Study On The Stability Of Expansive Soil Slopes Stability Study By Anti-slide Piles In Southwest China

With the vigorous promotion of domestic railroads,highways,water conservancies and other infrastructure projects,there are more and more slopes with high airside,bringing great safety hazards to the surrounding roads and facilities in recent years.In actual engineering,expansive soil slope is a special natural geological body,and in widely Situated in Southwest China.Under self-weight and rainfall,the expansive soil on the slope shows the characteristics of water loss and shrinkage,water absorption and swelling and fissure development,etc.The change of soil ontological parameters can cause the slope body to produce a downward sliding trend and even lead to slope instability when the situation is serious.Once the slope is damaged,it can significantly lose the national economy and even cause casualties.Therefore,how to reasonable and efficient analysis and treatment of stability of expansive soil slope is one of the focuses of attention in engineering practice.This thesis carried out analytical methodology Study of slope stability for the expansive soil slopes in Southwest China using the limit equilibrium method,energy conservation principle and multi stratum clay shear strength theory and considering the hygroscopic expansion characteristics of the local soil.Based on ABAQUS finite element secondary development platform,the finite element simulation of expansive soil slope stability under the action of an anti-slide pile was carried out by using the two-parameter reduction coefficient method and UEXPAN subroutine.In addition,the influence of various parameters on slope stability was Studied.The specific contents of this thesis are as follows:(1)According to the soil’s hydrological and hygroscopic expansion characteristics in Southwest China,the influence of matric suction on the water content was predicted.The intrinsic relationship between hygroscopic expansion and thermal expansion was established.The expansion force was introduced into the soil stress-strain relationship,and the formula for shear strength of expanded soil was derived.(2)Using Fellenius’ s bar-partition assumption and the Mohr-Coulomb yielding criterion,a model for calculating the stability of expansive soil slopes in Cartesian coordinates was established.Under the assumption that the slip surface was a circular arc,the corresponding safety coefficients of all potential slip surfaces were calculated.The minimum safety coefficient was obtained to determine the radius of the most unstable slip surface and the location of the center of the circle.Based on the radius of the most unstable slip surface and the center of the circle obtained by the Fellenius method,the equation of the most unstable slip surface in polar coordinates was derived.(3)Combined with the principle of conservation of energy,the radial strip division method was introduced to divide the circular arc surface.Based on the principle of virtual displacement,the potential energy of gravity of slope body and the dissipation work generated by frictional force,cohesive force and expansive force of slip surface was analyzed,and the safety coefficient of expansive soil slope under the radial energy bar splitting method is determined accordingly.Furthermore,the stability safety coefficients of the Felleniu method,simplified Bishop method and Radial energy method strip method for multi-layered expansive soil slopes were derived by using the clay theory of multi-layered slopes to average the cohesion force,friction angle and gravity force,respectively,taking the length ratio of slip surface in each layer as the weighting factor.(4)Based on the force form of the antiskid pile,the full section of the antiskid pile was divided into the cantilever section and anchorage section,and the internal force of the loaded section of antiskid pile was calculated by applying the cantilever pile method and elastic foundation beam method respectively.Since the effect of expansion force was relatively small,only the effect of soil pressure was considered in the anchorage section.This section’s force analysis was carried out using the elastic foundation beam method,and the equations of displacement,bending moment and shear force with depth are derived for the whole section of the anti-slip pile.Furthermore,given the force characteristics of the anti-slip pile on the sliding surface,the stability equations of the expansive soil slope based on the Felleniu method and the simplified Bishop method under the action of the anti-slip pile were derived.(5)Using the UEXPAN subroutine in ABAQUS finite element software,the connection between heat-absorbing expansion and moisture-absorbing expansion was established.And the effect of the moisture-absorbing expansion of expansive soil was simulated.Furthermore,by introducing the two-parameter strength discount factor method,the finite element model of the slope of expansive soil under the action of anti-slip piles was established.And the effects of antislip pile spacing and elastic modulus on the safety coefficient of the slope of expansive soil as well as the displacement,shear force and bending moment of anti-slip piles were investigated.