基于流固耦合试验的k-n表达式探讨

Expression of k-n Based on Fluid-solid Coupling Experiment

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 c ru c ia l in th e analysis an d c a lcu lat io n of f lu id -so lid coupl ing problems ingeotechnical engineering. The rela tio n sh ip of k -n o b ta in ed from conventiona l laboratory seepage te s t d ev iate s fromreality as the f luid-solid coupl ing effect is not co n s id e red. To get a more a c cu ra te re la tiopermeability coefficient , tr iaxial flu id -so lid coupl ing te s t u n d e r varying consolidation p re s su re was co n d u c ted on a self-developed SRS-1 se epage an d cre ep co upl ing te s t a p p a ra tu s. The variation of porosity ag a in s t time was o b-tained ,and the fitted expressions of k -n with an d without f lu id -so lid co upl ing effect a re a c q u i r e d. The expressionstogether with Kozeny-Caman ’ s emp ir ica l formula were analyzed an d th en were u sed in one-dimensional saturated foundation consolidation in cons iderat ion of f lu id -so lid co u p l in g. sults were compared with the re sul t of cla s s ic a l seepage m e ch an ics m e th o d. Re su l ts show th a t 1） f lu id -so lid coupl ing effect should be taken into cons iderat ion as porosity ch an g es dynamically in th e process of s e e p a g e; 2） flu id -so lid coupling problem should not be solved with c la s s ic a l se epage m e ch an ics method , otherwise th e er ro r is too b ig; 3）since Kozeny-Caman ’ s empir ic a l formula , which is widely u sed in num e ric a l simulation of f lu id -so lid coupl ing problem , could not accurately ref lec t th e rela tio n sh ip between p erme ab il ity coefficient an d porosity of clay , we donot recommend it for numerical mo d e l in g; 4） th e expression of k -n in cons iderat ion of f lu id -so lid co upl ing effect isrecommended to improve the a c cu racy of n ume ric a l simulation re su l ts.