Anchor rod for treating seasonal frost heave of tunnel surrounding rock and construction method thereof

Abstract

The present invention discloses an anchor rod and a construction method for treating seasonal frost heave of tunnel surrounding rock, which relates to the field of tunnel disease treatment construction, and comprises a hollow and sealed rod body, wherein the rod body comprises an evaporation section, a heat insulation section and a condensation section, wherein the evaporation section is filled with an easily evaporable liquid medium, and a heat sink is arranged outside the condensation section. The anchor rod and the construction method can not only play the role of reinforcing the surrounding rock, but also prevent the freezing of the shallow surrounding rock in the cold season, avoid the generation of frost heave force of the surrounding rock, block the potential frost heave force that may be generated by the shallow surrounding rock, eliminate the seasonal frost heave hazard of the tunnel surrounding rock, and do not occupy the existing space in the tunnel, and the construction is simple.

Description

Technical Field

[0001] The invention relates to the field of tunnel disease treatment construction, and in particular to an anchor rod for treating seasonal frost heave of tunnel surrounding rocks and a construction method thereof. Background Art

[0002] At present, anchor rods are widely used as a major technical means in both new tunnel construction and tunnel disease treatment projects. The main function of anchor rods is to strengthen the surrounding rock and improve the bearing capacity and stability of the surrounding rock. Anchor rods are an important part of the New Austrian Tunneling Method (NATM) tunnel construction.

[0003] In recent years, more and more tunnels have been built in seasonal frozen soil areas such as high latitudes and high altitudes in my country, and many cases of lining cracking caused by seasonal frost heaving of surrounding rocks have occurred. For example, in a railway in Northeast China, among the six tunnels along the entire line, four tunnels had frost heaving cracks of varying degrees on the side walls at the beginning of tunnel penetration. The main manifestations were longitudinal horizontal cracks on the side walls at a height of 2 to 3 meters on the ditch cover within a few hundred meters of the tunnel entrance. The crack width was 0.5 to 5 mm, and some even had misalignment. Judging from the frequency of such cases in recent years, the phenomenon of lining side wall cracking caused by seasonal frost heaving of surrounding rocks seems to be on the rise, seriously affecting the tunnel structure and train operation safety.

[0004] In order to deal with seasonal frost heave of surrounding rock, adding insulation boards is the most effective measure. However, for railway tunnels, general insulation materials cannot meet the A-level fire protection requirements required for railway operation. Therefore, after laying the insulation boards, fireproof mortar still needs to be sprayed, which makes the construction process complicated. Moreover, for most tunnels, there is no spare space for adding insulation boards in their inner contours, and the measure of adding insulation boards cannot be implemented in such tunnels. For such tunnels, when it is confirmed that they have the hidden danger of seasonal frost heave of surrounding rock, the usual treatment method is to remove the lining, expand the section, add insulation layer, and re-apply lining. This treatment method has high engineering cost, high construction difficulty, long construction time, and huge impact on tunnel traffic.

[0005] Based on this, the present application provides an anchor rod and a construction method thereof for dealing with seasonal frost heave of tunnel surrounding rock, which can effectively eliminate the hazards of seasonal frost heave of surrounding rock, does not occupy existing space in the tunnel, and is simple to construct. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an anchor rod and a construction method for dealing with seasonal frost heave of tunnel surrounding rock, which can not only reinforce the surrounding rock, but also prevent the freezing of shallow surrounding rock in the cold season, avoid the generation of frost heave force of the surrounding rock, block the potential frost heave force that may be generated by the shallow surrounding rock, eliminate the seasonal frost heave hazards of the tunnel surrounding rock, and do not occupy the existing space in the tunnel, and the construction is simple.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] An anchor rod for treating seasonal frost heave of tunnel surrounding rock and a construction method thereof, comprising a hollow and sealed rod body, the rod body comprising an evaporation section, a heat insulation section and a condensation section, the evaporation section is filled with an easily evaporable liquid medium, and the condensation section is provided with a heat sink outside.

[0009] Furthermore, the easily evaporable liquid medium is selected from one of liquid nitrogen, liquid carbon dioxide, liquid propane and liquid Freon.

[0010] Furthermore, a heat insulation layer is arranged outside the heat insulation section.

[0011] Furthermore, it also includes a screw rod, a nut and a gasket, wherein the screw rod is fixedly arranged at one end of the rod body close to the condensation section, the gasket is sleeved on the screw rod, and the nut is connected to the screw rod through a thread.

[0012] Further, the following steps are included:

[0013] Step 1: Calculate the maximum freezing depth of the surrounding rock in the cold season according to the thermophysical parameters of each rock layer at the site of the diseased tunnel and the meteorological parameters of the tunnel site, and determine the length of the anchor selected to deal with the seasonal frost heave of the tunnel surrounding rock according to the maximum freezing depth of the surrounding rock;

[0014] Step 2: Calculate and determine the negative bending moment area of ​​the tunnel side wall caused by the seasonal frost heave force of the surrounding rock based on the thermophysical parameters of the surrounding rock and the meteorological parameters of the tunnel site, and determine the arrangement mode and construction quantity of the anchor rods based on the range of the negative bending moment area;

[0015] Step 3: According to the determined anchor arrangement, construction quantity and anchor length, use a drilling rig to drill the corresponding anchor installation holes in the negative bending moment area of ​​the side wall. The installation hole diameter is 2-3 cm larger than the selected anchor diameter, and the installation hole axis is at an angle of 15-30° to the horizontal direction. Ensure that the height of the evaporation section of the anchor is lower than the height of the condensation section after installation;

[0016] Step 4: Place the anchor rod into the installation hole, then grout the evaporation section and insulation section of the anchor rod to make the anchor section, and at the same time make the condensation section of the anchor rod contact the surrounding rock through the heat sink, and the screw at the end of the anchor rod passes through the lining;

[0017] Step 5: After the strength of the grouting body in the anchoring section meets the design requirements, install the gasket and nut in sequence on the end of the screw that passes through the lining, and apply prestress to the anchor rod through the nut.

[0018] Furthermore, the anchor selected in step one is required to have a condensation section whose length is greater than the maximum freezing depth of the surrounding rock, and ensure that after installation according to the angle of the mounting hole in step three, the insulation section of the selected anchor is outside the surrounding rock area of ​​the maximum freezing depth.

[0019] Furthermore, the total length of the anchor rod selected in step one is greater than or equal to 3 meters and less than or equal to 5 meters.

[0020] Furthermore, during construction, the anchor rods are arranged in a plum blossom pattern with a spacing of 1~1.5m×1~1.5m.

[0021] The beneficial effects of the present invention are:

[0022] The anchor rod is used in seasonal frozen soil tunnels. When in use, the evaporation section of the anchor rod is set in the deep surrounding rock, and the condensation section of the anchor rod is set in the shallow surrounding rock. In the cold season, the liquid medium in the evaporation section can absorb heat and evaporate at the temperature of the deep surrounding rock. The evaporated gas rises to the condensation section through the hollow channel of the anchor rod to release heat and condense. In the process of heat absorption and heat release, heat exchange between the deep surrounding rock and the shallow surrounding rock is achieved. By heating the surface surrounding rock, seasonal frost heave can be prevented, and then the frost heave force can be prevented, and the damage to the lining caused by frost damage can be reduced. At the same time, the anchor rod has the functions of ordinary anchor rods all year round, that is, it reinforces the surrounding rock, improves the bearing capacity and stability of the surrounding rock, and provides safety protection for the tunnel. The construction of the anchor rod does not occupy the existing space in the tunnel, and the construction is simple and has strong applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic cross-sectional view of the structure of an anchor rod for treating seasonal frost heave of surrounding rock of a tunnel according to the present invention;

[0024] Figure 2 This is a schematic diagram of the use status of an anchor rod for treating seasonal frost heave of tunnel surrounding rock according to the present invention;

[0025] Figure 3 A schematic cross-sectional view of an anchor rod arranged in a tunnel for treating seasonal frost heave of tunnel surrounding rock according to the present invention;

[0026] In the figure, 1-evaporation section, 2-insulation section, 3-condensation section, 4-liquid medium, 5-heat sink, 6-insulation layer, 7-screw, 8-nut, 9-gasket, 11-shallow surrounding rock, 12-deep surrounding rock. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0028] like Figures 1 to 3As shown, an anchor rod for treating seasonal frost heave of tunnel surrounding rock comprises a hollow and sealed rod body, wherein the rod body comprises an evaporation section 1, a heat insulation section 2 and a condensation section 3. The evaporation section 1 is filled with an easily evaporable liquid medium 4 such as liquid nitrogen, liquid carbon dioxide, liquid propane or liquid Freon. The condensation section 3 is provided with a heat sink 5 outside, and the heat insulation section 2 is provided with a heat insulation layer 6 outside.

[0029] In specific implementation, the anchor rod is used in seasonal frozen soil tunnels. When installing, the anchor rod is installed downward, that is, the evaporation section 1 of the anchor rod is lower than the height of the condensation section 3, and the evaporation section 1 of the anchor rod is set in the deep surrounding rock 12, and the condensation section 3 of the anchor rod is set in the shallow surrounding rock 11.

[0030] In the cold season, the temperature in the tunnel gradually decreases until it is in a negative temperature state. As the negative temperature time increases, the temperature of the shallow surrounding rock 11 will gradually decrease until negative temperature occurs, and the shallow surrounding rock 11 will freeze. At this time, the temperature of the deep surrounding rock 12 is still at a positive temperature, and the liquid medium in the evaporation section 1 absorbs heat and evaporates. The evaporated gas rises to the condensation section 3 through the hollow channel of the anchor rod. At this time, because the shallow surrounding rock 11 is at a negative temperature, the gas in the condensation section 3 releases heat and condenses. The condensed liquid flows back to the evaporation section 1 along the inner wall of the hollow channel of the anchor rod under its own weight. This cycle is repeated. In the above-mentioned heat absorption and heat release process, continuous heat exchange between the deep surrounding rock 12 and the shallow surrounding rock 11 is achieved, and the shallow surrounding rock 11 is heated. The above process can effectively prevent the formation of a surrounding rock freezing circle, avoid the generation of surrounding rock frost heaving force, and prevent the lining from being damaged by seasonal frost heaving of the surrounding rock. At this time, the anchor rod can not only play its heat exchange characteristics, but also play its reinforcement role. Through the combined effect of these two functions, it can effectively cope with the destructive effect of seasonal frost heave on the tunnel lining.

[0031] In the warm season, the temperature in the tunnel is high, the shallow surrounding rock 11 is at a positive temperature, and the temperature is higher than that of the deep surrounding rock 12. At this time, the medium convection in the anchor stops, the heat exchange effect of the anchor stops working, the surrounding rock does not freeze, and there is no frost heave force. At this time, the anchor plays the reinforcement role of the traditional anchor.

[0032] Furthermore, a screw rod 7 is fixedly provided at one end of the condensation section 3, a gasket 9 is sleeved on the screw rod 7 and a nut 8 is threadedly connected thereto. During installation, one end of the screw rod 7 passes through the lining layer, and the gasket 9 and the nut 8 are installed on the screw rod 7. A certain prestress is applied to the anchor rod through the nut 8 to block the potential partial frost heave force that may be generated by the shallow surrounding rock.

[0033] The specific construction steps of an anchor rod for treating seasonal frost heave of tunnel surrounding rock are as follows:

[0034] Step 1: Select an anchor rod of appropriate length. The selection method is: first calculate the maximum freezing depth of the surrounding rock in the cold season according to the thermophysical parameters of each rock layer at the site of the diseased tunnel, the meteorological parameters of the tunnel site, etc., that is, determine the thickness of the shallow surrounding rock 11; then select an anchor rod of appropriate length according to the thickness of the shallow surrounding rock 11. When calculating the maximum freezing depth, radial temperature measuring points can be buried in the frozen tunnel, and the maximum freezing depth can be determined by on-site measurement of the temperature field of the surrounding rock in the cold season. It can also be determined by numerical calculation method, and the specific calculation process is as follows:

[0035] 1. Establish a numerical calculation model based on the geometric parameters of the tunnel entrance;

[0036] 2. Collect meteorological data of the tunnel site for more than 2 years, use sine or cosine trigonometric functions to regress the daily average temperature data, and obtain the trigonometric function conditions of the average temperature.

[0037] T=T0+Asin(ωt-φ)

[0038] T0 is the annual average temperature, A is the annual temperature amplitude, ω=2π / T, and φ is the phase.

[0039] Using the boundary layer principle, the average air temperature trigonometric function is converted into the average ground temperature trigonometric function.

[0040] T=T1+Asin(ωt-φ)

[0041] For natural surfaces, T1=2.5+T0; for gravel and crushed stone surfaces, T1=4.0+T0.

[0042] In the calculation model, the average geothermal boundary condition is adopted on the ground surface, the average air temperature boundary condition is adopted in the tunnel, the adiabatic boundary condition is adopted on both sides, and the temperature gradient boundary condition is adopted at the bottom of the model. The thermophysical parameters of the surrounding rocks required in the calculation are mainly determined based on indoor experiments or obtained by consulting relevant specifications.

[0043] When selecting, the length of the condensation section 3 of the anchor rod is required to be greater than the thickness of the shallow surrounding rock 11, and ensure that after installation, the insulation section 2 of the selected anchor rod is outside the shallow surrounding rock 11; the total length of the anchor rod should be greater than three times the thickness of the shallow surrounding rock 11.

[0044] In addition, to achieve better results, the total length of the anchor rod should be greater than or equal to 3 meters to meet the structural requirements; at the same time, the length of the anchor rod should be less than or equal to 5 meters to ensure convenient construction. If the total length of the anchor rod is not greater than three times the thickness of the shallow surrounding rock 11, the selection conditions can be appropriately relaxed to give priority to the requirement that the total length is within the range of 3 meters to 5 meters.

[0045] Step 2: Determine the layout and number of anchor rods. The determination method is: first calculate and determine the negative bending moment area of ​​the tunnel side wall caused by the seasonal frost heave force of the surrounding rock based on the thermophysical parameters of the surrounding rock and the meteorological parameters of the tunnel site; then determine the layout and number of anchor rods based on the range of the negative bending moment area. In the specific implementation, the anchor rods are arranged in a plum blossom pattern with a spacing of 1~1.5m×1~1.5m. The spacing between the anchor rods is within the range of 1 meter to 1.5 meters. The specific spacing is determined based on the actual negative bending moment area mentioned above and the effective range of the anchor rods. The plum blossom pattern arrangement can make the anchor rods more evenly stressed and heated.

[0046] The above negative moment area can be determined by numerical calculation method. The specific calculation process is as follows:

[0047] 1. Collect the original soil samples of surrounding rock and obtain the frost heave rate of surrounding rock through indoor experiments;

[0048] 2. According to the geometric parameters of the tunnel opening, a numerical calculation model containing a freezing circle is established based on the maximum freezing depth of the surrounding rock. The mechanical boundary conditions all adopt displacement boundary conditions, and normal displacement constraints are applied to the bottom and two sides of the model. The surrounding rock frost heave is realized by assigning an expansion coefficient to the freezing circle. The surrounding rock mechanical parameters required in the calculation are determined based on geotechnical tests, or obtained by consulting geological survey data and relevant specifications. Then, through calculation, the area where the tunnel lining structure on both sides of the side wall shows deformation into the cave is the negative bending moment area of ​​the tunnel side wall caused by the seasonal frost heave force of the surrounding rock.

[0049] Step 3: According to the anchor arrangement and construction quantity determined in the above step 2 and the anchor length determined in the above step 1, use a drilling rig to drill the corresponding anchor installation holes in the negative bending moment area of ​​the side wall. The installation hole diameter is required to be 2-3cm larger than the anchor diameter to facilitate the grouting of the anchoring section to play a role; the axis of the installation hole is at an angle of 15-30° to the horizontal direction, ensuring that the height of the evaporation section 1 of the anchor after installation is lower than the height of the condensation section 3 and the liquid medium 4 in the anchor is at one end of the anchor in the deep surrounding rock 12, thereby ensuring that the liquid medium in the anchor after installation is at the deep surrounding rock end when not working, and the fluid medium in the anchor body can evaporate smoothly to the shallow surrounding rock section when working, and can flow back to the bottom of the anchor smoothly after solidification.

[0050] Step 4: Place the anchor used to deal with seasonal frost heave of tunnel surrounding rock into the installation hole, and then grout the evaporation section 1 and the insulation section 2 of the anchor, that is, the evaporation section 1 and the insulation section 2 are used as anchoring sections; at the same time, the condensation section 3 of the anchor is in contact with the surrounding rock through the heat sink 5 to facilitate heat exchange with the shallow surrounding rock 11, which is used to heat the shallow surrounding rock 11 in the cold season. In addition, the screw 7 at the end of the anchor is passed through the lining.

[0051] Step 5: After the grouting strength of the anchoring section meets the design requirements, install the gasket 9 and the nut 8 in sequence on one end of the screw 7 passing through the lining, and apply prestress to the anchor rod through the nut 8 to block the potential partial frost heave force that may be generated by the shallow surrounding rock.

[0052] According to the calculation results, the normal stress σ of the surrounding rock and lining surface in the negative bending moment area and the prestress F applied by the anchor are obtained. 预应力 The size is determined by the normal stress σ and the effective treatment area A of the anchor. 有效 Consider 50% of the product, that is

[0053] F 预应力 =0.5σ×A 有效

[0054] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A construction method for anchor rods used to treat seasonal frost heave of tunnel surrounding rock, characterized in that: The anchor rod comprises a hollow and sealed rod body, wherein the rod body comprises an evaporation section (1), a heat insulation section (2) and a condensation section (3); the evaporation section (1) contains an easily evaporable liquid medium (4), and the condensation section (3) is provided with a heat sink (5); The easily evaporable liquid medium (4) is selected from one of liquid nitrogen, liquid carbon dioxide, liquid propane and liquid Freon; A heat insulation layer (6) is arranged outside the heat insulation section (2); It also comprises a screw rod (7), a nut (8) and a gasket (9), wherein the screw rod (7) is fixedly arranged at one end of the rod body close to the condensation section (3), the gasket (9) is sleeved on the screw rod (7), and the nut (8) is connected to the screw rod (7) by means of a thread; The construction method based on the anchor rod comprises the following steps: Step 1: Calculate the maximum freezing depth of the surrounding rock in the cold season according to the thermophysical parameters of each rock layer at the site of the diseased tunnel and the meteorological parameters of the tunnel site, and determine the length of the anchor selected to deal with the seasonal frost heave of the tunnel surrounding rock according to the maximum freezing depth of the surrounding rock; Step 2: Calculate and determine the negative bending moment area of ​​the tunnel side wall caused by the seasonal frost heave force of the surrounding rock based on the thermophysical parameters of the surrounding rock and the meteorological parameters of the tunnel site, and determine the arrangement mode and construction quantity of the anchor rods based on the range of the negative bending moment area; Step 3: according to the determined anchor arrangement, construction quantity and anchor length, use a drilling machine to drill corresponding anchor installation holes in the negative bending moment area of ​​the side wall. The diameter of the installation hole is 2-3 cm larger than the diameter of the selected anchor. The axis of the installation hole is at an angle of 15-30° to the horizontal direction. Ensure that the height of the evaporation section (1) of the anchor is lower than the height of the condensation section (3) after installation. Step 4: Place the anchor rod into the installation hole, then perform grouting on the evaporation section (1) and the insulation section (2) of the anchor rod to form the anchor section, and at the same time make the condensation section (3) of the anchor rod contact the surrounding rock through the heat sink (5), and the screw rod (7) at the end thereof passes through the lining; Step 5: After the strength of the grouting body in the anchoring section meets the design requirements, a gasket (9) and a nut (8) are sequentially installed on one end of the screw rod (7) passing through the lining, and prestress is applied to the anchor rod through the nut (8); Among them, in step 1, when calculating the maximum freezing depth, a numerical calculation method is used to determine it. The specific calculation process is as follows: (1) Establish a numerical calculation model based on the geometric parameters of the tunnel entrance; (2) Collect meteorological data of the tunnel site for more than 2 years, use sine or cosine trigonometric functions to regress the daily mean temperature data, and obtain the trigonometric function conditions of the average temperature; T = T0 + Asin (ωt-φ); T0 is the annual mean temperature, A is the annual temperature amplitude, ω=2π / T, φ is the phase; Using the boundary layer principle, the average air temperature trigonometric function is converted into the average ground temperature trigonometric function; T = T1 + Asin (ωt-φ); For natural surfaces, T1 = 2.5 + T0; for gravel and crushed stone surfaces, T1 = 4.0 + T0; In the calculation model, the average geothermal boundary condition is adopted on the ground surface, the average air temperature boundary condition is adopted in the tunnel, the adiabatic boundary condition is adopted on both sides, and the temperature gradient boundary condition is adopted at the bottom of the model. The thermophysical parameters of the surrounding rocks required in the calculation are mainly determined based on indoor experiments or obtained by consulting relevant specifications.

2. The method for constructing an anchor rod for treating seasonal frost heave of surrounding rock of a tunnel according to claim 1, characterized in that: The anchor selected in step one requires that the length of its condensation section (3) is greater than the maximum freezing depth of the surrounding rock, and ensures that after installation according to the angle of the installation hole in step three, the insulation section (2) of the selected anchor is outside the surrounding rock area of ​​the maximum freezing depth.

3. A construction method for anchor rods for treating seasonal frost heave of tunnel surrounding rock according to claim 2, characterized in that: The total length of the anchor rod selected in step 1 is greater than or equal to 3 meters and less than or equal to 5 meters.

4. The method for constructing an anchor rod for treating seasonal frost heave of surrounding rock of a tunnel according to claim 1, characterized in that: During construction, the anchor rods are arranged in a plum blossom pattern with a spacing of 1~1.5m×1~1.5m.

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