Identification of soil strength parameters for assessing stability of a sliding slope

Abstract

The article presents the results of assessment of stability of the sliding slope, which was performed with the use methods of limit equilibrium and numerical modeling of the stress-strained state of the slope soils. It is obvious that usage of soil strength parameters c and φ without their clarification (identification) can lead to an overestimation of the value of the safety factor and thus slopes will be mistakenly classified as stable. The choice of the correct soil parameters is a key factor in the calculations in order to obtain calculated slip surfaces close to the actually recorded ones. The object of the study is an artificial landscape massif located on a slope. The site has the shape of an amphitheater in the form of stairs that occupy half of the entire area in the central part and sloping surfaces at the edges. The radius of the upper face is 42.20 m, the lower face is 21.95 m. The total number of steps is six. The absolute mark of the first step is 289.00 m, the mark of the bottom of the amphitheater is 280.00 m. During construction works related to the formation of a stepped landform of the landmass, a landslide happened on the territory of the object, therefore, during the calculation of the stability of the slope, the main task was to choose the correct values of c and φ so that the modeling results coincide with the data of field observations and on the basis of these data, it would be later on possible to make reasonable engineering decisions about measures to stabilize the slope and ensure its stability at the stage of operation. To assess stability of the slope, a series of calculations was performed in the initial (natural) state and in the current state with characteristics changed due to wetting. Soil parameters were identified on the basis of engineering and geological investigations. As a result of specifying the strength parameters, the coefficients of the stability were determined, which reflect the ultimate equilibrium of the slope, which corresponds to the real picture in the area. For numerical modeling, the initial stability coefficients had the following values: for 3 steps K=2.396; with complete excavation K=1.428. After adjusting c and φ, they decreased by 2.3 times and 1.4 times, respectively. A similar situation occurred for the assessment of slope stability using the limit equilibrium method. For three steps, the initial coefficient K=2.70 decreased by 2.5 times; with complete excavation, K=1.54 decreased by 1.5 times.