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Building the forest fire prevention road in mountainous areas is an effective means to prevent forest fire from spreading wantonly. Nevertheless, adverse influences are that the construction of these roads has destroyed the inherent stability of the original slope, resulting a large number of unstable slopes appear in the catchment, which could trigger human-generated landslides and debris flows. On June 17, 2022, a landslide-generated debris flow occurred in the Longjiagou catchment, Mianning County, Sichuan Province. The initial landslide that induced this debris flow is one of the unstable slopes on the forest fire prevention road. After the debris flow event, we conducted a detailed on-site investigation of the Longjiagou catchment. Many unstable slopes have been found near the road, and the width of cracks at the rear edge of some unstable slopes has exceeded 10 cm. This is already a very dangerous precursor signal for landslides or debris flow. And several soil samples were collected in the catchment to test the hydraulic conductivity and particle size distribution of soil at different locations. Combined with multi-source data, we comprehensively analyzed the cause and mechanism of the disaster. The dynamic process modeling framework of earth-surfaced flow—Massflow—was adopted to simulate the dynamic process of the debris flow to support the quantitative analysis of this disaster. The results show that the simulation results are basically consistent with the actual situation. Based on field reconnaissance and numerical simulation, the mechanism of debris flow is comprehensively analyzed, which can provide important insights and guidance for the prediction and prevention of such debris flow disasters. [ABSTRACT FROM AUTHOR]

A consequent slope, comprising weak planes in the same dip direction along the slope face, is the most dangerous type of rock slope. Herein, a consequent landslide that occurred on May 5, 2018, in Mabian County, Southwest China, was investigated. This landslide occurred in a region with a complex geological background and strong geological activity and is considered a typical consequent landslide. Field investigations and aerial photographic interpretations revealed that the rock mass slipped along the contact surface of the strongly and moderately weathered rock mass, triggered by continuous rainfall. A depth-integrated continuum method was used to study the dynamic process of the landslide. The applicability of the depth-integrated method was verified by comparing the moving boundary of the landslide extracted from a video with the simulation results. The results show that the velocity of the landslide first increased and then decreased from the top to the bottom of the landslide and reached a maximum of 21 m/s in the middle of the landslide. Based on this method, we predicted the potential danger zones and velocity distribution of unstable masses next to the Mabian landslide. On comparing the calculated results of a depth-integrated continuum method with the Scheidegger method, in the case of the Mabian landslide, a reduction factor λ was added to the Scheidegger formula to achieve a modified formula that determines the velocity of such consequent landslides relatively accurately. This work could provide reference for the study of landslide velocity and disaster prevention. [ABSTRACT FROM AUTHOR]

Construction solid waste (CSW) landfill landslides, such as the Guangming New District landslide, which occurred in Shenzhen (hereafter the Shenzhen landslide), occur when the material is loose and saturated. They usually exhibit characteristics such as abrupt failure and whole collapse. During the propagation of landslides, dilatation behavior plays an important role in causing liquefaction, resulting in high velocity and exceptionally long run-out dynamics. We propose a dynamic model for describing fluidized CSW landslides by integrating the dilatancy model into smoothed particle hydrodynamics (SPH). The dilatancy model implies that the occurrence of dilation or the contraction of the granular-fluid mixture depends on the initial solid volume fraction. The dynamic model is used to simulate the Shenzhen landslide, and special attention is paid to the effects of different initial solid volumes on the mobility of the CSW landslide. The results show that when the solid volume fraction is higher than the critical value, contraction occurs, the excess pore water pressure increases, and the basal friction resistance is reduced. CSW landslide mobility is based on the initial solid volume fraction (or initial void ratio) of the granular-fluid mixture; a slight change in the initial volume fraction significantly affects the mobility of the CSW landfill landslide. [ABSTRACT FROM AUTHOR]