節理岩體滲透係數之先天異向性與應力引致異向性

Inherent and stress-dependent anisotropy of permeability for jointed rock masses

鄭允嘉(Yun-Chia Cheng)

指導教授 ： 董家鈞

國立中央大學/地球科學學院/應用地質研究所/碩士(2006年)

摘要

受節理切割之岩體，其不連續面所形成之複雜網絡往往是地下水滲流之重要通道。過去研究顯示，由室內試驗獲得之岩石材料滲透係數值，要明顯較由現地試驗所得之值低了幾個數量級，室內實驗所得岩體之滲透係數值之所以與現地極為不同，主要即因現地岩體滲透係數受現地之斷層、節理、裂隙等不連續面所影響。不連續面異向性分佈，將造成滲透係數之異向性。除了不連續面之異向性分佈外，異向性應力將造成不同方向之不連續面內寬閉合量不同，因此異向性應力亦將導致節理岩體之滲透係數異向性。本研究利用擬連續體模式，計算異向性節理岩體不連續面內寬隨正向應力改變之滲透係數張量（Permeability Tensor），此一滲透係數張量為節理岩體所受現地應力之函數。經參數敏感度分析結果顯示滲透係數異向性（k11/k33）將隨節理分佈異向性以及應力異向性（σ11/σ33）增加而增加；隨著節理長度增加，k11/k33不致造成明顯改變；節理正向勁度常數h與形狀係數c，雖將造成k11/k33值改變，但影響並不明顯。根據車籠埔鑽井岩心獲得之不連續面密度與方位資料，運用組構張量分析技術，可獲得節理空間分佈之定量資料，配合現地應力估計值，即可求得車籠埔鑽井附近節理岩體之破裂張量（Crack Tensor），進而探討車籠埔鑽井附近岩體之滲透係數張量異向性。於本研究假設之參數範圍內，k1/k3可達4～7之間。

關鍵字

內寬 ； 滲透係數 ； 岩體 ； 不連續面 ； 應力

並列摘要

The fracture networks are major flow paths in jointed rock masses. Experiment results suggest that a marked difference exist between the permeabilities measured in the laboratory and in situ. The difference is due to the presence of faults, joints and other discontinuities in situ. Not only the anisotropic distribution of discontinuities, stress anisotropy can also cause permeability anisotropy. In this study, stress-dependent permeability tensor was evaluated using continuum approach. Based on the parameter sensitivity analysis, the ratio of anisotropic permeability, defined as k11/k33 , increases with the increasing anisotropy of the distribution of orientation of joints and stress ratio which defined as k11/k33 . The influence of joint size, normal stiffness constant and aspect ratio on anisotropic permeability. Based on the orientation of joints from deep drilling (TCDP) borehole image, the crack tensors can be determined using fabric tensor and in situ stress states. The anisotropy of permeability tensors in jointed rocks near the TCDP borehole can be estimated. The ratio of anisotropic permeability k1/k3 near the TCDP borehole is between 4 ~ 7.

並列關鍵字

Discontinuity ； Aperture ； Permeability ； Stress ； Rock mass

參考文獻

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