Safety Risk Assessment Of Deep Foundation Pit Support Construction For High-Rise Residential Buildings

With the rapid development of my country’s economy and the vigorous integration of urban construction and townships,the demand for space in urban development has gradually increased,high-rise buildings have gradually developed toward the trend of deep underground and high ground,and deep foundation pit projects have gradually emerged.The scale and depth of excavation are increasing,and the construction difficulty and existing risks are gradually increasing.Once an accident occurs,it not only causes economic losses,but also threatens people’s lives and safety,delays the construction period,and will also lead to the collapse of surrounding buildings and the destruction of the underground pipeline network,causing bad social impact.In this paper,through identification,evaluation and research on the supporting risks of the deep foundation pit project during the construction of high-rise residential buildings,we hope to put forward effective measures to prevent accidents in the deep foundation pit project,and optimize the construction management environment and risk prevention and control of the deep foundation pit project.Deep foundation pit construction is a multi-disciplinary complex system engineering that integrates excavation,support and monitoring and measurement.The construction conditions are difficult and the process is complex.There are many risks that threaten the normal construction of deep foundation pits,and even the safety of construction personnel.The risk analysis process of deep foundation pit mainly adopted in this paper is risk identification-risk assessment-risk response.(1)In the risk identification link,a deep foundation pit construction risk identification model based on the principle of fuzzy complementary judgment matrix sorting was established,and the model was used to identify the risk of deep foundation pit construction,supporting pile + prestressed anchor construction The main risk factors are the risk of the plan,the risk of soil nail wall support,the risk of prestressed anchor cable,the risk of foundation pit support monitoring and the surrounding environment.Among them,the main risk factors in the survey stage are: insufficient survey scope and depth,and inaccurate test results;the main risk factors in the design stage are: poor understanding of the actual situation on the site,simply relying on the survey report;supporting piles + prestressed anchors The main risk factors of the cable support scheme are: positioning line release deviation,guard tube embedding deviation,pile hole offset tilt and excessive sediment at the bottom of the hole;the main risk factors of the soil nail wall support scheme are: soil nail hole layout,Soil nail rod placement and grouting and shotcrete in the hole;the main risk factors for the construction of prestressed anchor cables are: rod setting,grouting in the hole and anchor tension,etc.;the main risk factors in the monitoring phase of foundation pit support are: monitoring The intensity is too low,the monitoring and forecasting is not timely and the detection accuracy is insufficient.(2)In the risk assessment link,by optimizing the method of determining the degree of fuzzy membership,a fuzzy comprehensive assessment model of the construction risk of deep foundation pit engineering is established.Taking the deep foundation pit support project of Zifeng Building in Xifeng District of Qingyang City as the risk assessment object,according to the risk identification result matrix,a special assessment was carried out for each risk factor set of the deep foundation pit support project from the investigation,design and construction stages.The specific risk level is obtained,and the overall risk of each specific evaluation result is evaluated as a risk indicator,and the probability of risk in the entire project is obtained.The results show that the risk of supporting pile + prestressed anchor cable construction plan,prestressed anchor cable risk,and foundation pit support monitoring risk are at level IV(high)risk,and other risk factors are at medium risk;the overall project risk is between medium risk and Between high risk.The countermeasures against construction risks are given according to the causes of risks.