國立交通大學模型檔土牆之設計與建造

Abstract

本研究主要在探討模型擋 土牆之設計與建造。根據過去各國外大學所設計的模型檔土牆中，雖各有優缺點，可是，各模型皆無法充分模擬現地之情況。希望經由本研究所設計之模型研究結果，能增進大地工程師對土奪力變化的瞭解，因而使得擋土結構物的設計及施工更為安全。 本文首先針對過去國外各大學所設計的模型擋土牆加以回顧，綜合各家之所長，並針對一些未盡善之處加以修改。以下是本模型設計之各項特點： 1.藉由調整上下傳動軸之速度，可達成各種不同之牆移動型式。 2.將矽油（Silicon Grease）塗抹於側牆，並舖上一層橡膠薄膜，來減少回填土及側牆間之摩擦力，以達到所假設的平面應變狀況。 3.土壓力計之安排採取交錯排列，使其能更精確的量測土壓力隨深度變化之情形。 4.本模型可模擬傾斜之回填土及水平回填所造成之土壓力情形。 5.在模型牆下方之回填土內，留有113mm之空間，可供發展完整之對數螺旋破壞曲面。 6.回填土兩邊側牆採用透明之壓克力建造，可清楚的觀察到各點之位移。

In this paper, the design and construction of National Chiao Tung University model retaining wall are introduced. To investigate th effects of wall movement on earth pressure, several universities have bulit model retaining walls. The advantages and drawbacks of their design have been discussed in this paper. In order to enhanced the experimental study of earth pressure, a new model retaining wall is designed and constructed at National Chiao Tung University (NCTU). The advantages of the NCTU model wall are summarized as follows: 1.By adjusting speeds of the upper and lower driving rods, many types of wall movement (at-rest, active, passive states, with RB, RT, T, RBT, and RTT modes) could be generated. 2. Since the friction between the backfill and the side walls has been minimized to near-frictionless, so that shear stresses induced on the planes of the side wall become negligible. 3. A total of 11 earth pressure transducers are mounted on the wall surface to provide closely spaced data points for observing the variations of earth pressure. 4. The inclination of backfill is considered as important factor to simulate the field condition. 5.According to the general wedge theory (Terzaghi, 1967), the passive log spiral failure surface would develop to backfills below the base retaining wall. For the model wall proposed, there is enough space in the soil bin to develop the complete log sprial failure suraface. 6. Since the side walls of the soil bin are transparent, backfill displacement due to wall movement can be clearly observed.