Abstract: The hole digging foundation in the strong weathered rock mass is often considered as the main footing form of overhead transmission line project in mountainous area. This paper focused on the shaft foundations and the spread foundations embedded in the strong weathered rock mass. The load-displacement relationships of sixteen full-size foundations were obtained through a series of full-scale pull-out test in site. The test results show that the load-displacement curves of the foundation are similar as that of on the ground surface. They can be divided into three stages: initial straight-line phase, transition curve phase and ending straight line phase. The parameter M is selected to represent the percentage of displacement in the corresponding stage. The M values at different load-displacement stages are different. M decreases as the distance away from the foundation edge increases. A normalized load-displacement curve obeying the hyperbolic relation for the shaft foundations and the spread foundations was presented, and parameters Q/QL2 and s were conducted by curve fitting. The comparative analysis for the same footing under different foundation conditions such as loess and strong weathered rock shows that the parameter b value is negatively related to the shear strength parameters of soil or rock. The uplift bearing capacity of foundation in above two foundation conditions increases successively with shear strength parameter c and ?. Finally, comparative analysis of the predict results using hyperbolic model proposed in the paper and the field test results concludes that the evaluation model to load-displacement response above was available in engineering design.

Key words: strong weathered rock, full-size digging hole foundation, pull-out test in site, load-displacement curve, ultimate uplift load, hyperbolic model parameters