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采用不同重量的重锤自不同高度处自由落体捶击荷载板,研究不同能量大小的循环荷载对黄河水下三角洲土体的动力响应过程。在土体内埋设检波器探头和孔压探头,用以监测荷载能量在土体内的吸收传播和引起的孔压变化,同时在每轮振动前后分别测量土体的强度变化。通过研究发现,80%的振动能量在0.6m土体深度内吸收,能量的衰减量沿深度可用对数曲线表示;振动能量越大,土体产生的超孔压越大,且超孔压所在的深度也越大;根据孔压随振次的变化关系,将现场振动过程中的孔压变化分为四个阶段,即初始阶段、增长阶段、稳定阶段和衰减阶段。最后,讨论振动荷载引起的土体强度变化以及土体液化与振动能量的关系,提出土体临界液化功率的概念,并给出若干深度的范围值。
Different weights of hammers were used to free-fall pallets at different heights to study the dynamic response of cyclic loads of different energy to the Yellow River subaqueous delta. The geophone probe and the pore pressure probe are buried in the soil to monitor the absorption and propagation of the load energy in the soil and the pore pressure changes caused by the soil. At the same time, the soil strength changes are measured before and after each vibration. Through the research, it is found that 80% of the vibrational energy is absorbed within the depth of 0.6m, and the attenuation of energy can be expressed logarithmically along the depth. The larger the vibration energy is, the larger the excess pore pressure is, and the excess pore pressure is According to the relationship between pore pressure and vibration times, the pore pressure changes during the on-site vibration are divided into four stages, that is, the initial stage, the growth stage, the steady stage and the decay stage. Finally, the relationship between the soil strength caused by the vibration load and the liquefaction energy of the soil is discussed. The concept of the critical liquefaction power of the soil is proposed and some depth values are given.