A construction method for controlling the hydration temperature rise of cast-in-place concrete for vertical shaft lining

Abstract

The present invention belongs to the technical field of engineering construction, and relates to a construction method for controlling the hydration temperature rise of cast-in-place concrete for a vertical shaft wall, which comprises the following steps: exposing the shaft wall of the excavated part; drilling holes at different positions of the shaft wall and arranging heat pipes in each hole; binding the steel reinforcement cage required for pouring the concrete shaft wall in the excavated part and fixing each heat pipe on the steel reinforcement cage, and driving each heat pipe to work through the temperature difference between the concrete shaft wall and the freezing wall to control the temperature rise of the concrete shaft wall; repeating the above steps until the pouring of the concrete shaft walls at other positions of the vertical shaft is completed. By combining the freezing method construction with heat pipes, the present invention conveys the cold quantity in the freezing wall into the concrete shaft wall, reduces the temperature in the concrete shaft wall, effectively controls the temperature in the concrete shaft wall, greatly reduces the temperature difference gradient between the inside and outside of the concrete shaft wall, effectively reduces the penetrating cracks caused by temperature stress, and significantly improves the stability and integrity of the shaft wall structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of engineering construction, and relates to a construction method for controlling the hydration temperature rise of cast-in-place concrete for a vertical shaft wall. Background Art

[0002] The vertical shaft is the key passage of a mine, and its supporting structure, the shaft wall, is required to have reliable supporting strength and good water sealing performance. Therefore, the freezing method is often used to construct the vertical shaft wall. Through artificial refrigeration technology, the water in the stratum is frozen into ice to form a solid freezing wall to support the soil around the shaft, prevent collapse and water inrush, so as to safely carry out shaft excavation and support construction. However, under the harsh temperature conditions of shaft sinking by the freezing method, the curing conditions of the cast-in-place concrete shaft wall are poor. The temperature of the shaft wall sometimes drops as low as -20°C, while the pouring temperature of the cast-in-place concrete is generally 15 - 20°C. After the concrete is poured for 1 - 2 days, the hydration heat of the concrete rises to above 40 - 70°C, and the temperature difference between the inner and outer surfaces of the shaft wall may be as high as 30°C. Under the action of a huge temperature gradient, the temperature deformations of various parts of the shaft wall structure itself are inconsistent and mutually constrained, generating temperature stress, which may cause penetrating temperature cracks at the inner and outer edges of the shaft wall. According to relevant data, from the whole process of shaft wall masonry to the restoration of the stratum to the normal geothermal temperature after the freezing wall thaws, the axial tensile stress of the shaft wall caused by temperature deformation can reach 1.9 - 2.1 MPa. Therefore, for the freezing shaft wall, temperature stress is the main influencing factor causing its cracking during shaft sinking, and the microcracks in the shaft wall concrete are very likely to expand and develop into penetrating visible cracks.

[0003] Currently, in order to reduce the hydration heat of concrete, the commonly used methods are as follows: First, use low-hydration heat cement or reduce the cement dosage in the concrete. Considering the preparation of high-strength concrete, using low-hydration heat cement will increase the cost of concrete, and increasing the cement dosage is also required to prepare high-strength concrete. Therefore, using low-hydration heat cement has poor economy, and reducing the cement dosage in the concrete to reduce the hydration heat also has limitations; Second, improve the early strength of the concrete or use slightly expanded concrete. To prepare high-strength concrete, the cement dosage must be increased, which increases the hydration heat of the concrete, is not beneficial to the temperature control of the cast-in-place concrete shaft wall, and has limited effect on improving the early anti-cracking performance of the concrete. Even if slightly expanded concrete is used to compensate for the temperature tensile stress, adding a slightly expanded agent will increase the cost of the concrete, and the slightly expanded concrete technology cannot fundamentally prevent the shaft wall from cracking; Third, reduce the pouring temperature of the concrete. Add ice cubes to the mixing water of the shaft wall concrete to reduce the pouring temperature of the concrete. However, reducing the pouring temperature is not beneficial to the development of the early strength of the concrete, and the relevant construction specifications for the shaft wall clearly stipulate that the pouring temperature of the concrete in winter construction cannot be lower than 15°C. Therefore, the method of reducing the pouring temperature of the concrete cannot effectively control the temperature rise of the concrete and fundamentally prevent it from cracking. Summary of the Invention

[0004] The purpose of the present invention is to provide a construction method for controlling the hydration temperature rise of cast-in-situ concrete for vertical shaft lining, which can effectively control the concrete temperature rise and fundamentally avoid concrete cracking.

[0005] To achieve the above object, the technical solution provided by the present invention is as follows:

[0006] A construction method for controlling the hydration temperature rise of cast-in-situ concrete for vertical shaft lining includes the following steps:

[0007] Construct the vertical shaft lining by the freezing method, excavate the frozen wall according to the section height required by the freezing method construction, and expose the shaft wall of the excavated part.

[0008] Drill holes at different positions of the shaft wall respectively, and install heat pipes in each drill hole. One end of the heat pipe is fixed in the corresponding drill hole, and the other end of the heat pipe is exposed in the vertical shaft.

[0009] Bind the steel reinforcement cage required for pouring the concrete shaft lining in the excavated part, fix each heat pipe on the steel reinforcement cage, and finally pour the concrete shaft lining according to the requirements of the freezing method construction. Drive each heat pipe to work through the temperature difference between the concrete shaft lining and the frozen wall, and control the temperature rise of the concrete shaft lining.

[0010] Repeat the above steps until the pouring of the concrete shaft lining at other positions of the vertical shaft is completed.

[0011] The characteristics of the present invention also lie in:

[0012] When drilling holes at different positions of the shaft wall respectively, the diameter of each drill hole is larger than the diameter of the corresponding heat pipe, and the gap between each heat pipe and the corresponding drill hole is filled with filling material.

[0013] The length of each heat pipe exposed in the vertical shaft is less than the thickness of the shaft lining.

[0014] The length of each heat pipe located in the drill hole is 1.0 m to 1.2 m.

[0015] A plurality of heat pipes are arranged in a ring on the cross-section of the shaft lining, and the distance between adjacent two heat pipes is 0.5 m to 0.7 m.

[0016] When fixing each heat pipe on the steel reinforcement cage, binding or welding is adopted.

[0017] The outer shell of each heat pipe is made of carbon steel material, and the working medium filled in each heat pipe is refrigerant.

[0018] The installation method of each heat pipe is horizontal or inclined.

[0019] The structure of the part of each heat pipe exposed in the vertical shaft is straight or wavy.

[0020] A construction method for controlling the hydration temperature rise of cast-in-place concrete in a vertical shaft wall of the present invention has the following advantages:

[0021] First, by combining the freezing method construction with heat pipes, the present invention transports the cold energy in the frozen wall into the concrete shaft wall, reduces the temperature inside the concrete shaft wall, effectively controls the temperature inside the concrete shaft wall, greatly reduces the temperature difference gradient between the inside and outside of the concrete shaft wall, effectively reduces the penetrating cracks caused by temperature stress, and significantly improves the stability and integrity of the shaft wall structure.

[0022] Second, in the present invention, the heat pipes use the phase change heat transfer characteristics to quickly transfer the cold energy to the inner layer of the concrete, which can significantly reduce the temperature rise during the cement hydration process, thus avoiding the stress concentration problem caused by high temperature difference in the concrete.

[0023] Third, the temperature control process of the present invention completely relies on the efficient phase change heat transfer principle of the heat pipes, without consuming electricity or other external energy sources, has the advantages of environmental protection, and reduces the construction cost at the same time.

[0024] Fourth, the temperature control effect of the present invention continuously runs through the whole process from concrete pouring to hardening, and has a wide coverage range. It can effectively control the temperature of the full size range of the shaft wall thickness, not only limited to surface cooling, ensuring the comprehensiveness and durability of the temperature control effect.

[0025] Fifth, the present invention makes full use of the frozen wall as a cold source. It has a large cold energy storage and stable temperature, avoiding the need for additional independent cooling systems, and greatly reducing the complexity and construction difficulty of the temperature control system.

[0026] Sixth, the present invention reduces the generation of temperature cracks, not only improves the structural strength of the shaft wall, but also enhances its water sealing performance, contributing to ensuring the long-term safety and reliability of the shaft wall in a harsh underground construction environment.

[0027] Seventh, the present invention is designed for the special construction conditions of the frozen shaft wall, and can adapt to complex environmental problems such as low temperature of the shaft wall and rapid temperature rise of the concrete, providing a reference for concrete temperature control in other similar complex environments. Brief Description of the Drawings

[0028] Figure 1 It is a schematic diagram of the supported section height and its shaft wall structure of the present invention.

[0029] Figure 2 It is a schematic diagram of the structure of the excavated section to be supported of the present invention.

[0030] Figure 3 It is a schematic diagram of the completed structure of the supported excavated section of the present invention.

[0031] Figure 4 It is a schematic diagram of the heat transfer principle of the heat pipe in the present invention.

[0032] Figure 5 For the present invention Figure 2 Schematic diagram of the structure of part I

[0033] Reference numerals:

[0034] 1. Supported section, 2. Excavated section to be supported, 3. Frozen wall, 4. Unfrozen stratum Specific implementation manner

[0035] The technical solutions in the present invention will be clearly and elaborately described below with reference to the accompanying drawings. Among them, in the description of the embodiments of the present invention, unless otherwise specified, " / " means "or". For example, A / B may mean A or B. The "and / or" in the text is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present invention, "a plurality" means two or more than two. The following terms "first" and "second" are only used for descriptive purposes and cannot be construed as implying or indicating relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features

[0036] As Figure 1 , Figure 2 , Figure 3 , Figure 4 shown, the present invention provides a construction method for controlling the hydration temperature rise of cast-in-place concrete for a vertical shaft wall, comprising the following steps

[0037] Construct the vertical shaft wall by the freezing method, and excavate the frozen wall 3 according to the section height required by the freezing method construction to expose the shaft wall of the excavated part

[0038] Drill holes at different positions of the shaft wall, and install heat pipes in each drill hole. One end of the heat pipe is fixed in the corresponding drill hole, and the other end of the heat pipe is exposed in the vertical shaft

[0039] Bind and pour the steel reinforcement cage required for the concrete shaft wall in the excavated part, and fix each heat pipe on the steel reinforcement cage. Finally, pour the concrete shaft wall according to the requirements of the freezing method construction, and drive each heat pipe to work through the temperature difference between the concrete shaft wall and the frozen wall 3 to control the temperature rise of the concrete shaft wall

[0040] Repeat the above steps until the pouring of the concrete shaft wall at other positions of the vertical shaft is completed

[0041] In summary, the present invention first constructs the vertical shaft wall by the freezing method, excavates the frozen wall 3 according to the section height required by the freezing method construction, exposes the shaft wall of the excavated part, then drills holes at different positions of the shaft wall respectively, and installs heat pipes in each hole. One end of the heat pipe is fixed in the corresponding hole, and the other end of the heat pipe is exposed in the vertical shaft. Then, the steel reinforcement cage required for pouring the concrete shaft wall is tied in the excavated part, and each heat pipe is fixed on the steel reinforcement cage. Finally, the concrete shaft wall is poured according to the requirements of the freezing method construction. The temperature difference between the concrete shaft wall and the frozen wall 3 drives each heat pipe to work, controlling the temperature rise of the concrete shaft wall. Finally, the above steps are repeated until the pouring of the concrete shaft wall at other positions of the vertical shaft is completed. Therefore, the present invention transports the cold quantity in the frozen wall 3 to the concrete shaft wall by using heat pipes, reduces the temperature in the concrete shaft wall, realizes the effective control of the temperature in the concrete shaft wall, greatly reduces the temperature difference gradient between the inside and outside of the concrete shaft wall, effectively reduces the penetrating cracks caused by temperature stress, and significantly improves the stability and integrity of the shaft wall structure.

[0042] Among them, when drilling holes at different positions of the shaft wall respectively, the diameter of each hole is larger than the diameter of the corresponding heat pipe, and the gap between each heat pipe and the corresponding hole is filled with a filling material to prevent the cast-in-place concrete of the shaft wall from pouring into the hole. The filling material is soil or other materials.

[0043] As Figure 5 shown, the length of each heat pipe exposed in the vertical shaft is less than the thickness of the shaft wall. The length of the heat pipe located in the hole is X1, and the length of the heat pipe exposed in the shaft center is X2 (X1 + X2 is the total length of the heat pipe). The maximum value of X2 should not exceed the thickness of the shaft wall, so that the heat pipe can be completely buried in the frozen wall 3 and the shaft wall. The length of each heat pipe located in the hole is 1.0 m to 1.2 m, that is, X1 is 1.0 m to 1.2 m, preferably 1.1 m.

[0044] Among them, multiple heat pipes are arranged in a ring on the cross-section of the shaft wall, and the distance between adjacent two heat pipes is 0.5 m to 0.7 m, preferably 0.6 m, so that the cold quantity transfer is more uniform.

[0045] Among them, when fixing each heat pipe on the steel reinforcement cage, binding or welding is used to ensure that the position of each heat pipe will not move during the pouring process.

[0046] Among them, the outer shell of each heat pipe is made of carbon steel material, and the working medium filled in each heat pipe is a refrigerant. By using the low boiling point characteristic of the refrigerant, the transmission efficiency of the cold quantity in the frozen wall 3 is improved.

[0047] Among them, the installation method of each heat pipe is horizontal or inclined.

[0048] Among them, the structure of each heat pipe exposed in the vertical shaft is straight or wavy, and each heat pipe is preferably a wavy structure to increase the contact area between the heat pipe and the shaft wall, thereby improving the heat exchange efficiency.

[0049] Example 1

[0050] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown, a certain mine uses the freezing method to construct a vertical shaft. The shaft diameter is 8.5m, the thickness of the frozen wall 3 is 6m, the side of the frozen wall 3 away from the shaft is the unfrozen stratum 4, and the average temperature of the frozen wall 3 is about -15°C. The shaft wall is a single-layer shaft wall structure with a wall thickness of 1m, a single pouring height of 4m, and a concrete strength grade of C70. The shaft wall temperature is as low as -10°C, and the hydration temperature rise of concrete within 1 to 2 days after pouring is expected to be as high as 75°C. The temperature difference between the internal and external surfaces may be as high as 10 to 20°C. Similar projects have previously caused penetrating temperature cracks due to excessive temperature gradients in the concrete, affecting the support strength and water sealing performance of the shaft wall. The specific steps for constructing the mine using the construction method of the present invention are as follows:

[0051] Step 1, material preparation. According to the thickness of the freezing wall 3 and the well wall structure design, a heat pipe with a diameter of Φ40 mm and a length of 2 m is selected as the heat transfer equipment. The heat pipe shell is made of carbon steel and the working fluid filled inside is a low-boiling point refrigerant to ensure efficient phase change heat transfer capability under the freezing wall cold source of -15°C.

[0052] Step 2, use the freezing method to construct the shaft wall, and excavate the freezing wall 3 according to the section height required by the freezing method construction, expose the shaft wall of the excavated part, that is, the excavated section 2 to be supported, and arrange the heat pipes in a ring shape in the excavated section 2 to be supported, that is, drill holes on the shaft wall of the excavated section 2 to be supported along the circumference of the shaft wall, so that the heat pipes are arranged in a ring shape and pre-buried between the freezing wall and the shaft wall. The spacing between each heat pipe is 0.6m, covering the entire thickness range of the shaft wall to ensure full coverage of temperature control, and insert each heat pipe into a drilled hole on the freezing wall according to the designed position. The cold end of each heat pipe is buried 1.1m in the freezing wall to ensure full contact with the cold source. The hot end of each heat pipe is exposed 0.9m in the shaft to achieve uniform transfer of cold.

[0053] Step 3, tie the required steel cage for pouring concrete well wall in the excavated section 2 to be supported, and fix each heat pipe on the steel cage. During construction, the temperature of concrete entering the mold is controlled at 15°C. After the concrete pouring is completed, the excavated section 2 to be supported becomes the supported section 1, and the heat pipe starts working to quickly transfer the cold energy of the frozen wall to the inner layer of the concrete.

[0054] Step 4: Repeat the above steps to continue the excavation of the next section of the frozen wall 3 until the concrete shaft lining at other positions of the vertical shaft is completed.

[0055] By combining the construction method of freezing method with heat pipes, the mine utilizes the phase change heat transfer effect to efficiently conduct the hydration heat of the concrete to the frozen wall 3, and the temperature difference between the inside and outside of the concrete shaft lining is always controlled within 10°C. Within 7 days after pouring, the maximum temperature of the concrete shaft lining is controlled within 50°C, and the maximum temperature difference between the inside and outside of the concrete shaft lining is 12°C, effectively avoiding the situation of too large temperature gradient.

[0056] It can be understood that the present invention is described through some embodiments. Those skilled in the art know that without departing from the spirit and scope of the present invention, various changes or equivalent substitutions can be made to these features and embodiments. In addition, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present invention belong to the scope protected by the present invention.

Claims

1. A construction method for controlling the hydration temperature rise of cast-in-place concrete for the shaft wall of a vertical shaft, characterized in that, It includes the following steps: The vertical shaft lining is constructed by the freezing method, and the frozen wall is excavated according to the section height required by the freezing method construction, and the shaft wall of the excavated part is exposed; Holes are drilled at different positions of the shaft wall respectively, and heat pipes are arranged in each hole. One end of the heat pipe is fixed in the corresponding hole, and the other end of the heat pipe is exposed in the vertical shaft; The steel reinforcement cage required for pouring the concrete shaft lining is tied in the excavated part, and each heat pipe is fixed on the steel reinforcement cage. Finally, the concrete shaft lining is poured according to the requirements of the freezing method construction, and each heat pipe works by the temperature difference between the concrete shaft lining and the frozen wall to control the temperature rise of the concrete shaft lining; Repeat the above steps until the pouring of the concrete shaft lining at other positions of the vertical shaft is completed.

2. The construction method for controlling the hydration temperature rise of cast-in-place concrete for a vertical shaft wall according to claim 1, wherein, When drilling holes at different positions of the shaft wall respectively, the diameter of each hole is larger than the diameter of the corresponding heat pipe, and the gap between each heat pipe and the corresponding hole is filled with a filling material.

3. The construction method for controlling the hydration temperature rise of cast-in-place concrete for vertical shaft lining according to claim 1, characterized in that, The length of each heat pipe exposed in the vertical shaft is less than the thickness of the shaft lining.

4. The construction method for controlling the hydration temperature rise of cast-in-place concrete for vertical shaft lining according to claim 1, characterized in that, The length of each heat pipe located in the hole is 1.0 m to 1.2 m.

5. The construction method for controlling the hydration temperature rise of the cast-in-place concrete of the vertical shaft wall according to claim 1, characterized in that, A plurality of the heat pipes are arranged in a ring shape on the cross section of the shaft lining, and the distance between two adjacent heat pipes is 0.5 m to 0.7 m.

6. The construction method for controlling the hydration temperature rise of cast-in-place concrete for vertical shaft lining according to claim 1, characterized in that, When fixing each heat pipe on the steel reinforcement cage, binding or welding is adopted.

7. The construction method for controlling the hydration temperature rise of the cast-in-place concrete of the vertical shaft wall according to claim 1, characterized in that, The outer shell of each heat pipe is made of carbon steel material, and the working medium filled inside each heat pipe is a refrigerant.

8. The construction method for controlling the hydration temperature rise of cast-in-place concrete for vertical shaft lining according to claim 1, characterized in that, The installation method of each heat pipe is horizontal or inclined.

9. The construction method for controlling the hydration temperature rise of cast-in-place concrete for vertical shaft lining according to claim 1, characterized in that, The structure of the part of each heat pipe exposed in the vertical shaft is straight or wavy.

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