Researches In The Influence Of Foundation Excavation On Engineering Properties Of Foundation Rock In High Arch Dam

Bedrock body structure, crag body quality, deformation modulus and intensity parameters of foundation rock were always affected by foundation excavation during the process of foundation excavation in hydroelectric power station high arch dam. The blast-impact load caused by the dam base excavation could produce a certain scope blasting relaxation zone in the crag body. On the other hand, the influence on rock engineering properties were large which produced by earth stress redistribution, especially the stress concentration produced by river foundation excavation on the high earth stress zone.This article taking foundation excavation inLa xiwa hydroelectric power station for example, through the reexamine of dam infrastructure base, studied the impacts of foundation excavation in high arch dam to engineering properties of foundation rock. By investigation of crag body structure, crag body quality, crag body distortion model, blasting relaxation and intensity parameter of the foundation rock, author synthetically appraised the extent of the influence of foundation excavation and the determinant factors to the influence. The effects of foundation excavation in crag body structure mainly expressed as crag body crevasse yawning due to intense demolition impact, producing new blasting crevasse, reducing the body wave velocity at a large scale and the complete coefficient. Moreover, during excavating in construction, the elimination of crag body reduced carries, caused a snapping back to distort to the spatial surface,produced discharge crevasses as a result of reducing the earth stress of the bedrock body, and decreased the wave velocity and the complete coefficient. Furthermore, the extent of the influence gradually decreased to the mountain. In the article, remarkable reduction in crag body wave velocity generated by blasting was considered to be the main character for deducing a blasting relaxation zone in existence during dam shoulder excavation. To determine the influence of foundation excavation on foundation rock quality, the wave velocity and the complete coefficient were made as chief parameters and the space of the crevasse as the assistant parameter when wave velocity was absent. The determination of the influence of foundation excavation on deformation modulus and intensity parameter of foundation rock was on the basis of wave velocity and scene deformation experiment. Related equations of wave velocity, modulus of deformation and intensity parameter were established, and blasting relaxation zone, stress relaxation zone and original belt were estimated respectively. The effect of foundation excavation in high stress area of foundation rock in river bed mainly was the effect of the pot-bottom type excavation in stress redistribution of the river bed. The influence that the excavation type of the pot-bottom in river foundation under high earth stress made on engineering properties of foundation rock was estimates mainly using the actual scene investigation and finite element numerical simulation of 2D.The results showed that effects of high arch dam foundation excavation in engineering properties of foundation rock included changes of crag body structure, crag body quality, deformation modulus and reduction in the intensity parameter. Moreover, as a result of blasting, excavation produced blasting relaxation zone at a certain scope, and the way of excavation determined the character of earth stress redistribution.