The Studies On Rock And Soil Engineering Properties And Rational Selection Of Foundation Types In Hangzhou City

Hangzhou city is located in the south of the Yangtze River Delta, west of the Hangzhou Bay, lower reaches of the Qian Tang River. In such a natural environment with plentiful rivers, lakes and mountains, the engineering properties of the rock and the soils in this area are very complicated. It is composed of not only marine and soft soil of alluvial formation, but also silts and hard rocks, which brings certain difficulty to the selection of buildings foundation type.In this thesis, based on all geomorphic unit of Hangzhou city, the engineering geological zoning was made, and the engineering properties of rock and soil in every zone were summarized and classified. By means of comprehensive and comparative analysis, the summary evaluation was then done. Meanwhile, physical and mechanical indexes of all soils and features of the main bearing layers were suggested and listed.Besides, the problems about the selection of foundation type under different geological conditions were discussed. On the basis of the analyses for different geomorphic units, the foundation methods and foundation types commonly used in Hangzhou area were classified, and the main problems encountered in various foundation methods and the respected reasons were illustrated. Moreover, the related prevention and treatment measures were proposed.It was found that the rock in the southwest of Hangzhou city had its distinguished geographical characteristics. To increase the bearing capacity of single pile thrusting into such rock with low compressive strength, some people choose to increase the pile length blindly. However, a considerable number of static load tests show that this will results in the bearing capacity of such single pile being not played fully. In order not to waste, therefore, we should select the bearing capacity of pile tip accurately, and determine pile length reasonably. The author deems that the bearing capacity of pile tip in soft rock relates greatly to the material composition and structural planes of the rock. It is only after detailed investigation and analysis that the bearing capacity of pile tip in the soft rock can be determined reasonably.