| In view of the conservative design of the traditional soil-nailed wall surface,some scholars have proposed a new type of support structure that uses geotextile surface layer combination reinforcement instead of traditional concrete pavement,which was named as flexible surface layer soil nailing wall.This paper conducts model tests by designing an indoor model by itself,and simulate the whole construction process of the flexible surface layer soil nailing wall according to the numerical simulation method,also study the supporting structure’s deformation and destruction rules of the flexible surface layer soil nailing wall during the excavation and loading process,so that people can know about this new-type supporting structure futher,which would promote its application on engineering and perfect the relevant standards.The main contents are as follows:(1)According to the similarity theory,the similar parameters of the model test are determined,and the similar materials in line with the test characteristics are selected:loess,barite powder,river sand,Shuangfei powder,water and engine oil to complete the model soil ratio test,determine the model soil ratio,and design the corresponding model test and monitoring equipment.(2)Completed the indoor model tests of three different surface structures,plain surface layer,flexible surface layer and rigid surface layer,and analyzed the three different kinds of surface layers’ changes of the surface displacement,earth pressure,soil nail axial,and vertical displacement at the top of the slope during the excavation and loading process.The action mechanism of the flexible surface soil-nailed wall are obtained as well.The results show that the development of horizontal displacement can be effectively restrained by the flexible surface,the stiffness of the surface decreases,the horizontal displacement increases,and the horizontal displacement of the flexible surface increases by one time compared with that of the rigid surface;The maximum earth pressure of the flexible surface is located in the middle of the foundation pit,while the maximum earth pressure of the rigid surface is located in the lower part of the foundation pit;Under the action of load,the axial force of soil nailing on the flexible surface layer is significantly less than that on the rigid surface layer near the surface layer;The failure process of soil nailing wall with flexible surface is progressive plastic failure.There are two sliding surfaces in the failure process,shallow and deep.The soil behind the sliding surface is more involved in anti sliding and delay soil cracking.(3)The three-digit numerical validation model of the flexible surface soil-nailed wall and the rigid surface soil-nailed wall was established to verify the rationality of the model parameters according to ABAQUS finite element analysis software;two three-digit numerical calculation models of soil nailing wall were established.The changes of horizontal and vertical displacements,the surface earth pressure,the plastic strain and the soil nail axial force of the soil nailing wall during the excavation and loading were analyzed,and the deformation laws and failure characteristics of soil-nailed walls with different surface structures were obtained.By changing the supporting parameters of the flexible surface soil-nailed wall,the influence laws of different arguments on different supporting structures were studied and the instructional advices of the design of the flexible surface soil-nailed wall were obtained.The results show that:under the action of load,the settlement of the flexible surface soil nailing wall near the top of the slope increases,and the influence range of the rigid surface load on the top of the slope increases,but the settlement decreases;The soil pressure of flexible surface soil nailing wall layer changes in a wave crest pattern along the depth direction,and the soil pressure in the middle of the surface layer is the largest;The plastic strain of the soil nailing wall with flexible surface develops from the top of the slope to the bottom of the slope toe,and that of the soil nailing wall with rigid surface develops from the back of the middle of the foundation pit to the top and bottom of the slope toe;In order to control the deformation of the supporting structure better,the length of the middle soil nail should be increased appropriately;The vertical spacing of soil nailing has a significant effect on the deformation of the supporting structure,while the horizontal spacing of soil nailing has a small effect on the deformation of the supporting structure. |
