• Geomechanics and Engineering
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• 제9권4호
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• pp.499-511
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• 2015

The creep property of salt rock significantly influences the long-term stability of the salt rock underground storage. Triaxial creep tests were performed to investigate the creep behavior of salt rock. The test results indicate that the creep of salt rock has a nonlinear characteristic, which is related to stress level and creep time. The higher the stress level, the longer the creep time, the more obvious the nonlinear characteristic will be. The elastic modulus of salt rock decreases with the prolonged creep time, which shows that the creep damage is produced for the gradual expansion of internal cracks, defects, etc., causing degradation of mechanical properties; meanwhile, the creep rate of salt rock also decreases with the prolonged creep time in the primary creep stage, which indicates that the mechanical properties of salt rock are hardened and strengthened. That is to say, damage and hardening exist simultaneously during the creep of salt rock. Both the damage effect and the hardening effect are considered, an improved Maxwell creep model is proposed by connecting an elastic body softened over time with a viscosity body hardened over time in series, and the creep equation of which is deduced. Creep test data of salt rock are used to evaluate the reasonability and applicability of the improved Maxwell model. The fitting curves are in excellent agreement with the creep test data, and compared with the classical Burgers model, the improved Maxwell model is able to precisely predict the long-term creep deformation of salt rock, illustrating our model can perfectly describe the creep property of salt rock.

• Geomechanics and Engineering
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• 제18권3호
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• pp.291-298
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• 2019

In order to study the mechanical properties of rock salt, triaxial compression tests under different temperatures and confining pressure are carried out on rock salt specimens, the influence of temperature and confining pressure on the mechanical properties of rock salt was studied. The results show that the temperature has a deteriorative effect on the mechanical properties of rock salt. With the increase of temperature, the peak stress of rock salt decreases visibly; the plastic deformation characteristics become much obvious; the internal friction angle increases; while the cohesion strength decreases. With the increase of confining pressure, the peak stress and peak strain of rock salt will increase under the same temperature. Based on the test data, the Duncan-Chang constitutive model was modified, and the modified Duncan-Chang rock salt constitutive model considering the effect of temperature and confining pressure was established. The stress-strain curve calculated by the modified model was compared with the stress-strain curve obtained from the test. The close match between the test results and the model prediction suggests that the modified Duncan-Chang constitutive model is accurate in describing the behavior of rock slat under different confining pressure and temperature conditions.

• Geomechanics and Engineering
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• 제10권3호
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• pp.325-334
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• 2016

Rock salt is a near-perfect material for gas storage repositories due to its excellent ductility and low permeability. Gas storage in rock salt layers during gas injection and gas production causes the stress redistribution surrounding the cavity. The triaxial cyclic loading and unloading tests for rock salt were performed in this paper. The elastic-plastic deformation behaviour of rock salt under cyclic loading was observed. Rock salt experienced strain hardening during the initial loading, and the irreversible deformation was large under low stress station, meanwhile the residual stress became larger along with the increase of deviatoric stress. Confining pressure had a significant effect on the unloading modulus for the variation of mechanical parameters. Based on the theory of elastic-plastic damage mechanics, the evolution of damage during cyclic loading and unloading under various confining pressure was described.

• 한국식품영양학회지
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• 제22권2호
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• pp.238-245
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• 2009

The principal objective of this study was to investigate the association of variable salts with the hardness of cubed white radish. We analyzed the contents of domestic sun-dried salt, Chinese sun-dried salt, domestic refined salt, Australian rock salt and Australian industrial sun-dried salt in the radish samples. Our assessment of the water content of variable salts showed that domestic refined salt was highest(7.27%) and Australian rock salt was lowest(0.16%). The NaCl contents of variable salts were as follows : 93.23% in refined salt, 93.76% in Australian rock salt, 87.85% in domestic Shinan sun-dried salt and 87.98% in Chinese sun-dried salt. The content of insoluble matter in water were $0.03{\sim}0.05%$ in all salts except 0.85% in Australian industrial sun-dried salt. The pH values of salts were as follows : 8.93 in domestic sun-dried salt, 8.62 in Chinese sun-dried salt, 6.69 in refined salt, 5.83 in Australian rock salt and 6.41 in Australian industrial sun-dried salt. Regarding the mineral component content assays, domestic salt was found to harbor lower Na content but far higher Mg, K, Ca contents than other salts. In our evaluation of the hardness of cubed white radish, we detected a continuous increase in the hardness of cubed white radish soaking in a 4% salt solution of domestic Shinan natural salt, but an initial increase followed by a decrease in the hardness of cubed white radish soaking in a 4% solution of the other salts.

• Geomechanics and Engineering
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• 제9권1호
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• pp.25-37
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• 2015

To predict the surface subsidence of salt rock storage, a new surface subsidence basin model is proposed based on the Logistic function from the phenomenological perspective. Analysis shows that the subsidence curve on the main section of the model is S-shaped, similar to that of the actual surface subsidence basin; the control parameter of the subsidence curve shape can be changed to allow for flexible adjustment of the curve shape. By using this model in combination with the MMF time function that reflects the single point subsidence-time relationship of the surface, a new dynamic prediction model of full section surface subsidence for salt rock storage is established, and the numerical simulation calculation results are used to verify the availability of the new model. The prediction results agree well with the numerical simulation results, and the model reflects the continued development of surface subsidence basin over time, which is expected to provide some insight into the prediction and visualization research on surface subsidence of salt rock storage.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.557-560
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• 2003

Some well-known artificial weathering tests such as freezing-thawing, acid immersion, and salt crystallization are adopted to examine the change of rock properties during the processes of artificial weathering. Granites and other rock types of limestone, marble and basalt collected from different quarries in south Korea were sampled for this study. All tests were performed up to 30 cycles and physical properties were measured after experiencing every ten cycles of artificial weathering tests. During the tests, the variation trends of rock properties were too variable to draw generalized variation patterns but it can be concluded that weathering agents have different effect on rock properties depending on weathering circumstance and time. Even in short terms of salt crystallization tests, some rocks were severely deformed and then burst, and in the early stages of salt weathering, recrystallized salts filling pores and cracks in rocks could be a important factor affecting rock properties.

• Geomechanics and Engineering
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• 제7권5호
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• pp.569-587
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• 2014

Triaxial compression creep tests were performed on salt rock samples using cyclic confining pressure with a static axial pressure. The test results show that, up to a certain time, changes in the confining pressure have little influence on creep properties of salt rock, and the axial creep curve is smooth. After this point, the axial creep curve clearly fluctuates with the confining pressure, and is approximately a straight line both when the confining pressure decreases and when it increases within one cycle period. The slope of these lines differs: it is greater when the confining pressure decreases than when it increases. In accordance with rheology model theory, axial creep equations were deduced for Maxwell and Kelvin models under cyclic loading. These were combined to establish an axial creep equation for the Burgers model. We supposed that damage evolution follows an exponential law during creep process and replaced the apparent stress in creep equation for the Burgers model with the effective stress, the axial creep damage equation for the Burgers model was obtained. The model suitability was verified using creep test results for salt rock. The fitting curves are in excellent agreement with the test curves, so the proposed model can well reflect the creep behavior of salt rock under low-frequency cyclic loading. In particular, it reflects the fluctuations in creep deformation and creep rate as the confining pressure increasing and decreasing under different cycle periods.

• Geomechanics and Engineering
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• 제15권1호
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• pp.615-620
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• 2018

In order to analyze the healing effectiveness of rock salt cracks affected by the applied stresses and time, we used the ultrasonic technology to monitor the ultrasonic pulse velocity (UPV) variations for different initial stress-damaged rock salts during self-healing experiments. The self-healing experiments were to create different conditions to improve the microcracks closure or recrystallized, which the self-healing effect of damaged salt specimens were analyzed during the recovery period about 30 days. We found that: The ultrasonic pulse velocity of the damaged rock salts increases rapidly during the first 9 days recovery, and the values gradually increase to reach constant values after 30 days. The damaged value and the healed value were identified based on the variation of the wave velocity. The damaged values of the specimens that are subject to higher initial damage stress are still keeping in large after 30 days recovery under the same recovery condition It is interesting that the damage and the healing were not in the linear relationship, and there also existed a damage threshold for salt cracks healing ability. When the damage degree is less than the threshold, the self-healing ratio of rock salt is increased with the increase in damage degree. However, while the damage degree exceeds the threshold, the self-healing ratio is decreased with the increase in damage.

• 전산구조공학
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• 제8권4호
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• pp.107-115
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• 1995

지하 방사성 폐기물 저장소의 오랜기간동안의 거동은 지반의 파괴와 변형에 영향과 암염의 비선형변형의 예측은 어려운 실정이다. 따라서 본 연구는 암염의 비선형파괴 메커니즘과 비선형 연속체거동의 유한요소모델을 개발하였다.

• 한국가스학회지
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• 제28권2호
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• pp.7-16
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• 2024

본 연구에서는 대규모 수소 저장을 위한 암염 공동(salt cavern) 저장 공법의 기술 특성과 현장사례 분석을 수행하였다. 암염 공동 저장 방식은 공동을 구성하는 암염(rock salt)의 낮은 공극률(porosity)과 투과도(permeability)로 인해 누출이 잘 일어나지 않고, 운영을 위한 쿠션 가스(cushion gas)의 양이 적어 타 공법 대비 효과적인 수소 저장이 가능하다. 암염-수소 간 화학적 반응이 거의 일어나지 않으며 다수의 주입/배출 사이클을 수행할 수 있어 피크 쉐이빙(peak shaving) 및 단주기 저장에 효과적이다. 공동은 크게 침출(leaching), 염수제거(debrining), 충진(filling)의 3단계로 형성되며 누출 실험을 통해 공동의 안정성을 평가한다. 현재 영국과 미국 Texas 주의 4개소에서 주변 지역의 산업 수요를 충당하기 위한 현장 적용이 이루어지고 있으며, 독일, 프랑스와 같은 유럽 지역에서 에너지 저장을 위한 암염 공동 운영을 준비하고 있다. 본 연구 결과는 향후 수소 저장 프로젝트 설계를 위한 기초자료로 활용될 수 있을 것으로 기대된다.