嵌岩桩竖向承载力的研究

Vertical Bearing Capacity of Rock-socketed Piles

综合研究了国内外２０余年来对本课题的研究所取得的进展。通过对１５０例现场实测资料和两例原位长期观测资料的分析，得出了嵌岩桩在竖向荷载下桩端阻力分担荷载比（Ｑ＿ｂ／Ｑ）随桩的长径比（Ｌ／ｄ）而变化的一般规律，这些规律与通常认为嵌岩桩均属端承桩的传统观念迥然不同。并阐述了形成这些规律的机理；探讨了不同长径比的嵌岩桩可能成为端承桩或摩擦端承桩的必要条件，以及嵌岩桩适宜的嵌岩深度。认为当不符合所述条件时，桩一般不宜嵌入中等风化程度以上的岩层。最后，提出了能反映上述规律，而用经验参数确定嵌岩桩竖向承载力的合理的计算通式。

This paper summarizes 20 years developments at home and abroad on the given subject.Througj analyzing 150 cases of field test results and 2 cases of long-term in-situ observations,somegeneral relationships between the base resistance/pile capacity ratio (Q_b/Q)of rock-socketed pilesunder vertical load and their length/diamter ratio(L/d)are found.They are quite in contrast with theconventional concept that rock-socketed piles are all end-bearing in nature. Mechanism that governs thementioned relationships is explained and the necessary conditions and appropriate socket lengths forrock-socketed piles of different L/d ratios to be end-bearing or frictional end-bearing are discussed.Piles not satisfyng the conditions are unnecessary to be socketed into any rock superior to moderatelyweathered stage. Finally,a general formula with empirical paranleters for reasonably determining thevertical bearing capacitu of rock-socketed piles is presented.