Application Of Grouting Steel Pipe Front Brace In Foundation Pit Support In Soft Soil Area

The grouting steel pipe front support is the latest support program proposed by current researchers,and it has been promoted and applied mainly in Shanghai and nearby areas.In terms of the realization principle,the steel pipe is first driven into the supporting layer of the base with the aid of a tool and connected to the supporting pile,and then the strength of the soil is changed based on the method of grouting,thereby achieving the effect of stabilizing the foundation pit.The grouting steel pipe front support system is a green,efficient and recyclable new foundation pit support technology;the construction speed is faster,and the open excavation of the earth can be realized;the construction scope does not exceed the red line of the land,which affects adjacent projects or buildings Small;the combination of front support steel pipe and pit bottom cushion is beneficial to the control of horizontal displacement by the row of piles,which can greatly improve the overall stability and anti-overturning stability of the supporting structure.Compared with concrete supports,it avoids the construction,maintenance and dismantling of concrete supports,which can save a lot of time and cost;and the front support steel pipes can be recycled after the earthwork is excavated,so as to avoid dust pollution when dismantling supports.At this stage,in order to ensure that the original building structure and layout lines are not disturbed,many cities in China have specially formulated perfect and feasible protection schemes,and put forward rigorous and comprehensive management methods for deep foundation pit projects.It also expressly prohibits the use of anchor cables,soil nails and other related auxiliary tools,which has caused great restrictions on the use of anchor bolts and soil nails in foundation pit engineering.Therefore,more types of foundation pit support systems are needed to deal with foundations under different conditions.For pit engineering,the grouting steel pipe front support system has great application prospects as a new type of foundation pit support technology.The research object of this article is the grouting steel pipe front support system,which focuses on the following aspects to carry out targeted discussions and research:(1)While clarifying the status quo of this research,the related classic theories are sorted out,the advantages and disadvantages and applicable scenarios of several types of deep foundation pit support that are currently widely used are analyzed,and the application of this thesis is briefly introduced.Numerical simulation software.(2)Using finite element analysis software,a numerical analysis model based on the deep foundation pit project of Wanda Plaza in Yuhuan City,Zhejiang Province was established,and the comparison with the monitoring data confirmed the rationality of this method in foundation pit engineering research.On this basis,the calculation results obtained are systematically summarized and analyzed to explore the evolution law of the foundation pit,and calculate and analyze the force of the front support of the grouting steel pipe.(3)The finite element numerical simulation software,which is currently highly respected and favored by the industry,is used to conduct single-factor analysis of foundation pits in deep silt areas,and the following important conclusions are obtained:(1)The maximum surface settlement occurs at a distance of 10m～15m from the foundation pit,the maximum pile displacement and deformation occurs at a distance of1m～3m from the bottom of the foundation pit,and the minimum value of the pit bottom uplift curve appears at the pile foundation and support.(2)Through single factor analysis of silt thickness,it is found that the thickness of silt soil layer is not the result of a single factor,but is closely related to related factors such as surface settlement,pile displacement and deformation value.Under normal circumstances,as long as the thickness of the silt soil layer reaches a certain level,the more severe the settlement,the farther the distance between the ground and the side of the foundation pit,and the greater the depth of the pile,the more serious the displacement and deformation,but the maximum uplift position at the bottom of the pit is not Nothing changes.Through in-depth analysis,it is further discovered that as long as the thickness of the silt soil layer continues to increase,the settlement of the foundation will become more and more significant,and the soil will also undergo large-scale displacement.(3)Through single factor analysis of grouting steel pipe front support parameters,it is found that when the support spacing changes,the foundation pit will basically not deform,but it will cause the support axial force to fluctuate.This shows that there is a close relationship between them.The effective parameters obtained through model analysis can provide a strong reference for this engineering research.