突水是地下工程常遇到的主要和危害严重的工程地质现象。工程实例分析表明，地下工程中大的涌水和突水大多与地质结构面，特别是断裂有关。文中分析了断裂控制地下水赋存和运移的规律，以及可能导致突水的富水优势断裂的特征。由于断裂突水的复杂性和众多的影响因素，将地质机制分析、经验判断和定量指标与评价模型相结合是重要的，也是可行的。文中介绍了一种富水优势断裂的量化分级方法，讨论了相应的预测与防治工程对策。

地下工程常常面临突水灾害的威胁。除了采动破裂导致岩层阻水能力丧失外，剪应力集中区内结构面错动引起地下水的导升亦是突水发生的重要机制。围岩的层状特征和岩性差异，使得某些位置的软（硬）岩层成为控稳优势层。以突水系数等经验方法为参照，通过对优势层及其组合特征的分析，明确其有利或不利的控稳机制，可为突水防治提供更为科学、可靠的依据. 图5，表2，参13。

工程地质岩组的划分是岩体质量评价的基础。当大型工程揭露土层很多时，进行土体工程地质层组的划分亦是十分必要的。它可以更为清晰的反映场地地质结构的变化规律，便于地质模型的概化和参数研究，有助于抓住主要工程地质问题进行评价，便于设计师的理解和应用。以南京地铁南北线一期工程为例，探讨了土体工程地质岩组的划分问题。通过以层组为基础的参数离散性统计、工程地质模型与工程地质问题的分析可以看出该层组划分方案的合理性与工程意义。

Rock-gas outbursts, including sandstone-gas outbursts, become more and more serious with increasing depth of engineering and more difficult geological environments and their prediction and prevention are one of the major challenges to the rock mechanics and rock engineering community. Comparatively speaking, sandstone-gas outbursts have not been well studied and are less documented than coal-gas outbursts. So the exchange of information, especially in the field of the prediction and prevention of sandstone-gas outbursts, is important. This paper outlines an outburst in which over 2000 tonnes of oil-bearing sandstone were ejected with 900,000m3 of gas in the air shaft of Haishiwan Colliery; this is the largest sandstone-gas outburst in China to date. The theoretical and technical investigation relating to the prediction and prevention of such sandstone-gas outbursts, taking the Haishiwan Colliery project as the background, are described in the paper. A comprehensive prediction method employing a suite of macro-and micro-indices gained from test drilling and laboratory testing on rock cores is proposed in the paper. It is found that the combination and comparison of the results of field observations, measurements and laboratory tests are helpful to ensure the reliability of outburst prediction. The principle and scheme of preventive drilling and discharging, including the pattern and number of releasing boreholes and the safety distance for drilling, were studied. It is revealed that discharging of gas can also release rock mass strain energy, which should be taken into consideration in the determination of the number of releasing boreholes. For the purpose of releasing, the Tubular Destressed and Depressurized Protective Zone (TDDPZ) pattern proposed in the paper is more efficient and economical than the currently applied fan-shaped pattern of releasing boreholes. The accuracy of prediction and the efficiency of the preventive measures were verified by successful excavation through the oil-and gas-bearing sandstone units in Haishiwan Colliery.

Currently, there are six cities constructing their metro systems in China, among which, the Nanjing metro project is characterized by its complicated and unfavorable geological conditions, such as varied topography, rugged bedrocks, many faults passing through, rapid variation in lithology and geotechnical properties, soft ground, high groundwater table and multiple groundwater types. Therefore, the geological and geotechnical investigations play a vital role in the project. This paper describes and discusses the investigations taken in the project. From a seismological point of view, the project is in a relatively stable tectonic setting, the major regional active faults are a little far. Among many faults found in the city area, the NWW Dinghuaimen-Gulou fault and the NNW Nanjing-Hushu fault merit attention to their influences on the foundation stability. High groundwater table and multiple groundwater types feature the hydrogeological conditions. The paper describes the hydrogeological characteristics and parameters on the basis of groundwater type division. The inflow prevention of abundant pore water in ancient riverbed, fault water in Gulou and karst water in Xiaohongshan are diffcult. Along the metro axis, the local morphology can be divided into five sections: three sections of tectonic denudated lowrise hills and two sections of ancient channel alluvial plains. As many as 50 of Quaternary soil formations have been encountered. They are too many for architects to conceive and establish the engineering geological model. Therefore, generalization and division of engineering geological strata groups is necessary. The Quaternary deposits at the Metro site were divided according to their origin and relevant age into four engineering geological strata groups and subdivided on the basis of their composition, physical state and geotechnical properties into distinct subgroups. Data from this study indicate that the division is feasible and the subgroup II2 (CS) and III2 (CS), which are soft cohesive soils of Holocene and late Pleistocene respectively, represent the most sensitive and weak geotechnical unit, and the Holocene sandy soils subgroup II4 (SL) is of the most potential danger of liquefaction. None of the current rock mass classification systems has been found to originate from and be adequate for the shallow metro tunnel. The CGIMC, Vp and BQ systems have been combined in this study. The study indicates that the combination of multiple systems, qualitative and quantitative, is helpful to ensure the reliability of rock masses evaluation. To overcome the deficiency of the rock mass intactness index Kv and the BQ system in the national standard, their determination methods were modified. The paper describes in details the modified Kv and BQ procedure taking account of the characteristics of the rock masses at the metro site. The rock masses are categorized into very poor, poor and fair quality. The poor conditions of the rock masses are largely due to intensive weathering and dense fracturing. Along the metro axis, eight geotechinal zones were divided according to their identical characters of topographical, engineering geological and hydrogeological conditions and construction methods. The paper highlights the different geotechnical problems and challenges that will be encountered in different geotechnical zones.