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采用一种新型的地基处理方式——变径水泥土搅拌桩,处理了浙江省湖州地区深达20多米的深厚软土地基,通过对载荷试验和桩身应力实测资料的分析,研究了深长变径搅拌桩的承载特性和荷载传递机制。研究表明,受到桩身强度的限制,荷载沿桩身传递限定在一定范围内;由于桩径的变化,桩身应力在变截面处出现了应力集中现象;桩身轴力沿深度逐渐衰减,且在变径位置以上桩体衰减速率较下部快;最大侧摩阻力发生在桩顶附近,在变径处附近由于扩大头端承作用而锐减,但变径位置以下一定深度范围内的桩侧摩阻力得到提高;扩大头端承力随桩顶荷载的增加而逐渐变大,但占总荷载的比例不大,桩侧摩阻力仍提供了大部分的承载力,因此变径水泥土搅拌桩属于有支点端承力的摩擦桩。结合3种不同单桩破坏模式,提出了深长变径搅拌桩的单桩极限承载力计算公式,经过试算发现与现场试验结果相差在10%以内,计算结果可靠,可推广应用于实际工程中。
In this paper, a new type of foundation treatment, a variable-diameter cement-soil mixing pile, is adopted to treat the deep soft soil foundation which is more than 20 meters deep in Huzhou, Zhejiang Province. Based on the analysis of the load test and the measured data of pile stress, Bearing characteristics and load transfer mechanism of agitating pile. The research shows that due to the limitation of the pile body strength, the load transfer is limited within a certain range along the pile body. Due to the variation of the pile diameter, the stress of the pile body appears stress concentration at the cross section. The axial force of the pile body gradually attenuates along the depth The pile body attenuation rate is faster than the lower part at the location of the variable location; the maximum side frictional resistance occurs near the top of the pile, decreases sharply near the diameter reduction place due to the enlarged end bearing function, but the pile side within a certain depth range The friction resistance is improved; the bearing capacity at the head increases gradually with the increase of pile top load, but the proportion of the total load is not large, and the friction at pile side still provides most of the bearing capacity. Therefore, Belonging to the fulcrum end of the friction pile. Combining with the failure modes of three different single piles, the formula for calculating the ultimate bearing capacity of single piles with deep, variable-diameter mixing piles is put forward. After the trial calculation, the calculated results are within 10% of the experimental ones, the results are reliable and can be generalized and applied in practical engineering .