【作者】 徐钺； 郑榕明； 林天健；

【Author】 Y.Tsui Department of Civil & structural Engineering,Hong Kong University Y.M.Cheng Department of Civil & Structural Engineering,Hong Kong Polytechnic

【机构】 香港大学土木及结构工程系； 香港理工学院土木及结构工程系；

【摘要】 由于人口与商业活动的迅速发展,在香港等地存在着一个建造深基础的趋势。许多种护壁和施工方法业已被用于香港的客运铁道以及许多高层建筑基础的施工。护壁起着抵挡由于土、水和超载而产生的横向荷载的挡护结构作用。某些护壁在承担很大的竖向荷载时也起着深基础的作用。在地下室施工期间,可能会发生大量问题。主要的是包括排水与开挖的岩土施工过程能对土介质和护壁产生很大荷载。在香港的一些深基础施工期间,伴随有建筑物与公用设施损坏的地基大位移是人们共有的经验。有必要对结构系统、土介质及周围环境的施工效应进行分析,以便事前采取必要的预防措施。现时大多数地下室的设计系使用泰沙基(Terzaghi)和皮克(Peck)提出的土压力包络线或静止土压力的常规设计方法。忽略了土—结构物协同作用和复杂的非线性、途径相关的土的本构特性。地基位移、地面沉降和应力变化不可能藉常规设计方法得到。在香港,应用着广泛的并因而花钱的监测检验设备于深基础的施工。这些方法是昂贵的并且是被动的,因为由施工引起的不利效应不可能事先估计和避免。地下室的施工过程通常包括:1.排水;2.开挖;3.安装和拆除临时支撑或永久支撑;4.支撑或预应力锚杆的应用。这整个结构系统用有限元法进行了模拟。此外,一个较逼真的土的本构模型被应用于描述土承受荷载时的性状。在模拟中对土—结构物的协同作用作了较着重的考虑。作者将讨论深基础建筑物有限元模拟的方法,施工过程和结构因素引致的效应将被论证。整个系统性能改善的可能性也将得到论证和讨论。这种方法的发展能1.调查准备进行的施工过程的性质和导致的效应;2.研究使由于采取最低费用的施工而导致的不利效应减至最小的方法;3.使工程师在合情合理费用下能接受必要的但非过分的使施工不利效应减至最小的预先施工工作。4.较好地提高对复杂土—结构物协同作用问题的认识。在过去的三十年中,地下施工方法有了惊人的进展,但设计方法仍远远落后于技术。作者的文章能够在现代分析方法与现代技术之间起一个桥梁的作用。更多还原

【Abstract】 Due to the rapid growth in population and commercial activities,there is an increasing trend of constructing deeper basements in Hong Kong and many other places。Many kinds of perimeter walls and construction methods have been used in the Mass Transit Railway construction and the basement construction of many high—rise buildings in Hong Kong.The perimeter walls act as retaining structures in resisting the lateral loads due to soil,water and surcharge.Some of the perimeter walls also act as deep foundations in taking very large vertical loadings. During the top down or bottom up basement construction,a lot of problems may occur. The most important geotechnical processes which include dewatering and excavation can induce great loadings on the soil medium and the perimeter walls.It is common to experience large ground movement with damages of buildings and utilities during deep basements construction in Hong Kong.It is necessary to analyze the effects of the construction on the structural system,soil medium and the surrounding in order to take necessary precautions before the problems occur. At present most of the basements are analyzed by the conventional design methods using either the lateral earth pressure envelopes proposed by Terzaghi and Peak or the at—rest earth pressure for deeper basement construction.The soil—sturcture interaction effects and the complex non-linear path—dependent constitutive behaviour of soil are neglected.The ground movement,surface settlement and the stresses induced by the construction cannot be assessed by the conventional design methods.Extensive and hence expensive monitoring instrumentation is used in H.K.for deep basement construction.This approach is both expensive and passive because the adverse effects due to construction cannot be assessed and avoided beforehand. The common basement construction processes including: 1.dewatering 2.excavation 3.installation and removal of temporary or permanent supports 4.application of struts/anchors preloading and the structural systems are simulated using finite element method.Furthermore a more realistic soil constitutive model is employed in representing the behaviour of soil when sub- jected to loadings.The soil—structure interaction effects are more vigorously taken into account in the simulation. The author will discuss the methodology in the finite element simulation of deep basement construction.The effects due to the construction processes and the structural elements will be demonstrated.The possibilities of improving the performance of the whole system will also be demonstrated and discussed. The development of such a method can: 1.investigate into the performance and the induced effects of the proposed construction processes. 2.investigate into the methods of minimizing the adverse effects due to the construction at a minimum cost. 3.the engineers can undertake the necessary but not excessive advance construction works at a reasonable cost in minimizing the adverse effects due to the construction. 4.enhance a better understanding into the complex soil—structure interaction problem. The underground construction methods have advanced tremendously in the past thirty years but the design methods are still far behind the technology.The author’s article can act as a bridge between the modern method of analysis and the modern technology.更多还原