Experimental study on mechanical property and pore structure of concrete for shotcrete use in a hot-dry environment of high geothermal tunnels

Cui, Shengai; Pin, Liu; Cui, Enqi; Su, Jiao; Huang, Bo

doi:10.1016/j.conbuildmat.2018.03.191

Cited by 75 publications

(28 citation statements)

References 28 publications

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“…where α is the angle between the direction of maximum horizontal principal stresses and the x-direction; ϕ is the azimuth of maximum horizontal principal stresses, and clockwise is defined as positive. Table 5 shows (1) the maximum residual of in situ stress magnitudes considering geo-temperature is 1.58 MPa, and the residual sum of squares for in situ stress magnitudes considering geo-temperature is Ψ = 1.32 + 6.06+ = 7.69(MPa) 2 . Similarly, the maximum residual and the residual sum of squares for in situ stress magnitudes without considering geo-temperature are −5.51 MPa and 84.77 (MPa) 2 , respectively.…”

Section: Discussionmentioning

confidence: 99%

“…The thickness of the strata for the constant temperature zone is about 3-5 m. The reason why geo-temperature does not change over time is that the heat flow from the Earth's interior and the thermal radiation from the Sun are in equilibrium near the constant temperature zone. (2) The variable temperate zone is defined as the stratigraphic zone that geo-temperature changes over time. The variable temperature zone is positioned above the constant temperature zone, and is about 20-30 m away from land surfaces.…”

Section: The Thermal Stress Of Rock Masses Caused By Geothermal Gradimentioning

confidence: 99%

“…With the gradual implementation of underground engineering projects in western China, such as the Sichuan-Tibet Railway and the Sichuan-Tibet Highway, deep, long, and high geo-stress tunnels have emerged in Tibetan areas [1][2][3]. In order to understand the state of in situ stresses in Tibetan areas, scholars have measured the in situ stresses of rock masses using the hydraulic fracturing and overcoring methods proposed by the International Society for Rock Mechanics (ISRM) [4,5].…”

Section: Introductionmentioning

confidence: 99%

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Back Analysis of the Initial Geo-Stress Field of Rock Masses in High Geo-Temperature and High Geo-Stress

Meng

2020

Energies

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In a high geo-temperature environment, it is rarely reported that geo-temperature has been considered during a back analysis. This may cause the initial geo-stress field that is obtained by a back analysis to be wrong. In this study, according to the theory of elasticity, the theoretical solution of the hydraulic fracturing equation is obtained in a high geo-temperature environment. Since the vertical stress that is obtained by the hydraulic fracturing method is calculated using the density of overlying strata, this vertical stress lacks the thermal stress that is caused by geothermal gradients. Therefore, in a high geo-temperature environment, inverting the initial geo-stress field of rock masses directly using the stress that is measured by the hydraulic fracturing method can cause serious errors. We propose that the regression coefficient of a gravitational stress field should be set to one during a back analysis if stresses are measured by the hydraulic fracturing method, and this regression coefficient should not be equal to one if stresses are measured by overcoring methods. We also propose a workflow for the back analysis of the initial geo-stress field of rock masses that considers geo-temperature, and this workflow is applied to the Sangzhuling tunnel in China.

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Section: Discussionmentioning

confidence: 99%

Section: The Thermal Stress Of Rock Masses Caused By Geothermal Gradimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Back Analysis of the Initial Geo-Stress Field of Rock Masses in High Geo-Temperature and High Geo-Stress

Meng

2020

Energies

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“…As can be seen from the data in Figure 4, when the humidity increases from 25 to 90% under the same conditions, the adhesion strength of the shotcrete-to-rock interface will be significantly improved, and it can be found that, under the same humidity conditions, when the temperature rises to a certain limit, the longer the curing age, the lower the adhesion strength. When the rock-surface temperature reaches the critical point, as the age increases, the free water in the capillary pores of the adhesion surface will gradually disappear, hindering the hydration reaction to proceed, and the temperature stress causes the crack at the adhesion surface to expand continuously so that the older the shotcrete, the lower the adhesion strength [37,38].…”

Section: Effect Of Temperature and Humidity On Adhesion Strength Of Smentioning

confidence: 99%

Influence of Ground Temperature on Shotcrete-to-Rock Adhesion in Tunnels

Duan

Zhang

Lai

2019

Advances in Materials Science and Engineering

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Long and deep tunnels are increasingly designed and built worldwide, often in severe geothermal environments characterized by high temperature in the rocks. is issue cannot be ignored because high temperature definitely affects the strength of the adhesion between the concrete and the surrounding rocks, whatever the lining cast in place, segmental or sprayed using shotcrete. e causes of geothermal heat and the effect of the temperature on tunnel linings during and after their construction are recalled and discussed in this paper. Both temperature and humidity are shown to be the most relevant factors affecting adhesion strength, whose loss is related to the microdamage in the shotcrete layers closest to the rock. Possible ways to improve adhesion strength and to minimize the high-temperature detrimental effect are also presented and discussed.

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“…At present, more than 150 1000 m-plus deep mines exist in the world (Xie, 2017). According to the statistics, the average geothermal gradient is 2.5∼4.0 • C/100 m, even up to 7 • C/100 m (Guo, 2010;Cui et al, 2018). At high geothermal temperatures, many threats stand out, such as soft rock mass, shortened equipment service life, increased accident rate and decreased labor efficiencies (Feng et al, 2017;Belle and Biffi, 2018;.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Heat Transfer and Phase Change Characteristics of Cold Load and Storage Functional CPB in Deep Mine

Wang

Lyu

et al. 2020

Front. Earth Sci.

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As high mine-cooling costs have become a restriction for deep mining, a new cooling method has been proposed. In the area of filling mining, the CPB (cemented paste backfill) was given the cooling function by mixing it with phase change material (PCM). In deep mines, the PCM (e.g., ice particles) absorb heat and change phases to cool the surrounding environment. A deep-mine-cooling mode based on the new CPB and upward sublevel filling method was designed, and the characteristics of the phase change were analyzed by numerical simulation. From the simulation results of the cooling period, this cooling method was effective during the whole stopes mining period. The CLS (cold load and storage) CPB mass concentration and the PCM initial proportion are the important factors controlling the cooling effect. It is concluded that the phase change duration decreased with the increasing mass concentration, while it increased with the increasing initial proportion of ice to water. Note that the thickness of CLSfunctional CPB should be as small as possible to ensure the cold release rate. This study provides a theoretical foundation of heat transfer for the design and implementation of deep mine cooling by applying CLS-functional CPB. Keywords: mine cooling, cold load and storage, mass concentration, proportion of ice to water, heat transfer HIGHLIGHTS -The phase change of CLS functional CPB in deep mines was investigated numerically. -The heat conduction model compound with hydration-porous-enthalpy model was applied. -The phase change and heat transfer law of CLS functional CPB was investigated. -The main influencing factors were analyzed and suggestions for engineering were presented.

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Experimental study on mechanical property and pore structure of concrete for shotcrete use in a hot-dry environment of high geothermal tunnels

Cited by 75 publications

References 28 publications

Back Analysis of the Initial Geo-Stress Field of Rock Masses in High Geo-Temperature and High Geo-Stress

Back Analysis of the Initial Geo-Stress Field of Rock Masses in High Geo-Temperature and High Geo-Stress

Influence of Ground Temperature on Shotcrete-to-Rock Adhesion in Tunnels

Numerical Investigation of Heat Transfer and Phase Change Characteristics of Cold Load and Storage Functional CPB in Deep Mine

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