EXPERIMENTAL STUDY ON PERMEABILITY OF HARD CLAY AT DEEP DEPTH IN SHANGHAI

The layer subsidence of hard c lay at deep depth in Shangh iai lags beh ind the w ater level change. It is necessary to study the permeability of the hard c lay. A series of tests on the clay permeability w as carried out in or der to settle some quest ions. These quest ions include initial hydraulic grad ien,t inf luence of hard agg lutinate to the permeab ility and re lation o f permeability to pressure and pore. The result show s that the seepage velocity keeps a linear relation to the hydrau lic grad ientw el,l abiding the Darcy law. The compact agglutinate has little influence on permeab ility. The permeability reduces w hile the stress increases and changes w ith pores fo llow ing the exponent ia l law. Base on the test resu lts, the permeab ility change o f the natura l hard clay during 1989- 2007 is estima ted. The boundary w ater level dropped almost 30 meters. The hard layer subsidence caused the perm eab ility reduction but the average permeability change w as not so much.