基于水下抽水试验的岩体渗透系数研究及应用

 通过分析水下岩体钻孔抽水试验的水力边界条件，运用势场叠加原理，将水力边界条件分解为水平补给和垂直补给2个部分。其中，水平补给原理与陆上承压水钻孔抽水补给原理相同；对于垂直补给部分，通过适当的简化假定，推导出垂直补给钻孔渗流量计算公式，从而得到适用于水下岩体钻孔抽水试验渗透系数计算的理论公式。利用该理论公式计算得出的渗透系数，采用数值方法模拟水下岩体现场抽水试验，计算结果与试验结果比较接近。为便于比较，利用基于陆上岩体抽水试验渗透系数计算公式得到的渗透系数，进行抽水试验的数值模拟。计算结果表明：相比基于陆上渗流理论的渗透系数计算公式，本文的理论计算公式能够更合理、更接近实际地反映水下岩体抽水试验的渗流特性。最后，根据本文渗透系数的计算公式，采用数值方法和经验公式预测某拟建海底隧道工程施工期的涌水量，两者结果比较一致，可为隧道选择设计方案和施工方法提供参考。

RESEARCH ON PERMEABILITY COEFFICIENT OF ROCK MASS BASED ON UNDERWATER PUMPING TEST AND ITS APPLICATION

Hydraulic boundary conditions of borehole pumping test for underwater rock mass are analyzed. Based on the principle of superposition of potential field，the conditions are divided into horizontal recharge condition and vertical recharge one. The theory of horizontal recharge is the same as that of land-based artesian water borehole pumping recharge. For the vertical recharge，the calculating formula for the borehole water flow is derived with some appropriate assumptions and simplifications；and the theoretical calculating formula is deduced and applied to obtain the permeability coefficient theoretical formula for underwater rock mass pumping test. Using this permeability coefficient calculated by the theoretical formula，the in-situ pumping tests for underwater rock mass are simulated by numerical methods. The calculating results are close to the test results. For the convenience of comparison，the permeability coefficient calculated by land-based formula is used to simulate the in-situ pumping tests. The calculating results show that compared with the permeability coefficient formula based on the land-based seepage theory，the permeability coefficient calculated by the theoretical formula is more reasonable，more realistic；and it can better reflect the seepage characteristics of underwater rock mass pumping test than those by land-based formula. Finally，according to the permeability coefficient calculated by the formula，the numerical method and empirical formula are used to predict the water inflow during constructions of a submarine tunnel. The results of water inflow obtained from the two methods are nearly the same，which can provide references to the selection of design plan and the construction of submarine tunnel.