不同工况多孔抽水试验的渗透系数测定及影响规律研究

Study on Permeability Coefficient Measurement and Influence Law Based on Porous PumpingTest under Different Working Conditions

岩土层的渗透系数k是岩土工程勘察和水文地质勘察中的重要参数,不同试验方法得出的渗透系数不同。本文采用多降深的稳定流抽水试验方法,设计三个观测孔对野外现场抽水试验孔进行水位测量,并对抽水试验不同工况及观测条件下的试验结果影响规律进行分析,结果表明,简易单孔抽水试验容易造成孔位水位波动,导致观测不准,同时由于水跃的存在,影响渗透系数的精度。设置一定距离的观测孔,则水流呈稳定流状态,试验结果表明仅两个观测孔则可以消除紊流影响,符合经典理论计算条件,获得较为准确的数据。试验采用三个降深的方法,并保持稳定时长在4 h,较好减少了因地层不均性出现的局部地层水流阻塞、过水断面变得过于狭窄而出现的紊流现象。本研究可为工程勘察现场抽水试验工作提供参考。

The permeability coefficient K of rock and soil layer is an important parameter in geotechnical engineering and hydrogeological investigation. The permeability coefficient obtained by different test methods is different In this paper,the steady flow pumping test method with multiple drawdowns is adopted,and three observation holes are designed to measure the water level of the field pumping test holes,and the influence laws of the test results under different working conditions and observation conditions are analyzed.The results demonstrated that simple single-hole pumping test is easy to cause the fluctuation of water level at the hole lev el,resulting in inaccurate observation At the same time,due to the existence of water jump,the accuracy of permeability coefficient is affected;if observation holes are set at a certain distance,the water flow is in a stable state.The test results show that only two observation holes can eliminate the influence of turbulence,which conforms to the classical theoretical calculation conditions and obtain more accurate data;the method of three drawdown is adopted in the test,and the stability was maintained for 4 hours,which effectively reduced the turbulence phenomenon caused by local formation water flow blocking and water crossing section becoming too narrow due to the heterogeneity of the formation itself.This study can provide reference for the pumping test of engineering investigation site.