Study On The Risk Assessment Of Deep Foundation Above The Tunnel

The increasingly dense urban underground traffic network brings convenience to the public and poses new challenges to the construction of the city.For some special reasons,the construction unit has to carry out deep foundation pit construction work at the top of the underground tunnel.The deep foundation pit excavation involves a wide range of fields.It requires high and complex technology and a long construction period,which is affected by various factors such as investigation,design,construction and monitoring.The safety of the deep foundation pit construction process is reduced because of a mistake in the construction link.It is caused the possibility of the dangerous accident is increased.The difficulty of the deep foundation pit excavation and the additional risk of a tunnel under a foundation pit are increased when the subway tunnel is under the deep foundation pit.At present,the scholars at home and abroad have done many related studies on the theory and monitoring of the deformation of the tunnel foundation pit in the special working conditions.But there is no comprehensive risk assessment system for the deep foundation pit construction on the subway,which serves this kind of project.Therefore,this paper intends to conduct a study on the establishment of a risk assessment system for the deep foundation pit engineering above the tunnel to reduce the risk and the occurrence of the accident.To this end,the following experiments were carried out.(1)The establishment and solution of the risk assessment model for the deep foundation pit engineering above the tunnel has been researched.It provides a theoretical basis for the exploration of the source of risk through the analysis and summary of the deformation mechanism and influencing factors of the deep foundation pit and the tunnel.The causes of accidents in design,construction and monitoring were analyzed in order to get the risk factors of for the deep foundation pit engineering above the tunnel.The advantages and disadvantages of various risk assessment methods at home and abroad are analyzed in order to choose the suitable risk assessment method for the deep foundation pit engineering above the tunnel.The risk assessment model of the deep foundation pit engineering above the tunnel is established by collecting the expert opinions,the project case analysis and the theoretical analysis results and integrating the ALARP criteria and the risk assessment levels recommended in GB/T28002.(2)The auxiliary calculation program for the risk assessment model of the deep foundation pit engineering above the tunnel has been compiled.There are some difficulties in the operation of the high-order judgment matrix,such as large amount of computation and complicated steps.It is difficult to adjust the data when the computing can't pass the consistency check.By comparing the characteristics of the related auxiliary computing software,the MATLAB software is selected for the compilation of the convenient computing program.The calculated procedure can effectively reduce the calculation steps in the process of risk assessment and improve the accuracy of the calculation results.(3)The risk assessment system for the deep foundation pit engineering above the tunnel has been studied on practical engineering.The risk assessment system for this project was applied to the practical engineering to verify the practical application effect.Combined with the construction monitoring data of the project,the actual situation of the engineering construction and the analysis of the results of the simulation analysis of the ABAQUS,the results show that the risk assessment system for the deep foundation pit engineering above the tunnel helps the project to avoid the risk and reduce the occurrence of the accident effectively.The auxiliary calculation program is effective in assisting the calculation of the risk assessment model in practical engineering,which plays a role in saving time and improving efficiency.