Abstract:
The in-situ liquefaction test is a new and exploratory research approach for soil liquefaction in geotechnical engineering in recent years. At present, in the in-situ liquefaction tests by previous researchers, the overburden pressure of the liquefiable soil is commonly below 20kPa, which certainly differs from the real conditions in the field. This limitation extremely makes the investigations on soil liquefaction unreliable through these in-situ tests. Based on the basic idea for multiple case, feasibility, repeatability and low cost, a new in-situ liquefaction testing method is proposed in this paper, which can account for the effect of overburden pressure on soil liquefaction. Taking dry sands as a reference, two cases of liquefaction tests under the overburden pressure for 25kPa and 50kPa, respectively, were carried out. Combined with the current understandings of soil liquefaction, the dynamic responses and characteristics obtained in the tests were analyzed and used to verify that the proposed testing method is credible and reliable. The main points are as follows:(1) a new concept of testing pore pressure ratio is proposed, which can be used to preliminarily evaluate the results of an in-situ liquefaction test considering the effect of overburden pressure; (2) under the low-stress level of overburden pressure(0-50kPa), approximately buried at a depth of 0-5m in the field, it should be emphasized that the overburden pressure is a sensitive factor to affect the dynamic responses of soil liquefaction; and (3) when the induced volumetric strain of saturated sand is in a range of 0.1-1%, the residual pore pressure increases rapidly. When the residual pore pressure ratio reaches 0.6, the ground surface settlement response of a dry sand site differs from that of a saturated soil site under identical experimental conditions. The results presented in this paper can provide a new alternative to soil liquefaction research in which the experimental conditions are closer to the real field, in the 1-g gravity environments.