SHAKING TABLE TESTS FOR DYNAMIC STABILITY OF HEAVY-DUTY EQUIPMENT-PILE BOX FOUNDATION-SAND GRAVEL SOILS SYTEM

A heavy-duty equipment-pile box foundation-sand gravel ground model system was designed and then tested on a shaking table. The dynamic displacement feature of the main equipment structure and the dynamic stability of the tested system were analyzed in detail. The test results indicated the structure dynamic displacement with a big-end-up triangle distribution was controlled by the first mode of the structure. In addition, the reaction increments on the two sides of the box foundation base were unbalanced during the vibration. The rotation effects of the box foundation, induced by the horizontal inertia force effects of the superstructure, were remarkable. This was also the major factor resulting in the declivity of a box foundation. The vibration of the box foundation made the surrounding soils compacted. The rotation of the foundation could obviously influence the distribution modality of the soil pressure on the side wall. Additionally, the excess pore water pressure ratio of the tested sand gravel soils could be reached to 0.3-0.5. The build-up and dissipation of the excess pore water pressure might beget the extra settlement of the box foundation. These conclusions supplied some references for the seismic design of the box foundation in sand-gravel ground.