Storage in lined hard-rock cavens: results of a pilot study

Spiraling natural gas consumption has increased the demand for high-pressure underground gas storage facilities. The proven methods of gas storage in porous geological formations and salt caverns are limited to locations with suitable geological conditions. At present, innovative techniques for high-pressure underground gas storage in lined hard rock caverns are being investigated in order to increase the number of potential sites and raise supply security. Because of the permeability of the generally jointed hard rock masses, these caverns have to be sealed by a lining system. This paper reports the results of a feasibility study of high-pressure gas storage in lined hard rock caverns. The paper commences with a look at the potential uses of hard rock caverns for gas storage, and pertinent design requirements. A preliminary concept for the caverns and the gas plant is discussed, with specific emphasis on geological boundary conditions, rock mechanics and construction. The paper concludes with a discussion of technical and economic feasibility considerations for this storage concept.     

Latest technology of underground rock cavern excavation in Japan

Four major projects with large-scale rock underground caverns are discussed in this report; two hydropower stations, one underground oil storage facility and one underground museum in Japan. The technology applied to the construction of these caverns have some unique characteristics and can be applied to various other underground uses for different purposes and applied to larger-scale underground rock caverns with different geological and in situ stress conditions. Generally, construction of an underground cavern is comprised of five major activities: geological investigation; cavern stability analysis; initial rock support design; excavation works; and redesign of rock support according to the observational construction method. Weighted factors allocated among these factors should be established based on the rock properties and the purpose of the underground cavern use, which would define the major characteristics of the construction project. This report discusses some of major characteristics of these projects in Japan.     

大型地下石油洞库自然水封性应力-渗流耦合分析

根据地质条件,地下水封石油洞库可以选择自然水封或人工水封方式。以中国首个大型地下水封石油洞库为背景,开展了岩石三轴压缩试验和现场水文试验,获得了洞库围岩变形特征和渗透特性,采用应力-渗流耦合理论,分析了该地下石油洞库的自然水封性与稳定性。岩石三轴实验表明,岩体受剪作用下体积变化情况与剪胀性密不可分。现场水文试验表明,洞库渗透系数存在一定的不确定性。通过数值分析得出如下结论：自然水封条件下,洞库水位将不满足水封要求;地下水封洞库实现水封条件的水头受水力梯度和岩体渗透性影响;洞库施工期涌水量与渗透系数存在着分形关系;施工期各洞室拱顶沉降为19～32 mm,水平收敛为16～35 mm。研究成果为中国首个大型地下水封石油洞库工程建设提供了科学依据。     

废弃盐穴地下储气库稳定性研究

国际上公认盐岩体是地下能源（石油、天然气）储存最理想的介质，作为储气库的盐岩溶腔，一般都是根据设计要求通过水溶开采形成。目前，国内外鲜见利用地下废弃盐岩溶腔作为天然气储气库的先例。通过对ABAQUS有限元的二次开发，对某废弃盐岩溶腔的储气库围岩和岩柱的蠕变变形规律及腔顶蠕变损伤区的范围进行数值模拟，并对废弃溶腔作为储气库时的工作压力和储库套管鞋高度设计作了有益的探讨，这对指导工程实践具有一定的指导意义。     

地下盐穴处理核废料的方法

核废料对环境和人类安全具有较大危害,如何安全高效处理常常是困扰人类的棘手问题,目前认为有效的处理方式是深部埋藏处理,利用盐穴进行核废料的深埋处理是一种较为安全的方法。盐穴就是在地下盐层中通过钻井,利用水循环的方法,将盐层溶解,最终形成一个体积较大的空洞。利用地下盐穴可以进行各种工业废料的埋藏处理,特别是对具有放射性污染的核废料。建设埋藏放射性核废料的盐穴需要选择地质条件好,具有良好封闭性的盐层中,造穴方式主要是通过水溶洗盐形成地下溶洞。埋藏核废料需要通过一系列的特定工艺才能完成,放射性核废料埋藏处理后需要进行监测以防止产生污染事故。一般来说,由于地下盐穴埋深大、盐穴封闭性好,具有较高的安全性。利用盐穴进行核废料的埋藏具有费用低、容量大、占地少、安全性高等优点,是一种可以推广应用的核废料处理新方法。     

基于单元重构的岩土工程复杂地质断层建模方法

 针对岩土工程数值分析中地质断层建模困难的问题,提出基于单元重构的岩土工程复杂地质断层建模方法。该方法首先对分析对象进行独立离散,建立不考虑地质断层的模型。再通过单元重构,可将地质断层嵌入已建模型,实现复杂地质断层的自动建模。所谓单元重构,是首先使用八节点六面体单元,建立不考虑断层的分析模型,再借助四节点四面体,五节点四棱锥和六节点三棱柱等单元形态,对地质断层穿过的网格进行处理,重构为由多种单元形态构成的模型。然后结合岩土工程断层建模实例,将该方法应用于复杂地下岔管、重力坝坝肩和坝基以及大型地下洞室群的断层建模,可证明其有效性。进一步以大型地下洞室群为例,将考虑地质断层的洞室群模型导入通用软件,采用实体单元模拟地质断层进行开挖计算,并与不考虑断层的情形对比分析发现,考虑地质断层后,围岩位移和应力分布都呈现出不连续性,被断层切割部位的围岩变形增大,应力出现松弛。这表明含有地质断层的重构模型可以用于数值计算,且能有效反映出地质断层对洞室围岩稳定的影响,从而可证明该建模方法的可靠性,为岩土工程的复杂地质断层建模提供便捷的实现途径。     

Proposed future underground projects in sweden

The author describes a number of underground projects proposed by Swedish architects, engineers and planners. These include an underground wind tunnel built in rock, an underground museum, underground gas storage facility, an underwater traffic tunnel for Stockholm, and a large conference center under Stockholm, an underground concert hall in Jönköping, underground grain storage and oil storage facilities in rock caverns, and an underground pipeline to bring fuel to Stockholm airport, underground peak power-stations, and an underground waste treatment facility.     

盐岩地下储气库地表沉降风险失效概率的计算分析

盐岩地下储气库在运营过程中,因盐腔蠕变体积收缩引起地表沉降变形,从而对盐矿区地面设施(如建筑物、桥梁、路基等)产生不良影响,为了评估该影响,建立盐岩地下储气库地表沉降风险失效概率的计算方法,即：首先通过数值计算获得盐岩储气库的体积收缩率,然后通过SRAKA SCHOBER矿山法获得盐腔体积收缩引起的地表沉降,并建立地表沉降风险功能函数表达式,最后采用基于随机变量的蒙特卡洛方法可计算获得盐腔体积收缩引起的地表沉降风险失效概率。将该方法应用于金坛盐岩地下储气库,有效获得储气库体积收缩引发的地表沉降对盐矿区地面建筑的影响,为储气库区地面设施风险安全控制提供理论依据。     

Engineering geological characteristics,failure modes and protective measures of Longyou rock caverns of 2000 years old

The Longyou rock caverns are a group of large ancient underground caverns. They were caved manually in pelitic siltstone in the Quxian Formation of Upper Cretaceous. They have the following five characteristics: more than 2000 years old, man-caved, large spanned, near ground surface and medium to hard surrounding rock. They were unearthed by local farmers who were pumping water out of five small pools on a rough-flat ground in 1992. This discovery called the attention of many specialists from China, Japan, Poland, Singapore and USA. One of the most interesting and challenging questions is why the five caverns have been able to keep their integrity for more than 2000 years. To address this question, this paper presents the engineering geological conditions of the caverns and their adjacent areas. They include the following five conditions: (a) geological setting, (b) hydrogeological conditions, (c) seepage in integrity caverns, (d) fractures in integrity caverns and (e) failed caverns. Based on these investigation results, the paper further examines the potential failures of the integrity caverns and their protective measures.     

基于非侵入式随机有限元法的地下洞室可靠度分析

提出了地下洞室变形可靠度分析的非侵入式随机有限元法。介绍了随机多项式展开的基本原理,采用 GEOSLOPE 的 SIGMA/W 模块进行确定性有限元分析。提出了随机多项式展开与 SIGMA/W 模块接口方法及其流程图,从而实现了确定性有限元分析和随机分析一体化。最后研究了非侵入式随机有限元法在地下洞室变形可靠度分析中的应用。结果表明：非侵入式随机有限元法使得随机分析与确定性有限元分析互不耦合,其计算效率是传统的蒙特卡罗模拟方法无可比拟的,它是地下洞室变形可靠度问题分析一种有效的方法。采用二次衬砌支护是提高地下洞室可靠度有效的方法。此外,岩体变形模量的变异性对地下洞室变形可靠度有非常明显的影响,而岩体重度的变异性对可靠度基本上没有影响。因此,在地质勘查中要尽可能准确地确定岩体的变形模量,从而有效地提高地下洞室变形可靠度。     

在盐矿中储存有毒和放射性废物的地质力学安全分析的新思想与新方法

1 INTRODUCTION The objective of the permanent disposal of radioactive waste is to isolate the radioactive and other toxic particles from the biosphere in such a way that even the release of radionuclides，as a result of not completely excludable migration processes at least in case of scenario analysis，will not lead to the breaking of any dose thresholds at any time in the future. Therefore，the behaviour of the disturbed rock zone (DRZ) in conjunction with geotechnical barriers such as drift or shaft seals ...     

地下水封洞库岩体渗透系数估算研究

 在分析现有主要岩体渗透系数估算模型适宜性的基础上,根据地下水封洞库区岩体渗透性特征,依据烟台LPG洞库岩体渗透系数测试数据,以岩石质量指标(RQD)、岩体完整性指标(RID)、裂隙宽度指标(AD)、岩石渗透性指标(LPD)为建模指标,建立地下水封洞库岩体渗透系数估算模型--RMP模型,并采用该RMP模型估算青岛地下水封洞库区14个钻孔277段岩体的渗透系数。研究结果表明,青岛地下水封洞库岩体渗透系数空间分布随机性较大,其中57.04%的渗透系数集中于10－4 m/d≤K＜10－3 m/d的区间内。研究成果对地下水封洞库工程的水幕系统设计和水封效果评价具有一定理论意义和工程参考价值。     

Discrete element analysis of hydro-mechanical behavior of a pilot underground crude oil storage facility in granite in China

The hydro-mechanical behavior of a pilot underground crude oil storage facility in granite in China is analyzed using Discrete Element Method (DEM). Characterization of hydro-mechanical coupling behavior of rock mass was performed using geological investigation, laboratory test, field monitoring and case study. Geological investigations were performed to obtain the geometrical properties of joints. Direct shear tests were performed to obtain the mechanical behavior of joints. A case study was performed to obtain the hydro-mechanical parameters of rock mass around the facility. Discrete element method was employed to assess the hydro-mechanical behavior of the facility. The groundwater pressure distribution and flow rate of the facility under different water curtain pressures were obtained. The groundwater inflow, deformation and stability of the caverns were obtained through the numerical simulations. It was found that the water seal property could not maintain if there is no water curtain system for the facility. The groundwater flow rate increases with the water curtain pressure. Both groundwater flow rate and crown settlement from this study are comparable to those from field measurements. However, the simulated flow rate and crown settlement are less than those predicted using empirical equations, due to the interaction between neighboring caverns and the effect of groundwater table dropdown.     

Numerical modeling of thermally-induced fractures in a large rock salt mass

Numerical modeling of thermally-induced fractures is a concern for many geo-structures including deep underground energy storage caverns. In this paper, we present the numerical simulation of a large-scale cooling experiment performed in an underground rock salt mine. The theory of fracture mechanics was embedded in the extended finite element code used. The results provide reliable information on fracture location and fracture geometry. Moreover, the timing of the fracture onset, as well as the stress redistribution due to fracture propagation, is highlighted. The conclusions of this numerical approach can be used to improve the design of rock salt caverns in order to guarantee their integrity in terms of both their tightness and stability.     

Design and operation problems related to water curtain system for underground water-sealed oil storage caverns

The underground water-sealed storage technique is critically important and generally accepted for the national energy strategy in China.Although several small underground water-sealed oil storage caverns have been built in China since the 1970 s,there is still a lack of experience for large-volume underground storage in complicated geological conditions.The current design concept of water curtain system and the technical instruction for system operation have limitations in maintaining the stability of surrounding rock mass during the construction of the main storage caverns,as well as the long-term stability.Although several large-scale underground oil storage projects are under construction at present in China,the design concepts and construction methods,especially for the water curtain system,are mainly based on the ideal porosity medium flow theory and the experiences gained from the similar projects overseas.The storage projects currently constructed in China have the specific features such as huge scale,large depth,multiple-level arrangement,high seepage pressure,complicated geological conditions,and high in situ stresses,which are the challenging issues for the stability of the storage caverns.Based on years' experiences obtained from the first large-scale(millions of cubic meters) underground water-sealed oil storage project in China,some design and operation problems related to water curtain system during project construction are discussed.The drawbacks and merits of the water curtain system are also presented.As an example,the conventional concept of "filling joints with water" is widely used in many cases,as a basic concept for the design of the water curtain system,but it is immature.In this paper,the advantages and disadvantages of the conventional concept are pointed out,with respect to the long-term stability as well as the safety of construction of storage caverns.Finally,new concepts and principles for design and construction of the underground water-sealed oil storage caverns are proposed.     

水封油库地下水位动态变化特性数值研究

为认识水封石油洞库区地下水位的动态变化过程,以黄岛地下水封石油洞库的基本地质条件为依据,采用饱和非饱和非恒定流数值分析方法,对水封油库在施工期和运行期可能出现工况下的地下水位变化情况进行了全过程数值仿真计算,分析了不同时期洞库区附近岩体的地下水位分布特点及变化过程。研究表明水封油库区内的地下水位变化过程主要受岩体渗透系数、洞库开挖方式和运行方式的影响;当洞库区岩体渗透系数大于 m/s 时,洞顶上方岩体中的地下水将被疏干,必须设置水幕系统来保证洞库的水封效果。     

盐岩地下油气储库设计参数优化研究

 针对盐岩地下油气储库在不同地质条件下腔体几何参数、围岩内腔体布局、套管靴高度等设计参数对储库结构稳定性、密闭性和使用性等方面的影响进行数值计算,分析提出盐岩地下油气储库设计参数优化准则。在盐丘、厚盐层地质条件下为减小对油气储库围岩损伤影响,应采用中部扩大圆柱形腔体;为减小对腔体收敛、地面沉降影响,应采用顶部扩大圆柱形腔体;在薄盐层地质条件下为保证腔体稳定性,应采用长短轴比为7/3的椭球形腔体。围岩内腔体布局应保证腔体间矿柱间距在盐丘、厚盐层地质条件下大于3倍腔体直径,在薄盐层地质条件下大于2倍腔体直径;最小顶板厚度应综合考虑在最大允许内压条件下腔体不泄露、不发生坍塌、地面无严重沉降等因素综合确定。为保证储库的密闭性,腔体顶部套管鞋顶部应位于腔体顶部盐体蠕变容许影响范围之外。     

盐岩中能源(石油和天然气)地下储存库稳定性评价标准研究

由于盐岩属于一类特殊的岩体，储存库的稳定性分析的评价标准与其他岩体有差别，在各国并没有统一的标准和设计规范，多数是用数值计算的方法来评价储存库的稳定性。主要做法是根据具体的储存库及其岩体力学特性，预先设置储存库稳定性的一些标准，然后对盐岩及其相关的岩石进行大量的试验研究，得到所需要的计算参数，最后通过数值计算来确定储存库的稳定性。系统地提出了盐岩中能源储存库的稳定性研究的内容和评判标准，这些标准归纳起来有3个方面，即：(1)储存库稳定性标准如不允许出现片邦，不允许出现蠕变破坏、安全矿柱和地面沉降控制准则；(2)储存库密封性标准如最大内压控制准则；(3)储存库可使用性标准如储存库体积收敛性。同时给出一个算例，以说明如何评价储存库的稳定性，并说明对储存库稳定性评判标准可以根据具体的情况做必要的修改。