Monitoring And Analysis Of Construction Effect Of Deep Foundation Pit Of Underground Garage

Deep foundation pit engineering,which includes structural engineering,geotechnical engineering,the corresponding construction technology and monitoring technology and other disciplines.Because of complex underground engineering geology and diverse urban underground space support forms,the deep foundation pit engineering always experiences higher construction difficulty.Moreover,deep excavation of the upper part of the soil unloading will inevitably lead to changes in the nature of the soil and then lead to deformation of the supporting structure,which make monitoring and analysis of the deep foundation pit construction process very important.Because it can not only guarantee the smooth construction,but also provide the basis for the subsequent construction and similar construction.Therefore,in this paper,the deformation theory of deep foundation pit support structure was expounded.In addition,according to the engineering site and the geological situation,relevant design software was used to calculate the typical section of the project,methods of major deep foundation pit constructions,such as support pile construction and precipitation construction,were developed,meanwhile,the construction of the typical section was monitored and analyzed.The main conclusions are showed in the following passages:(1)After the identification of typical section of the support structure,support pile and soil nailing wall were adopted,nine rows of soil nails were used at the upper side.During the calculation on typical section support structure,seven working conditions of excavation and supporting were considered and calculated to figure out the soil pressure on the support structure,as well as related displacement,bending moment and shearing force of the support structure.Of which,the maximum calculated displacement was 34.13 mm.(2)According to project features and related design calculation results,basin excavation was selected as the earthwork method,moreover,the whole excavation process was divided into five stages,section by section,layer by layer,in order to control the environmental deformation caused by excavation.(3)Horizontal displacement monitoring was conducted on the foundation pit slope crest of the typical section,in 35 months,2 monitoring stations recorded accumulated displacement deformation amount of 17.7 mm and 18.3 mm,respectively,which were approximately 1/2 of the design calculation value,shows that basin excavation can effectively control foundation pit deformation.(4)Vertical displacement monitoring was conducted on the foundation pit slope crest of the typical section,2 monitoring stations recorded accumulated vertical displacement deformation amount of 8 mm and 8.8 mm,respectively.In-site monitoring showed that for support structure,the sedimentation of slope crest was proportional to the maximum horizontal displacement.As for this project,the ratio of sedimentation of slope crest to horizontal displacement was 1/2.(5)All monitoring data of this project were within the index range stipulated by related regulations and design specifications,which demonstrated the effectiveness and feasibility of the support pattern and construction method,respectively.Furthermore,this project provided an reference for similar works.