centrifuge model test to reproduce the field stress conditions. A dynamic centrifuge model test was completed on an experimental model consisting of dry sandy soil, a foundation and a single degree-of-freedom structure. The acceleration of the structure and the settlement of the foundation system were measured during base shaking. For the unconnected pile system, the structural seismic load reduction effect due to rocking behaviour was confirmed, and the unconnected pile foundation with the interposed layer with large stiffness had less vertical settlement than the conventional shallow foundation. Finally, the rotational stiffness and damping ratio for the foundation system used in the centrifuge model tests were derived and discussed.