Embankment dams are often constructed on soft rock foundations. When this is done, it is important precisely predict deformation of the foundations caused by the fill placement of embankment dams at the design stage. Plate loading tests (PLTs) are commonly used to evaluate deformability of the foundations of dams. Therefore, it is necessary to enhance the accuracy of the evaluation of deformability of the foundations using PLTs. In this paper, laboratory PLTs for artificial soft rocks. The test and the numerical analysis considering nonlinear deformability of artificial soft rocks, are carried out and the behavior of soft rocks during PLTs in detail has been studied.
When large-scale structures, such as dams and foundation structures for bridges are constructed, it is necessary to evaluate safety of the structure from the deformation of foundations. Concerning the dams, embankment dams are often constructed on the soft rock foundations because of the flexibility of the dam body compared to the concrete dams. Even in this case, it is Important to precisely predict deformations of the foundations for embankment dams at the design stage to guarantee the safety of the dam body and its foundation. Plate loading tests (PLTs) are generally utilized to evaluate deformability of the foundations of dams. The deformation behavior of the foundations is predicted using numerical analysis with the deformability of the foundations evaluated by PLTs. Therefore, it is important to enhance the accuracy of the evaluation of the deformability using PLTs. In this study, we carried out laboratory PLTs using artificial soft rocks. Triaxial compression tests (TCTs) with Local Deformation Transducers (LDTs) (Goto et al. 1991) were also made to precisely evaluate nonlinear deformability of artificial soft rocks used for laboratory PLTs. In addition, the stress-strain behavior of artificial soft rocks during laboratory PLTs was examined by numerical analysis using the finite element method considering nonlinear deformability of artificial soft rocks evaluated by TCTs.
We used artificial soft rocks for the laboratory PLTs with an unconfined compressive strength q2 of about 1.5 MPa on the assuming of the strength of soft rock foundations for embankment dams which should be considered by the design of the inspection gallery. Based on the results of preliminary mixture tests, the mixture ratio that meets this condition of the cement, the water and the sand is 6:24:70 by weight. High early- strength portland cement and silica sand #7 were used in the experiment. Table I shows the physical properties of silica sand #7. The artificial soil rocks for the laboratory PLTs were made with a height of about 40 to 45 cm in the cylindrical mold with an inner diameter of 60-cm. The cement, the water and the sand were mixed in the cylindrical mold, and consolidated at a pressure of 980 kPa for 24 hours. In order to eliminate bedding errors between the loading plate and the loading face of the artificial soft rocks.
