tailieunhanh - Báo cáo nghiên cứu khoa học: "VACUUM PRELOADING WITH VERTICAL DRAINS THEORY AND RECENT DEVELOPMENTS - APPLICATIONS"

Giới thiệu Hợp nhất chân không gây ra (VIC), lần đầu tiên được đề xuất bởi Kjellman vào năm 1952, là một phương tiện hiệu quả để thúc đẩy sự cải thiện của đất bão hòa mềm, trong khi ngăn ngừa thất bại hình thành trước khi tải thực sự. | VACUUM PRELOADING WITH VERTICAL DRAINS THEORY AND RECENT DEVELOPMENTS - APPLICATIONS MSc. Vu Manh Quynh Prof. Dr. Wang Bao Tian Geotechnical Research Institute Hohai University Nanjing 210098 P. R. China 1. Introduction Vacuum induced Consolidation VIC firstly proposed by Kjellman in 1952 is an effective means for accelerating the improvement of saturated soft soils while preventing pre-loading indeed formation failures. The soil site is covered with an airtight membrane and a vacuum state is created underneath it by using vacuum pumps. The technology can provide an equivalent pre-loading of about high as composed with a conventional surcharging fill. Instead of increasing the effective stress in the soil mass by increasing the total stress conventional mechanical surcharging vacuum-assisted consolidation preloads the soil by reducing the pore pressure while maintaining a constant total stress. A typical construction site layout of vacuum preloading is showed in Fig 1. Fig 1. Site layout of vacuum preloading a site in Nanjing China A nominal vacuum load of 80 kPa is normally used in design although a higher vacuum pressure of up to 90 kPa may be achieved sometimes. When a surcharge load higher than 80 kPa is required a combined vacuum and fill surcharge can be applied. For the treatment of very soft ground the vacuum preloading method is faster than the fill surcharge method as the 80 kPa vacuum pressure can be applied almost instantly without causing stability problem. Field experience indicates a substantial cost and time savings by this technology compared to conventional surcharging. The vacuum preloading method is cheaper about 30 compared with the fill surcharge method for an equivalent load Shang et al. 1998 Chu et al. 2000 . This method has been successfully used for soil improvement or land reclamation projects in a number of countries like China France Japan Thailand Singapore Chen and Bao 1983 Bergado et al. 1998 Chu et al. 2000 Indraratna et al. .