Health Assessment And Engineering Application Research Of Existing Foundation Pit Slope

With the continuous development of China’s economy and the acceleration of urbanization,various large-scale super high-level buildings are emerging.It is obvious that the construction of such large-scale engineering projects cannot be completed overnight.Therefore,various large-scale construction foundation pits in the early stage of the construction process may exist for years or even longer.Existing foundation pit works are generally located in the core area of the city,and there are dense buildings around.If the slope of the foundation pit is damaged,it is likely to cause collapse and damage to the surrounding buildings and casualties.Therefore,it is of great significance to make a scientific and reasonable assessment of the health status of the existing foundation pit slopes in the operation and maintenance period,and to make targeted health management based on the assessment results.The existing foundation pit slope health assessment is to collect and sort out the "disease" information of the existing foundation pit slope by means of investigation and detection,and then use the relevant evaluation theory to analyze it,and ultimately make a comprehensive judgment on the health status of the existing foundation pit slope.At present,the existing foundation pit slope health assessment lacks clear norms and systems that can be referred to,and the formulation of similar health assessment programs is basically based on the experience of front-line engineers,lacking of theoretical and objective.In this context,this paper combines the example of a deep foundation pit slope project of an existing building in Chongqing during the operation and maintenance period,and focuses on the core needs of scientific and comprehensive health assessment of existing foundation pit slopes.A set of practical methods and procedures for the health assessment of existing foundation pit slopes,thereby improving the city’s health management capabilities in foundation pit slope engineering,ensuring the normal operation and use of existing foundation pit slopes,and reducing existing foundation pits’ probability of an accident in the slope and its surrounding buildings.The main research contents of the thesis are as follows:(1)In the full study of the common “diseases” of existing foundation pit slopes,the assessment targets are confirmed,and the existing foundation pits are divided according to the engineering information sorting,“disease” survey,on-site inspection,extraction evaluation factors,and evaluation and grading.The slope health level and the corresponding health assessment system have been established,which has improved the shortcomings of previous engineering evaluations that rely too much on the subjective judgment of engineering personnel.(2)Based on the above-mentioned health assessment system,carry out detailed engineering field investigation and inspection on an example of a deep foundation pit slope project of an existing building in Chongqing,sort out and analyze the “disease” situation and conduct on-site material performance experiments for the next step.The health assessment of the slope provides a data base.(3)By analyzing and arranging the “disease” of existing foundation pit slopes,five evaluation factors including stability coefficient,slope top displacement,material performance degradation,hydrogeology and slope height are extracted,based on the classification of existing national codes.The membership function of the corresponding evaluation factor is established,and the standardization of each health assessment factor is realized by calculating the membership degree.(4)Based on the residual resistance of the supporting structure,a calculation model for the stability of the plane slip surface of the existing foundation pit slope is proposed.The generalized Hoek-Brown criterion based on GSI is used to influence the environmental disturbance and the physical weathering of the hydraulic environment.The rock mass strength correction is carried out on the slope of the rock foundation pit.The stability analysis of the deep foundation pit slope project of an existing building in Chongqing is carried out,which provides a reference for the stability analysis of the existing foundation pit slope.(5)Applying the fuzzy theory to the health assessment of existing foundation pit slopes,using the analytic hierarchy process to assign weights to each evaluation factor and based on this,the fuzzy synthesis suitable for the health assessment of existing foundation pit slopes is proposed.According to the above ideas and methods,a health evaluation of a deep foundation pit slope project of an existing building in Chongqing was carried out.(6)Based on the settlement prediction curve around the peck foundation pit,a quantitative formula for the influence of the existing foundation pit slope on the surrounding buildings is proposed.The original assessment results are supplemented by evaluating the health of the building under the influence of the existing foundation pit slope.Provide a basis for the health management of existing foundation pit slopes and surrounding buildings.