【作者】 殷德顺；

【导师】 王保田；

【作者基本信息】 河海大学 ， 岩土工程， 2005， 硕士

【摘要】 随着我国改革开放和经济建设的进一步发展,城市地下空间的开发利用已经成为各大型城市的热点,而地下空间的开发利用基本上都是与基坑开挖相联系的。由于受到周围环境的限制,必须防止基坑开挖过程可能引起周围建筑的变形。目前基坑开挖设计已逐步由强度控制转变为变形控制,在变形控制当中如何准确地确定作用在支护结构上的土压力是至关重要的,而作用在支护结构上的土压力又与支护结构相邻土体的变形紧密相关。土体的变形特性与应力路径密切相关。针对上述问题本文做了以下几方面的工作: (1)通过分析,认为基坑支护外侧的土体有可能产生侧向加载和卸载两种应力路径,所以进行了侧向卸载、加载的应力路径实验,本文还根据D-C模型的思路推导了侧向卸载、加载的切线弹性模量公式。 (2)利用有限元方法,通过对实例的计算,发现用本文推导的侧向卸载、加载的切线弹性模量公式,可以得到很好的计算结果。同样利用有限元方法,本文还进行了土压力位移关系的研究,在主动土压力区域即基坑支护外侧,当水平位移增加到H/100(H为支护长度)之前,土压力与支护位移基本呈线性关系;本文还分析了支护结构上水平压力和坑底竖向压力分别卸载对支护水平位移的影响。 (3)通过考虑土压力位移关系,对支护设计中的等值梁法进行了改进,使该方法不仅能够根据强度来设计支护,而且可以根据变形需要来设计,本文了编制程序,并通过算例比较了改进前后的变化。 (4)总结了目前常用的水土合算与水土分算的缺陷,基于粘性土,由于有效应力理论的假设不符合它的实际情况,利用孔隙比e考虑水土作用面积,对有效应力理论进行了修改。以此为基础,分别考虑静水压力和稳定渗流作用,对基坑支护上水土分算公式进行了改造,同时还给出了较为实用的为水土压力计算公式。通过算例比较了改进前后的水土压力的变化。更多还原

【Abstract】 With the Chinese economy growing at a fast pace, utilizing underground space has become a new focus for municipal development, it fundamentally relates with excavation of the foundation pit. Due to the limitation of the surrounding environment, current excavation design has gradually shifted from strength control to deformation control. In applying deformation control, it is vitally important to accurately determine the soil pressure being applied to the retaining structure, which is also closely dependent on the deformation of the adjacent soil. Obviously, the deformation characteristics of soil are also influenced by factors such as stress path. In this thesis, four subjects were discussed.1. Based on a preliminary analysis, it is estimated that the soil layer at outer of the retaining structure could produce lateral loading and unloading stress paths. Therefore, a series of experiments were performed with different lateral loading and unloading stress paths. Based on D-C model, formulas to calculate tangent elastic modulus were developed for lateral loading and unloading conditions.2. A good agreement was observed between experimental data and results from finite element analyses using the previously mentioned tangent modulus model. A study on the relationship between soil pressure and retaining structure deformation was also conducted using finite element method. It was found that, if the horizontal displacement on the retaining structure dose not exceed H/100 (H is the length of retaining structure), there exists a linear relationship between the soil pressure and the structural displacement. In active zone. Additionally, the influence on retaining structure displacement of separate unloading of lateral and vertical pressures was also studied.3. Taking into account the relationship between soil pressure and displacements, a modification was made to the isobeam method for designing retaining structures. Retaining structures can designed according to not only strength using moment but also the practicl need of distortion .A computer program was also developed and examples were presented to illustrate the difference in numerical results with and without the proposed modification.4. Disadvantages have been summarized for two numerical methods, in which water and soil pressures are computed either jointly or separately. Using void ratio eto calculate the interacting area between soil and water, a modification to the effective stress theory was introduced for clay. Using this modified theory and a separate estimate of hydrostatic pressure and steady seepage influence, improvement was also made to the numerical method for calculating water and soil pressure on retaining structures. Some examples were presented to illustrate the difference in numerical results with and without the proposed modification.更多还原