A framework for identifying the onset of landslide acceleration based on the exponential moving average(EMA)

Predicting the failure time of a landslide is considered as challenging work in the field of landslide research,and inverse velocity is proved to be an effective and convenient method.The onset of acceleration(OOA)has a crucial effect on the prediction failure time from the inverse velocity method.However,a simple method to identify OOA points is lacked,and most of the identifications rely on expert experience.Therefore,this study presents an application of a simple framework developed to identify the OOA by analyzing monitoring velocity data in three steps,including selection of the absolute value of velocity,reliable area identification and OOA identification.A new parameter based on exponential moving average(EMA)is developed to identify the landslide OOA.The framework is applied to three historical case studies to test its practicability and effectiveness.The forecasting results show a good correspondence between the accuracy rate and the coefficient of determination(R2).The predicted failure time according to the linear extrapolation starting from the identified OOA points is acceptable with a high R2 and high accuracy.

EXPERIMENTAL INVESTIGATION OF THE FAILURE OF CASCADE LANDSLIDE DAMS

This paper presents results of model tests for the landslide dam failure of a single dam and cascade dams in a sloping channel. The dams were designed to be regular trapezoid with fine sand. A new measuring method named the labeled line locating method was used to digitalize the captured instantaneous pictures. Under two different inflow discharges, the morphological evolution and the flow patterns during one dam failure and the failure of cascade dams were investigated. The results indicate that when the inflow discharge is large, the deformation pattern of the downstream dam is similar to that of the upstream dam, and both dams are characterized with the overtopping scour throughout the dam failure process. When the inflow discharge is small, the upstream dam is scoured mainly through a sluice slot formed by the longitudinal incision, and the downstream dam is characterized with the overtopping scour. The data set presented in this paper can be used for the validation of numerical models and provide a reference for the flood risk management of cascade landslide dams.

Inverse-square-root-acceleration method for predicting the failure time of landslides

Predicting the failure time of unstable slopes is one of the most pivotal issues. In this paper, the inverse square root acceleration(INSRA) method was proposed to estimate the time-of-failure(TOF) of landslides. Four collapsed slopes were presented in the three open-pit mines, two of them were probed by ground-based radar, and two of them were obtained from previous scientific papers. The inverse velocity(INV) method and INSRA method were adopted to analyze these four landslides and one slope which had great deformation but did not reach failure. Compared with the traditional INV method, the INSRA method can promote the forecasting effectiveness and has the advantage of higher accuracy.

A case study of the Tangjiashan landslide dam-break

The Tangjiashan landslide dam failed on June 10, 2008, which was the largest one formed during the Wenchuan earthquake in China. No human lives were lost in this dam failure. This paper presents a description of the dam, including the dam geometry, the hydrograph and the reservoir capacity, the diversion channel and the drainage from the lake. Several empirical models are applied to predict the breach parameters, the peak outflows and the reservoir volumes during this breach event. The main objective of the study is to compare various prediction models and to make recommendation of the best model for the prediction of the breach width, the failure time, and the peak outflow. The breach widths predicted by the Froehlich methods with considerations of the reservoir storages and the effect of failure mode are considered to be more reasonable. All prediction methods discussed in this paper are found to underestimate the breach formation time due to the complex material and the large thickness of the dam. The results from the soil conservation services（SCS） method compare well with the observed peak outflow. The Marone method in combination with the coefficient expressions proposed by Macchione gives excellent results in the simulation of the reservoir volume-level curve.