scholarly journals The Influence of Operation Pressure on the Long-Term Stability of Salt-Cavern Gas Storage

2014 ◽  
Vol 6 ◽  
pp. 537679 ◽  
Author(s):  
Jianjun Liu ◽  
Qiang Xiao
Keyword(s):  
Internal Pressure ◽  
Element Model ◽  
Gas Storage ◽  
Salt Cavern ◽  
Term Stability ◽  
Long Term Stability ◽  
Rock Creep ◽  
Operation Pressure ◽  
Salt Cavern Gas Storage

The operation pressure of underground salt-cavern gas storage directly affects its stability. Because of seasonal demand and other emergency reasons, the gas storage working pressures always change from high to low or from low to high cyclic variation. In order to analyze the effect of gas storage pressure changing on its long-term stability, considering the salt rock creep, a 3D finite element model was built using the software Abaqus. Moreover, the deformation and analyzed results of the storage under 0 MPa, 4 MPa, 6 MPa, 8 MPa, 10 MPa, and 12 MPa and also circulating changes pressure operation were given in the 10-year creep. It concluded that how working pressures have effect on long-term stability of salt-cavern gas storage. The research results indicated that the long-term creep performance of underground salt cavern gas storage is affected by internal pressure, the smaller the internal pressure creep is, the more obvious the creep and the greater deformation of gas storage are. The greater the internal pressure is, the smaller the deformation of the gas storage is. The low pressure and excessive high pressure must be avoided during the operation of gas storage. These results have an important significance on determining the reasonable pressure of gas storage operation and ensure the long-term stability of gas storage.

Towards the Optimal Crown-to-Implant Ratio in Dental Implants

2017 ◽  
Author(s):  
T. J. Sego ◽  
Yung-Ting Hsu ◽  
Tien-Min Gabriel Chu ◽  
Andres Tovar
Keyword(s):  
Dental Implants ◽  
Strain Distribution ◽  
Mechanical Stability ◽  
Element Model ◽  
Equivalent Strain ◽  
Skeletal Tissue ◽  
Term Stability ◽  
Long Term Stability ◽  
Clinical Scenarios

Short dental implants are commonly recommended to be implemented with small crown-to-implant (C/I) ratios due to their mechanical stability — decreasing C/I ratios cause less deformation in skeletal tissue under occlusal force. However, the long-term stability of short implants with high C/I ratios remains a controversial issue due to biomechanical complications. This study evaluates the strain distribution and functional implications in an implant-supported crown with various C/I ratios using a high-fidelity, nonlinear finite-element model. Several clinical scenarios are simulated by loading implants with various implant lengths (IL) and crown heights (CH). Strain distribution and maximum equivalent strain are analyzed to evaluate the effects and significance of CH, IL, and the C/I ratio. The study shows underloading for certain implant configurations with high C/I ratio. Increasing IL and decreasing C/I in moderation demonstrates a positive effect in long-term stability.

Rock Long-Term Strength Parameters Determination of a Salt Cavern Gas Storage

2013 ◽  
Vol 353-356 ◽  
pp. 1685-1688
Author(s):  
Li Na Ran ◽  
Hua Bin Zhang ◽  
Zhi Yin Wang
Keyword(s):  
Mechanical Properties ◽  
Rock Salt ◽  
Gas Storage ◽  
Surrounding Rock ◽  
Creep Process ◽  
Term Strength ◽  
Salt Cavern ◽  
Study Results ◽  
Salt Cavern Gas Storage

In order to determine the long-term mechanical properties of surrounding rock of salt cavern gas storage, long tri-axial creep test studies on rock salt of the field were carried out. Based on the test data, long-term strength of rock salt was determined, and comparatively analysis was conducted combined with of the instantaneous test. The study results show that: Considering the axial strain, radial strain and volumetric strain to determine the long-term strength of rock salt can ensure reliability of the results. Under the same condition, the less salt content, the value of long-term strength is higher. Tri-axial creep process has a different effect degree between cohesion and internal friction angle; it is more sensitive to cohesion. The strain limit should be considered for the stability analysis of multi-bedded salt cavern gas storage construction and pay more attention about the mechanical properties of the interlayer parts. The study results provide references for researching the surrounding rock long-term mechanical properties of salt cavern gas storage.

scholarly journals Creep Behaviours of Argillaceous Sandstone: An Experimental and Modelling Study

2020 ◽  
Vol 10 (21) ◽  
pp. 7602
Author(s):  
Huaiguo Zheng ◽  
Qingxiang Cai ◽  
Wei Zhou ◽  
Xiang Lu ◽  
Ming Li ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Creep Model ◽  
Nonlinear Creep ◽  
Underground Excavations ◽  
Creep Theory ◽  
Term Stability ◽  
Long Term Stability ◽  
Rock Creep ◽  
Confining Pressures

Understanding the creep behaviours of rocks is essential for the long-term stability of underground excavations in mining engineering. Creep behaviours are more important when the mining depth is greater, which leads to the emergence of weak rock masses and high in situ stresses. In this study, the creep behaviours of argillaceous sandstone (AS) were systematically investigated. For the experimental investigation, creep tests were conducted on AS with different confining pressures (3, 6, 9, 12, 15, and 18 MPa) using an MTS815.02 rock mechanics test system. The mechanical characteristics of AS were analysed. For the numerical study, a nonlinear creep model of AS under equal and different confining pressures was established based on rock creep theory and plastic theory. The results showed that confining pressure could effectively improve the creep failure strength of AS, accelerating its creep deformation rate and process and reducing the final expansion volume. The nonlinear creep model was embedded in the FLAC3D software, and the experimental and numerical results agreed well. The experimental investigation and proposed creep model can provide important guidance in underground mines for safe long-term stability of underground excavations.

Stability of unsupported tunnels in clay

1992 ◽  
Vol 29 (4) ◽  
pp. 609-613 ◽  
Author(s):  
Z. Eisenstein ◽  
L. Samarasekera
Keyword(s):  
Finite Element ◽  
Stress Field ◽  
Limit Equilibrium ◽  
Element Model ◽  
Soil Parameters ◽  
Term Stability ◽  
Long Term Stability ◽  
Shallow Tunnels ◽  
Starting Point

An overall long-term stability of unsupported shallow tunnels in overconsolidated clays which is directly related to the stand-up time is investigated. A new approach that combines finite element methods and the limit equilibrium theory is used to overcome limitations of current design practice. A more realistic initial stress field, unloading due to excavation, and variation of strength and modulus with depth are used. The pore-pressure change is analysed using a finite element model that incorporates an uncoupled consolidation theory. These pore pressures along with the previously obtained stress field are utilized to predict the variation of stability with time for given soil parameters such as strength and coefficient of earth pressure at rest. The results obtained employing a simple mechanism are presented using non-dimensional quantities. These results relate time, stability of the tunnel, and soil strength. The analysis showed that, under certain circumstances, the initial undrained stability may be of no practical value and may only be used as a starting point for more practical long-term stability. This procedure explains the stand-up time phenomenon in tunnels and may also be used in design as a direct tool for its evaluation. Key words : overconsolidated clay, long-term stability, stand-up time, shallow tunnels, finite elements, limit equilibrium.

Sign in / Sign up

Export Citation Format

Share Document