The effect of sorption on the migration of 7Be from a high energy accelerator constructed on a chalk site

The radioactive nuclides produced in rock surrounding a high energy accelerator installation may migrate from the accelerator environs if subjected to the hydraulic gradients of ground water. Under such conditions it might be possible for neighbouring ground water systems to become contaminated by long-lived radionuclides. This study concerns itself with the influence of chemical sorption in rock surfaces and its influence in minimizing leach rates. A specific study of the migration of ⁷Be, an important radionuclide produced in accelerator shields, through ground predominantly composed of chalk is reported. Sorption is shown to play a dominant role in minimizing leach rates.     

高地温隧道地温特征及预测研究

尼格隧道属长大深埋隧道,兼有高水温与高岩温,最高水温达63.4 ℃,最高岩温达88.8 ℃,最高气温达56.4 ℃。为了研究隧道地温特征并进行地温预测,针对性地设计了一系列地温测量方案,研究成果表明:灰岩段表现为高水温,水温＞气温＞岩温,水温与气温随着隧道进深及埋深呈现上升趋势,出水量及水温在接触带附近达到高值,洞内气温受水温、隧道出水量、积水量影响大;花岗岩段表现为高岩温,无水,岩温与气温随隧道进深及埋深呈现上升趋势,两者差值约为25~30 ℃;超前钻孔在孔深＞2 m时岩温达到稳定;一个完整施工循环的施工环境气温呈现4个阶段:气温下降阶段(打钻施工环节),气温骤升阶段(爆破施工环节),气温快速上升阶段(新爆围岩散热),气温缓降阶段(出渣施工环节),出渣环节由于车辆及挖机等机械作业影响,气温出现多处异常高值;施作二衬后,二衬内外壁温差约3.4 ℃;利用热量传递理论、地热成因理论预测的最高地温值与实测值较为吻合。该工程案例颇为典型,本文研究对西南高地热区隧道工程建设具有指导意义。     

A model of unfrozen water content in rock during freezing and thawing with experimental validation by nuclear magnetic resonance

The unfrozen water content of rock during freezing and thawing has an important influence on its physical and mechanical properties.This study presented a model for calculating the unfrozen water content of rock during freezing and thawing process,considering the influence of unfrozen water film and rock pore structure,which can reflect the hysteresis and super-cooling effects.The pore size distribution cu rves of red sandsto ne and its unfrozen water conte nt under different temperatures during...     

Time-dependent tests on intact rocks in uniaxial compression

The influence of strain history on rock specimen deformation during multi-level loading and unloading cyclic uniaxial compression creep tests is studied with a creep testing machine. An experimental data processing method for such creep tests is suggested. The correction formulas to determine the rheological model parameters are derived for the case when load relaxation is considered. Creep and relaxation tests under uniaxial compression on four types of rocks are conducted using an electronic hydraulic servo-controlled stiff testing machine. The creep and relaxation laws of the different rocks are compared. The complete stress–strain curves for red sandstone specimens are obtained at nine strain rates from 2.43×10⁻⁶ to 4.38×10⁻³/s. The effects of strain rates on rock strength and limit strain are discussed. Empirical equations to evaluate the strain rate dependence of rock mechanical properties are presented.     

Safe rapid drifting – Support selection

Current drift advance rates in mining fall short of expectations with advances in drilling and blasting technologies. Quick access to orebodies improves their net present value (NPV). This is critical for block cave mining where several kilometers of drift network is initially required at high capital cost. Many mining companies are now planning block caving because of its long-term low production cost. This paper critically reviews the developments in tunnelling and mine drift development rates with advances in drilling and explosives technologies. Current drift support practice during development is also critically reviewed together with the rock mass classification systems. These reviews show that, while drilling and explosive technologies have drastically improved since 1850, current drift advance rates in the Canadian metalliferrous mining industry have either remained stagnant or dropped below the1960 advance rate levels and in comparison to advance rates in civil tunnelling. It is also established that a major cause for this stagnation is the use of long-term support in good ground conditions where only temporary support is required near-face for worker safety in the short-term. Long-term support takes up 46% of development cycle time. The paper presents a methodology for drift support design for underground hard rock conditions typically found in current mining practice in the Canadian Shield and discusses the rationale for optimizing ground support systems installed near-face during drift development. An improved Q-system called Q-star (Q^*) that accounts for discontinuous joints (rock bridges) and roughness of short joints in the rock mass is developed to more reliably estimate the self-support capacities of rock masses. It is recommended that construction damage be accounted for in the rock mass rating for safe support selection during development. A procedure is developed for the adjustment of Q^* to account for construction damage. Perimeter blasting is recommended as pre-requisite for rapid drift development in order to minimize construction damage, reduce support demand and scaling and mucking times. A support matrix is presented based on rock mass quality and stress level for safe rapid drift development. Two case histories in active mines are presented to validate the procedure. The methodology is applicable to stress-induced damage and may not apply where complete relaxation occurs. While the procedures presented are focused on typical conditions in the Canadian Shield underground mines, they may be applicable in civil engineering tunneling and other underground mines where drill-and-blast is used as the excavation method.     

深埋长大公路隧道高地应力岩爆和岩溶涌突水问题及对策

对二郎山和华蓥山隧道在建设过程中的高地应力岩爆与岩溶涌突水问题进行了研究，概述了二郎山隧道地应力场，岩爆及围岩变形的监测预报，并对华蓥山隧道岩溶涌突水的特征，原因及对隧道的影响进行了研究：提出了岩爆和涌突水的防治措施，并予以实施。     

Micromechanical modelling of the mechanical properties of a granite under dynamic uniaxial compressive loads

A micromechanics-based model is used to study the mechanical properties of a granite under dynamic uniaxial compressive loads. The model is based on interacting sliding cracks uniformly distributed in the rock material. A dynamic crack growth criterion, which is related to crack growth velocity and dynamic fracture toughness of the rock material, is employed in the analysis. Under dynamic loads at strain rates from 10⁻⁴ to 10⁰ s⁻¹, the crack growth velocity is small compared to the critical crack growth velocity and the effect can be ignored. The strengths of the granite obtained by micromechanical modelling agree with the experimental results. A constitutive relation of the granite is derived from the energy equilibrium equation and correlated with the experimental results.     

Experimental study of a ground-coupled heat pump combined with thermal solar collectors

This paper presents the experimental study of a ground-coupled heat pump used in a 180 m² private residence and combined with thermal solar collectors. This process, called GEOSOL, meets domestic hot water and heating–cooling building energy needs. Solar heat is used as a priority for domestic hot water heating and when the preset water temperature is reached, excess solar energy is injected into the ground via boreholes. This system has the advantage to contribute to the balance of the ground loads, increasing the operating time of the solar collectors and preventing overheating problems. After 11 months in operation, the power extracted and injected into the ground had average values of 40.3 and 39.5 W/m, respectively. Energy injected into the ground represents 34% of the heat extracted, and the heat pump's coefficient of performance (COP) in heating mode had an average value of 3.75. In addition, the domestic hot water solar fraction had an average value higher than 60% for the first 11 months in operation.     

Deterioration behavior of gypsum breccia in surrounding rock under the combined action of cyclic wetting-drying and flow rates

The cyclic wetting-drying (W-D) phenomenon, which is a part of weathering processes, plays a vitally important role in affecting rock materials’ properties. In this paper, the gypsum breccia, an environmentally sensitive rock, was taken as the research object, which has the characteristics of high solubility. The deterioration behavior of gypsum breccia under W-D cycles with different flow rates was investigated. A one-dimensional water saturation test was conducted to study the coupling mechanism of water saturation-dissolution of gypsum breccia. A series of W-D cycle tests with different flow rates (0, 10, and 20 l/h) for gypsum breccia were conducted to reveal its deterioration behavior. Furthermore, the influence of these effects on the stability of the tunnel was discussed. The results show that gypsum breccia has a coupling behavior of water saturation and dissolution in the water environment. The effect of W-D cycles is the primary reason for the formation of visible cracks in gypsum breccia, while the flowing water will wash away the loose particles caused by the action of W-D cycles and accelerate the development of visible cracks and dissolution in gypsum breccia. The combination of these two actions gradually deteriorates the self-stability of the surrounding rock, which eventually leads to lining damage due to overload. The study can provide references for the engineering design of tunnels in gypsum breccia.

     

Ground behaviour and rock mass composition in underground excavations

Underground excavations like tunnels, caverns shafts, are located in a vast variety of rock mass and ground conditions with different modes of behaviour. The paper describes the main parameters and features determining the behaviour of the ground surrounding an underground excavation, namely: (1) the ground conditions (rock mass, stresses and water) and (2) the project related features, (size and shape of the opening and excavation method). Based on this a simple, qualitative division of the rock masses is presented, which together with the influence of stresses, ground water and dimension of the excavation, is used to find the probable behaviour. This may help the user to select appropriate rock engineering tool(s) for the geotechnical design as has been described by the two authors in an earlier paper.     

Effects of loading rate on rock fracture

By means of a wedge loading applied to a short-rod rock fracture specimen tested with the MTS 810 or SHPB (split Hopkinson pressure bar), the fracture toughness of Fangshan gabbro and Fangshan marble was measured over a wide range of loading rates, =10⁻²–10⁶ MPa m^1/2 s⁻¹. In order to determine the dynamic fracture toughness of the rock as exactly as possible, the dynamic Moiré method and strain–gauge method were used in determining the critical time of dynamic fracture. The testing results indicated that the critical time was generally shorter than the transmitted wave peak time, and the differences between the two times had a weak increasing tendency with loading rates. The experimental results for rock fracture showed that the static fracture toughness K_Ic of the rock was nearly a constant, but the dynamic fracture toughness K_Id of the rock ( ≥10⁴ MPa m^1/2 s⁻¹) increased with the loading rate, i.e. log(K_Id)=a log +b. Macroobservations for fractured rock specimens indicated that, in the section (which was perpendicular to the fracture surface) of a specimen loaded by a dynamic load, there was clear crack branching or bifurcation, and the higher the loading rate was, the more branching cracks occurred. Furthermore, at very high loading rates ( ≥10⁶ MPa m^1/2 s⁻¹) the rock specimen was broken into several fragments rather than only two halves. However, for a statically fractured specimen there was hardly any crack branching. Finally, some applications of this investigation in engineering practice are discussed.     

Norwegian oil and gas storage in rock caverns-Technology based on experience from hydropower development

Underground storage in rock caverns is widely used in Norway for many different petroleum products,such as crude oil,fuel,propane and butane.Basically,the caverns for such storages are unlined,i.e.containment is ensured without using any steel lining or membrane.The main basis for the storage technology originates from the extensive hydropower development in Norway.As part of this activity,about 4500 km of tunnels and shafts have been excavated,and around 200 large powerhouse caverns have been constructed.The hydropower tunnels are mainly unlined,with hydrostatic water pressure on unlined rock of up to 1000 m.Some of the projects also include air cushion chambers with volumes of up to 1×10⁵m³and air pressure up to 7.7 MPa.Many lessons which are valuable also for underground oil and gas storage have been learnt from these projects.For a storage project to become successful,systematic,well planned design and ground investigation procedures are crucial.The main steps of the design procedure are first to define the optimum location of the project,and then to optimize orientation,shape/geometry and dimensions of caverns and tunnels.As part of the procedure,ground investigations have to be carried out at several steps integrated with the progress of design.The investigation and design procedures,and the great significance of these for the project to become successful will be discussed.Case examples of oil and gas storage in unlined rock caverns are given,illustrating the relevancy of experience from high-pressure hydropower projects for planning and design of unlined caverns for oil and gas storage.     

影响液体速凝剂作用效果的试验研究

液体速凝剂和粉状速凝剂相比有很多优点,但液体速凝剂的促凝效果受许多因素的影响。为了分析影响其作用效果的因素,本文主要从萘系高效减水剂,高效氨基减水剂,速凝剂掺入方式,水泥品牌,速凝剂掺量这5个方面对铝酸盐液体速凝剂凝结时间的影响进行了研究。     

Methodology for tunnel and portal support design in mixed limestone, schist and phyllite conditions: a case study in Turkey

The purpose of this study is to present a methodology for tunnel and support design in mixed limestone, schist and phyllite conditions through investigating two highway tunnel case studies that are located along the Antalya–Alanya Highway in southern Turkey. The main lithologies of the project area are regularly jointed, recrystallized limestone and the weak lithologies of the schist unit (i.e., pelitic schist, calc schist, graphitic phyllite and alternations of these lithologies). A detailed geological and geotechnical study was carried out in the project area, and the tunnel ground support types and categories were determined according to the Q-system, rock mass rating method and New Austrian Tunneling Method (NATM). The shear strength parameters and geomechanical properties of the rock masses were obtained by using the geological strength index (GSI). The deformation moduli and post-failure behavior of the rock masses have been determined. Slope stability analyses were performed at the portal, side or cut slope sections. Kinematic and limit equilibrium analyses incorporating the effects of water pressure were performed for the regularly jointed failed rock slopes. Circular failure analogy was used for the slope stability analyses of irregularly jointed, highly foliated lithologies. Slope support system recommendations were made. A back analysis on a failed slope was performed. The results of the back analysis compared well with the results obtained through the GSI method. The tunnel grounds were divided into sections according to their rock mass classes. The deformations and stress concentrations around each tunnel section were investigated and the interactions of the empirical support systems with the rock masses were analyzed by using the Phase² finite element software. The regularly jointed rock masses were modeled to be anisotropic and the irregularly jointed, highly foliated and very deformable soil-like lithologies were modeled to be isotropic in the tunnel finite element analyses.     

Influence of physical and geometrical properties of granite and limestone aggregates on the durability of a C20/25 strength class concrete

This paper presents an experimental study to evaluate the influence of physical and geometrical properties of granite and limestone aggregates on the durability of a C20/25 strength class concrete. Different granite and limestone aggregates were collected from seven quarries. Physical, geometrical and mechanical properties of aggregates as well as the rock weathering state were quantify by several tests such as, abrasion, surface hardness, uniaxial compressive strength, ultrasonic pulse velocity, water absorption by capillarity, vacuum water absorption and oxygen permeability.

Using aggregates from each quarry, several C20/25 strength class concrete mixes have been produced, with the same workability and volume proportions. Concrete specimens have been cured under water for 90 days; after that time concrete durability parameters were obtained through tests such as, vacuum water absorption, capillarity water absorption, water permeability and oxygen permeability.

Relevant statistical correlations have been obtained between absorption and permeability test of rock material and rock deterioration state (weathering). Valid statistic correlation was also obtained between durability parameters as well as among aggregates geometrical properties and concrete durability parameters.     

Nitrogen inputs to stream water from forests along an elevational gradient in New Mexico

Studies of nitrogen inputs in precipitation and outputs in stream water for a number of terrestrial ecosystems support the hypothesis that undisturbed communities have the ability to reduce losses of nitrogen via stream water. In spite of different levels of biomass, productivity and stream discharge for these communities, net losses of nitrogen were similar. Maintaining nitrogen in an organic or cation form (NH₃, NH₄⁺) is an important factor in minimizing loss. This may be accomplished by slow rates of mineralization, rapid plant uptake, and denitrification through the electron sink pathway. Denitrification by the dissimilatory pathway may also be important.     

Use of geosynthetic clay liner as a remedial measure of claystone degradation in Lam Ta Khong hydropower plant

In this study, the downstream slope of a dam impounding the upper reservoir of Lam Ta Khong (LTK) hydroelectric energy storage in Thailand was found to slide at a higher pace during the rainy season. After a thorough site investigation, laboratory tests, and numerical modeling to identify the main cause of the movement, it was found that as rainfall infiltrated the upper soil layer, the claystone of the downstream slope deteriorated when in contact with the water. As a remedial measure, 174,750 m² of geosynthetic clay liner (GCL) was used to cover the entire downstream slope of the dam, and proved to be an effective and economical solution for reducing the ongoing movement. The GCL included a textured high-density polyethylene (HDPE) layer for improving the resistance and minimizing the slippage at the interface between the GCL and underlying rock. Before the dam's remediation, the settlement point demonstrated a movement of nearly 0.1 m/year. In contrast, after the placement of the GCL, almost all settlement points moved less than 0.1 m for a recorded period of more than 4 years.     

The influence of water on the shear behaviors of intact sandstone

The shear behavior of rock is markedly affected by the presence of water. To study the influence of water on the shear behaviors of rock, a series of direct shear tests were conducted on intact sandstone specimens with different water soaking durations (from dried to saturated) under three levels of normal stresses. Before direct shear tests were performed, water absorption experiments were conducted to guide the different levels of water saturation required for the direct shear tests. The influences of water on shear stress-shear strain responses and peak and residual shear strength envelopes were investigated. The results show that soaking duration significantly impairs the peak and residual shear strengths and other shear properties (e.g., cohesion, friction angle and shear stiffness). The reductions in fracture energy and friction coefficient and the chemical and corrosive deterioration are the main mechanisms for the decrease of intact sandstone’s shear strength. A novel observation is that the failure patterns of specimens are sensitive to different water distributions. The results provided in this study reveal that the stability of rock engineering is affected by changes in water levels.

     

河南新商断裂对地热资源形成的控制作用及资源潜力分析

新商断裂是一条几乎横贯河南的区域性深大断裂,构成了济源-开封凹陷和通许凸起两大地热单元的边界。在其及影响带附近分布着新乡-延津、兰考、民权、宁陵-商丘等大型地热田,蕴藏着丰富的中深层地热资源。该文通过分析新商断裂的构造特征和地热流体特征,系统分析了深大断裂对地热资源的控制作用,以商丘项目为例分析了其资源潜力。区内地下热水的分布特征严格受控于新商断裂的展布方向,地下热水的温度取决于盖层的厚度及围岩的放射性含量,地热资源潜力巨大,地热可采资源量约140.37×10⁴ m³/a,地热流体含热能量71.94×10¹² J/a,折合标准煤2454.6 t/a,可减少CO₂排放5856.8 t/a,该研究为今后在该地区开展地热资源勘查工作具有一定的指示意义。     

青海红旗沟—深水潭金矿水文地质条件及矿坑涌水量预测研究

对青海都兰红旗沟-深水潭金矿开展的水文地质条件分析及矿坑涌水量预测研究表明:红旗沟-深水潭金矿水文地质单元可分为第四系松散岩类孔隙水和基岩裂隙水两类,后者包含块状基岩裂隙水和层状基岩裂隙水;金矿体均产于当地侵蚀基准面之上的基岩山区,因此,第四系松散岩类孔隙水不是矿床的直接充水水源;矿体多产于构造破碎带及蚀变接触破碎带中,也为块状基岩裂隙水和层状基岩裂隙水的赋存部位,因此,块状基岩裂隙水和层状基岩裂隙水是矿床的直接充水水源;红旗沟-深水潭首采区段的预测矿坑涌水量为115~265m^3/d,涌水量较小,矿坑涌水量与大气降水呈正比关系,且随季节性变化较为明显,但是涌水量总体上随着开采时间的增长而逐渐降低。