南部沿海基岩地区地表风化层渗透特性研究

Permeability Characteristics of Bedrock Weathering Layer in Southern Coast Area of China

[目的]研究基岩地区地表风化层渗透特性,寻求其渗透系数的确定方法,可为孔隙—裂隙岩体地下工程的性能评价提供科学依据。[方法]以中国南部沿海花岗岩为研究对象,采用张力入渗仪,重点针对基岩风化层开展入渗试验研究,利用非线性回归法、多压力法、WS方法以及瞬态方法中的单盘测定法计算渗透系数,开展不同方法的综合对比与地质统计分析,确定研究区场地基岩表层风化层的渗透系数及其空间分布规律。[结果]①研究区基岩全风化层渗透系数分布在0.023~3.918 m/d,平均渗透系数约为0.971 m/d,与经验值相符;②研究区地形较高处基岩风化层渗透能力相对较强,地形较低处渗透能力较弱;③不同计算方法获得的渗透系数存在一定的差异性;④多压力方法更适合研究区基岩风化层渗透系数的确定。[结论]研究区基岩风化层渗透系数可采用张力入渗仪和多压力方法确定,其渗透性能整体较弱。

[Objective]The permeability characteristics of the bedrock weathering layer were determined in order to propose a corresponding experimental method of hydraulic conductivity,and thereby provide a scientific reference for the performance assessment of underground engineering facilities in a porous and fractured medium.[Methods]We focused on granite at an underground engineering site in the southern coastal area of China.A tension infiltrometer was used to conduct the infiltration tests on the bedrock weathering layer.A nonlinear regression model,the White and Sully method,a multi-pressure method,and the Smettem and Turner method were adopted to calculate the hydraulic conductivity and carry out a comprehensive and comparative analysis.The spatial distribution of the hydraulic conductivity of the bedrock weathering layer was determined based on a geologic statistical method.[Results]①The hydraulic conductivity of the fully weathered bedrock in this area was between 0.023 and 3.918 m/d,and the measured mean value was around 0.971 m/d,which was consistent with the empirical value.②The permeability capacity of the bedrock weathering layer in this area was stronger in the high terrain area than in the low terrain area.③There were some differences in hydraulic conductivity obtained by using different calculation methods.④The multi-pressure method was more suitable for determining the hydraulic conductivity in the study area.[Conclusion]The hydraulic conductivity of the bedrock weathering layer in the study area was obtained by using a tension infiltrometer and the multi-pressure method.The permeability capacity of the bedrock weathering layer was found to be relatively weak.