Shallow stability and parameter sensitivity analysis of soil slope with frame protection under rainfall seepage

Frame protection is a commonly used solution to maintain the shallow stability of soil slope under rainfall seepage. Currently, the frame structure's design is empirical, and its theoretical analysis method considering the influence of seepage is scarce. Based on the instability model of the infinite slope, the shallow stability calculation model of soil slope under the rectangular frame protection is established in this paper. The calculation results show that it is beneficial to maintain the shallow slope stability by reducing the skeleton spacing and increasing the cross-sectional size of the frame structure. Also, geometric parameters' sensitivity analysis of the frame structure is carried out based on the orthogonal experimental design methods. Therein, an optimal scheme evaluation function was constructed to balance the relationship between the safety factor and the construction material consumption. The calculation model and results included in this paper can guide the design of the rectangular frame protection to soil slope under rainfall seepage.

Simulation of Slope Failure Distributions Due to Heavy Rain on an Island Composed of Highly Weathered Granodiorite Based on the Simple Seepage Analysis

To fully and rapidly develop a real-time early warning judgment system for slope failure at the time of heavy rains including overseas, it is necessary to predict water movement in the soil at the time of rainfall. In addition, to apply the system to a place where insufficient geotechnical and geological data have been amassed, it is necessary to evaluate the risk of slope failure based on physical properties obtained from a simple soil test. Therefore, in this study, the authors set Gogoshima Island in Ehime Prefecture as a study site and evaluated the water movement over time in the soil during heavy rain using a simple prediction equation of rainfall seepage process. Soil properties were determined through simple in-situ and laboratory tests. As a result, it was found that the factor of safety for slope failure in the head and wall of a valley dissecting the hillside slope composed of granodiorite in which weathering has progressed can be planarly evaluated using the simple prediction equation.

Seismic Stability of Loess Tunnel with Rainfall Seepage

Rainfall seepage changes the mechanical properties of loess masses. Considering fluid-solid coupling, the calculation model of a loess tunnel is established according to the finite element method (FEM). Based on porous media seepage theory and rainfall infiltration depth theory and considering the infiltrated depth of the loess surface for different rainfall intensities over a certain period, the stability of a loess tunnel under different rainfall amounts and loess cover thicknesses is studied using the dynamic finite element static strength reduction method. The results show that under the same rainfall intensity, the safety factor increases with the depth of the tunnel; the safety factor of the loess tunnel with the same loess cover thickness decreases with increasing infiltration depth. The plastic strain is mainly distributed on both sides of the vault and the arch feet. The stability of the loess tunnel is directly related to the loess cover thickness and rainfall seepage.

Behavior analysis by model slope experiment of artificial rainfall

In this study, we performed a model slope experiment with rainfall seepage, and the results were compared and verified with the unsaturated slope stability analysis method. In the model slope experiment, we measured the changes in water content and matric suction due to rainfall seepage, and determined the time at which the slope failure occurred and the shape of the failure. In addition, we compared and verified the changes in the factor of safety and the shape of the failure surface, which was calculated from the unsaturated slope stability analysis with the model experiment. From the results of experiment and analysis, it is concluded that the unsaturated slope stability analysis can be used to accurately analyze and predict rainfall-induced slope failure. It is also concluded that in seepage analysis, setting the initial conditions and boundary conditions is very important. If engineers will use the measured porewater pressure or matric suction, the accuracy of analysis can be enhanced. The real-time monitoring system of porewater pressure or matric suction can be used as a warning of rainfall-induced slope failure.

Behavior analysis by model slope experiment of artificial rainfall

In this study, we performed a model slope experiment with rainfall seepage, and the results were compared and verified with the unsaturated slope stability analysis method. In the model slope experiment, we measured the changes in water content and matric suction due to rainfall seepage, and determined the time at which the slope failure occurred and the shape of the failure. In addition, we compared and verified the changes in the factor of safety and the shape of the failure surface, which was calculated from the unsaturated slope stability analysis with the model experiment. From the results of experiment and analysis, it is concluded that the unsaturated slope stability analysis can be used to accurately analyze and predict rainfall-induced slope failure. It is also concluded that in seepage analysis, setting the initial conditions and boundary conditions is very important. If engineers will use the measured pore water pressure or matric suction, the accuracy of analysis can be enhanced. The real-time monitoring system of pore water pressure or matric suction can be used as a warning of rainfall-induced slope failure.

Numerical Analysis of Geocell Protective Slope Stability

Geocell protective slope is a kind of important ecological protection form, which is widely used in the geotechnical engineering field. Based on the finite element software ABAQUS, and combining with protective slope body’s mechanics performance in shallow soil, the finite element model of geocell slope protection is established under the conditions of rainfall seepage, and then we simulate the shallow and the overall stability of slope in rainfall seepage cases. The results show that the safety factor of slope body increased by about 14% when using geocell slope protection and it reduces the displacement of slope surface effectively, it prolongs the destruction time of the slope under the condition of continuous reduction of soil shear strength, and it further helps reducing the collapse or part of slope sliding of slope disasters.

Monitoring Deterioration in a Catchment’s Sewerage System

Groundwater seepage through cracks in the sewerage pipeline is a major maintenance issue in most cities’ sewer networks. The more the sewer pipes crack – and the wider these cracks are – the worse the rainfall seepage problem becomes. The total volume of rainwater seepage into the sewer pipes for a catchment is correlated with deterioration and can therefore be used to estimate the rate of deterioration. This paper describes a monitoring system that can be used to identify significant trends in sewer deterioration. Effective monitoring by asset managers can highlight the need for early maintenance such as removing tree roots from pipe cracks and patching the cracks.