Reliability Analysis Of Slope Excavation And Support Design Based On Random Field

With the continuous improvement of economy,infrastructure construction enters a period of rapid development.In order to meet the needs of development,a large number of slopes have been excavated.If the stability of slopes cannot be evaluated accurately during excavation or the support method cannot be selected reasonably,the possibility of engineering accidents will significantly increase.Traditional slope excavation stability analysis and support research are often performed based on deterministic model,which cannot consider ubiquitous uncertainties in practical engineering.Therefore,the reliability analysis method based on random variable model is introduced into the field of slope excavation stability analysis and support design.However,the random variable model ignores the spatial variability of soil parameters.This study made corresponding improvements and introduced the random field model in the research.Considering the distribution characteristics of random soil parameters,the internal friction angle and cohesion are simulated as stationary random field and non-stationary random field,respectively.The main contents and conclusions are summarized as follows:1.The stability of slope under excavation is first analyzed based on the deterministic model.According to the results of horizontal displacement contour and shear strain increment contour,it is found that in the process of excavation,the sliding mode of the slope changes.Initially,the potential slip surface cuts through the original slope surface and after three steps of excavation,the potential slip surface cuts through the newly excavated slope surface.The increase of failure probability in the later stage of excavation may be related to this change.The failure probability of a two-dimensional soil slope under excavation is calculated based on the random field model and the random variable model.The results indicate that if the random variable model is used,which does not consider the spatial variability of soil parameters,the instability possibility of slope under excavation will be overestimated,resulting in conservative judgment on the safety of excavation project.2.The parameters of prestressed anchors are designed based on the random filed model and the accepted failure probability approach.In the study,the failure probabilities of slope reinforced by prestressed anchor with different parameters are calculated.The optimal anchor inclination angle is determined from the relationship curve of failure probability versus inclination angles.In addition,three design schemes with appropriate pretension and length of prestressed anchor that meet the reliability requirements are obtained through comparison.Results indicate that compared with the reliability design method based on the random variable model,the support design of prestressed anchor based on the random field model proposed in this study can reduce the cost of construction under the premise of meeting reliability requirements.3.Considering the influence of "edge effect" of three-dimensional soil slopes,this paper extends the analysis based on random field theory to three-dimensional.In the study,the failure probabilities of slope obtained based on two-dimensional and three-dimensional models are compared,and the spacing arrangement of anchors is optimized.Results indicate that the stability of three-dimensional slope depends on the edge-section constraints.The results obtained based on the free constraint condition are basically consistent with that based on the two-dimensional model,and the stability of slope under the half constrain and full constraint has been significantly improved,therefore,the failure probability of slope is smaller.Supporting effects of anchors at different positions are also compared and it is found that anchors at the middle and upper parts of slope play a relatively small role.Therefore,the amount of anchors in this part can be appropriately reduced in practice.