Characterizing Excavation Damaged Zone and Stability of Pressurized Lined Rock Caverns for Underground Compressed Air Energy Storage

In this paper, we investigate the influence of the excavation damaged zone (EDZ) on the geomechanical performance of compressed air energy storage (CAES) in lined rock caverns. We conducted a detailed characterization of the EDZ in rock caverns that have been excavated for a Korean pilot test program on CAES in (concrete) lined rock caverns at shallow depth. The EDZ was characterized by measurements of P- and S-wave velocities and permeability across the EDZ and into undisturbed host rock. Moreover, we constructed an in situ concrete lining model and conducted permeability measurements in boreholes penetrating the concrete, through the EDZ and into the undisturbed host rock. Using the site-specific conditions and the results of the EDZ characterization, we carried out a model simulation to investigate the influence of the EDZ on the CAES performance, in particular related to geomechanical responses and stability. We used a modeling approach including coupled thermodynamic multiphase flow and geomechanics, which was proven to be useful in previous generic CAES studies. Our modeling results showed that the potential for inducing tensile fractures and air leakage through the concrete lining could be substantially reduced if the EDZ around the cavern could be minimized. Moreover, the results showed that the most favorable design for reducing the potential for tensile failure in the lining would be a relatively compliant concrete lining with a tight inner seal, and a relatively stiff (uncompliant) host rock with a minimized EDZ. Because EDZ compliance depends on its compressibility (or modulus) and thickness, care should be taken during drill and blast operations to minimize the damage to the cavern walls.     

An Analytical Solution for Mechanical Responses Induced by Temperature and Air Pressure in a Lined Rock Cavern for Underground Compressed Air Energy Storage

Mechanical responses induced by temperature and air pressure significantly affect the stability and durability of underground compressed air energy storage (CAES) in a lined rock cavern. An analytical solution for evaluating such responses is, thus, proposed in this paper. The lined cavern of interest consists of three layers, namely, a sealing layer, a concrete lining and the host rock. Governing equations for cavern temperature and air pressure, which involve heat transfer between the air and surrounding layers, are established first. Then, Laplace transform and superposition principle are applied to obtain the temperature around the lined cavern and the air pressure during the operational period. Afterwards, a thermo-elastic axisymmetrical model is used to analytically determine the stress and displacement variations induced by temperature and air pressure. The developments of temperature, displacement and stress during a typical operational cycle are discussed on the basis of the proposed approach. The approach is subsequently verified with a coupled compressed air and thermo-mechanical numerical simulation and by a previous study on temperature. Finally, the influence of temperature on total stress and displacement and the impact of the heat transfer coefficient are discussed. This paper shows that the temperature sharply fluctuates only on the sealing layer and the concrete lining. The resulting tensile hoop stresses on the sealing layer and concrete lining are considerably large in comparison with the initial air pressure. Moreover, temperature has a non-negligible effect on the lined cavern for underground compressed air storage. Meanwhile, temperature has a greater effect on hoop and longitudinal stress than on radial stress and displacement. In addition, the heat transfer coefficient affects the cavern stress to a higher degree than the displacement.     

Cyclic Thermo-Mechanical Analysis of Wellbore in Underground Compressed Air Energy Storage Cavern

The compressed air energy storage (CAES) method is a viable method of storing surplus energy underground when there is a mismatch between energy generation and demand. Wellbores embedded in rock are an integral part of energy storage structures, and are used for injecting and extracting the compressed air. During injection and production cycles, the storage reservoir and wellbore are subjected to cyclic change in external pressure and temperature, which may cause failure of the wellbore. In this paper, cyclic thermo-mechanical analysis of a horizontal wellbore in an underground CAES cavern is performed using finite element analysis. The rock behavior is simulated using the Mohr-Coulomb constitutive law. The reduction in the yield strength of rock with increase in the number of loading cycles is taken into account in the analysis. Parametric sensitivity studies are carried out to study the effects of dilation and friction angles of rock, the ratio of in situ horizontal and vertical stresses, loading frequency, and the magnitude of the temperature cycles in the cavern on the wellbore performance for different types of rock. The thermo-mechanical cyclic behavior leads to plastic strains that are greater than those obtained by performing mechanical analysis only. Significantly large deformation is generated in rock for large dilation angle and high loading frequencies.     

黄岛地下储油库渗流场模拟

为预测黄岛地下水封油库洞库运营期间洞库涌水量和研究设置水幕的必要性,利用FEFLOW软件,首先对黄岛地下水封石油洞库分别建立无水幕和有水幕条件下的三维地下水数值模型,进而对两种条件下的洞库涌水量做预测以及洞库上方的水位变化分析,结果指出：洞库在无水幕条件下前期涌水量为530m^3／d,常规涌水量为249m^3／d。有水幕条件下前期涌水量为643m^3／d,常规涌水量为309m^3／d。相对于无水幕条件,有水幕条件下有力保证洞库的水封条件,水封效果较好,有力的保证了地下水封石油洞库的储油安全。     

Optimizing Method of Main Caverns in Large Underground Water-Sealed Storage Cavern

Geotechnical and Geological Engineering - Underground water-sealed storage cavern is an important way for petroleum strategic reserve in China, which owns lots of outstanding advantages, such as...     

黑洞大型古地下洞室群工程地质条件及岩体稳定性分析

位于浙江天台县蟹山山体内的黑洞洞室群, 以其优越的工程地质条件和完整的岩体结构, 自隋朝以来成为大型古地下采石场。洞室群包括总面积达24 000 m²的21个洞室, 其长轴方向基本沿两组主要地质结构面走向展布。研究显示:总体采石层系上白垩统塘上组(K₂t)第6层灰白色含玻屑熔结凝灰岩;岩体质量指标Q值计算结果为53(I级)。按现代地下洞室设计理念, 其长期稳定最大跨度应不大于50 m, 但实际上5号洞最大跨度达81 m, 可望成为地下人工岩石单洞跨度之最。现场调查发现, 古人在蟹山山脚残留多处地质探洞。古代工匠在洞室开挖过程中遇到断层破碎带时, 采用了近垂直、小断面、高台阶穿越技术方法, 有效保证了不良地质体中无支护开采的安全性和长期稳定性, 这对现代地下工程具有借鉴和工程类比意义。     

二氧化碳地质储存逃逸通道及环境监测研究

CO2地质储存逃逸通道可分为人为逃逸通道、地质构造逃逸通道以及跨越盖层和水力圈闭逃逸通道三类.在CO2地质储存场地选址和场地勘查阶段,应高度重视区域地壳稳定性、地震危险性和CO2逃逸通道专门性地质调查评价工作,避免因CO2逃逸造成对人群健康和生态系统产生影响,导致地下水污染和诱发地质灾害发生.同时要对可能的CO2逃逸通道进行灌注前CO2背景值监测,灌注工程运营期CO2控制监测和封场后长期监测,确保CO2地质储存的有效性、安全性和持久性.     

地下水封洞库深部岩体结构面连通性研究

地下水封洞库工程是我国正在大力实施的战略石油储备重点工程,研究建库裂隙岩体的连通性是评价水封效果的关键。结合地下水封洞库工程的岩体特征,以钻孔电视成像技术为手段,通过分析影像中结构面位置、地质特征等,建立不同钻孔间结构面连通的条件,并分析了钻孔ZK11和ZK12,ZK12和ZK14的变质分异结构面的几何连通性;以洞库区钻孔地下水位的陡降与施工巷道开挖的相关关系,建立了巷道地下水排泄与钻孔水位下降的水力联系,分析了结构面的水力连通性;通过几何连通和水力连通的综合分析,确定了深部岩体结构面的连通性。研究结果表明,施工巷道开挖引起钻孔地下水位的显著下降,两者存在明显水力联系;变质分异结构面(J)在钻孔ZK12、ZK11和①号施工巷道0+379.424m处满足位置连通、结构面特征连通和水力连通,为连通性结构面;结构面(J′)在钻孔ZK12和ZK14处满足位置连通和结构面特征连通,不满足水力连通,为非连通性结构面。这对地下工程深部岩体结构面连通性的研究具有参考和借鉴价值。     

Modeling of a Space Heating System Coupled with Underground Energy Storage

Mathematical Geosciences - Heat pump systems and radiant floor heating systems are extensively employed to adjust indoor temperatures. Both types of system can reduce energy consumption and...     

Experimental Study on Rock Failure Characteristics of Ejective Rock Burst Based on Energy Compensation

Geotechnical and Geological Engineering - Rock burst is a typical type of dynamic geological disaster in the process of underground engineering excavation under high in-situ stress. Based on the...     

Propagation Characteristics of Blasting Stress Waves in Layered and Jointed Rock Caverns

The existence of joint fissures makes explosive actions between rock masses more complex. Therefore, it is of great significance to carry out experiments studying blasting stress waves propagating in jointed rock masses. Based on the Froude Similarity principle, the geological mechanical models of intact rock masses and jointed rocks have been proposed. A blasting vibration experiment was carried out and demonstrated that the propagation of the blasting stress waves and changing structures have an important relationship. A numerical simulation of the blasting stress wave propagation law in a layered jointed rock mass was carried out. This study found that with an increase in the joint angle, the peak velocity of blasting stress wave, transmission coefficient and reflection coefficient all gradually increased, while the attenuation coefficient gradually decreased. With an increase in joint spacing, the attenuation rate of the blasting stress waves increased.     

高陡临空面附近地下采空区覆岩破坏响应研究

近年来,山区煤矿地下开采诱发地质灾害的问题日益突出。本文以贵州省兴仁市彭家洞高陡采动斜坡为原型,利用离散元数值模拟,研究煤矿开采对斜坡的影响,并分析该类斜坡的覆岩变形破坏特征及损伤规律。研究结果表明：高陡临空斜坡煤层地下开采引起覆岩下部产生的变形以垂直变形为主,且变形近似呈对称状分布,但在覆岩上部的斜坡陡崖部位,由于覆岩不完整,变形传递到该部位时会逐渐产生向临空面方向的水平位移;采空区覆岩损伤产生的裂纹主要为拉张裂缝,且裂纹在覆岩中近似呈“倒梯形”分布,在上山和下山方向的影响边界角分别为56°和68°;该类斜坡地下采空引起的覆岩损伤变形由下至上可分为三个带：冒落带、裂隙带和弯曲带。     

盐岩地下储气库体积收敛失效概率分析与模型试验验证

盐岩地下储气库受盐岩蠕变特性影响会产生较大的体积收缩变形,影响储气库安全稳定运行。目前对地下储气库体积稳定性分析方法和评价准则各国没有统一标准,国内主要采用数值计算的方法来评价储气库体积稳定性。以江苏金坛盐矿地下储气库体积收敛数值分析为基础,借鉴国外盐岩地下储气库稳定性评价标准,建立盐岩地下储气库体积收敛失效风险评价矩阵,采用一次二阶矩法显示功能函数分析储气库体积收敛失效概率,分析得出：储气库在长期恒定内压工况下体积收敛失效概率随内压的增大而减小;在短期调峰低压工况下体积收敛失效概率随内压的减小而增大;最小内压应保持在4.2 MPa以上。通过交变气压条件下层状盐岩地下储气库大型三维地质力学模型试验得出:储气库体积收敛变形随内压的增大而减小;短期运行最小内压应大于4.0 MPa。模型试验结果与失效概率分析结论较为相似。因此,为避免盐岩地下储气库产生体积收敛破坏,应保证调峰短期最小内压在4.0 MPa以上。