No abstract

Tests of interface between compacted clay and concrete were conducted systematically using interface simple shear test apparatus. The samples, having same dry density with different water content ratio, were prepared. Two types of concrete with different surface roughness, i. e., relatively smooth and relatively rough surface roughness, were also prepared. The main objectives of this paper are to show the effect of water content, normal stress and rough surface on the shear stress-shear displacement relationship of clay-concrete interface. The following were concluded in this study: 1) the interface shear sliding dominates the interface shear displacement behavior for both cases of relatively rough and smooth concrete surface except when the clay water content is greater than 16% for the case of rough concrete surface where the shear failure occurs in the body of the clay sample; 2) the results of interface shear strength obtained by direct shear test were different from that of simple shear test for the case of rough concrete surface; 3) two types of interface failure mechanism may change each other with different water content ratio; 4) the interface shear strength increases with increasing water content ratio especially for the case of clay-rough concrete surface interface.

A total number of 24 consolidated undrained triaxial shear tests on reconsolidated saturated Hong Kong marine clay (HKMC) have been performed in both compression and extension shear states. The specimens were prepared in four different overconsolidation ratios (OCRs) and sheared at three different axial strain rates. The strain-rate dependency of undrained shear strength, pore-water pressure, stress path, and secant Young's modulus are investigated. The influence of OCR on the stress–strain–strength behavior of HKMC is also examined. The results of all tests are presented and interpreted. The interpreted results are compared with the results in the literature. For the HKMC with OCR varying from 1 to 8, the average value of the strain-rate parameter [Formula: see text] 0.15 is 5.5% for compression tests and 8.4% for extension tests. Most interpreted results are conclusive and consistent with the published results, whereas some results are not conclusive. A new parameter for describing the strain-rate dependency of undrained shear strength of overconsolidated soil is introduced.Key words: strain-rate effects, clay, overconsolidated, triaxial, shear strength, pore-water pressure.

It has been reported that the excess pore-water pressure in clay underneath Tarsiut caisson retained island increased for many months following completion of construction (with vertical load unchanged). It was thought that this increase might be caused by the creep behaviour of the soft clay. However, the phenomenon of excess pore-water pressure increase under constant loading has not been simulated successfully at the Tarsiut Island site. In this paper, a newly developed elastic viscoplastic (EVP) model is implemented in a finite element (FE) program for consolidation analysis. This FE program is used to model the consolidation behaviour of the clay under Tarsiut Island loading. The phenomenon of pore-water pressure increase with time following completion of construction of the island has been successfully simulated using the FE program with the new EVP model. The mechanism of the pore-water pressure increase is explained. It is found that the creep compression nature of the clay is the main internal factor causing the increase. However, the volumetric strain (change) produced due to the dissipation of excess pore-water pressure is the external factor which combines with the internal factor to cause decreasing effective stress and increasing pore-water pressure.Key words: elastic, viscoplastic, finite element, pore-water pressure, consolidation, creep, clay.