穿越破碎带夹层的嵌岩桩承载性能模型试验研究

Experimental Study on Load Bearing Behaviors of Rock-Socketed Piles Driven Through Interlayer of Crushed Zone

为研究穿越破碎带夹层的嵌岩桩承载和变形性能,以武穴长江公路大桥为背景,将实际地层按1∶100缩尺比制作地层模型,设计、制作力学性质与真实桩近似的模型单桩(模型桩长534、585、635、685、785 mm,沉渣厚度0、0.5、2 mm),考虑沉渣厚度、穿越破碎带夹层后是否嵌岩、桩长等影响因素,分析各级荷载作用下模型单桩的桩顶沉降、轴力和侧摩阻力分布规律。试验结果表明:模型单桩桩顶沉降量对沉渣厚度敏感,在相同荷载下,有沉渣模型单桩的沉降量明显大于无沉渣模型单桩;沉渣厚度为0.5 mm时,模型单桩的荷载~沉降曲线前段呈缓变特征,沉渣厚度为2 mm时,模型单桩的荷载~沉降曲线呈“台阶型”特征。沉渣厚度0.5 mm条件下,荷载较小时,各模型单桩的荷载~沉降曲线基本一致,但穿越破碎带夹层的非嵌岩桩的承载性能明显弱于嵌岩桩;穿越破碎带夹层的嵌岩桩越长极限承载力越大,但增长幅度呈减缓趋势;基于桩顶沉降控制法确定该组模型单桩的有效桩长为635 mm。

The Wuxue Changjiang River Highway Bridge is used as a case to study the load bearing behaviors and deformation performance of the rock-socketed piles that would have to be driven through interlayer in crushed zone.A soil stratum model of 1∶100 scale and model piles with similar mechanical property to the real piles were prepared.Loads were applied to the top of the model piles to investigate the pile-top settlements as well as axial forces and lateral friction resistance distribution of piles under different levels of loads,considering multiple influential factors,including the sediment thickness(0,0.5 and 2 mm),the insertion state of the piles in the rock after passing through the interlayer of crushed zone,and different pile lengths(534,585,635,685,and 785 mm).The test results demonstrate that the pier-top settlements of the model piles are sensitive to the sediment thickness,under the same loads,the settlements of model piles with sediments are greater than those without sediments.With a sediment thickness of 0.5 mm,the front sections of the load-settlement curves of model piles exhibit mild changes,but when the sediment thickness is increased to 2 mm,the load-settlement curves reveal stepped variation.For the 5 mm-thick sediments,the load-settlement curves of piles with different lengths are basically the same under small loads,but the load bearing capacities of the piles that are not socketed in the rock are greater than those of the piles socketed in the rock.The longer the rock-socked piles,the greater the load bearing capacities,but the increase gradually slows down.The effective pile length calculated by the pile-top settlement control method for the model piles is 635 mm.