Experiments on mechanical properties of salt rocks under cyclic loading

The primary purpose of underground gas storages is to provide gas for seasonal consumptions or strategic reserve.The periodical operations of gas injection and extraction lead to cyclic loading on the walls and surrounding rocks of gas storages.To investigate the mechanical behaviors of different host rocks in bedded salt deposit,laboratory experiments were conducted on the samples of rock salt,thenardite,glauberite and gypsum.The mechanical properties of rock samples under monotonic and cyclic loadings were studied.Testing results show that,under monotonic loading,the uniaxial compressive stress(UCS) of glauberite is the largest(17.3 MPa),while that of rock salt is the smallest(14.0 MPa).The UCSs of thenardite and gypsum are 16.3 and 14.6 MPa,respectively.The maximum strain at the peak strength of rock salt(halite) is much greater than those of the other three rocks.The elastic moduli of halite,thenardite,glauberite and gypsum are 3.0,4.2,5.1 and 6.8 GPa,respectively.Under cyclic loading,the peak strengths of the rock specimens are deteriorated except for rock salt.The peak strengths of thenardite,glauberite and gypsum decrease by 33.7%,19.1% and 35.5%,respectively;and the strains of the three rocks at the peak strengths are almost the same.However,the strain of rock salt at the peak strength increases by 1.98%,twice more than that under monotonic loading.Under monotonic loading,deformation of the tested rock salt,thenardite and glauberite shows in an elastoplastic style.However,it changes to a ductile style under cyclic loading.Brittle deformation and failure are only observed for gypsum.The results should be helpful for engineering design and operation of gas storage in bedded salt deposit.     

甘肃省武都区塘坝金矿工程地质条件特征

塘坝金矿区位于甘肃省武都县,属琵琶乡管辖,气候为温暖带大陆性季风湿润气候,区内水系发育,属长江流域嘉陵江水系。塘坝金矿床是赋存在坚硬、半坚硬的碳酸盐岩和碎屑岩层中,灰岩和硅质角砾岩等硬性岩石一般为完整-较完整,岩体结构类型为块状结构,岩石稳定,工程地质条件较好,千枚岩等软弱岩石和断裂影响范围内的岩石一般稳定性差,岩石较破碎,岩体结构类型主要为层状碎裂结构和散体结构。矿区工程地质勘探属于第三类——层状岩类,工程地质勘探的复杂程度划分为中等型,属工程地质条件中等矿床。     

Model test of immersed tube tunnel foundation treated by sand-flow method

In order to explore the immersed tunnel foundation treated by sand-flow method, modeling principles for the full-scale model test of sand flow were put forward. In addition, a sand-flow test model was built, which consisted of model system, equipment system and measurement system. The situation of sand-deposit expanding and the water pressure in the foundation trench were evaluated through the model test. The results show that a semi-closed space was formed between the model board and the expanding sand deposit, which made the water pressure in it rising with little range of volatility. The sand deposit gradually became non-circular truncated cone which shaped with its expanding radius, and the difference of the water pressure increased at each direction. The water pressure in crater had a linear increase with the sand-deposit radius, with a maximal value of 0.015 2 MPa. The volatility of the water pressure under the tunnel board and the water pressure value in the crater could be used as bases of construction control.     

山西省娄烦县尖东铁矿地质特征及矿床成因

通过对山西省娄烦县尖东铁矿区域地质背景、矿区地质特征、矿体特征等的综合分析,阐述了该区铁矿的成因类型,总结其成矿规律,为铁矿的进一步勘查开发提供地质依据。     

CO2 sequestration in depleted methane hydrate deposits with excess water

The recent increase in atmospheric CO₂ concentration makes it necessary to investigate new ways to reduce CO₂ emissions. Simultaneously, natural gas hydrate mining technology is developing rapidly. The use of depleted methane hydrate (MH) deposits as potential sites for CO₂ storage is relatively safe and economical. This method can alleviate the shortage of hydrate displacement gas with CO₂. The purpose of this study was to investigate CO₂ hydrate formation characteristics during the seepage process—in reservoirs with excess water—and their effect on CO₂ storage. The experimental process can be divided into 5 parts: MH formation, water injection, MH dissociation, CO₂ hydrate formation, and CO₂ hydrate dissociation. Magnetic resonance imaging was employed to monitor the distribution of liquid water, and the effects of different parameters on the formation and dissociation of CO₂ hydrates were analyzed. It was found that a state of initial water saturation can effectively control hydrate saturation in artificial MH reservoirs for hydrate reservoirs with excess gas. In the process of CO₂ flow, initial water saturation was not the main controlling factor for CO₂ hydrate formation. Increasing the flow pressure and reducing the flow rate were beneficial for CO₂ hydrate formation. This study is of great significance for advancing the science of CO₂ geological storage in the form of deep‐sea hydrates.     

滇西北普朗地区自然重砂矿物异常及其找矿意义

自然重砂及其组合蕴含着丰富的源区岩性体信息,为找矿勘查提供了丰富的矿源信息。已有地质勘查及研究主要集中在金、钨锡矿等,而对铜铅锌矿等其他矿种研究较少。针对铜铅锌矿种及其不同成因的矿床开展研究,通过普朗地区自然重砂矿物的类型及分布特点开展综合对比研究,挖掘其所蕴含的铜多金属成矿作用信息及找矿意义。普朗地区自然重砂矿物及其组合成片集中分布,其异常对已知区内铜多金属矿床具有良好的响应,体现出铜多金属成矿模式及成矿作用特点,反映具有成因意义的成矿作用信息,对区域矿产勘查具有良好的指示意义。     

东北地区金矿自然重砂异常及其找矿指示意义

统计了黑龙江、吉林、辽宁等省典型金矿床的自然重砂情况,得出斑岩型、矽卡型、造山型和热液型的金矿所对应的自然重砂矿物组合。其中金自然重砂分布广泛,主要受地形特征和水系分布制约,具有一定的区带性特征,可以划分为12个异常集中区;多分布于隐伏断裂附近,且与金矿床响应具极好的相关性;自然金、黄铁矿、辰砂和白钨矿等矿物对金矿响应程度较高。不同成因类型金矿床的重砂矿物组合存在差异,斑岩型金矿为自然金—黄铁矿—辰砂—白钨矿—方铅矿—黄铜矿—锆石—金红石,矽卡型金矿为自然金—黄铁矿—辰砂—石榴子石—磷灰石,造山型金矿为自然金—黄铁矿—辰砂—白钨矿—方铅矿—黄铜矿,热液型金矿为自然金—黄铁矿—辰砂—白钨矿—方铅矿。综合研究认为,重砂异常对矿产地存在指示作用,重砂矿物的标型组合可以体现出特定成因金矿床的指示标志。     

广东牛尾岩—观音山多金属矿地质特征及找矿标志

牛尾岩—观音山多金属矿区位于吴川—四会深断裂中北端西侧,英德弧型构造前弧西翼,连阳岩体的北东缘,南岭地区重要多金属成矿带的南缘。赋矿围岩为石炭系下统石磴子组灰、深灰色至灰黑色中—厚层生物碎屑灰岩夹结晶灰岩、粒屑灰岩,局部夹薄层状泥质灰岩或少量的白云质灰岩。矿石类型主要为硫化物型铅锌多金属矿石及铁多金属矿石,矿体呈脉状或透镜状产出,与矿化关系密切的围岩蚀变主要有夕卡岩化、硅化等。夕卡岩化、硅化、黄铁矿化、褐铁矿化4种蚀变相伴出现,可作为该区的找矿标志。     

陕西池沟斑岩型铜矿地质特征与找矿前景分析

池沟矿区位于南秦岭礼县—柞水海西褶皱带东段,受山阳—凤镇断裂控制,矿区内发育燕山期中酸性小岩体群.铜矿体主要赋存于黑云母二长花岗岩、石英闪长岩、石英闪长玢岩及池沟组地层中,矿区内围岩蚀变强烈,分布范围较大,且具有明显的分带特征.铜矿化呈细脉状、浸染状、细脉浸染状分布,表现出典型的斑岩型铜矿特征.通过地质调查和物化探异常对池沟矿区的地质特征分析,认为该矿区找矿前景广阔.