【作者】 代志宏；

【导师】 吴恒；

【作者基本信息】 广西大学 ， 结构工程， 2003， 博士

【摘要】 城市是人类活动的产物，是人类密集居住的场所，也是人类向地质体施加作用最强烈的区域之一。城市地质环境是指城市所在部分的地壳表层在自然条件下，依其自然规律保持着动态平衡的系统，它是具有自身特征和功能的空间。 从地质学与力学的角度看，城市的大规模建设，等同于城市对地质环境施加规模和强度不断增大的荷载。当城市地质环境系统受到外界扰动的时候，系统会自行调整来维持平衡。但是，如果扰动过大，超过系统承受的极限，平衡将不再能恢复。所以，我们将城市所依附的地质体承受上部城市建设荷载的极限能力定义为城市建设荷载的城市地质环境极限，简称“地质极限”。 从而，本文从一个新的侧面切入城市地质环境与地质灾害问题。注重潜在的、缓慢的城市地质作用。以承载能力的极限为研究目标，重在提示附加应力对地质介质力学性状的作用，并由此揭示对地基破坏、区域地面沉降、含水层状态、地震波传输性状及断裂活动性诱发等存在的扰动机理。 首先利用理论推导、数值模拟，全面剖析了地质极限的内涵。作用于地质环境的外部荷载并不仅仅是以建筑物的重量、开挖卸荷等直接的方式出现。本文详细的分析了城市建设行为的荷载表达以及等效荷载转化为附加应力的作用机理。全面阐述由此引发的地质极限问题的表现形式和相应的触发条件。 城市地质环境向极限方向发展的根本原因是：建设荷载产生的附加应力不断向地下传递，改变了地质体的原始应力状态。因此，附加应力的研究是本课题的一个关键环节。 本文详细分析了附加应力的影响因素。并且考虑到：土体细观结构是附加应力传递的桥梁、分布的载体。所以，在因素分析基础上，结合理论分析建立了附加应力分布和传递的细观结构模型，并成功的解释了成层地基中应力集中和扩散现象。 通过分析，认识到土体附加应力系统是集外在随机性、确定性、内在随机性于一身的复杂、非线性系统.为了更深入揭示附加应力系统的特性，我们设计了:附加应力分布实验(均匀土体中的应力分布、具有硬壳层的土体中的应力分布、加载面积不断加大时的应力分布)、附加应力传递实验(纵向传递实验、横向传递实验)、附加应力混沌性试验、附加应力对土体的动力性质的影响试验、检验试验，共五类试验。文中对实验结果和实验中出现的现象进行了详尽的机理分析。 实验不但获得了大量附加应力系统的演化规律，并且通过对一些实验数据计算混沌表征量，证实了土体附加应力系统是具有主体演化规律的混沌系统。 以理论分析和实验结果为基础，建立了描述土体附加应力系统的时空特性(确定性)、混沌特性以及附加应力对土体动力特性的作用的一系列理论模型;总结了附加应力系统的主体演化趋势:综合分析了附加应力对城市地质极限的触发作用;利用所得结果对一些实际的地质极限现象进行了成功的解释，同时这些地质极限现象背后所隐藏的规律也是对我们所得结果有力的检验。更多还原

【Abstract】 City is a result of human activities, a dense resident place, and also an area influenced by people most hardly. The geological environment of city is a dynamic balance system, a space with itself character and function in the nature condition along nature rule.View from geology and mechanics, large-scale construct of city is equal that city put increase scale and intensity load on geological environment. When city environment is disturbed system will maintain balance though itself adjusting .But if the disturb is beyond the system endure limit, the balance will not resume. So we call the city construct limit load which act on geology object as geological environment limit of city. In short, as geological limit.So we study geological environment of city and geological disaster from a new side and pay attention to potential and slow action of city geology. This paper aimed at the limit of carrying capacity and lay stress on the action which additional stress put on geological medium. By that disturbing mechanism can be found which caused ground invalidity, large-scale ground subsidence, quality of aquifer, vibration characteristics of ground and Induced earthquake.First this paper analysis the meaning, forms and spring conditions of the geological limit by theory reasoning and numerical simulation. The direct mode, building load and unloading of excavation, is not the only one. The expression of load caused by activity of city construct and the mechanism that equivalent load is transformed into additional stress were analysis.The essential reason is that the transfer of additional stress caused by construct load changed original stress state of geological mass which induced geological limit. Hereby the study of additional stress is one of important key in this problem.The influencing factors of additional stress were discussed in this paper. Because mesoscopic structure is bridge and carrier of additional stress, we built the mesoscopic structure mode about the transfer and distribution of stress and explained the phenomenon of stress congregate and diffuseness in stratification ground successfully by theory reasoning.We waked up to that additional stress system of mass is a complex and nonlinear system with credibility, randomicity and internal randomicity. Five types of experiments are designed to further reveal the characters of additional stress system. They are experiments of additional stress distribution (including the distribution in even soil, in soil with hardcore and with extension loaded areas), transfer (vertical and horizontal transfer), Chaos, its affect to soil dynamic character and validating experiment. Analysis to the experimental results and phenomenon in tests are given in details in this paper.Not only large number of develop patterns about the additional stress system are obtained; the system is also verified to be an Chaos system with main development pattern through the Chaos calculation from the experimental data. A serial of theory models are established based on the theory analysis and the experimental results. The models describe time and space (determine), Chaos characters of the soil additional stress system, and its affect to the soil dynamic character. The main develop trend of the additional stress system is summarized. The additional stress triggering cities’ geological limit is synthesize analyzed. Base on the models and patterns in the experiment, successful explain to the practical geological limit phenomenons is presented, and the patterns behind the geological limit phenomenon test the results strongly.更多还原