軟弱岩石內模型基樁之物理與數值模擬試驗

Abstract

岩鎖基樁因為岩體在基樁受載時有剪脹的行為，其樁面摩擦力通常大於根據原現地應力與介面摩擦係數計算所得之承載值。本研究之主要目標是在新竹地區軟弱岩層內進行樁基礎承載力試驗，用以明瞭當樁基礎受力時周圍岩體以及樁體的變形變化情形。基樁內部以及周圍岩體內加裝光纖應便監測系統，這些監測系統包括光纖光柵(Fiber Bragg Grating, FBG)以及傳統之測傾儀。在基樁載重試驗時使用這些儀器量測基樁不承載力之傳遞以及周圍岩體內變形之分佈。另外再利用複降伏數值模擬模式模擬基樁之受載行為，藉以驗證實驗的結果。模擬所需之參數根據先前現地已進行過之傍壓儀試驗而建立。可能因為施工不良，試樁在估計極限承載值約1/10之受力時即斷裂。但，所收集到之光纖監測數據證明基樁周圍軟弱岩層內是有剪脹行為，而這些讀數也與傾斜儀結果一致。

The rock around the pile surface tends to dilate during shearing. As a result, the shear resistance of a rock socketed pile is likely to be larger than a simple multiplication of in situ lateral stress and friction angle at the rock/pile interface. The main objective of this research is to perform a pile load test in soft rock located in Hsin-Chu area and obtain the results of load induced displacement in rock. Optic Fiber Bragg Gratings (FBG) along with traditional inclinometer probe were used to measure the deformation within the pile and in the surrounding rock mass during the load test. The behavior of the rock mass was also studied using a numerical simulation. Parameters required for the simulation were obtained based on pressuremeter tests performed before. The test pile collapsed prematurely. Nevertheless, the available FBG sensor measurements did demonstrate significant deformation in the rock mass as a result of the load test. These measurements were consistent with inclinometer readings performed at the test site. These are indications that shear related militancy did occur in the rock mass during the load test.