Influencing Factors and Corresponding Values of Ultimate Shaft Resistance and Tip Resistance Coefficients for Piles of Rock-Socketed Sections
The assumed composition of the ultimate compression and uplift bearing capacity of rock-socke-ted piles is essentially the same in current Chinese codes.In addition,the same method is adopted to cal-culate the ultimate shaft resistance and tip resistance of piles for rock-socketed sections by using the ulti-mate shaft resistance coefficient ξs and tip resistance coefficient ξb to multiply uniaxial compressive strength fucs of rock.However,the values of the aforementioned ξs and ξb in the criteria are quite different.Based on test data of rock-socketed piles under compression loads,influence laws of pile diameters,rock-socketed depths,ratios of rocketed depths to diameters,and uniaxial strength of rock on ultimate shaft resistance and shaft resistance coefficients as well as ultimate tip resistance and ultimate tip resistance coefficients of rock-socketed sections were analyzed.It was indicated that there was no significant correlation between pile di-ameters and ultimate shaft resistance coefficients as well as ultimate tip resistance coefficients of rock-socke-ted piles.With increase in rock-socketed depths and ratios of rocketed depths to diameters,the ultimate shaft resistance and ultimate tip resistance of rock-socketed piles generally decreased.There was an opti-mum rock-socketed depths and a ratio of rocketed depths to diameters,which could make the ultimate shaft resistance and tip resistance of rock-socketed sections played their roles most fully and coordinately.The ultimate shaft resistance and tip resistance increased but the ultimate shaft resistance coefficients and tip re-sistance coefficients decreased with increase in the uniaxial compressive strength of rock.The strength of rock was a significant factor to determine the coefficients of shaft resistance and tip resistance.There was a good statistical correlation between them,which could be respectively fitted as ξs=0.436 fucs-0.68 and ξb=4.183 fucs-0.79.
rock-socketed pileultimate shaft resistance coefficienttip resistance coefficientratio of rock-eted depths to diametersunconfined compressive strength of rock
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