Guidance of professional knowledge (1): research on application technology of flat shovel lateral expansion test

Flat dilatometer test (DMT) has been applied in more than 40 countries since it was founded by Italian scholar Marchetti in 1970s. The dilatancy test of flat shovel started in China at 1995, and has been listed in the national standard "Code for Geotechnical Engineering Investigation" (GB5002 1-200 1) and Shanghai Engineering Construction Code "Code for Geotechnical Engineering Investigation" (DGJ08-37-2002), and relevant measuring instruments have been prepared.

DMT-W 1 Flat Shovel dilatometer was developed by Zhejiang Nanguang Geological Instrument Factory. The tester consists of a flat shovel probe, a measuring and controlling box device, a gas-electric pipeline, a gas pressure source, a penetration device and a probe. The indoor and outdoor comparison of Shanghai Survey Institute, East China Electric Power Design Institute and other units and the field application of many projects (the test depth is 39.8m, and the pressure measurement value is 3. 1MPa) show that the instrument has stable performance, rapid and accurate test, and has the functions of similar products abroad. By borrowing foreign empirical formulas, geotechnical parameters can be calculated [3].

Domestic research institutions that use DMT to determine soil parameters mainly include Tongji University Department of Underground Architecture and Engineering, Shanghai Geotechnical Engineering Survey and Design Institute Co., Ltd., Shanghai Shenyuan Geotechnical Engineering Co., Ltd., Shanghai Tunnel Engineering Rail Transit Design and Research Institute, China Shipbuilding Industry Survey and Design Institute, etc. These units are located in Shanghai, and their series of research work is almost unified in this field in China. The research contents mainly include DMT test [5-7, 9- 10] and the distribution law of soil (material) index ID, horizontal subgrade reaction coefficient Kh and foundation bearing capacity fa in Shanghai. In addition, Li Xiongwei of Nanjing University of Technology compared the results of flat dilatometer test with those of static penetration test, standard penetration test and geotechnical test, and put forward empirical formulas such as vertical drainage modulus and undrained shear strength of flat dilatometer test according to the geological conditions of a site in Nanjing [4]. Meng Qingwen, the Third Survey and Design Institute of the Ministry of Railways, etc. A formula [8] for measuring the coefficient of horizontal subgrade by dilatometer test is put forward.

There is a lot of research abroad. Marchetti, as a pioneer of DMT theory, put forward the calculation formulas of soil (material) index ID, lateral expansion modulus ED, horizontal stress index KD and pore pressure index UD [1 1]. Viggiani put forward the formula KH [12] for calculating the reaction coefficient of horizontal subgrade; Doboku Gakkai refers to the literature of Japan, Europe and Southeast Asia, and puts forward a modified equation for calculating soil parameters with DMT [13].