梨山地區崩積層成因與崩積材料之力學行為

Abstract

梨山崩積層是由破碎板岩與其風化形成之土壤所構成，經侵蝕作用造成凹凸起伏之地形。此種地形、地質條件極易於豪雨或地震後產生滑動。本研究藉由地質鑽探取得之完整鑽心及既有之地質資料對此區域之崩積層形成之崩塌機制加以分析探討。隨後於實驗室進行一系列的一般物理性質試驗及三軸壓密不排水試驗，利用試驗結果分別對崩積材料的力學行為與粒徑分佈及岩塊含量等關係進行分析討論，來幫助釐清崩積材料力學性質與滑動關係，使整個梨山區域之崩積材料特性及崩積層形成之崩塌機制更為明瞭。 本文針對梨山地滑區B13滑動體B1鑽孔所鑚得之崩積材料進行一系列的三軸不排水試驗，結果顯示滑動面材料之岩塊含量低於16%，主要為基質土壤所構成，越深層滑動帶越有過壓密之現象。綜合劉盛華(2007)對梨山崩積層軟弱材料之試驗結果得出，此區域之灰色黏土夾板岩碎屑類材料之C’≒0.3 kg/cm2，Φ’≒20.6°。另外綜合羅文驤(2007)對梨山區域板岩夾粘土類材料比較發現，其強度有隨岩塊含量增加而增加之趨勢。此外，結合唐禎國(2007)及黃玉麟(2006)之資料，由劈理位態分布狀況推估梨山地區崩積層之形成可能為大規模之山坡潛移導致。研究場址B13滑動體下層軟弱層區亦應為潛移剪切作用形成。

The Lishan colluvial deposits are composed of fractured slate and its weathered soils. The ground surface exhibits concave-convex relief which were formed by erosion. Thus, the terrain and geology indicate that landslide is easy to be triggered by rainfall or earthquake. The study aims to investigate the origin of the colluvial deposits and the mechanical behavior of the deposits. Hence, two borehole are drilled at the landslide area, one at zone 5 and the other at zone 13. A series of physical property tests and undrained triaxial compression tests of colluvial cores are conducted. The colluvial cores drilled from the sliding belt of the landslide zone 13 shows that sliding interfaces are composed of grey clay with 16% less of slate detritus. Besides, a series test of liquid limit and plastic limit on the core specimens are perfomed. The test results show that the deeper of sliding interface is the more over-consolidation of the interface material. The results of undrained triaxial compression tests show that the strength parameters of gery clay with slate detritus C’ and Φ’ are about 0.3 kg/cm2 and 20.6°, respectively. The test results also show that the triaxial peak strength increase with the increase of block content. Finally, the study integrates the site investigation results of Huang(2006) and Tang(2007) and concludes that the Lishan colluvial deposits may be formed by large-scale hillslope creep. The deeper sliding belt at landslide zone 13 is also formed by a large-scale hillslope creep.