An experimental study of the displacement characteristics of dry sand under dilatometer penetration
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摘要:
扁铲侧胀试验（DMT）已在国内外岩土工程勘察、地基加固效果评价等领域中得到广泛应用。DMT的测试过程在扁铲探头贯入到测试位置后进行，因此探头的贯入过程对土体造成的扰动在一定程度上将直接影响测试结果。目前关于扁铲探头的贯入机理，以及贯入过程可能引起的土体扰动及其对测试结果的影响尚未研究清楚。通过室内模型试验手段，进行扁铲探头贯入不同初始密实状态下均质干砂的试验研究，分析了探头贯入过程中产生的土体位移场分布特征。试验结果表明：扁铲探头的楔形部和膜片所在的侧胀部贯入产生的挤压作用是引起土体变形扰动的主要原因；探头楔形部的贯入过程表现为向下和向斜侧面挤压土体，竖向位移量很小，产生向两侧扩展为主的扁状位移场，而探头侧胀部的贯入过程主要表现为向两侧面水平向挤压土体，产生半椭圆状水平位移场且分布范围明显更大，同时探头侧面表现为一定的剪切作用而产生较窄范围的竖向位移场。另外，扁铲探头贯入干砂产生的位移场受砂土初始密实状态的影响较小，主要表现为探头楔形部周围的位移场分布范围随密实度增大而扩大。
Abstract: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.
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Key words:
- flat dilatometer test (DMT) /
- penetration process /
- displacement /
- model test /
- dry sand
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表 1 试验分组及相关试验参数
Table 1. Test groups and related test parameters
试验编号 干密度ρd /（g·cm−3） 初始相对密度Dr 初始密实状态 No.1 1.73 0.25 松散 No.2 1.77 0.44 中密 No.3 1.83 0.75 密实 
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