载体桩在奉节草堂地区卵石地层中的应用研究

Applied Research of Carrier Pile in Pebble Stratum in Caotang Area of Fengjie

载体桩作为一种新型的桩基础形式近年来在工程中被广泛运用,其基本原理是通过柱锤夯击成孔并对桩端以下土层及填料夯实形成复合承载体,提高单桩竖向承载力。目前载体桩在砂土、黏性土、粉土及软土中均取得了一定的研究成果,而在卵石地层中的研究较少。以奉节地区某标准厂房桩基工程为例,研究载体桩在奉节草堂地区卵石地层的设计与施工,结合载荷试验成果对载体桩受力机理分析。研究结果表明:以卵石作为持力层的载体桩在奉节草堂地区具有较好的适用性,静载试验与沉降观测表明载体桩承载性能良好,是一种安全经济的基础形式;载体桩静载试验Q-s曲线一般呈缓变型,表明载体桩在卵石地层中的受力形式更接近于端承桩;卵石地层中载体桩的适用性与卵石成分、级配密切相关,土体大颗粒孤石可能使柱锤夯击受阻,施工前应先进行试桩及超前地质钻探。

As a new form of pile foundation,carrier pile has been widely used in engineering in recent years.Its basic principle is to tamp the hole through column hammer and tamp the soil layer and filler below the pile end to form a composite bearing body,so as to greatly improve the vertical bearing capacity of single pile.At present,the carrier pile has achieved some research results in sandy soil,cohesive soil,silt and soft soil,but there is less research in pebble stratum.Taking the carrier pile project of a standard plant as an example,the design and construction of carrier pile in pebble stratum in Caotang area were studied,and the stress mechanism of carrier pile combined with the load test results was analyzed.The results show that the carrier pile using pebbles as the bearing layer has good applicability in the Caotang area of Fengjie.Static load tests and settlement observations indicate that the carrier pile has good bearing performance and is a safe and economic foundation form.the Q-s curve is generally of slow variation type,indicating that the stress form of carrier pile in pebble stratum is closer to that of end bearing pile.The applicability of carrier pile in pebble stratum is closely related to pebble composition and gradation.Large particle boulder in soil may hinder the tamping of column hammer.Pile test and advance geological drilling should be carried out before construction.