As a new type of reinforced material, geocells are widely used in flexible reinforced retaining wall projects, and a lot of practical experience shows that the geocell retaining wall has a great effect on earthquake resistance, but theoretical research lags behind engineering practice, and the deformation and failure mechanism under earthquake need to be further studied. In this paper, we use the FLAC3D nonlinear, finite-difference method to study the failure mechanism of geocell-reinforced retaining walls under earthquake, to analyze the advantages of the geocell retaining wall in controlling deformation compared with the unreinforced retaining wall and geogrid-reinforced retaining wall, and we try to study the deformation of the reinforced wall by changing the length of the geocell and reinforcement spacing of the geocell. Research indicates the horizontal displacement of the wall edge of the reinforced retaining wall under the earthquake is slightly smaller than that of the center of the wall and the back of the wall. The geocell can effectively reduce the horizontal displacement of the retaining wall, and the effect is better than the geogrid. Increasing the length of the geocell and reducing the spacing of the geocell can effectively reduce the horizontal displacement of the retaining wall, and the effect of displacement controlling at the top of the wall is better than in other positions.
In the slope stability analysis, how to make the slip surface of the structure more precise and smoother has been the focus of research when fitting the slip surface with known numerical points. The study found that the logistic function has both advantages in fitting the slip surface. The related parameters (M, A, and K) are derived by the threshold, symmetry, and precision control of its function. Logistic function constructs the slip surface and compares it with the broken-line slip surface; the numerical results show that the slip points on the two slip surfaces are consistent, indicating that the logistic function fits the curve correctly; the logistic function smooths the original polyline curve, which facilitates solving the direction vector of the curve.
In the past, when performing dynamic response analysis of dams on deep overburden, the dam body and the overburden have often been discussed separately. In this paper, the overburden and the dam body are considered as a whole, and the dynamic response analysis is carried out by using a completely nonlinear dynamic analysis method. From the acceleration of the earth's surface, the displacement of the dam, and the stress distribution of the panel, the dynamic response of the structure is shown to increase first and then decrease with increasing cover thickness, and the overburden layer thickness corresponding to the extreme point is called the critical thickness. The results obtained in this study can provide a design basis for a face rockfill dam built on a deep overburden layer.
Three sets of indoor model tests of reinforced retaining walls were conducted to study the effects of reinforcing material placement on the displacement of reinforced retaining walls, wall top settlement, earth pressure distribution, and potential failure surface. The test results show that under different reinforcement laying conditions, the maximum horizontal displacement of the lower wall panel appears at the top of the lower retaining wall, and the maximum horizontal displacement of the upper wall panel appears at 0.6H. The settlement of the top of the wall decreases by about 9.1% when the reinforcement is laid in the lower layer. Under the condition of 160 kPa, the maximum horizontal and vertical earth pressures increase by about 19.2 and 12.4%, respectively, and the position of the potential fracture surface of the lower wall moves up to the back of the wall with the position of the reinforcement laying. When the reinforcement is laid in the upper layer, the fracture surface of the upper wall is furthest away from the panel.
Traditional rigorous limit equilibrium methods satisfy all equilibrium conditions and usually have high accuracy, however, which are less efficient for slope reliability analysis. The main reason is that the limit state functions are highly nonlinear implicit functions of safety factor. Complex numerical iterations are required, which may sometimes lead to computational convergence problems. A new method for computing slope reliability calculation with high efficiency and accuracy was proposed. This method was based on the rigorous limit equilibrium method by modifying normal stresses over the slip surface. The critical horizontal acceleration factor K c {K}_{c} , which can be expressed explicitly, was used to replace the implicit safety factor as a representation of slope stability. The difference between K c {K}_{c} and the known value K c 0 {K}_{c0} was used as the limit state function. Two slope examples were analyzed. The results showed that the calculation results of this method were in good agreement with those of the traditional Morgenstern–Price limit equilibrium method, but the computational efficiency was significantly improved. When this method was combined with the subset simulation method, the calculation time was only a few seconds. Therefore, this method can be used for rapid calculation of slope reliability.
In order to further explore the influence of reinforcement materials laying position on the dynamic characteristics of reinforced retaining walls, based on FLAC3D finite difference methods for solving nonlinear problems, established with the same size of the retaining wall in practical engineering, the reinforcement material’s relative position in the retaining wall for the normalized processing, under seismic load, and the panel under the conditions of different reinforcement arrangement were analyzed, and the horizontal displacement of slope, the vertical and horizontal earth pressures behind the wall, and the distribution of potential sliding surface were calculated. The relationship between the maximum horizontal displacement of the panel and the laying position of the reinforcement was fitted by MATLAB. The results show that the horizontal displacement of the panel is about 40% smaller when the upper layer of the reinforcement is arranged than that in the lower layer for step 1, and the horizontal displacement of the reinforcement in step 2 is about 30% lower than that in other conditions when the reinforcement is arranged at the top of the slope. The reinforcement arranged in the lower layer of step 1 and the upper layer of step 2 can minimize the wall top displacement. In step 1, the vertical earth pressure and horizontal earth pressure are 19% and 5% smaller than those in other conditions when the reinforcement is arranged near the middle and lower layer of the step. In step 2, the difference between vertical and horizontal earth pressure is not obvious, and the difference between the two conditions is controlled within 5%. At the same time, soil liquefaction and uplift occur under the action of earthquake. The position of sliding crack surface has no obvious regularity with the position of reinforcement, but the position of reinforcement at the step classification is obviously better than other conditions. The fitting formula can describe the relationship between the panel displacement and the position of the reinforcement well. The conclusions can provide a point of reference for practical engineering.
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