臺灣斷層泥之特性及斷層泥力學評估的新發展

New Developments Assessing Mechanical Properties of Fault Gouges

林銘郎(Ming-Lang Lin) ； 鄭富書(Fu-Shu Jeng) ； 翁作新(Tzou-Shin Ueng) ； 洪如江(Ju-Jiang Hung)

《地工技術》 79期 (2000/06) Pp. 91-106

https://doi.org/10.30140/SG.200006.0008

摘要

當隧道施工通過斷層帶時，常因鑽開斷層泥構成之不透水帶造成高壓湧水、或由於斷層泥吸水弱化後發生擠壓造成大量變形，導致工程災害。斷層帶中包含被剪裂的岩塊及粉砂狀至黏土狀的斷層泥，後者係因劇烈剪切作用與裂隙水的物理及化學作用所形成。斷層泥係由高度剪動摩擦所形成，故具有硬黏土的基本特徵：具裂隙產狀、低滲透性、高度過壓密、高回脹潛能等力學性質。本文比對國內外斷層泥之組成、力學性質及探討其對工程之影響。相較於國外，國內斷層泥中膨脹性粘土礦物成份極少；故國內隧道工程案例遭遇大量變形困難，應不是由斷層泥的化學性膨脹所造成，而是應力所造成之擠壓現象所導致。比對國內斷層泥力學回脹之行為，發現隨著過壓密比的增加，回脹係數隨之減小，二次回脹指數卻隨之增加之趨勢。斷層泥之回脹特性亦與取樣地點有關：隧道內取樣的斷層泥具有較高的回脹潛能，地表斷層泥則相當已經回脹後的地質材料。斷層泥的摩擦性質與剪動速率有關，於高速剪動下造成斷層泥殘餘剪力強度下降。此特性直接影響活斷層的摩擦穩定性，決定該斷層是否會孕育地震、或發生較為穩定的潛變。

關鍵字

斷層泥 ； 回脹 ； 擠壓 ； 過壓密 ； 滯動 ； 摩擦穩定 ； 活斷層 ； 斷層帶

並列摘要

Highly fractured rock blocks and fault gouge are the common materials found within a fault zone. Fault gouge is a fine soil with silt and clay particles, which is the product yielded by the physical and the chemical actions during the shearing process of the fault. As fault gouge has been severely sheared, it possesses poor permeability, over-consolidated behavior and has a high potential to dilate, when confining pressure is relieved, as well.The mechanical properties of the fault gouge sampled in Taiwan are analyzed and compared. It is found that fault gouge in Taiwan contains very little swelling clay minerals, e.g. montmorillonite. Therefore, the squeezing condition encountered in tunneling practice in Taiwan cannot be the consequence of chemical swelling but the mechanical swelling of the gouge instead. It is also observed that: the greater the OCR, the less the swelling index and the greater the secondary swelling index. Gouge sampled deep in tunneling sites has much greater tendency to dilate than those sampled near ground surface. Finally yet importantly, the shearing rate dominates the frictional stability of gouge, whether stable slide or instable stick-slip displacement would occur. In turn, this factor may serve as the under-lain mechanism whether an active fault will creep stably or will induce earthquake during the shearing movement.

並列關鍵字

fault gouge ； swelling,squeezing ； overconsolidation ； stick - slip ； frictional stability ； active fault ； and fault zones