A case study on soil slope landslide failure and parameter analysis of influencing factors for safety factor based on strength reduction method and orthogonal experimental design.

In civil engineering, stability analysis of slope is one of the main content of design. By using the finite element limit analysis software OptumG2, a landslide geological model is established to simulate the failure process of the landslide in Huadu District, Guangzhou City, China. The analysis focused on the deformation and failure characteristics, as well as the mechanical mechanism of landslide; the landslide mode of homogeneous soil is circular sliding. Additionally, investigating the influencing factors affecting slope stability is crucial in engineering implementation; in which the five influencing factors are considered as follow: slope height, slope gradient, soil cohesion, soil internal friction angle, and soil unit weight, respectively. A stability calculation model for a soil slope is established under 25 working conditions based on strength reduction method and orthogonal experimental design, in which the relationship between the safety factor and slope height, slope gradient, soil cohesion, soil internal friction angle, and soil unit weight is obtained. As the slope height increases from 5m to 45m, the safety factor of soil slope gradually decreases from 2.21 to 0.94; As the slope gradient increases from 20° to 60°, the safety factor of soil slope decreases approximately linearly from 1.80 to 0.95; As the cohesion of soil increases from 10kpa to 30kpa, the safety factor of soil slope increases approximately linearly from 1.04 to 1.60; As the internal friction angle of soil increases from 10° to 30°, the safety factor of soil slope increases approximately linearly from 1.00 to 1.81; As the unit weight of soil increases from 13kN/m3 to 21kN/m3, the safety factor of soil slope decreases approximately linearly from 1.50 to 1.21. The influencing factors affecting the safety factor of soil slope in descending order are slope height, slope angle, soil internal friction angle, soil cohesion, and soil unit weight. The research has reference significance for studying the stability and failure laws of soil slopes and conducting landslide control on soil slopes.

Study on the failure characteristics of sliding surface and stability analysis of inverted t-type retaining wall in active limit state.

This paper investigates the sliding surface failure characteristics, earth pressure distribution law and stability safety factor of inverted T-type retaining wall by using the finite element limit analysis software OptumG2, the effects of width of wall heel plate, width of wall toe plate, thickness of bottom plate, soil-wall interface friction angle, soil cohesion and soil internal friction angle of filling on the failure characteristics of sliding surface, the earth pressure distribution law and stability safety factor of retaining walls are analyzed, The stability safety factor of the retaining wall showed a gradually increasing trend as the width of wall heel plate and wall toe plate increased; as the bottom plate thickness increases, the stability safety factor of the retaining wall gradually increases; as the soil-wall interface element reduction coefficient rises, that is, the internal friction angle of the soil-wall gradually increases to the soil internal friction angle, the stability safety factor of the retaining wall gradually increases; as the soil cohesion and internal friction angle increase, the stability safety factor of the retaining wall progressively increases. The safety factor of retaining wall increases by 0.45 for every 0.5m increase in the width of the wall heel plate; the safety factor of the retaining wall increases by 0.29 when the width of the wall toe plate increases by 0.5m; for every 0.5m increase in the width of wall plate thickness, the safety factor of the retaining wall is increased by 0.62; for every 0.25 increase in soil-wall interface element reduction coefficient, the safety factor of the retaining wall increases by 0.29; for every increase of 5KPa in soil cohesion, the safety factor of the retaining wall increased by 1.16; for every 5° increases in soil internal friction angle, the safety factor of retaining wall increases by 0.6. The research is significant for studying the failure laws and stability of retaining walls and providing references for retaining wall design.

Non-limit passive earth pressure against cantilever flexible retaining wall in foundation pit considering the displacement.

A series of model tests are carried out on flexible retaining walls such as cantilevered piles, continuous walls, and sheet pile walls in the foundation pit to study the deformation, failure surface, and earth pressure distribution of soils in a passive zone. The shape, displacement, and shear strain of slip failure surface of sand in a passive area are analyzed by Particle Image Velocimetry. The slip failure surface is a broken line, the upper end slides out from the top of the soil, and the lower end is close to the zero displacements of the retaining wall. With the increase of the flexural deformation and horizontal displacement of the wall, the shear strain of the soil increases, and the shear fracture zone in the upper part of the sliding surface is more prominent. Based on the broken line rupture surface in the test results, the passive area can be divided into two zones, the limit state zone and the non-limit state zone. Then the mechanical models are set up respectively. Considering soil displacement, the upper and lower soil layer's internal friction angle and wall-soil interface friction angle mobilize differently. The relationship between mechanical parameters along the retaining wall and horizontal displacement is estimated. Finally, the earth pressure distribution is obtained by using the horizontal differential layer method. The calculation results of this paper are consistent with the existing research results and the model test results in terms of earth pressure distribution. With the increase of depth, the unit earth pressure increases in the limit state zone. Still, after entering the non-limit state zone, the unit earth pressure rises to a certain extent and decreases rapidly.

Active earth pressure against flexible retaining wall for finite soils under the drum deformation mode.

A reasonable method is proposed to calculate the active earth pressure of finite soils based on the drum deformation mode of the flexible retaining wall close to the basement's outer wall. The flexible retaining wall with cohesionless sand is studied, and the ultimate failure angle of finite soils close to the basement's outer wall is obtained using the Coulomb theory. Soil arch theory is led to get the earth pressure coefficient in the subarea using the trace line of minor principal stress of circular arc after stress deflection. The soil layers at the top and bottom part of the retaining wall are restrained when the drum deformation occurs, and the soil layers are in a non-limit state. The linear relationship between the wall movement's magnitude and the mobilization of the internal friction angle and the wall friction anger is presented. The level layer analysis method is modified to propose the resultant force of active earth pressure, the action point's height, and the pressure distribution. Model tests are carried out to emulate the process of drum deformation and soil rupture with limited width. Through image analysis, it is found that the failure angle of soil within the limited width is larger than that of infinite soil. With the increase of the aspect ratio, the failure angle gradually reduces and tends to be constant. Compared with the test results, it is shown that the horizontal earth pressure reduces with the reduction of the aspect ratio within critical width, and the resultant force decreases with the increase of the limit state region under the same ratio. The middle part of the distribution curve is concave. The active earth pressure strength decreases less than Coulomb's value, the upper and lower soil layers are in the non-limit state, and the active earth pressure strength is more than Coulomb's value.