Method for accurately measuring elastic modulus of tunnel rock in cold region after repeated freeze-thaw damage

A technology of repeated freeze-thaw and elastic modulus, which is applied in measurement devices, strength characteristics, instruments, etc., can solve the problem of not considering the effect of freeze-thaw cycles on the frost heave force of surrounding rock.

Active Publication Date: 2019-01-29
CHINA UNIV OF GEOSCIENCES (BEIJING)
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Problems solved by technology

[0004] Although many scholars have carried out in-depth research on the frost heaving force of rock tunnel surrounding rock from the aspects of theory and experiment, it still needs to be further improved.
As mentioned above, the theoretical calculation model [4-8] None of them considered the effect of freeze-thaw cycles on the frost heave force of surrounding rock, but only the frost heave force under the condition of a single frost heave can be calculated

Method used

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  • Method for accurately measuring elastic modulus of tunnel rock in cold region after repeated freeze-thaw damage
  • Method for accurately measuring elastic modulus of tunnel rock in cold region after repeated freeze-thaw damage
  • Method for accurately measuring elastic modulus of tunnel rock in cold region after repeated freeze-thaw damage

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Effect test

Embodiment 1

[0083] Embodiment 1. Calculation of frost heaving force of surrounding rock based on elastic theory.

[0084] Computational models such as figure 1 , in order to simplify the problem, firstly, the frozen zone and unfrozen zone in the tunnel lining and surrounding rock are regarded as a stress system composed of three axisymmetric elastic bodies in complete contact with each other, in which the tunnel is a circle located in an infinite mountain a, b, and c are respectively the inner diameter of the lining, the inner diameter of the frozen zone (also known as the outer diameter of the lining), and the outer diameter of the frozen zone, and the following assumptions are made: (1) The surrounding rock is a homogeneous and isotropic continuous medium; (2) The stress on the tunnel lining and surrounding rock belongs to the plane strain problem of elastic mechanics; (3) The frozen zone is always in a saturated state; (4) The self-weight of surrounding rock and tunnel lining is not co...

Embodiment 2

[0114] Embodiment 2. Crack initiation criterion and propagation direction of a single microcrack under the action of frost heaving force.

[0115] Because the rock contains many microcracks, the essence of freeze-thaw damage is that the water in the microcracks is frozen into ice at low temperature, resulting in volume expansion, and then the microcracks expand under the action of expansion force, resulting in the deterioration of rock properties. Then when the temperature rises, the ice melts into water, which flows along the expanded microcracks. If the water supply is sufficient and the melting time is long enough, it can be considered that the microcracks will always be in a saturated state. When the temperature drops, the water freezes into ice again, causing the microcracks to expand further and repeating itself. Each freeze-thaw cycle will cause a certain degree of damage to the rock, which is manifested as an increase in the length of microcracks at the micro level, an...

Embodiment 3

[0125] Embodiment 3, the extension length of a single microcrack under the action of frost heaving force.

[0126] When frost heaving occurs in the micro-cracks, the inner wall will act with evenly distributed frost-heaving force, and the micro-cracks will expand in the x and y directions accordingly, such as image 3 , the following assumptions are made when studying the growth of micro-cracks frost heave [14]: ① micro-cracks before and after frost heave are plane ellipse, that is, the shape and center position remain unchanged, and only the size changes; ② water migration and rock skeleton deformation are ignored ; ③ The microcracks are always in a saturated state; ④ The microcracks expand stably, and conform to the linear elastic fracture theory.

[0127] According to the Griffith energy release rate theory, when the water in the microcrack freezes into ice, the volume expands, but due to the restraint of the microcrack surface, the ice body generates expansion pressure on ...

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Abstract

The invention discloses a method for accurately measuring the elastic modulus of tunnel rock in a cold region after repeated freeze-thaw damage. The method comprises the steps of: A, micro-crack propagation half-length 1N=Delta 1N+1(N-1) (32); B, the corresponding micro-crack density parameter beta is expressed as the formula(33) shown in the specification; C, the number of propagated and activated micro-cracks in the unit volume is as the formula(34) shown in the specification; D, the effective elastic modulus of the rock is expressed as the formula(30) shown in the specification; and E, substituting the formulas (32) to (34) into the formula (30), and solving the EN to obtain the equivalent elastic modulus of tunnel surrounding rock after N times of freeze-thaw. According to the method for accurately measuring the elastic modulus of tunnel rock in a cold region after repeated freeze-thaw damage, the method has the advantages of being accurate and fast; the foundation is provided forthe calculation of the frost heaving force of the surrounding rock under the repeated freeze-thaw damage condition; and a practical guide is provided for the direction and the method of the construction operation of the rock tunnel maintenance engineering.

Description

technical field [0001] The invention relates to the technical field related to tunnel mechanics measurement and calculation in cold regions, in particular to a method for accurately measuring and calculating the elastic modulus of rock in tunnels in cold regions after repeated freeze-thaw damage. Background technique [0002] The failure of rock mass engineering caused by freezing and thawing is an important problem often encountered in engineering construction in cold regions. For example, the cracking of tunnel lining caused by frost heaving of surrounding rocks is considered to be one of the main forms of tunnel damage in cold regions. In the construction of tunnels in cold regions, the calculation of frost-heaving force of surrounding rock is the premise and basis for the design of lining structures. Because the rock mass contains many pores and fissures, when water enters it and freezes at low temperature, it will generate huge frost heaving force [2] , which leads to ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/60G01N25/14
CPCG01N3/60G01N25/14G01N2203/0075G01N2203/0224
Inventor 刘红岩赵雨霞祝凤金葛紫微戴华龙谢天铖周月智
Owner CHINA UNIV OF GEOSCIENCES (BEIJING)
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