Experimental Study on the Shearing Behavior of Saturated Sandy Silts Based on Ring Shear Tests

Abstract

飽和された砂質シルトのせん断挙動を調べるために、シルト質の硅砂にレスを重量百分率で10, 20, 30, 50, 70%混合した試料に対し、非排水及ぴ自然排水リングせん断試験を実施した.その結果、非排水状態において、ピークせん断強度と定常状態強度は、細粒部分の比率が高いほど小さくなる、そして、自然排水状態においては、低速・中速ギア両方で、細粒分含有率が大きい程、ピークせん断強度が減少した.また、100mまでの長距離せん断後のせん断強度はM10では十分に回復しているのに対して、細粒分の多いM50は低い値を維持した.細粒分の含有率、すなわち透水性の大小が粒子破砕による過剰間隙水圧の蓄積・発散特性に影響したためと考えられる.自然排水リングせん断試験(中速ギア)の試験前後で行った定水位透水試験の結果より、せん断後の透水係数はせん断前に比べて3桁低下した事がわかった.

The shearing behavior of saturated silty soils has been studies extensively by performing drained and undrained ring shear tests on samples with different fine -particle contents.These samples were made by mixing loess into a fine-grained silica sand with 10, 20, 30, 50, and 70% bess by weight. By performing tests at different initial void ratios, the shear behavior of samples with different loess contents at loose and medium/dense states was presented and discussed. Undrained shear test results showed that both the peak and residual shear strengths decrease with increasing loess content. Meanwhile, by shearing the sample with different shear speed under naturally drained condition, the gen eration of pore pressure within the shear zone was analyzed. It is found that even in naturally drained condition, high pore water pressure could be built -up within the shear zone and kept for a long time with increasing in shear speed or fine-particle (bess) content on the sample.