Design And Numerical Analysis Of Subsection Combined Support For Deep Foundation Pit

With the rapid development of cities in China,deep foundation pit projects are widely used in projects,and the surrounding environment of foundation pits has become more complex.As a result,more and more problems occur in design and excavation of deep foundation pit projects,which makes it important to,choose a reasonable support scheme and cooperating with a suitable construction program on the premise of guaranteeing project quality and ensuring safety.Based on the project“Xinji Yanleyuan Commercial Center”,the project selected the deep foundation pit support scheme.The scheme includes the subsection combined support plan with slope soil nailing wall support,pile anchor support and pile anchor-inner support,Lizheng software was used to design and calculate the supporting structure strength,foundation pit displacement and overall stability.At the same time,research and formulation the deep foundation pit on-site monitoring plan was set up,and the monitoring results were analyzed.Simlates was completed with the ABAQUS finite element software,comprising the excavation process of foundation pits and the supporting effects of different supporting schemes.The main conclusions are as follows:(1)When there is a great environmental difference of the deep foundation pit,a reasonable segmental combined support scheme can be adopted.It can reduce tue cost of project while ensuring the quality of foundation pit.(2)The results of the monitoring data of the foundation pit indicate that the support scheme of the project is well-designed,and the cracks and settlements of the surrounding buildings,the vertical and horizontal displacements of the slope top meet the specification requirements;in the pile-anchor support structure and the soil nail support structure,large cracks are likely to appear near the roots of the anchor bolts and the soil nailing roots,attention should be paid to the excavation and monitoring of the foundation pits;the horizontal displacement of the foundation pit increases significantly with the distance from the pit corner.,For the special-shaped foundation pit,the horizontal displacement of the central bulge is especially significant,and the support measures for these locations should be strengthened during the design and excavation of foundation pits.(3)The simulation results of ABAQUS show that the slope top displacement and monitoring results of the three supporting methods are consistent.The ABAQUS finite element can be used for analysis deep foundation pit support and excavation,and it can provide calculation basis for deep foundation pit support scheme design;Numerical simulation results of soil nailing support show that the horizontal displacement of the slope top of the foundation pit decreases with the decrease of the slope,and it is advisable to reduce the excavation slope of the foundation pit as far as possible under the condition of slope.The horizontal displacement of the slope top increases with the incidence angle of the soil nail,and the incidence angle of soil nails should not be larger than 15~°.The pile anchor supporting structure of the numerical simulation results show that the horizontal displacement of pile decreases with increasing diameter of pile,increased with the increase of pile spacing.Increasing the prestress of the anchor can effectively reduce the horizontal displacement of the pile,however,it will increase the internal force of the pile which indicates it is needed to be considered comprehensively.