低围压下埕北海域重塑粉土振动孔压模型试验研究

An experimental research of vibration pore water pressure of remolded silt under low confining pressure:A case from Chengbei sea area

开展了低围压条件下固结不排水振动三轴实验,对埕北海域重塑粉土振动孔压发展模型进行研究.低围压条件下粉土孔压随振次的发展曲线呈现两种形态,具体呈现何种形态与粉土轴向动应力和临界循环应力有关.对孔压数据进行了归一化处理,发现低围压条件下粉土孔压模型可以用指数函数进行拟合,且黏土含量并不影响孔压模型形式,只会影响a、b两个实验参数.孔压影响因素分析表明,少量黏粒含量的加入可以使粉土的孔压发展速度增大;振动频率对粉土孔压发展的影响也存在一个临界值,约0.2 Hz,当振动频率小于该值时,粉土孔压增长速度随频率的增加而减缓;当振动频率大于该值时,粉土孔压增长的速度随频率的增加而增大.

A triaxial experiment for vibration pore water pressure of remolded silt was carried out in Chengbei sea area under low confining pressure and consolidated undrained conditions.The results indicate the pore water pressure curve of the silt shows two forms at low confining pressure,depending on the axial vibration stress and/or critical cyclic stress of the silt.After the vibration pore water pressure data was normalized,it is found that the vibration pore water pressure of the silt at low confining pressure changes following a pattern of exponential function and the clay content does not affect much the model except the two experimental parameters a and b.Study of the factors that affect pore water pressure shows that even a small amount of clay may increase the growth rate of pore pressure in remolded silt but there is a threshold of about 10~11%.When the clay content exceeds this threshold the rate of pore pressure will significantly slow down.There is a threshold of vibration frequency in a figure of 0.2 Hz.The increase of the vibration frequency will slow down the growth rate of pore water pressure when the vibration frequency is less than 0.2 Hz but accelerate with the increase in vibration frequency when the vibration frequency is greater than 0.2 Hz.