Abstract
In Southwestern China, there exists deep river valleys and abundant rainfall, which leads to a large number of reverse-dip rock slopes. In order to investigate the evolution characteristics of toppling deformation of reverse-dip slope under the influence of rainfall, and a typical reverse-dip slope was taken as an engineering case. Firstly, the temporal and spatial evolution nephogram of toppling displacement under different rainfall was obtained based on the discrete surface displacement monitoring data of bank slope. Then, taking bank slope, gully buffer zone, and development degree of bank slope as development characteristics based on geological field survey, afterward, the evolution characteristics in different strong deformation zones were analyzed by superimposing the development characteristic partition and the spatial and temporal displacement nephogram. The results showed that the horizontal displacement mainly occurred on the right front and middle rear of the bank slope while large vertical displacement occurred on the middle of the bank slope under the influence of rainfall. As the rainfall increased to the maximum, the toppling deformation reached the peak, and vertical displacement was more sensitive to the rainfall than horizontal displacement. After the superposition, the largest strong deformation zone was located in the middle and rear part of the bank slope, which is characterized by medium and high slope and mature stage and 50 m gully buffer zone. This paper explores the deformation and failure process of reverse-dip rock slope considering the change of rainfall through real displacement monitoring data and focuses on the real deformation evolution law of each characteristic zone combined with different development characteristics partition.
Highlights
Toppling deformation is a kind of phenomenon that the reverse-dip rock mass bends and breaks to the free face under the coupling function of gravity and in situ stress
Longitudinal Displacement. e monitoring results of the longitudinal section of the bank slope midline 2-2′ showed that the horizontal displacement (Figure 3(a)) gradually developed from the front to the rear edge of the bank slope and increased with the amount of rainfall; the vertical displacement (Figure 3(b)) developed from the front to the back of the bank slope with larger displacement in the middle and first increased and decreases; when the rainfall reached the peak, the trailing edge went upward, which was mainly manifested as the bending and toppling deformation of the reverse-dip rock slope
It can be concluded that the right side of the bank slope is dominated by horizontal displacement and the middle part is dominated by vertical displacement
Summary
Toppling deformation is a kind of phenomenon that the reverse-dip rock mass bends and breaks to the free face under the coupling function of gravity and in situ stress. Some researchers conduct the centrifugal model test to study the bending deformation and analyze the influence of rock layer inclination, tensile strength, internal friction angle, and joint spacing on slope toppling deformation and failure [18, 29]. Many scholars generally studied the toppling deformation characteristics of the slopes by establishing engineering geological models but giving up mechanical models by which satisfying results can be yielded based on proper constitutive relations or limit equilibrium theory; in addition, it should be noticed that the mechanical model is difficult to be applied to bank defamation cases because of lacking monitoring data, and the influencing mechanism of external factors such as rainfall and reservoir water cannot be well solved by mechanical models. To monitor the displacement of the Xiaodongcao bank slope, 22 surface displacement monitoring points were evenly distributed throughout the study area; among them, 17 monitoring points were arranged on the bank slope and 5 were arranged outside the bank slope. e monitoring period is from January to December 2017, and the research area can be divided into five cross sections and three longitudinal sections according to the layout of the monitoring system (Figure 2)
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