梨山崩坍區大規模崩積地層之形成機制

The Origins of the Colluvial Deposits of the Li-Shan Landslides

廖志中(Jyh-Jong Liao) ； 潘以文(Yi-Wen Pan) ； 林志平(Chi-Pin Lin) ； 唐禎國(Chen-Kuo Tang) ； 黃玉麟(Yu-Lin Huang) ； 羅文驤(Wen-Hsiang Lo)

《中華水土保持學報》 42卷4期 (2011/12) Pp. 303-312

https://doi.org/10.29417/JCSWC.201112_42(4).0004

摘要

本文利用高品質鑽探、孔內造影以及震波試驗，並根據過去地質資料等結果，探討梨山崩塌區大規模崩積地層的形成機制。結果顯示梨山地區的板岩劈理位態與邊坡方位不一致，崩積層不應為沿劈理大規模順向滑動所堆積形成。調查結果亦顯示早期梨山地區主要受大甲溪侵蝕而不穩定，逆向的板岩邊坡可能因重力造成大規模邊坡潛移滑動，並堆積成大規模的崩積地層。崩積地層後因向源侵蝕所形成的蝕溝侵蝕坡腳，造成崩體上大、小規模沿黏土界面的滑動。由岩心檢視、地下水位變化、深層岩層位態等顯示，梨山崩積地層內的軟弱層約可區分為淺層級深層兩類，淺曾軟弱層可能因地下水位改變而使風化板岩加速風化而形成；深層軟弱層可能由潛移破壞造成上下岩層剪動而形成。

關鍵字

中新世廬山層 ； 潛移滑動 ； 崩積層 ； 孔內造影

並列摘要

This study aims to propose the model of the origin of the Li-Shan colluvial deposits and the weak layers in the deposit. Review of historical data, geological boring, and borehole tests including borehole discontinuity measurements and borehole PS wave velocity measurements were conducted in this study. Based on the historical geological data and the results of the discontinuity measurements, the Li-Shan colluvial deposits may be formed by one or several occurrences of large-scale hillslope creep. Moreover, the creep failure may have been induced by the bank-toe erosion of the Ta-Chia River. Then, the following slope failures of colluvial deposits were formed by surface erosion. The failures occurred along the weak -clay interfaces in the deposit. Two types of weak zones (shallow zone and deep zone) in the deposit were examined from rock cores and the results of in-situ tests. The shallow zone with weak-clay may have been formed by weathering caused by ground water fluctuation. The deep zone of weak clay may be the weathered product of the shear bands induced by deep creep of slate.

並列關鍵字

Colluvial deposits ； borehole televiewer ； origins of colluvial deposits ； hillslope creep