A Study of Compressive Characteristics of Peats under Repeated Loading

通过循环里程计固结试验和反复排水饱和试验，评价了泥炭地基中水位作用或交通荷载反复作用对地面沉降的影响。试验结果总结如下：1.由于二次压缩的影响，长程循环试验的沉降率要大于静力固结试验的沉降率。另一方面，高固结压力下的短程循环试验的固结速率小于静力固结试验的固结速率。在恒定加载压力随卸载压力变化的循环加载中，当卸载压力与固结屈服应力值基本相同时，固结应变最大。短时先期固结在循环加载初期固结应变增大。但随着循环次数的增加，应变值逐渐减小，经过一定的循环周期后，塑性应变呈现一个恒定值，且与预固结时间无关。由于二次压缩速率高于短程循环试验，长程循环试验的固结应变表现出较高的数值。然而，长程循环试验和短程循环试验的固结速率并无差异。排水饱和试验中的最大固结应变在相当于固结屈服应力两倍的应力下达到。在该应力水平下，固结应变随循环次数的增加而增加，而在高于或低于上述应力水平的其他应力水平下，随着循环次数的增加，固结应变保持不变。

A cyclic odometer consolidation test and a repeated drainage-saturation test were conducted in order to evaluate the effects of the functuation of water level in peaty ground, or of the repeated action of traffic load on the ground settlement. The tests results are summarized as follows ;1. The rate of settlement in long-range cyclic test was found to be relatively larger than that in statical consolidation test because of the effect of secondary compression. In the other hand, the rate of consolidation in short-range cyclic test with high consolidation pressure was smaller than that in statical consolidation test.2. In the cyclic loading of constant loading pressure with varying the unloading pressure, the maximum value of consolidation strain was found at the unloading pressure that is nearly same value as the consolidation yield stress.3. The consolidation strain increased at the beginning of cyclic loading of the short time preconsolidation. However, the value of strain decreased with increase of repeated cycles, and the plastic strain showed a constant value, which is independent from the preconsolidation time, after a certain cyclic period.4. The consolidation strain of long-range cyclic test showed relatively high value because the rate of secondary compression was higher than that of short-range cyclic test. However, there was no difference of the rate of consolidation between the long-range cyclic test and short-range cyclic test.5. The maximum strain of consolidation in the drainage-saturation test reached at the stress that is equivalent to twice as higher as the consolidation yield stress. While the consolidation strain increased with increase of repeated cycles in that stree level, the consolidation strain was keeping constant wiht increase of repeated cycles in other stress levels that is higher, or lower than the aforementioned stress level.