Nonlinear Numerical Analysis Of Retaining Structure With Anchor Bolt Considering Dynamic Construction Process

With the development of geotechnical anchoring technology,prestressed retaining structure with anchor bolt has been widely used in slope project,in which frame beam,ribbed beam or pile are used as the components of load undertaking and transferring.Through interactions between anchor bolt,frame beam etc.and slope,anchoring loads are transmited to deep stable rock and soil layers,as a result an active retaining mechanism is formed.As known,in order to ensure its stability during the construction process,the slope is generally excavated and reinforced by steps,but it is usually designed under final stress states in actual projects,less considering the impact of construction process.However,there are some uncertainties in the construction process,such as the design form and construction sequence of excavation and reinforcement,may lead to slope failure or dynamic changes of retaining structure's stress condition during construction process.Currently,linear elastic or ideal elastic-plastic geo?materials constitutive model is mostly used in the numerical analysis of the retaining structure with anchor bolt for slope project,but due to the big deviation between they and actual nonlinear constitutive relation,it is difficult to obtain results of quantitative calculation accuracy.Therefore,based on a slope excavation and reinforcement project examples,this paper focus on the use of nonlinear constitutive model,by using the finite element software ABAQUS to carry out the following work:Firstly,main points to achieve the simulation of slope's dynamic construction process by using the finite element method are briefly introduced,which mainly include the introduction of non-linear finite element software ABAQUS and its applicability for geotechnical engineering,the introduction of Duncan-Change Ev and Mohr-Coulomb constitutive model and the selection of constitutive model in this paper,the development and application of Duncan-Change Ev constitutive model subroutines and initial state variables subroutines,the review and selection of initial geostress balance method in abaqus.Secondly,as for the load dispersive anchor bolt,a new anchor currently applied in practical pojects,the equivalent force method is used,which is more corresponded to stretching and locking conditions in practical engineering,to build three-dimensional numerical models of tension concentrated anchor,pressure concentrated anchor,tension dispersive anchor,pressure dispersive anchor and tension-pressure dispersive anchor.Axial force of anchor,stress and displacement of surrounding rock,stress state of grout are respectively analyzed,revealing the load transfer mechanism for different structure types of anchor.Thirdly,based on a slope excavation project example,a two-dimensional finite element model of the slope is established,considering the excavation construction process.The stress,displacement and excavation relaxation area of the model are analyzed by using 2D Duncan-Chang Ev constitutive model subroutine,which can better consider the difference between loading and unloading conditions,and its result is compared with the measured data and results of Mohr-Coulomb constitutive model.In addition,the stability of the slope is analyzed by using Mohr-Coulomb constitutive model and finite element strength reduction method.Forthly,a three-dimensional finite element model of the slope project is established,in which excavation and reinforcement construction process are considered simultaneously,and the retaining method is frame beam with prestressed anchor.During the construction process,the axial force of anchor,stress of grout,moment and shear of frame beam are studied,furthermore,on which the affects of dynamic construction process are also analyzed,by using 3D Duncan-Chang Ev constitutive model subroutine.