基坑坑底抗隆起稳定性影响因素分析

基坑工程的坑底抗隆起影响因素众多,且各因素对坑底稳定性的影响程度存在较大差异,设计中明确各因素的影响程度对保证基坑安全具有重要意义。考虑土体横观各向同性特征,推导了坑底抗隆起计算公式,并就土体参数和支护结构参数变化对基坑坑底稳定性的影响程度进行了探讨。研究结果表明:增大内聚力c、内摩擦角φ和墙体插入比或减小土体重度γ、最下层内支撑高度和地面超载以及进行坑底加固均能提高基坑抗隆起稳定性。当土体重度γ较小、内聚力c较大、内摩擦角φ较小、墙体插入比较小、最下层内支撑高度较大、地面超载较大时,应尤其注意土体横观各向同性特征的影响。

Analysis on Influencing Factors of Basal Stability in Deep Foundation

The basal heave of deep foundation in soft clays is influenced by many factors, and the extent of each factor is different. It is important to define the influence degree of each factor for safety in deep foundation design. A formula was proposed considering the transverse isotropy strength of soft clays in order to estimate the basal stability, then the influence degree of soil parameters and supporting structure parameters was estimated based on this formula. It is shown that the basal stability will be increased if the cohesion c, internal friction angle φ, and retaining wall insertion ratio is increasing, but the unit weight γ, and ground overload is reducing, the lowest strut height is dropping, as well as the pit bottom soil layer is reinforced. What is more, the transverse isotropy should be considered more cautiously when soil unit weight γ, internal friction angle φ, etc. is rather small, as well as the cohesion c, etc. is rather large.