试桩测试方法对桩基承载特性的影响研究

吉利黄河公路特大桥施工了2根相同直径的试桩,分别采用锚桩法和自平衡试桩法进行静载荷测试。根据S2(自平衡试桩法,50m)上段桩与S1(锚桩法,32m)桩的平均摩阻力进行的对比,二者表现出相似的变化规律,均可采用双曲线模型很好的拟合,取趋于稳定的同一位移(12mm)进行比较,在中密卵石层中平均负摩阻力约为平均正摩阻力的0.84倍。桩S1,S2的Q-S曲线均呈缓变型,在曲线前半段,两条曲线非常接近。在后半段,随着荷载增大,S1桩的下降速率明显大于S2桩,若取同一位移30mm进行对比,S2的承载力为59.5×103kN,S1的承载力为48×103kN。S1的端阻力占总荷载的比例为22.46%,为摩擦端承桩。S2端阻力占总荷载的比例只有3.59%,桩顶沉降基本由桩身压缩引起,为摩擦桩。

Study on the influence of test methods on the bearing behaviors of piles

Two test piles with the same diameter for the Jili-Yellow River Bridge were tested with the self-balanced test and the anchored pile method respectively.According to the contrast of average shaft resistances of two piles,the regularity of the relationship between settlement and average shaft resistances is similar,they could be fitted with the hyperbolic model.While settlement is 12 mm,the average negative shaft resistance is 0.84 times of the normal one.The Q-S curves is very close in the first part,but with the increase of loads,the descending rate of the curve of S1 is faster than that of S2.While settlement is 30 mm,the capacity of S2 is 59 500 kNt,he capacity of S1 is 48 000 kN.The ratio of base resistance of S1 to the total load is 22.46 %,this pile is a friction-base pile;the ratio of base resistance of S2 to the total load is 3.59 %,this pile is a friction pile.