Abstract: The expanding ratio and the embedment depth in rock are considered as the two most significant factors influencing the ultimate uplift resistance of the hole digging foundation in rock. In order to investigate the influence of the embedment depth in rock and the expanding ratio upon the ultimate uplift resistance of the hole digging foundation in rock, the uplift static load tests of full-size foundations in site are carried out to analyze the response of displacement verse load, the ultimate uplift resistance of the hole digging foundation and the failure mode of foundation rock mass with different expanding ratios and different embedment depths in rock. Results show that the expanding ratio has the significant impact on load-displacement curve in initial liner phase, Using graphic method, three different parameters QL1, QDLI, QL2 representing uplift bearing performance of low, medium and high respectively are achieved. Further analysis shows that the ultimate uplift resistance will increase with the increase of the expanding ratio and the depth of the rock respectively. But the difference of influence mechanism is found that the QL1 value representing lower uplift resistance in initial elasticity phase are affected obviously by the expanding ratio; and the QDLI, QL2 values representing medium and higher uplift resistance respectively in plasticity phase are affected significantly by the embedment depth in rock. Through the analysis of the distribution of surface cracks in the rock mass on ground damage characteristics, the following conclusions can be achieved. The failure mode of the rock mass upper foundation had nothing to do with the foundation structure style. Cracks are generated from the bottom edge of foundation at first, and then extended to the ground along opening with a predetermined angle until failure of foundation occurs. At the same time, destroy range decreases with the increase of the embedment depth in rock. Comprehensive considering construction safety, economy and mechanization degree, measures to increase the embedment depth in rock shall be preferred.

Key words: expanding ratio, embedment depth in rock, hole digging foundation in rock, ultimate uplift resistance, failure mode