Study On Application Of Long And Short Pile Combined Support System In Deep Mud Foundation Pit

In order to meet the continuous development and growth of urban land needs,the development and construction of many soft soil areas around cities have also been put on the agenda.In the southern part of Guangzhou,there are large areas of deep silt,and higher cost foundation pit support schemes are inevitably used during the excavation process of deep silt areas.Foundation pit engineering is a temporary project.Generally speaking,while ensuring the provision of safe and stable basement construction,it is the economic goal that every engineer hopes to pursue to adopt a lower cost method for support.Due to the presence of uplift at the bottom of the pit and the kick effect,the support piles often need to pass through the silt layer,resulting in an excessively long embedded depth of the support pile row.Some of the support pile materials in the entire support pile row cannot be fully utilized.On the premise of meeting the requirements for resistance to uplift damage and bending moment,this type of foundation pit engineering can use long and short piles instead of equal length piles,which can shorten the construction period and reduce costs.It is a relatively novel and advanced support method selection.Studying the design calculation and stress characteristics of long and short piles has great practical significance.This article will explore and research from the following aspects:(1)A systematic analysis was conducted on the selection dilemma of foundation pits in deep silt areas,the characteristics of damage and deformation in foundation pit engineering,the theory of calculation methods for long and short pile forces,and the design theory of foundation pit support systems with long and short pile combinations.(2)By using the example of Guangzhou Liandong Nansha Phase II project for foundation pit design and calculation,and based on the original design scheme,optimizing the design of long and short piles by changing the pile type,pile diameter,pile length,and reinforcement soil depth,and comparing them with design schemes such as equal length SMW piles and equal length cast-in-place piles,economic analysis and comprehensive comparison are finally conducted.(3)Using Midas GTS NX software,simulate the engineering with two types of equal length pile support and long and short pile support,and study the stress and deformation characteristics of long and short pile design.(4)Using the model established by Midas GTS NX software,analyze and study the impact of changes in length,diameter,combination and other parameters on the design of long and short piles,providing a basis for the design of long and short piles.