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Caterpillar 336D Trimming Soil Slope

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Learn more about Soil Slope

Types of Failures of Rock and Soil Slopes

Bhawani Singh, R.K. Goel, in Engineering Rock Mass Classification, 2011

Publisher Summary

The classification of rock and soil slopes is based on the mode of failure. In the majority of cases, the slope failures in rock masses are governed by joints and occur across surfaces formed by one or several joints. Some common modes of failure, which are frequently found in the field, are described in this chapter. One of the failures discussed is planar (translational) failure; it takes place along prevalent and/or continuous joints dipping toward the slope with strike nearly parallel (±15°) to the slope face. Stability condition occurs if critical joint dip is less than the slope angle and mobilized joint shear strength is not enough to assure stability. In addition, wedge failure is also discussed, which occurs along two joints of different sets when these two discontinuities strike obliquely across the slope face and their line of intersection daylights in the slope face. The wedge failure depends on joint attitude and conditions and is more frequent than planar failure. The factor of safety of a rock wedge to slide increases significantly with the decreasing wedge angle for any given dip of the intersection of its two joint planes.

 
 

Computer Implementation of the MPM

Xiong Zhang, ... Yan Liu, in The Material Point Method, 2017

4.7.4 Failure of Soil Slope

The failure process of a soil slope as shown in Fig. 4.5 under gravity is simulated. The left side AF and right side DE are constrained in the horizontal direction and free in the vertical direction, while the bottom side EF is fully constrained. In this simulation, the transverse direction of the computational model is constrained to yield a plane strain state[120].

Figure 4.5. Soil slope under gravity.

The soil is modeled by the Drucker–Prager model with the parameters listed in Table 4.7. The slope is discretized into 19,640 particles with an initial spacing of 0.5 m. The grid spacing is chosen as 1 m. For comparison, this problem is also simulated with the use of LS-DYNA with 19,640 elements and 30,273 nodes. The input file of this example is “Slopfail.mpm”.

Table 4.7. Material Parameters of Soil

E (MPa) ν ρ(g/cm3) ϕ∘ ψ∘ c (kPa)
70 0.3 2.1 20 0.0 1.0
σt (kPa)  (kPa)    
27.48 0.3545 0.974 0    

Fig. 4.6 compares the failure process obtained by the MPM3D-F90 and LS-DYNA, in which the color represents effective plastic strain. The results obtained by the MPM3D-F90 agree well with those obtained by LS-DYNA, but the computational cost of the MPM3D-F90 is much lower than that of LS-DYNA due to its element distortion, as shown in Table 4.8.

Figure 4.6. Slope failure process obtained by (a) MPM and (b) FEM.

Table 4.8. Comparison of Computational Cost

 Δtmax (μs)Δtmin (μs)Number of time stepsCPU time (min)
MPM 944 944 15,888 9
FEM 261 8.21 1,175,935 468

Table 4.8 compares the maximum time step size Δtmax, minimum time step sizeΔtmin, and total number of time steps used in the MPM and FEM simulations. The time step safety factor is chosen as 0.2. The time step size in the FEM simulation is reduced from its initial value of 261 to 8.21 μs due to element distortion. The same regular background grid is used in the whole simulation process with the MPM such that its time step size keeps constant during the simulation. The CPU time used in the MPM simulation is only 1/52 of that used in the FEM simulation.

 
 

Geotechnical engineering software

Ruwan Rajapakse PE, CCM, CCE, AVS, in Geotechnical Engineering Calculations and Rules of Thumb (Second Edition), 2016

26.2.1 Reinforced soil slopes (RSS)

This program is capable of designing and analyzing reinforced soil slopes (RSS). The programs are based on the FHWA manual, Reinforced Soil Structures Volume I – Design and Construction Guidelines (FHWA-RD-89-043).

This program analyzes and designs soil slopes strengthened with horizontal reinforcement. The program also analyzes unreinforced soil slopes. The analysis is performed using a two-dimensional limit equilibrium method. The program is a predecessor of a very popular STABL computer program of the 1990s (Federal Highway Administration, USA, http://www.fhwa.dot.gov/index.html).

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