Limit Analysis For 3D Stability Of Unsaturated Inhomogeneous Slopes Reinforced With Piles

Stability analysis of slopes is a classic topic in geotechnical engineering research.In many engineering practices,setting retaining structures such as piles is an effective way to improve the stability of slopes.Anti-slide pile is a kind of passive retaining structure that is widely used in slope reinforcement projects because of its advantages of flexible pile location and good support effect.It can effectively resist the shear force on the curved sliding surface to guarantee the safety of slope engineering.To thoroughly study the reinforcement effect of anti-slide piles on slopes,this paper analyzes the stability of 3D piled slopes under complex conditions based on the upper limit analysis theorem and considers the influence of soil suction and soil inhomogeneity on the stability of slopes.The main research contents of this paper are as follows:(1)For the three-dimensional stability problem of unsaturated inhomogeneous soil slope reinforced with piles,the effects of pile lateral force,soil suction,unsaturated effective weight and soil inhomogeneity are considered based on the upper limit analysis theorem,and the expressions of external force power and internal energy dissipation power are derived for three failure patterns(face-,toe-and base-failure),and the safety factor is obtained by the weight-increasing method(GIM).The explicit solution of the Genetic algorithm(GA)is used to optimize the minimum safety coefficient of the slope and the related optimization variables.Feasibility of the proposed method was demonstrated by comparing with prior research.The influence of slope geometry parameters,soil parameters,3D effects,soil suction,unsaturated unit weight,soil inhomogeneity,pile location and pile spacing on soil slope stability were investigated by parametric analysis.(2)To address the 3D stability of unsaturated inhomogeneous soil slopes reinforced with piles under seismic effects,the modified pseudo-dynamic method is introduced,the effects of time-varying effects of seismic waves and soil damping are considered based on the previous step,the formula of external power due to work done by seismic effects is derived,and the 3D effects,soil inhomogeneity,modified pseudo-dynamic method parameters(damping ratio,horizontal seismic coefficient,normalized frequency)and soil type on the stability of soil slopes were studied by parametric analysis.(3)For the 3D stability problem of unsaturated inhomogeneous soil slopes reinforced with piles under the nonlinear strength criterion,the nonlinear Mohr-Coulomb yield condition is used based on the upper bound limit analysis theorem,and the nonlinear shear strength parameters are considered as optimization variables,and the instantaneous cohesive strength and instantaneous cohesive force are obtained iteratively from the nonlinear failure criterion.The expressions for the external power and internal energy dissipation of the slope under the nonlinear strength criterion are derived,and the safety factor of the slope is calculated by the gravity increase method.The influence of the key parameters on the stability of the soil slope is studied by parametric analysis.