【作者】 曹亮；

【导师】 李晓昭；

【作者基本信息】 南京大学 ， 地质工程， 2012， 博士

【摘要】 城市地质环境影响着地下空间资源的质量特征与开发难度。对地下空间开发难度的科学评估,需要以城市三维地质建模和关键影响因素的识别评价为基础。而城市地质建模,则要以关键工程地质层组及其工程特性的把握为基础,目前国内外在这方面的研究还处于起步阶段。本次研究以苏州城市地调和国家国际合作项目(城市地下资源与可持续开发-中瑞典型城市对比研究)为依托,围绕城市地下空间开发的地质环境识别评价与建模研究这一主题,需在以下几个方面开展工作：一方面,借助现场监测、室内土工试验、模型试验等对城市地质体中关键层组的工程特性展开多尺度试验研究、内在结构的精细化识别；另一方面,借助计算机的三维可视化建模技术来模拟城市地质环境、分析地层条件、解决实际工二程问题,并利用GIS系统对各种地质环境要素制约下的地下空间开发难度做出评价。本次研究工作通过大量钻孔数据的统计分析,多尺度试验技术的应用、城市地质体的三维地质建模、ArcGIS的空间统计分析功能对上述研究目标展开了全面细致的工作,得到了以下主要研究成果：(1)综合考虑沉积时代、成因类型、沉积环境及土性特征等要素,对苏州东部堆积平原区进行了工程地质层组划分,并对城市地质体的关键持力层组和软弱敏感层进行了判识；确定了上述层组的土体代表参数,并利用递推空间法对水平及竖向的土层自相关距离进行了求取；根据工程地质分区受控要素,将苏州城市规划区划分为两大工程地质分区；基于岩土体的分布特征及其工程特性,对两大工程地质分区各亚区的场地建设条件、地下空间开发的利用形式、开发过程中可能遇到的地质问题、规避地质灾害的措施进行了讨论；(2)采用自由活塞薄壁取样器和冷冻掰断-粘贴法,制作了用于微观结构分析的土样。基于扫描电镜图像的处理分析,对苏州软弱敏感层的软土微观尺度结构特征进行了对比研究,得到了原状土天然状态下的微观结构类型,颗粒排列的定向特征,颗粒偏心度,定向概率熵等量化指标,为深入理解其基本工程性质,建立土体沉积环境、微观结构与宏观工程特性的联系提供了重要的试验依据；考虑到目前用于地下工程围岩热物性测试的试验技术存在取样难、扰动强、误差大、无法有效反映地层复杂地质条件(比如地层组合等)的缺点,对基于扫描电镜图像的土体结构数值建模技术进行了研究,探讨了土体内在结构对其宏观热物性的影响；自行研发了基于微观结构分析的室内模型试验取土方法与取土装置,以便无扰动条件下从模型箱中取出土样进行导热特性测试(对土体扰动敏感)和微观结构研究；(3)收集了大量能用于工程地质层组层序分析、建立层序标准体系的钻孔资料和地层剖面资料,通过统一各层组顶、底板标高,选用普通克里金插值以及有块金指数变差模型进行了地质建模。建立的苏州东部平原区三维地质模型可为城市地下空间开发和具体工程问题的解决提供三维可视化支持。在地质建模软件Geolep-3D中对模型空间数据进行提取,转换成ArcGIS软件中的Shapefile文件,并利用ArcGIS的绘图、统计分析等功能对苏州基坑建设过程中的流砂问题、盾构隧道施工问题进行了评价；(4)结合苏州现阶段地质调查的重点区域与关键地质要素,确定了地形地貌、建筑场地类别、不良岩土体条件、水文地质特征、地质灾害等五个方面为地下空间开发难度评估的主题层。运用层次分析法(AHP)、专家调查法确定各了指标因素的权重,基于目标线性加权函数建立了数学评估模型,分别对苏州浅层(0-15m)、次浅层(15-30m)的地下空间开发难度进行了评估。更多还原

【Abstract】 Urban geological environment gives rise to a lot of restriction on the underground space development and its quality characteristic. In addition, a scientific assessment requires the support of unban geological modeling, as well as the identification of key impact factors. In order to establish the sound geological model, we should make a clear recognition of key underground stratum and understand its geotechnical engineering characteristics. However, research of this aspect is still in the initial stage at present. Therefore, based on the Suzhou Geological Survey and Sino-Swiss Cooperation Project (comparison between Sino-Swiss typical cities for sustainable underground exploration in urban areas), we need to carry out following work oriented by the subject of this research. First up, we need to take in-situ monitoring, indoor soil tests and model tests to realize multi-scale experimental study, including the study of engineering properties and inner structures of key strata. On the other hand,3-D visualizing modelling technology is also necessary to simulate the urban geological environment, conditions of strata, solution of engineering problems. Then geological and environmental evaluation for the underground space development is also indispensable. Therefore, based on the analysis of massive boreholes’data, application of multi-scale experimental tests and3-D urban geological modelling and spacial analysis functions by software ArcGIS, we can get following research results:(1) Taking into full account of the sedimentary environment and history, formation origin and soil characteristics and other factors from the geological survey in Suzhou City, engineering geological strata groups of soil mass on the eastern plains area were divided, as well as key bearing strata group and weak-sensitive strata were also indentified. Then the representative value of key bearing strata and weak-sensitive strata were predicated. In addition, horizontal and vertical spacial self-correlation distance was also calculated by using the Space Recursive Method. According to the dominant impact factors for engineering geological division, we could divide the urban planning area into two parts. It was based on the distribution characteristics of soil and rock mass and other engineering features. As for each sub-area, we have also made a detailed discussion on the site construction conditions, underground space utilization modes, potential geological hazards. And the corresponding countermeasures were also put forward. (2) A free piston thin wall sampler and frozen snapping-paste method were used to obtain undisturbed specimens for miro-structure analysis. Based on the analysis of digital images by Scanning Electron Microscope (SEM), comparative studies of two soft soil layers were carried out to analyze the natural microstructure characteristics, particles’orientation characteristics, eccentricity, orientation probability entropy and other quantitative indicators. Such a work was useful for better understanding the basic engineering properties of soft soil in Suzhou City, as well as providing important experimental data to establish the relationship between the sedimentary environment, micro-structure and macro-engineering properties. Considering the current thermal testing defects (sampling difficulty and disturbance, great errors, bad reflection of compounded formation with complex geological conditions) on surrounding rocks of underground engineering, we develop a numerical modeling technology to simulate the impact effects of soil micro-structures on its macro thermal properties. Besides, we have also designed a new sampling device and method for soil indoor model tests, in order to obtain undisturbed soil specimens for micro-structure analysis and thermal conductivity tests.(3) A lot of boreholes and stratigraphic profiles had been collected and classified in need, which could be consistent with the establishment and analysis the geological strata groups sequence. After unifying the top and bottom elevation for each stratum, ordinary kriging interpolation method and nugget-exponential model variogram were used to establish the geological model. The geological model of Suzhou Eastern Plain area can be utilized to solve the engineering problems of underground space exploration in the visual three-dimensional space. Beyond that, the spatial data could be extracted from the computed model by the geological modeling software Geolep-3D. Then the data were imported into ArcGIS, in order to convert the data to Shapefile file format. By utilizing of the function of chart drawing and statistical analysis in ArcGIS, the problems in the process of foundation pit and shield tunnelling construction were analyzed.(4) Topography conditions, types of construction sites, unfavorable geotechnical problems, hydro-geological characteristics and geological hazards were considered as the main indexes of the thematic layer for geo-environmental suitability evaluation. Furthermore, both the Analytical Hierarchy Process (AHP) and expert questionnaires survey methods were utilized to calculate the weights of evaluation indexes. At last, the mathematical evaluation model was established by massive aim linear weight function method to evaluate the exploration difficulty at the depth from0～15m (shallow depth) and15-30m (sub-shallow depth).更多还原