This paper puts forward a novel approach called cement-modified soil (CMS) blocking cushion technology to reinforce the subgrade in saline soil region: the cushion layer of composite foundation and a roadbed partition layer are combined into one CMS layer. The effectiveness of the proposed approach was verified through outdoor experiments on the saline soil section (DK821+600-DK821+900) of the newly built Lanxin High-Speed Railway. The experimental results show that the CMS layer can effectively adjusts the pile-soil stress ratio of the composite foundation, thereby enhancing the bearing capacity of the composite foundation and reducing the total settlement of the subgrade; it is also verified that the CMS layer greatly suppresses the upward migration of capillary water and water vapor in the foundation soil, and curbs the migration of salt, preventing the secondary salinization of the railway subgrade. Overall, this research provides a simple and low-cost subgrade reinforcement technique for saline soil regions, shedding new light on the engineering application of the CMS.

To explore the staged catastrophic evolution mechanism and failure process of bedding rock landslides under construction disturbance and rainfall conditions, we selected water content, displacement, strain, and soil stress as the study objects and carried out a model test. Combining the test phenomena, the following conclusions are drawn: first, bedding rock landslides have experienced three different stages of initial, constant velocity, and accelerated deformation affected by construction and rainfall factors. Then, the mode of bedding rock landslides is both sliding and traction sliding compound sliding mode. Finally, in the initial and constant deformation stages, the stress and strain values in the soil both increase slightly. In the accelerated deformation stage, the horizontal and vertical deformation at the slope foot increases sharply. Meanwhile, the strain value increases greatly, the stress decreases, and the stress in the slope increases significantly. Therefore, stress, strain, and displacement can be used as early warning indicators for staged disasters of bedding rock landslides.

In order to further understand the instability mechanism and geohazard causation when the main sliding path of the slope body is parallel to the path of the bridge, the corresponding bridge-landslide parallel system is constructed for shaking table tests. This paper summarizes the combination forms of bridge-landslide model under different position and focused on the slope body located above the bridge deck. Firstly, based on the shaking table test results of El Centro (1940), the failure behavior of bridge-landslide parallel system was evaluated, and the changes of acceleration and deformation of bridge pile were subsequently analyzed. Then, the interaction bridge structure and sliding body were explained by the spectral features. The main conclusions are as follows. First, in the model test, the landslide belongs to the thrust-type landslide. Due to the barrier function of the bridge, the main failure site of landslide occurs in the middle and trailing edge of slope body. At the same time, the acceleration value of earthquake waves is 0.3 g, which is the key to this variation. Second, the acceleration response of the measuring points on the bridge pile and landslide increases with the increase of ground elevation. If the slope structure is damaged severely, the deformation response of weak interlayer is inconsistent with the surrounding soil structure. Third, with the increase of excitation power, the dominant frequency of bridge-landslide parallel system gradually transitions from low to high frequency rate, and the interaction of the parallel system weakens the influence of river direction on frequency. Finally, under the same working condition, the dynamic response of the measuring points has obvious regularity with the change of situation. But the response of the same points is not regular due to the different earthquake excitation intensity.

No abstract

No abstract