Numerical Analysis Of Support Patterns Of The Variation Combination Of Anchor On Slope Stability And Its Engineering Application

To search the optimal form of bolt layout in the slope engineering,the layout method of variation combination in bolt length is introduced.Firstly,a set of bolts laying at different position of the slope are discussed,finding that there is significant difference in arranging bolts in different position of slope,then,the effect of the slope layer place is raised and emphasized.In addition,considering economy of the variation combination in bolt length,the bolt was divided into three combination types:"long-medium-short type","medium-long-short type" and "short-long-medium type",by analyzing the difference of safety factor of slope,axial force ratio of bolts and position of sliding surface,the influence of arrangement methods of bolts to slope stability was studied.Then to test the slope reinforcement effect in each combination supporting through a special loading form:the load on the crest.Finally,the contents of the conclusion is applied to a real 3-D slope reinforcement supported by bolt(cable)and frame beams.The main results are as follows:1.There exists global optimum anchorage angle θopt and layer place effective bolt length Leff in the case of combinational bolts.The main controlling factors of safety coefficient and the position of the sliding surface continuously transfer among layer places with the increasing of anchorage angle,and the failure mode of the slope mutate from deep sliding to shallow sliding with the increasing anchor angle.Besides that,when the best anchorage angle of single layer anchor is used to lay the bolt group of each layer,the reinforcement effect is common,and there exists "combination-bolt group effect",the method of arranging each layer bolts divergently by small angle may be better.2.Loading at the top,the combination "short-long-medium type" is still the best combination form.But its particularity is reflected in the crest where the loading is applied to,which relates to the type(anchor bolt length)of arrangement on the top layer:the longer the top layer layout,the less the value of safety factor in the larger loading on the crest decline;the anchor range about the main layer(or anchor group)controlling the sliding surface of slope may change.3.the 3-D slope stability was improved obviously by adopting the combination of bolt(cable)and frame beams.The frame,the liner element,can be applied to reflect the prestressing force well,the form global failure basically would not occur,the secondary sliding surface disppeared.4.The slope excavation and slope reinforcement with prestressed anchor and frame beams,which is in nature a stress release-unloading rebound deformation、stress compensation processes.