动荷载下土体温度和孔隙水压力的变化规律

The temperature and pore water pressure in soil subjected to dynamic load

动荷载对土体的挤压作用能够改变土体内部孔隙的大小,进而导致土体内部孔隙水压力发生变化.为了验证该物理过程,通过模型试验,研究冻融循环作用下无荷载和动荷载时土体温度和孔隙水压力的变化规律.结果表明,冻融循环作用下,当外部温度达到最高值时,土体上部0~10 cm和底部20~40cm范围内的等温线密集,温度梯度较大,而10~20 cm范围内的等温线较稀疏,温度梯度较小;当温度达到最低值时,土体内部等温线分布均匀.在无荷载条件下,土体内部孔隙水压力随冻融次数增加呈增大趋势,动荷载条件下亦呈现同样规律.动荷载引起土体内部孔隙水压力在冻融过程中发生变化,在冻融初期,振动底板下方5 cm范围内的孔隙水压力为正值,其他区域为负值.随着冻融循环次数的增加,振动底板下方正孔隙水压力的范围扩大到10 cm,而且在振动底板下方20 cm处出现高孔隙水压力区域.

The pore scale and pore water pressure in soil change with the compression of dynamic load.The changes of the temperature and the pore water pressure in soil were studied with and without the dynamic load.The results indicate that the isotherms at the upper part of the soil(0?10 cm)and at the bottom part(20?40 cm)are intensively dense and temperature gradients are large,but isotherms are sparse and temperature gradients are small at the scope of 10?20 cm,when the temperature reaches the maximum value;the isotherms in soil distribute uniformly when the temperature reaches the minimum value.The pore water pressure increases with the increasing numbers of freezing-thawing cycles under the conditions of no load and the dynamic load.In the early freezing-thawing,the values of pore water pressures in soil is positive in the range of 0-5 cm below the vibration plate,and they are negative in other regions.With the increasing numbers of freezing-thawing cycles,the region of the positive pore water pressure under the vibration plate extends to the depth of 10 cm,and the high pore water pressure area appears at the depth of 20 cm under the vibration plate.