Research On The Regularity Of Supporting Design And Deformation Of Deep Foundation Pit In Guangzhou Lie De Building

With the rapid development of city modemization,more and more large-seale engineering facilities have been being constructed,a large number of deep foundation pit have been appearing.The excavation and support of deep foundation pit as one of the most complex technology on the field of civil engineering,has been becoming a focus and nodus.In this paper,taking the deep foundation pit of Guangzhou Lie De building as the research background,the optimal type of supporting structure was simulated,meanwhile,the on-site monitoring of the excavation and support of foundation pit was also carried out.(1)Considering that the deep foundation pit of Guangzhou Lie De building is a Grade Ⅰ foundation pit,which needs a large excavation area,and has a complex surrounding environment.Comparing the advantages of the various support programs synthetically,supporting method of row pile + anchor was selected ultimately in the main body of tj=he foundation pit,double row mixing pile was taken as a waterproof curtain.The supporting design and calculation of the BCI section of northweast corner and the A4A2 section of wast side was carried out.By calculating the distribution of earth pressure and maximum bending monment of each excavation stage,the parameters of piles and anchors were determinted.By calculating,the bored piles and four anchors were selected.The sizes of bored piles is that the diameter is 1200mm and pile sapacing is 1400mm,and the length is 26m.After checking,it meets the stability requirements.(2)The excavation and support of foundation pit by FLAC3D sofeware was simulated.The calculation results show that with the increase of excavation depth,the maximum vertical displacement of the soil which was around the foundation pit occurred near the pit wall.When it is closer to the pit wall, the horizontal displacement of the soil is larger. The largest horizontal displacement of the soil occurs in the upper part of pit wall. The deformation of it is about 20mm.The soil around the pit move to the inside of pit. The deformation value of foundation pit is less than the alert value, and the support structure is safe and reasonable.(3)In the process of whole foundation excavation and support construction, the on-site monitoring of the foundation pit was carried out. The maximum horizontal displacement of pile top is about 14.8mm, and the maximum settlement in the top of the foundation pit is about 7.21mm. It can be seen that the deformation of foundation pit have been well controlled in the supporting design, and the purpose of security is achieved.(4)When the simulation results were compared with the monitoring data of the lateral displacement,the numerical simulation data is greater than the final actual monitoring data,however , the overall trend is consistent. The results of numerical calculation is relatively conservative, which further illustrates the scheme of the row pile + anchor supporting is safety and rationality.