k-n关系是岩土工程流固耦合分析计算中的一个关键表达式,常规的室内渗透试验由于没有考虑到渗流过程中的流固耦合效应,因而得到的k-n关系与实际情况有偏差。为得到更精确的k-n关系,采用自主研发的SRS-1型渗流和蠕变耦合试验仪开展了各种不同固结压力下的三轴流固耦合试验,获得了渗流过程中土样孔隙率随时间的变化曲线,拟合得到了考虑流固耦合与不考虑流固耦合的k-n表达式,并对考虑流固耦合、不考虑流固耦合及Kozeny-Caman经验公式给出的3种k-n表达式进行了对比分析。将3种表达式分别用于考虑流固耦合效应的一维饱和地基固结的数值模拟,将计算结果与非流固耦合方法计算结果进行比较。结果表明:渗流过程中土的孔隙率是动态变化的,为得到更精确的k-n关系,应考虑渗流过程中的流固耦合效应;工程中的土体固结问题实际是一个流固耦合问题,不能按非流固耦合方法计算,否则产生的误差非常大;当前流固耦合数值模拟中被广泛使用的Kozeny-Caman经验公式不能很好地反映黏土k-n的关系,在数值计算中造成的误差非常大,因此不建议使用;为了提高数值模拟结果的准确性,建议采用考虑流固耦合效应的k-n表达式。

The expression of k-n is crucial in the analysis and calculation of fluid-solid coupling problems in geotechnical engineering. The relationship of k-n obtained from conventional laboratory seepage test deviates from reality as the fluid-solid coupling effect is not considered. To get a more accurate relationship between porosity and permeability coefficient, triaxial fluid-solid coupling test under varying consolidation pressure was conducted on a self-developed SRS-1 seepage and creep coupling test apparatus. The variation of porosity against time was obtained, and the fitted expressions of k-n with and without fluid-solid coupling effect are acquired. The expressions together with Kozeny-Caman's empirical formula were analyzed and then were used in the numerical simulation of one-dimensional saturated foundation consolidation in consideration of fluid-solid coupling. Then the calculation results were compared with the result of classical seepage mechanics method. Results show that 1) fluid-solid coupling effect should be taken into consideration as porosity changes dynamically in the process of seepage; 2) fluid-solid coupling problem should not be solved with classical seepage mechanics method, otherwise the error is too big; 3) since Kozeny-Caman's empirical formula, which is widely used in numerical simulation of fluid-solid coupling problem, could not accurately reflect the relationship between permeability coefficient and porosity of clay, we do not recommend it for numerical modeling; 4) the expression of k-n in consideration of fluid-solid coupling effect is recommended to improve the accuracy of numerical simulation results.