Earth Pressure at-Rest near A Vertical Rock Face

• Main Authors: Nan-Cheng Chen, 陳南成
• Other Authors: Yung-Show Fang
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/83854440950405937112

碩士 === 國立交通大學 === 土木工程系所 === 93 === This paper studies earth pressure at-rest near a vertical rock face. Dry Ottawa sand was used as backfill material. Horizontal earth pressures in loose (Dr = 35%) and compacted (Dr = 72%) soil mass were measured. The height of backfill is 1.5 m. The instrumented model retaining-wall at National Chiao Tung University was used to investigate the variation of earth pressure with different spacing d between model wall and interface plate. To simulate a vertical hard rock face, an interface plate covered with Safety-Walk (anti-slip material) and its supporting system were designed and constructed. The spacings between the wall and interface used are 1500, 1100, 900, 700, 500, 400, 300, 200, 100, and 50 mm. Based on the experiment results, the following conclusions are made. 1. The horizontal earth pressure σh for loose sand decreases with decreasing spacing d. Jaky’s solution can be considered as the upper bound for estimating earth pressure near a vertical rock face. 2. When the spacing d is very small (d �T 300 mm), the measured earth pressure σh is even lower than Rankine’s active pressure and appears not to change with depth. 3. Janssen’s method provides the best estimation for Ko,h coefficient under different wall-rock face spacing d. As for the factor of safety against overturning, Janssen’s prediction is the best method to estimate the overturning moment (Mo) about the wall base. 4. The lateral stress measured near the top is almost identical to the passive earth pressure estimated with Rankine theory. 5. The pressure coefficient Ko,h decreases with the decreasing of spacing d. None of the theories provide a good estimate of σh acting on a retaining structure with compacted backfill. Because these theoretical equations did not consider the effects of compaction.