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Abstract In this study, behaviors of rock mass and discontinuities around cavern are simulated using mechanical and thermal properties of rock at low temperature. Simulation results show that temperature difference between before and after storage. When low temperature materials are stored in cavern, the temperature gradient is steep in early stage but it becomes gradual with time. UDEC simulation for LNG cavern shows that the range of the plastic zone induced by low temperature is approximately equal to a Width of the cavern. Introduction As the consumption of LPG, LNG and refrigerated food increase, demands of the storage caverns for these materials are increasing in Korea. It is very likely that new facilities are located in underground space, because of the lack of ground space and safety concerns. The maintained temperature of LPG is about -40 to -45K and that of LNG is about -160K. Therefore, it is necessary to understand the characteristics of rock mass and discontinuities under the low temperature. In this paper, FLAC and UDEC programs using mechanical and thermal properties of rock at low temperature are used to simulate behaviors of rock mass and discontinuities around cavern. Input Data Generally, strengths and Young's modulus of rock increased as temperature lowered. (Inada, 1989, 1993) Rocks become stronger and stiffer as they are refrigerated. They become weaker and softer if they undergo thermal cycle.(Park at al, 1998) For thermal conductivity of rock, Kuriyagawa (1980) reported that thermal conductivity is 10 to 20% higher at -l00K than at room temperature. Sundberg (1988) reported that the thermal conductivity of granite is similar with gneiss, and that rock has the higher thermal conductivity according to amount of quartz. According to these results, authors choose the input data as table 1. For analysis, commercial programs, FLAC and UDEC were adopted with user-defined functions to consider thermal dependent characteristics for mechanical properties of rocks. The user-defined function is in consisted of formula that isin correlation between mechanical properties of rock and low temperature. As the programs have being calculated, it is started with data like table 1. However, as the calculation is progressed.
- Facilities Design, Construction and Operation > Natural Gas Conversion and Storage > Liquified natural gas (LNG) (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (0.98)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.90)
A Study of Dynamic Tensile Strength And Fracture Toughness Using Impact Test
Hjin, Yeon-Ho (Department of Mineral Resources and Energy Engineering, Chonnam National University, Rep. of Korea) | Yang, Hyung-Sik (Department of Mineral Resources and Energy Engineering, Chonnam National University, Rep. of Korea) | Park, Chul-Whan (Lab for Rock Engineering Group, Mining Department, KIGAM, Rep. of Korea)
ABSTRACT: In this study, static and dynamic tensile tests were carried out to study rock fracture mechanism. Brazilian test was adopted as the static tensile test with changing strain rates. while modified pipe test based on Hoppkins' effect was adopted as dynamic test. Vertical pipe test was modified to have inclination. By this modification, variable was reduced to friction force only. As a result of all these tests, the characteristics of rook including static &dynamic tensile strengths etc have been obtained. &a general relationship between tensile strength &strain rate is suggested by a formula. I. INTRODUCTION Dynamic testing as discussed in the literature covers various types of test such as creep, fatigue, impact and extends over a wide range of strain rates. Therefore, it is important to establish or define the load or strain rate associated with the type of dynamic test being conducted. In this paper the discussion will be concerned with dynamic tensile strength of Tae-Jeon granite in the strain-rate range of 5.67 × 10¹ - 3.6 × 106 /sec by tensile test. Static and dynamic tensile strength and fracture mechanism was studied. Brazilian test was adopted as the static tensile test with changing strain rates, while modified pipe test based on Hoppkins' effect was adopted as dynamic test. Vertical pipe test was modified to have inclination. By this modification, variable was reduced to friction force only. A simple dynamic tensile fracture experiment was designed to measure the dynamic tensile strength of a rock and its dynamic fracture energy. For Homogeneous rock material, the experiment can also measure the dynamic tensile strength. 2. THEORETICAL BACKGROUND The strain energy associated with a stress wave is the internal energy contained in the material in the form of elastic deformation energy. It is the product of stress and strain (divided by the material's initial density. if one wants to have the strain energy per unit mass rather than per unit volume). For a simple compressive or tensile wave. However, in the process of fracturing, only half of the impactor's kinetic energy can be used for deformation work at the fracture surfaces. The other half is transmitted back into the two separating parts in the form of elastic tensile waves. 3. EXPERIMENT Static and dynamic tensile strength tests were conducted on the Tae-Jeon granite of Korea. Strengths obtained from both test on 54 mm-diameter specimens. 3.1 Static tensile test Brazilian test was adopted as a static tensile strength test. Experimental results have suggested that the static tensile strengths or granite increasing loading rate, as shown in Table I. 3.2 Dynamic tensile test Fig. 2 shows a schematic picture of the overall experimental setup, Fig 3 shows the idealized wave velocity in the hammer and rock specimen at different times after impact. If hammer length is three times of rock specimen length, peak tensile wave force is generated at 100p sec or 120p sec. Table 2 shows results of pipe test, Table 3 shows dynamic tensile strength in high strain rate.
- Research Report > New Finding (0.49)
- Research Report > Experimental Study (0.35)
- Geology > Geological Subdiscipline > Geomechanics (0.72)
- Geology > Rock Type > Igneous Rock > Granite (0.68)