中风化花岗岩层与基桩侧摩阻性能现场试验研究

 结合港珠澳大桥桥梁试桩工程，采用自平衡法进行2组共4根桩(每组2根桩)的中风化花岗岩与基桩的侧摩阻性能现场试验。试验时，将荷载箱埋设于中风化岩层内的桩身进行测试，并同步观测不同试验荷载下桩顶、中风化花岗岩层顶面对应的桩身截面、荷载箱和桩底的位移和桩身轴力。2组试桩桩位处岩石强度有一定差异，且岩石完整程度不一，但各试桩荷载箱上方桩身的荷载–位移曲线均具有明显的突变特征。处于岩石强度小、破碎岩层内的试桩组，其荷载箱上方岩层与基桩侧摩阻力小于荷载箱下方岩层与基桩侧摩阻力；处于岩石强度高、较破碎岩层内的试桩组，其荷载箱上方、下方岩层与基桩侧摩阻力基本一致。荷载箱以上桩段岩石侧阻发挥系数实测值表现为岩石强度愈高，岩石侧阻发挥系数实测值也愈高；而荷载箱以下桩段，在本项目的试验条件下则表现为岩石强度愈高，侧阻发挥系数实测值愈低。

IN-SITU TEST RESEARCH ON SIDE FRICTION OF BRIDGE PILES IN MODERATE WEATHERED GRANITE

Two groups of in-situ tests with two testing piles in each group，which were part of testing engineering for Hong Kong-Zhuhai-Macao Bridge in China，were finished by Tomer-cell method(self-balanced method called in China). The side frictions of the testing piles in moderate weathered granite were analyzed by observing the axial force and the moving of pile toe，pile top and the pile section at top of moderate weathered granite during applying static axial compressive load through a group of jacks located in certain section in moderate weathered granite. The rock strength and integration level in location of each group were different but the load-settlement curve of each pile was all like a sudden-falling one. For the piles in the group located in broken rocks with lower strength，the side frictions of piles above the jacks were less than those under the jacks；but the side frictions of piles above and under the jacks were nearly the same for the other group located in little broken rocks with higher strength. The ratio of side friction to rock strength was higher when the rock strength was greater for the pile section above the jacks，but for the pile section under the jacks，such ratio was lower.