| Citation: | CHEN Zhongqing, WU Tianyu, GAO Yanbin, LYU Yue, LIU Shuai. An experimental study of the displacement characteristics of dry sand under dilatometer penetration[J]. Hydrogeology & Engineering Geology, 2021, 48(3): 119-125. doi: 10.16030/j.cnki.issn.1000-3665.202008046 | 
The flat dilatometer test (DMT) has been widely used in engineering such as geotechnical engineering investigation and evaluation of ground improvement effect at home and abroad. The test process of DMT is usually carried out after the blade insertion of DMT into test position, so the disturbance caused by the dilatometer penetration process will directly affect test results to a certain extent. However, the mechanism of dilatometer penetration and soil disturbance and its influence on test results caused by penetration process are not yet known. Homogeneous dry sand samples under different initial densities are prepared by the layered plate compaction method with low level rainfall, and several laboratory model tests of dilatometer penetration into these sand samples together with particle image velocimetry (PIV) are carried out to investigate the distribution characteristics of the soil displacement field during the blade penetration process. The test results show that (1) the extrusion effect caused by the penetration of both the wedge part and lateral expansion part of the blade mainly causes soil disturbance. (2) The surrounding soil is squeezed downward and sideward during the penetration of the wedge part of blade, resulting in small vertical displacement and a flat displacement field which mainly extends to both sides, while the surrounding soil is squeezed horizontally to the two sides during the penetration of the lateral expansion part of blade, resulting in a semi-elliptical horizontal displacement field with the distribution range being obviously larger, and meanwhile, the shear effect caused by side friction between the blade and soil produce a vertical displacement field with a narrow range. (3) Moreover, the displacement field of dry sand caused by dilatometer blade penetration is less affected by the initial sand density than that by cone probe penetration, and only the distribution range of displacement field around the wedge part of the dilatometer blade expands with the increase of the initial density to some extent.
		                | [1] | MARCHETTI S. In situ tests by flat dilatometer[J]. Journal of the Geotechnical Engineering Division,1980,106(GT3, Proc. Paper, 15290):299 − 321. | 
| [2] | ASTM D 6635—15. Standard Test Method for Performing the Flat Plate Dilatometer[S]. ASTM International, West Conshohocken, PA, USA, 2015. | 
| [3] | EN 1997—2: 2007. Eurocode 7: Geotechnical Design –Part 2: Ground Investigation and Testing[S]. CEN European Committee for Standardization, Brussels, Belgium, 2007. | 
| [4] | ISO 22476—11: 2017(E). Geotechnical Investigation and Testing –Field Testing –Part 11: Flat Dilatometer Test[S]. International Organization for Standardization, Geneva, Switzerland, 2017. | 
| [5] | 中华人民共和国建设部. 岩土工程勘察规范: GB 50021—2001(2009年版) [S]. 北京: 中国建筑工业出版社, 2009. National Standard of the People’s Republic of China. Code for Investigation of Geo technical Engineering: GB 50021—2001(2009) [S]. Beijing: China Building Industry Press, 2009. (in Chinese) | 
| [6] | MARCHETTI D. In situ tests by Medusa DMT [C] //Proceedings of Proceedings of the XVII ECSMGE-2019: Geotechnical Engineering foundation of the future, Italian Geotechnical Society, Rome, 2019. | 
| [7] | MARCHETTI D. Dilatometer and seismic dilatometer testing offshore: available experience and new developments[J]. Geotechnical Testing Journal,2018,41(5):20170378. doi: 10.1520/GTJ20170378 | 
| [8] | 程健, 张丹, 刘子文. 基于弯曲元的剪切波扁铲侧胀技术可行性试验研究[J]. 工程勘察,2018,46(3):12 − 16. [CHENG Jian, ZHANG Dan, LIU Ziwen. Feasibility study on flat shovel bulging technique with shear wave based on bending elements[J]. Geotechnical Investigation & Surveying,2018,46(3):12 − 16. (in Chinese with English abstract) | 
| [9] | 刘学彦, 朱定华, 袁大军. 扁铲侧胀仪的改进及应用[J]. 岩土工程学报,2013,35(7):1375 − 1380. [LIU Xueyan, ZHU Dinghua, YUAN Dajun. Improvement and application of flat dilatometer[J]. Chinese Journal of Geotechnical Engineering,2013,35(7):1375 − 1380. (in Chinese with English abstract) | 
| [10] | MARCHETTI S, MONACO P. Recent improvements in the use, interpretation, and applications of DMT and SDMT in practice[J]. Geotechnical Testing Journal,2018,41(5):20170386. doi: 10.1520/GTJ20170386 | 
| [11] | 杨超, 汪稔, 傅志斌, 等. 扁铲侧胀试验在滨海沉积软土中的应用[J]. 水文地质工程地质,2010,37(2):79 − 82. [YANG Chao, WANG Ren, FU Zhibin, et al. Application of flat Dilatometer Test in littoral deposit soft soil[J]. Hydrogeology & Engineering Geology,2010,37(2):79 − 82. (in Chinese with English abstract) doi: 10.3969/j.issn.1000-3665.2010.02.017 | 
| [12] | 徐超, 陈忠清, 邢皓枫, 等. 扁铲侧胀试验在地基处理效果评价中的应用[J]. 水文地质工程地质,2009,36(1):100 − 103. [XU Chao, CHEN Zhongqing, XING Haofeng, et al. Application of flat dilatometer test in evaluation of soft soil foundation improvement[J]. Hydrogeology & Engineering Geology,2009,36(1):100 − 103. (in Chinese with English abstract) doi: 10.3969/j.issn.1000-3665.2009.01.022 | 
| [13] | BALIGH M M, SCOTT R F. Quasi-static deep penetration in clays[J]. Journal of the Geotechnical Engineering Division,1975,101(11):1119 − 1133. | 
| [14] | HUANG A B. Strain-path analyses for arbitrary three-dimensional penetrometers[J]. International Journal for Numerical and Analytical Methods in Geomechanics,1989,13(5):551 − 564. doi: 10.1002/nag.1610130507 | 
| [15] | BENOÎT T J, STETSON K P. Use of an instrumented flat dilatometer in soft varved clay[J]. Journal of Geotechnical and Geoenvironmental Engineering,2003,129(12):1159 − 1167. doi: 10.1061/(ASCE)1090-0241(2003)129:12(1159) | 
| [16] | FINNO R J. Analytical interpretation of dilatometer penetration through saturated cohesive soils[J]. Geotechnique,1993,43(2):241 − 254. doi: 10.1680/geot.1993.43.2.241 | 
| [17] | LEVADOUX J N and BALIAH M M. Pore pressures during cone penetrckon in clays[R]. Research report R80-15, Massachusetts Institute of Technology, USA, 1980. | 
| [18] | 罗松. 扁铲侧胀试验机理有限元分析及其在地基处理效果检验中的应用[D]. 上海: 同济大学, 2006. LUO Song. The finite element analysis of the mechanism of DMT and the application of DMT on compaction control[D]. Shanghai: Tongji University, 2006. (in Chinese with English abstract) | 
| [19] | 周健, 崔积弘, 贾敏才, 等. 静力触探试验的离散元数值模拟研究[J]. 岩土工程学报,2007,29(11):1604 − 1610. [ZHOU Jian, CUI Jihong, JIA Mincai, et al. Numerical simulation of cone penetration test by discrete element method[J]. Chinese Journal of Geotechnical Engineering,2007,29(11):1604 − 1610. (in Chinese with English abstract) doi: 10.3321/j.issn:1000-4548.2007.11.002 | 
| [20] | JIANG M J, YU H S, HARRIS D. Discrete element modelling of deep penetration in granular soils[J]. International Journal for Numerical and Analytical Methods in Geomechanics,2006,30(4):335 − 361. doi: 10.1002/nag.473 | 
| [21] | 陈维家, 陈映南. 砂土静力触探机理分析[J]. 岩土工程学报,1990,12(2):64 − 72. [CHEN Weijia, CHEN Yingnan. Mechanism analysis of static cone penetration test of sand[J]. Chinese Journal of Geotechnical Engineering,1990,12(2):64 − 72. (in Chinese with English abstract) doi: 10.3321/j.issn:1000-4548.1990.02.008 | 
| [22] | 陈维家, 胡逸群. 用白光散斑法定量分析静力触探时土体的位移场[J]. 长沙铁道学院学报,1988,6(4):87 − 95. [CHEN Weijia, HU Yiqun. Determination of displacement fields of a cone during static-penetration test by white-light speckle photography[J]. Journal of Changsha Railway Institute,1988,6(4):87 − 95. (in Chinese with English abstract) | 
			            
			            
			            
			        Particle size curve of the standard sand
Blade of flat dilatometer:(a)front of blade and (b)side of blade
Picture of the model test
Probe of small-scale static cone penetrometer
Test box and sample preparation device
Variation of specific penetration resistance with depth
(a)displacement vector distribution and cloud graph of (b) horizontal displacement, (c) vertical displacement after blade insertion into loose sand
(a) Displacement vector distribution cloud graph of (b) horizontal displacement and (c) vertical displacement after penetrating medium dense sand
(a) Displacement vector distribution cloud graph of (b) horizontal displacement and (c) vertical displacement after penetrating dense sand