中文摘要：

根据深大基坑坑底弱透水层的一维越流模型,求解了承压水头变化引起的坑底弱透水层中的超静孔隙水压力和出逸比降的解析表达式。当坑底土层渗透系数较大时,出逸比降计算结果与传统方法的出逸比降求解结果一致,验证了出逸比降解析解的正确性。基于出逸比降解析解,分析了动态承压水作用下坑底出逸比降的变化规律和影响因素。结果表明：当基坑坑底弱透水层厚度一定时,土体渗透系数、压缩模量或承压水头波动周期越大,出逸比降波动越明显,幅值越大,相位差越小;出逸比降影响因素可通过与土体渗透系数和压缩模量正相关,与承压水头波动的角频率和弱透水层厚度的平方负相关的无量纲因子统一表示。最后通过工程实例表明,对于坑底弱透水层渗透系数较小的情况,降承压水头引起的出逸比降减小幅度不大并存在明显滞后性,对基坑的抗渗流稳定性具有不利影响。

英文摘要：

Based on one – dimensional leaky model for base aquitard of deep excavations, analytical solutions for the excess pore water pressure induced by variation of artesian water head and the corresponding exit gradients in the base aquitard are derived. If the value of permeability coefficient of the base soil is large enough, the calculated results of the exit gradient using the suggested method agree with the traditional ones, thus the validity of the suggested method is verified. According to the analytic solutions for the exit gradient, the variation laws and influence factors of the exit gradient in excavations under dynamic artesian water are analyzed. The results show when the thickness of the excavation base aquitard is certain, the greater the permeability coefficient, the compressibility modulus or the variation period of artesian water head of the soil, the more significantly the exit gradient fluctuated, the less its amplitude attenuated and phase shifted. The influence factor of the exit gradient is described by the dimensionless factor, which is positively correlated with the permeability coefficient and the compressibility modulus of the soil, but negatively correlated with the angular frequency of variation of artesian water head and the squared thickness of the aquitard. Finally, a practical project indicates that the lower permeability coefficient in the base aquitard leads to unapparent amplitude damping and significant phase lagging of the exit gradient induced by the artesian water head variation, which has detrimental effect on the seepage stability of excavation projects.