【作者】 刘琴；

【导师】 赵明华； 邹新军；

【作者基本信息】 湖南大学 ， 岩土工程， 2008， 硕士

【摘要】 作为一种有效的地基处理手段,复合地基近年来在工程中得到了广泛的应用。然而,复合地基计算理论却远远落后于工程实践。因此,复合地基计算理论的研究成为目前乃至今后一段时间内岩土工程研究发展的重要方向之一。复合地基中准确计算沉降及合理控制沉降都非常重要,根据这种情况提出了更适用于复合地基的按沉降控制的复合地基设计思路,这种设计方法既可保证建筑物安全又可节省工程投资。目前复合地基沉降理论仍不成熟,因此需要在现有的研究成果基础上,不断修改和完善沉降理论,提高复合地基位移场的计算精度。沉降的时间效应早已引起国内外学者关注,但是目前对复合地基沉降时间效应的研究还鲜有报道。复合基础设计中如能有效地预估其沉降将对控制建筑物的稳定性具有非常重要的意义,只有考虑沉降时间效应才能更好地提高复合地基沉降的计算水平,才能完善和发展复合地基计算理论,有利于复合地基技术的推广和应用。CFG桩复合地基作为一种经济和可靠的地基处理新技术,是岩土工程领域研究的难点之一,目前虽已广泛地应用于基础工程中,但是同样存在沉降计算理论相对落后于工程实践的问题。本文分别从理论推导、工程实测和数值模拟三方面对CFG桩复合地基的沉降时间效应进行了比较细致的研究。首先基于圆孔扩张理论和比奥固结方程超孔隙水压力三维解析解,推导出了一种由超孔隙水压力求解CFG桩复合地基固结度的计算方法,并进一步提出了反映沉降时效性的CFG桩复合地基任意时刻沉降量的计算方法。同时借助ABAQUS有限元软件分析了CFG桩复合地基的沉降特性,讨论了荷载水平、垫层厚度、垫层模量、桩以及桩间土模量、置换率、桩长等主要设计参数对CFG桩复合地基桩身和桩间土沉降的影响,以期能对复合地基沉降计算方法的改进和发展、以及CFG桩复合地基的推广起到一定的参考和帮助作用。更多还原

【Abstract】 As an effective way of ground improvement,composite foundation has been widely used in engineering practice in recent years.However,bearing mechanism and calculation method of composite foundation has far fallen behind engineering practice.Therefore,the theoretical research for calculation of composite foundation has been one of the important fields for research and development of geotechnical engineering at present and even for a long period in the future.Accurate calculation of settlement and reasonable control of settlement in composite foundation are very important,due to the situation, the idea of design according to settlement of composite foundation was proposed,it can be more appropriate for use in composite fondation.Moreover, design according to settlement of composite foundation can guarantee the safety of buildings and save project investment.At present the theory of composite foundation on settlement is still not mature, therefore, based on the existing research results,the theory of settlement shall be constantly modified and improved, and the accuracy of foundation displacement field is enhanced.The time effect of settlement has already aroused the concern of the domestic and foreign scholars,but few things about it were reported now.Effective prediction of settlement is important to control the building’s stability, only through studying the time effect of settlement can raise a higher level of calculation on settlement of composite foundation,and better develop its theory,also be helpful to promote the technique of composite foundation.As a kind of new economical and reliable technique for capacity of improving the weak ground,the CFG pile composite foundation is one of difficult points in the field of geotechnical engineering. However,in spite of being already widely applied in foundation engineering now,the theory for calculation of composite foundation has also far fallen behind engineering practice.Through three ways of theoretical derivation,measured data,numerical simulation,the time effect of settlement on the CFG pile composite foundation has been made relatively careful research.Firstly based on the theory of cavity expansion and the three dimension analytical formula of excess pore water pressure through Biot consolidation equation, a new kind of method to calculate the consolidation degree of subsoil in CFG piles composite ground is presented, and further a new kind of method that can reflect the time effect of settlement to calculate the anytime settlement of CFG piles composite ground is also presented.At the same time by using the finite element analysis software ABAQUS, the settlement characteristics of the CFG pile composite foundation has been analysed. the factors affecting the pile and pile-among soil settlement of the CFG pile composite foundation has been studied,including load level,cushion thickness,cushion module,pile and pile-among soil module, rate of eplacement,pile length and so on.These studies can play a referenced and helpful role to improve and develop calculation methods on settlement of composite foundation in the future, as well as help to promote the use of the CFG pile composite foundation.更多还原