崩積層之類併構岩材料力學行為與模式-以梨山地滑區為例

Abstract

本研究以梨山地滑區為研究場址，該地滑區之崩積層屬於「滑移型」。崩積層之組成相當複雜，由軟弱的沈泥質黏土至堅硬的新鮮岩盤均屬於其範疇。由於其組構行為複雜，常具不均質性，未必適合以一般土讓或岩石之行為視之，本研究借用「併構岩」的名稱來描述其組成，針對崩積層內類併構岩之行為，藉數值模擬進行「虛擬力學試驗」，進而歸納討論類併構岩之力學行為與性質。 梨山地滑區的類併構岩中岩塊與基質的強度與勁度的差異性極大，與以往其他學者所研究之併構岩材料間的差異性有甚大差距，因此其力學行為也與他人針對併構岩之研究結果不盡相同。本研究為確保所建立之模擬類併構岩試體的合理性，先以他人所製作人造併構岩之材料參數植入此研究所建立之模擬試體再與他人三軸試驗結果比對，確認所得趨勢相似度高，確立所建立之類併構岩模擬基本符合實際狀況。待確認模擬合理性後，本研究探討一些影響併構岩行為之重要參數：藉由虛擬力學試驗模擬所得之三軸試驗結果差異，分析岩塊體積比、岩塊傾角及岩塊長短軸比對力學行為與性質之影響趨勢。研究結果顯示：(1)試體整體強度及強度參數隨岩塊體積比增加而遞增，(2)岩塊傾角明顯影響試體力學行為的異向性，及(3)岩塊長短軸比則對於力學行為只有些微影響。本研究並討論崩積層試體尺寸對試體個別力學試驗結果變異性的影響，可發現當試體尺寸越大各試體間力學行為差異越小，當試體尺寸趨近於代表單元體積(representative elemental volume, REV)時，試驗結果漸趨於一致。 本研究並嘗試比較需虛擬力學試驗與實際實驗之結果，檢視兩者差異性，以供將來若室內實驗無足夠資料點可作分析時，或可透過虛擬力學試驗結果經修正預測值後提供參考實驗點，可能彌補現地取樣困難之問題。

The Li-Shan landslide region was adopted as an investigated site in this study. This region contains sliding-type colluvium; the colluvium is composed of hard rock and soft clay, which can be considered as a complicated composite geomaterial to be described as a “Blocks-in-matrix (Bimrock)” material. This study aims to model and analyze the mechanical behavior of colluvial materials as “resembled bimrock”. Unlike the bimrock materials studied by previous researchers, the strengths and stiffness of the rock blocks and matrix of the Li-Shan’s colluvium are quite different. As a result, the nature of the colluvial mechanical behavior is very different from the bimrock materials studied by others. Numerically simulated results of bimrock model were compared with the laboratory tested results of artificial bimrock specimens carried out by others to verify the appropriateness of the numerical model. After verification, this study carried out a series of numerical simulation as virtual mechanical tests and looked into the important factors that affect the mechanical properties of the colluvial as resembled bimrock. Factors taken into account include rock-block ratio, rock-block inclination, and rock-block aspect ratio. It was found that, for the modeled resembled bimrock: (1) the strength increases with the increasing block ratio, (2) rock-block inclination results in the anisotropy of mechanical behavior and properties, and (3) the rock-block aspect ratio only has a minor influence on the mechanical behavior/properties. In addition, the effect of specimen size on the mechanical behavior/properties of colluvium was also evaluated through a series of virtual mechanical tests. It was found the variation of mechanical behavior tends to converge as the specimen size approaching to a representative elemental volume (REV). Attempt was also made to compare the simulated results of colluvium as a resembled bimrock with the data of laboratory tested results. Due to the inevitable difficulties of obtaining identical colluvium specimens for laboratory tests, it may be possible to adopt virtual mechanical tests to complement insufficient data of laboratory tests, provided an appropriate calibration is made.