The Study On The Risk Assessment Of The Guan Hui Intercity Underpassing Guang Shen Expressway’s Pile Foundation Underpinning

With the rapid development of national economy and the high-speed urbanization in recent years, the political, economic and cultural exchanges among the cities become more and more closely. In order to optimize the urban pattern and to ease traffic problems in city agglomerations, intercity rail transit is widely used in traffic connection between cities. In the process of inter-city rail transit construction, it is usual to encounter the problem that beneath existing building(structure) pile foundation underpinning the case when buildings will be wearing. This paper is written under the background of Guanhui intercity rail Guangzhou-Shenzhen highway bridge engineering, because of the large traffic volume and the non-restriction of the vehicles’ running speed on it, the construction gets bigger risk and more difficulties. Result from that, this thesis is written on the basis of fuzzy network analysis. It has made the evaluation on the construction risk about the underpinning and proposed some measures to lower the risk.By combining with the investigation about the Guanhui Guangshen intercity beneath piles underpinning construction site’ geological conditions, traffic conditions and the typhoon, it has proposed the mechanism of pile foundation underpinning risk, identified the major risk factors that can affect the pile foundation underpinning, and constructed assessment system of pile foundation underpinning risk, which includes four first class indicators and fifteen second class indicators, the four first class inditors are security controls, construction, natural environment and design. This thesis gets data from the questionnaire, uses triangular fuzzy numbers as linguistic scale, takes fuzzy network analysis to establish complementary judgment matrix, and makes analytic hierarchy process to get the weight vector, then introduces fuzzy comprehensive evaluation theory to judge the final overall risk grade, thus it has completed the risk assessment model’s construction of Guanhui under the Guangzhou-Shenzhen intercity construction of pile foundation underpinning, and described the risk loss of the project quantitatively.Based on the above, it can be easily seen from the weight indexes that the pile foundation underpinning risk grade is four, which is a very serious level. During the construction, there will be some problems, such as uplift of surface grouting and the unsuccessful situation of the system conversion in the lifting process, etc. We need to improve the protection grade to ensure the safety of the traveling vehicle. While the surface’ grouting underpinning, pre-jacking and the formation lithology are most likely to cause significant losses to the project. Finally, according to the key risk factors identified by the research and the comprehensive evaluation results, we have made some reasonable safeguard measures which effectively reduce the risk in the construction process of pile foundation underpinning when there is non-restriction of the running speed of the vehicles.