砂土中桶形基础静压沉贯过程桶-土受力分析

Load analysis of bucket-soil interaction of bucket foundation in sand during jacked penetration

在砂土中采取负压沉贯桶形基础易出现液化、砂沸等现象,导致沉贯失败,而采用静压下沉则可有效避免此现象发生。在室内设计了不同尺寸桶形基础静压沉贯模型试验,探讨了沉贯过程中桶体内外土压力的变化情况,结合数字图像处理技术获取了桶形基础下沉过程中的土体位移场。试验结果表明:桶形基础在沉贯深度达到1倍口径时开始出现土塞效应,沉贯结束时土塞填充增量比值约为0.7;沉贯过程中贯入力与内壁土压力随深度线性增加,而当贯入深度达到0.5倍桶裙高时则呈现指数级增长;桶内土塞高度与口径相关,口径为10 cm时土塞高度达到15 cm,闭塞效果最为显著;桶内存在土拱效应,沉贯时首先在桶体端部形成被动土拱,随着贯入深度增加,被动土拱被破坏而形成主动拱。

liquefaction and sand boiling are common failure phenomenon during the suction penetration for bucket foundation. However, the jacked penetration can avoid such failure phenomenon. The jacked penetration tests of bucket foundation with different sizes is designed in the laboratory. The earth pressure internal and outer the bucket body is discussed in the process of penetration, meanwhile, the soil displacement field is obtained by using digital image processing technology. Test results show that the soil plugging effect of bucket foundation appears when the penetration depth reached 1 times of the diameter of bucket, and the incremental filling ratio of soil plug is about 0.7 after penetration. The penetration resistance and the inner earth pressure of bucket increase linearly with the penetration depth during the penetration, then exponentially grow when the penetration depth reaches half times of the height of bucket shirt. The soil plug is more effective with 10 cm in diameter of bucket, and the height of soil plug is 15 cm. There is a soil arching effect inside the bucket, a passive soil arch is formed first at the end of bucket, then destroyed as the penetration depth increase, and the active soil arch form.