钉形双向水泥土搅拌桩单桩承载特性研究

作为一种新型的软土地基处理方法,钉形双向水泥土搅拌桩的单桩承载特性异于常规双向搅拌桩。在现场载荷试验的基础上,通过数值模拟分析了钉形搅拌桩单桩承载特性。结果表明:钉形搅拌桩单桩承载性能受扩大头高度和上、下桩径比等设计参数影响,单桩极限承载力随着扩大头高度和上、下桩径比的增加而增大,但增长速度逐渐变缓,存在着最佳扩大头高度和最佳桩径比。并引用单桩极限承载力提高系数和单桩水泥用量增加系数两个指标从经济角度验证了最佳值的存在,得到最佳扩大头高度为1 m,最佳桩径比为2。最后,通过理论分析,基于单桩三种破坏模式给出了钉形双向水泥土搅拌桩单桩极限承载力计算方法,试算结果与实测值偏差在10%左右,较为可靠。

Research on Bearing Behavior of Single T-Shaped Bidirectional Deep Soil-cement Mixing Column

As a new technology for soft ground improvement, the bearing behavior of single T-shaped bidirectional deep soil-cement mixing column is different from traditional mixing column. Based on the field load tests, the bearing behavior is analyzed by numerical simulation. The results indicate that the bearing behavior of single T-shaped bidirectional soil-cement deep mixing column is influenced by the length of enlarged column cap, the ratio of upper column diameter to lower column diameter and other design parameters. While other parameters keep the value unchanged, the ultimate bearing capacity of single column increases rapidly with increase of enlarged column cap length and upper-lower column diameter ratio at first, and then begin to slow down, which means there exists a critical enlarged column cap length and diameter ratio. And, it’s demonstrated from the economic point by quoting the single column ultimate bearing capacity improvement coefficient and cement content increase coefficient, the optimal length of enlarged column cap is 1m and the optimal column diameter ratio is 2. At last, based on three failure modes of single T-shaped column, the ultimate bearing capacity calculation method is proposed through theoretical analysis. The ultimate bearing capacity calculated in proposed method agrees well with the measured results from field load tests, the error is about 10%.