高能量冲击作用下淤泥孔压特征规律试验研究

Experimental study of pore water pressure variation law of muck under high energy impact

以往动力排水固结室内试验,通常冲击能量不够,很难激发软土某些工程响应,对应加固机制难以发现。通过可提供高冲击能的多向高能高速电磁力冲击智能控制试验系统,针对淤泥类超软土进行静动力排水固结模型试验,获得了淤泥孔压等响应特征:夯击瞬间(6 ms)上部孔压增长及下降时间非常短,且其重复性好;初始两遍夯击结束后中部孔压变化呈双峰型,其时间间隔随着夯击遍数增加而逐渐变大,最后不复存在;每遍夯击瞬时中部土压均出现急剧增长与快速减小,增长幅度随夯击遍数增加呈减小趋势,但每遍夯完后数天内土压值均大于夯前值;每遍夯击孔压消散后最终值都小于初始孔压,说明在一定的排水条件下,淤泥这类超软土地基确实可夯击;夯击后残余应力作用机制存在,且其对沉降起主要作用,而一定静力荷载的这种机制不明显;排水板插设扰动效应不可忽视,但该扰动效应随软土埋深增大而减少。

General dynamic drainage consolidation laboratory test, as tamping impact energy is not enough, some basic mechanical responses of soft soil in the actual project are difficult to excite, and relative features of soil are difficult to find. Through the self-developed multi-directional high energy electromagnetic force impact test system which can provide high impact energy produced by electromagnetic force and therefore could simulate the tamping energy acted in practice engineering, static and dynamic drainage consolidation model test for muck, is carried out. The experimental study obtains the response characteristics of pore pressure of this ultra-soft soil as follows：the time that upper pore pressure increases sharply to the maximum, which is very short （only 6 ms） at impact instant, and after the peak it drops rapidly to a certain value;in the initial twice tamping, the curve of pore water pressure at middle deep position shows bimodal type, the time interval between the two peak increases with the increase of tamping times gradually, and finally disappeared;each tamping, instantaneous earth pressure in the middle position shows a sharp growth and rapid decrease, and growth magnitude with the increase of tamping times shows a trend of decrease, but earth pressure value after tamping several days later is still greater than the value before tamping each time;after each tamping dissipating, the final value of pore pressure is less than the initial pore pressure, which signifies that under the certain condition of drainage, such ultra-soft soil foundation can be, indeed, acted by dynamic loading; the action mechanism of residual stress produced by dynamic tamping for soil consolidation exists, and it plays a main role for settlement, but for certain static loading, corresponding mechanism is little; the disturbance effect of inserting drainage board could not be ignored, but the disturbance effect decreases with soft soil embedded depth.