Isothermal layered recursive pouring construction process for variable-cross-section large-volume raft concrete
By adopting isothermal layered recursive pouring construction technology in super-high-rise buildings, combined with the use of circulating cooling water pipes and temperature measurement devices, the temperature difference crack problem caused by different temperature and stress fields of variable cross-section rafts is solved, and concrete is realized. Stability and structural integrity.
Patent Information
- Application Number
- CN202411414872.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-11
- Publication Date
- 2024-12-31
AI Technical Summary
In super-high-rise buildings, variable-section rafts produce temperature differential cracks at the junction due to the differences in the internal temperature field and stress field, which is difficult to effectively solve in the existing technology.
Isothermal layered recursive pouring construction technology is adopted. By setting horizontal construction joints at the junction and installing circulating cooling water pipes and temperature measurement devices at the interface between the upper and lower concrete layers, the mold temperature and cooling are controlled, and the interface agent and cement mortar are used to ensure stickiness. junction quality reduces the influence of hydration heat superposition.
It effectively avoids temperature difference cracks at the junction of variable cross-sections, ensures the stability and structural integrity of concrete, and has universal promotion and application value.
Smart Images
Figure CN119221476A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of building construction, and in particular relates to an isothermal layered recursive pouring construction process for variable-section large-volume raft concrete. Background Art
[0002] For super high-rise buildings, the bottom plate of the core tube of the main building bears a large load, and the raft slab is thicker; the bottom plate outside the main building bears a relatively small load, and the raft slab is relatively thin. Therefore, in the raft foundation, in order to meet the requirements of different upper loads, the raft slab often adopts a variable cross-section design. Due to the different thickness of the raft slab, the hydration heat generated during the solidification process after concrete pouring (one-time pouring) is also different. The thicker raft slab generates high hydration heat, and the thinner raft slab generates low hydration heat. The temperature field and stress field generated inside the two raft slabs of different thicknesses are completely different. Therefore, at the junction of the two raft slabs with variable cross-sections, cracks will occur due to the difference in temperature field and stress field. In this regard, it is urgent to develop an effective method to solve this technical problem. Summary of the invention
[0003] The technical problem to be solved by the present invention is to provide an isothermal layered recursive pouring construction process for variable-section large-volume raft slab concrete, which can avoid temperature difference cracks at the junction of raft slabs with variable sections due to the differences in temperature fields and stress fields generated inside two raft slabs of different thicknesses.
[0004] The technical solution adopted by the present invention to solve the technical problem is: a variable-section large-volume raft concrete isothermal layered recursive pouring construction process, comprising the following steps: Step (1): installation of the bottom reinforcement of the lower raft slab, installation of the steel support, installation of the circulating cooling water pipe, installation of the temperature measuring device, and installation of the anchor steel bars at the interface; Step (2): pouring, temperature measurement, cooling and curing of lower raft concrete; Step (3): Treatment of construction joints at the interface; Step (4): Installation of upper steel support, raft slab reinforcement, circulating cooling water pipe, and temperature measuring device; Step (5): pouring, temperature measurement, cooling and curing of upper raft concrete.
[0005] Furthermore, in step (1), the installation of the bottom reinforcement of the lower raft slab, the installation of the steel support, the installation of the circulating cooling water pipe, the installation of the temperature measuring device, and the installation of the anchoring steel bars at the interface are specifically implemented as follows: a. Installation of bottom reinforcement of lower raft slab: Install according to the steel bar specifications and spacing in the design drawing; b. Installation of steel bracket: The steel bracket includes a steel bracket foot pad, a steel bracket column, and a steel bracket vertical and horizontal support. The steel bracket foot pad is welded to the bottom reinforcement of the lower raft slab, and the steel bracket column is welded to the steel bracket foot pad. During installation, the steel bracket column is vertical, and the steel bracket vertical and horizontal support is welded to the steel bracket column to ensure the stability of the bracket; c. Installation of circulating cooling water pipe: The circulating cooling water pipe is made of seamless steel pipe, placed on the vertical and horizontal support of the steel bracket, fixed with iron wire, and installed horizontally in the middle of the concrete. During installation, ensure that the joints are tightly sealed and the pipes are not damaged; d. Installation of temperature measuring device: The temperature measuring device includes an attachment rod, a temperature sensing piece, a sensing wire, and a temperature measuring piece. During installation, a steel bar is first installed vertically as the attachment rod, and then welded to the steel support nearby. The temperature sensing piece is connected with a sensing wire, and the sensing wire is led out of the concrete surface along the steel bar and tied to the steel bar with tape. The end of the sensing wire is hung on the steel bar and tied firmly with tape; e. Installation of anchor steel bars at the interface: Install anchor steel bars at the interface between the upper and lower layers of concrete to ensure effective connection between the two layers of concrete.
[0006] Furthermore, in step (2), the pouring, temperature measurement, cooling and curing of the lower raft concrete are specifically implemented as follows: a. Concrete pouring of the lower raft slab: strictly control the temperature of the mold, detect the slump in real time, vibrate and compact, and do not let the vibrating rod touch the circulating cooling water pipe, temperature measuring device, or anchor steel bars at the interface during vibration. Set a horizontal construction joint 50mm to 100mm below the interface of the large-volume concrete with variable cross-section; b. Temperature measurement: temperature measurement shall be started after the initial setting of the lower raft slab concrete, and temperature measurement records shall be kept. The temperature measurement records shall include temperature measurement time, mold entry temperature, maximum temperature rise, internal temperature, surface temperature, atmospheric temperature, water inlet temperature, water outlet temperature, cooling rate, etc. The temperature measurement time interval shall be implemented according to the design and specification requirements; c. Cooling: After the concrete at the height of the cooling water pipe begins to set, the cooling water will begin to circulate; d. Maintenance: After the concrete is poured, it is covered with geotextile and watered for maintenance after the initial setting. In order to ensure that the temperature difference between the concrete surface and the external environment is not too large, hot water from the circulating water outlet is used for maintenance, which can not only keep warm and moisturize, but also save water resources and have a good maintenance effect.
[0007] Furthermore, in step (3), the construction joint treatment of the interface is specifically as follows: a. Chiseling: Chisel away the floating slurry on the concrete surface, exposing at least 1 / 3 of the stone, with a chiseling depth of 5 to 10 mm and a chiseling rate of not less than 90%. Clean up the chiseled debris; b. Cleaning and correction of anchor steel bars at the joint surface: clean the concrete on the embedded anchor steel bars at the joint surface. If there is any tilt, correct it in time; c. Interface agent: Before pouring the upper raft concrete, spray a layer of interface agent on the surface of the lower raft concrete to ensure the bonding of the upper and lower layers of concrete; d. Wetting: Before pouring the upper raft concrete, sprinkle water on the lower raft concrete to moisten it in advance, but do not allow water to accumulate, to ensure that the upper raft concrete does not lose water when pouring and that the concrete is accurately matched when entering the warehouse; e. Grouting: Before pouring the upper raft slab concrete, pre-spread 50mm-100mm cement mortar with the same proportion as concrete on the surface of the lower raft slab concrete to prevent excessive gravel on the contact surface from affecting the bonding quality of the upper and lower layers of concrete.
[0008] Furthermore, in step (4), the upper steel support, raft slab reinforcement, circulating cooling water pipe and temperature measuring device are installed; specifically implemented as follows: a. Installation of upper steel bracket: including steel bracket foot pad, steel bracket column, steel bracket vertical and horizontal support, steel bracket top installation, the thickened part of the raft is connected to the lower steel bracket column, and the installation method of the non-thickened part is the same as the installation of the lower steel bracket; b. Installation of upper raft slab reinforcement: The upper raft slab reinforcement is placed on the top of the steel support, and the spacing and specifications of the reinforcement are in accordance with the design requirements; c. Installation of upper circulating cooling water pipe: The installation method is the same as the installation of lower circulating cooling water pipe mentioned above; d. Installation of the upper temperature measuring device: The installation method is the same as the installation of the lower temperature measuring device mentioned above.
[0009] Furthermore, in step (4), the pouring, temperature measurement, cooling and curing of the upper raft concrete are specifically implemented as follows: a. Casting of upper raft concrete: Before casting, complete the construction joint treatment of the above-mentioned interface, and the casting method is the same as that of the lower raft concrete; b. Temperature measurement of upper raft concrete: the temperature measurement method is the same as that of lower raft concrete; c. Cooling of upper raft concrete: The cooling method is the same as that of lower raft concrete; d. Maintenance of upper raft concrete: The maintenance method is the same as that of lower raft concrete.
[0010] Compared with the prior art, the present invention has the following beneficial effects: The invention adopts isothermal layered recursive casting for variable-section large-volume raft concrete, arranges a horizontal construction joint 50mm-100mm below the variable-section interface of the variable-section large-volume raft concrete, completes cooling of the lower layer of concrete during the time of installing the upper raft steel bracket, installing the raft surface layer steel bars, installing the post-casting belt water-stop steel plate and the closing installation, and installing the core tube steel bar template, so that the hydration reaction of the lower layer of concrete has less influence on the hydration heat superposition and the adiabatic temperature rise of the upper layer of concrete, avoids the generation of temperature difference cracks at the interface of the raft variable section due to the difference in temperature field and stress field generated inside two rafts of different thicknesses, can achieve good thermal shrinkage crack control effect, and has universal promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 It is a schematic diagram of the installation of the bottom reinforcement of the lower raft slab, the installation of the steel bracket, the installation of the circulating cooling water pipe, the installation of the temperature measuring device, and the installation of the anchoring steel bars at the interface of the present invention; Figure 2 for Figure 1 The structural schematic diagram of the steel support installation shown; Figure 3 for Figure 1 The schematic diagram of the connection node between the circulating cooling water pipe and the steel support is shown; Figure 4 for Figure 1 The schematic diagram of the temperature measuring device installation shown; Figure 5 for Figure 1 The schematic diagram of the installation of the anchor reinforcement at the interface is shown; Figure 6 for Figure 1 The schematic diagram of the lower layer concrete pouring is shown; Figure 7 It is a schematic diagram of the installation of the upper raft slab reinforcement, the installation of the steel support, the installation of the circulating cooling water pipe, and the installation of the temperature measuring device of the present invention; Figure 8 It is a cross-sectional view of the upper layer of concrete poured in the present invention; In the figure: 1. Bottom reinforcement of lower raft slab; 2. Foot pad of steel support; 3. Vertical column of steel support; 4. Vertical and horizontal support of steel support; 5. Top pressure of steel support; 6. Surface reinforcement of raft slab; 7. Circulating cooling water pipe; 8. Temperature measuring device; 9. Anchor steel bar of joint surface; 10. Concrete of lower raft slab; 11. Concrete of upper raft slab; 12. Construction joint of joint surface; 13. Iron wire; 14. Attachment rod; 15. Sensing wire; 16. Temperature sensor; 17. Temperature measuring plate; 18. Auxiliary steel bar; 19. Column reinforcement; 20. Bottom reinforcement of upper raft slab. DETAILED DESCRIPTION
[0012] The invention is further described below with reference to the accompanying drawings and embodiments.
[0013] Reference Figures 1 to 8 , a variable cross-section large volume raft concrete isothermal layered recursive pouring construction process, comprising the following steps: Step (1): installing the bottom reinforcement 1 of the lower raft slab, installing the steel support, installing the circulating cooling water pipe 7, installing the temperature measuring device 8, and installing the anchoring steel bars 9 of the interface; Step (2): pouring, temperature measurement, cooling and curing of the lower raft concrete 10; Step (3): Processing the construction joint 12 of the interface; Step (4): installing the upper steel support, the raft rib 6, the circulating cooling water pipe 7, and the temperature measuring device 8; Step (5): pouring, temperature measurement, cooling and curing of the upper raft slab concrete 11.
[0014] In step (1), the installation of the bottom reinforcement 1 of the lower raft slab, the installation of the steel support, the installation of the circulating cooling water pipe 7, the installation of the temperature measuring device 8, and the installation of the interface anchoring steel bars 9 are specifically implemented as follows: a. Installation of bottom reinforcement 1 of the lower raft slab: Install according to the steel bar specifications and spacing in the design drawing; b. Installation of steel bracket: The steel bracket includes a steel bracket foot pad 2, a steel bracket column 3, and a steel bracket vertical and horizontal support 4. The steel bracket foot pad 2 is welded to the bottom reinforcement 1 of the lower raft slab. The steel bracket column 3 is made of channel steel and welded to the steel bracket foot pad 2. During installation, the steel bracket column 3 is kept vertical with a spacing of 1200mm-1800mm. The steel bracket vertical and horizontal support 4 is made of angle steel. The first step is 50mm away from the steel bracket foot pad, with a spacing of 1200mm-1800mm. The installation height of the lower steel bracket column is 500mm-1000mm higher than the concrete pouring surface, so as to connect the upper layer. The steel bracket vertical and horizontal support 4 is welded to the steel bracket column 3 to ensure the stability of the bracket; c. Installation of circulating cooling water pipe 7: The circulating cooling water pipe 7 is made of seamless steel pipe, placed on the vertical and horizontal support 4 of the steel bracket, fixed with iron wire, with a horizontal spacing of 1500mm, and installed horizontally in the middle of the concrete. During installation, ensure that the joints are tightly sealed and the pipes are not damaged. Fill the pipes with cooling water before pouring concrete, and start circulating water immediately after initial setting; d. Installation of temperature measuring device 8: The temperature measuring device 8 includes an attachment rod 14, a temperature sensing piece 16, a sensing wire 15, and a temperature measuring piece 17. The lowest point of the temperature sensing piece 16 is installed 50 mm from the bottom, and the highest point is installed 50 mm from the casting surface. The distance between the middle points is not more than 500 mm. During installation, a Φ20 steel bar is first vertically installed as the attachment rod 14, and welded to the steel bracket nearby. The temperature sensing piece 16 is connected with the sensing wire 15. The sensing wire 15 is led out of the concrete surface along the attachment rod 14 and is tied to the attachment rod 14 with tape. The attachment rod 14 is 1500 mm higher than the lower concrete casting surface. The end of the sensing wire 15 is hung on the attachment rod 14 and is firmly tied with tape; e. Installation of anchor bars 9 at the junction: Anchor bars are installed at the junction of the upper and lower concrete layers to ensure effective connection between the two layers of concrete. The anchor bars are made of Φ20 threaded steel and made into a "[" shape with a hook length of 150mm, a vertical length of 1000mm, and a plum blossom shape with a spacing of 1000mm. Auxiliary steel bars 18 are used to hang at the junction and ensure that the length buried in the lower layer of concrete is half of the anchor bars 9 at the junction.
[0015] In step (2), the pouring, temperature measurement, cooling and curing of the lower raft concrete 10 are specifically implemented as follows: a. Casting of lower raft concrete 10: strictly control the temperature of the concrete entering the mold to be no more than 30°C, detect the slump in real time, vibrate and compact, and do not let the vibrating rod touch the circulating cooling water pipe 7, temperature measuring device 8, and joint surface anchoring steel bar 9 during vibration. Set a horizontal construction joint 50mm to 100mm below the interface of the large-volume concrete variable section; b. Temperature measurement: temperature measurement should be started after the lower raft slab concrete has initially set for 10 days, and temperature measurement records should be kept. The temperature measurement records should include temperature measurement time, mold entry temperature, maximum temperature rise, internal temperature, surface temperature, atmospheric temperature, water inlet temperature, water outlet temperature, cooling rate, etc. The temperature measurement time interval should be implemented according to the design and specification requirements; c. Cooling: After the concrete at the height of the cooling water pipe begins to set, the cooling water will begin to circulate; d. Maintenance: After the concrete is poured, it is covered with geotextile and watered for maintenance after the initial setting. In order to ensure that the temperature difference between the concrete surface and the external environment is not too large, hot water from the circulating water outlet is used for maintenance, which can not only keep warm and moisturize, but also save water resources and have a good maintenance effect.
[0016] In step (3), the treatment of the construction joint 12 of the interface is specifically implemented as follows: a. Chiseling: Chisel away the floating slurry on the concrete surface, leaving at least 1 / 3 of the stone exposed, with a chiseling depth of 5 to 10 mm and a chiseling rate of not less than 90%. Clean up the chiseled debris; b. Cleaning and correction of the anchor steel bars at the interface: clean the concrete on the embedded anchor steel bars at the interface, and correct them in time if there is any tilt; c. Interface agent: Before pouring the upper raft concrete 11, spray a layer of interface agent on the surface of the lower raft concrete 10 to ensure the bonding of the upper and lower layers of concrete; d. Wetting: Before pouring the upper raft concrete 11, the lower raft concrete 10 is sprinkled with water in advance to moisten it, but without water accumulation, to ensure that the upper raft concrete does not lose water when pouring and to ensure that the concrete is accurately matched when entering the warehouse; e. Grouting: Before pouring the upper raft concrete 11, a layer of cement mortar with the same mix ratio as the concrete is pre-paved on the surface of the lower raft concrete 10 to prevent excessive gravel on the contact surface from affecting the bonding quality of the upper and lower raft concretes.
[0017] In step (4), the upper steel support, the raft rib 6, the circulating cooling water pipe 7 and the temperature measuring device 8 are installed; the specific implementation is: a. Installation of upper steel bracket: including installation of steel bracket foot pad 2, steel bracket column 3, steel bracket vertical and horizontal support 4, steel bracket top 5. The thickened part of the raft is connected to the lower steel bracket column. The installation method of the non-thickened part is the same as that of the lower steel bracket; b. Installation of upper raft slab reinforcement 6: The upper raft slab reinforcement 6 is placed on the steel support top 5, and the spacing and specifications of the reinforcement are in accordance with the design requirements; c. Installation of upper circulating cooling water pipe 7: The installation method is the same as the installation of the lower circulating cooling water pipe mentioned above; d. Installation of the upper temperature measuring device 8: The installation method is the same as the installation of the lower temperature measuring device mentioned above.
[0018] In step (5), the pouring, temperature measurement, cooling and curing of the upper raft concrete 11 are specifically implemented as follows: a. Casting of the upper raft concrete 11: Before casting, the aforementioned construction joint 12 is processed, and the casting method is the same as that of the lower raft concrete 10; b. Temperature measurement of upper raft concrete 11: the temperature measurement method is the same as that of lower raft concrete 10; c. Cooling of the upper raft concrete 11: The cooling method is the same as that of the lower raft concrete 10; d. Maintenance of upper raft concrete 11: The maintenance method is the same as that of lower raft concrete 10.
[0019] The invention adopts isothermal layered recursive casting for variable-section large-volume raft concrete, arranges a horizontal construction joint 50mm-100mm below the variable-section interface of the variable-section large-volume raft concrete, completes cooling of the lower layer of concrete during the time of installing the upper raft steel bracket, installing the raft surface layer steel bars, installing the post-casting belt water-stop steel plate and the closing installation, and installing the core tube steel bar template, so that the hydration reaction of the lower layer of concrete has less influence on the hydration heat superposition and the adiabatic temperature rise of the upper layer of concrete, avoids the generation of temperature difference cracks at the interface of the raft variable section due to the difference in temperature field and stress field generated inside two rafts of different thicknesses, can achieve good thermal shrinkage crack control effect, and has universal promotion and application value.
[0020] The above description is only a detailed description of the specific implementation of the present invention, rather than a limitation of the present invention. Various substitutions, modifications and improvements made by those skilled in the relevant art without departing from the principle and scope of the present invention should be included in the protection scope of the present invention.
Claims
1. A variable cross-section large volume raft concrete isothermal layered recursive pouring construction process, characterized in that: The following steps are involved: Step (1): installation of the bottom reinforcement of the lower raft slab, installation of the steel support, installation of the circulating cooling water pipe, installation of the temperature measuring device, and installation of the anchor steel bars at the interface; Step (2): pouring, temperature measurement, cooling and curing of lower raft concrete; Step (3): Treatment of construction joints at the interface; Step (4): Installation of upper steel support, raft slab reinforcement, circulating cooling water pipe, and temperature measuring device; Step (5): pouring, temperature measurement, cooling and curing of upper raft concrete.
2. The isothermal layered recursive pouring construction process of variable cross-section large volume raft concrete according to claim 1 is characterized in that: In step (1), the installation of the bottom reinforcement of the lower raft slab, the installation of the steel support, the installation of the circulating cooling water pipe, the installation of the temperature measuring device, and the installation of the anchoring steel bars at the interface are specifically implemented as follows: a. Installation of bottom reinforcement of lower raft slab: Install according to the steel bar specifications and spacing in the design drawing; b. Installation of steel bracket: The steel bracket includes a steel bracket foot pad, a steel bracket column, and a steel bracket vertical and horizontal support. The steel bracket foot pad is welded to the bottom reinforcement of the lower raft slab, and the steel bracket column is welded to the steel bracket foot pad. During installation, the steel bracket column is vertical, and the steel bracket vertical and horizontal support is welded to the steel bracket column to ensure the stability of the bracket; c. Installation of circulating cooling water pipe: The circulating cooling water pipe is made of seamless steel pipe, placed on the vertical and horizontal support of the steel bracket, fixed with iron wire, and installed horizontally in the middle of the concrete. During installation, ensure that the joints are tightly sealed and the pipes are not damaged; d. Installation of temperature measuring device: The temperature measuring device includes an attachment rod, a temperature sensing piece, a sensing wire, and a temperature measuring piece. During installation, a steel bar is first installed vertically as the attachment rod, and then welded to the steel support nearby. The temperature sensing piece is connected with a sensing wire, and the sensing wire is led out of the concrete surface along the steel bar and tied to the steel bar with tape. The end of the sensing wire is hung on the steel bar and tied firmly with tape; e. Installation of anchor steel bars at the interface: Install anchor steel bars at the interface between the upper and lower layers of concrete to ensure effective connection between the two layers of concrete.
3. The isothermal layered recursive pouring construction process for variable cross-section large volume raft concrete according to claim 2 is characterized in that: In step (2), the lower raft slab concrete pouring, temperature measurement, cooling and curing are specifically implemented as follows: a. Concrete pouring of the lower raft slab: strictly control the temperature of the mold, detect the slump in real time, vibrate and compact, and do not let the vibrating rod touch the circulating cooling water pipe, temperature measuring device, or anchor steel bars at the interface during vibration. Set a horizontal construction joint 50mm to 100mm below the interface of the large-volume concrete with variable cross-section; b. Temperature measurement: temperature measurement shall be started after the initial setting of the lower raft slab concrete, and temperature measurement records shall be kept. The temperature measurement records shall include temperature measurement time, mold entry temperature, maximum temperature rise, internal temperature, surface temperature, atmospheric temperature, water inlet temperature, water outlet temperature, and cooling rate. The temperature measurement time interval shall be implemented in accordance with the design and specification requirements; c. Cooling: After the concrete at the height of the cooling water pipe begins to set, the cooling water will begin to circulate; d. Maintenance: After the concrete is poured, it is covered with geotextile and watered for maintenance after the initial setting. In order to ensure that the temperature difference between the concrete surface and the external environment is not too large, hot water from the circulating water outlet is used for maintenance.
4. The isothermal layered recursive pouring construction process for variable cross-section large volume raft concrete according to claim 3 is characterized in that: In step (3), the construction joint treatment of the interface is specifically as follows: a. Chiseling: Chisel away the floating slurry on the concrete surface, exposing at least 1 / 3 of the stone, with a chiseling depth of 5 to 10 mm and a chiseling rate of not less than 90%. Clean up the chiseled debris; b. Cleaning and correction of anchor steel bars at the joint surface: clean the concrete on the embedded anchor steel bars at the joint surface. If there is any tilt, correct it in time; c. Interface agent: Before pouring the upper raft concrete, spray a layer of interface agent on the surface of the lower raft concrete to ensure the bonding of the upper and lower layers of concrete; d. Wetting: Before pouring the upper raft concrete, sprinkle water on the lower raft concrete to moisten it in advance, but do not allow water to accumulate, to ensure that the upper raft concrete does not lose water when pouring and that the concrete is accurately matched when entering the warehouse; e. Grouting: Before pouring the upper raft slab concrete, pre-spread 50mm-100mm cement mortar with the same proportion as concrete on the surface of the lower raft slab concrete to prevent excessive gravel on the contact surface from affecting the bonding quality of the upper and lower layers of concrete.
5. The isothermal layered recursive pouring construction process for variable cross-section large volume raft concrete according to claim 4 is characterized in that: In step (4), the upper steel support, raft slab reinforcement, circulating cooling water pipe and temperature measuring device are installed; the specific implementation is as follows: a. Installation of upper steel bracket: including steel bracket foot pad, steel bracket column, steel bracket vertical and horizontal support, steel bracket top installation, the thickened part of the raft is connected to the lower steel bracket column, and the installation method of the non-thickened part is the same as the installation of the lower steel bracket; b. Installation of upper raft slab reinforcement: The upper raft slab reinforcement is placed on the top of the steel support, and the spacing and specifications of the reinforcement are in accordance with the design requirements; c. Installation of upper circulating cooling water pipe: The installation method is the same as the installation of lower circulating cooling water pipe mentioned above; d. Installation of the upper temperature measuring device: The installation method is the same as the installation of the lower temperature measuring device mentioned above.
6. The isothermal layered recursive pouring construction process for variable cross-section large volume raft concrete according to claim 5 is characterized in that: In step (4), the pouring, temperature measurement, cooling and curing of the upper raft concrete are specifically implemented as follows: a. Casting of upper raft concrete: Before casting, complete the construction joint treatment of the above-mentioned interface, and the casting method is the same as that of the lower raft concrete; b. Temperature measurement of upper raft concrete: the temperature measurement method is the same as that of lower raft concrete; c. Cooling of upper raft concrete: The cooling method is the same as that of lower raft concrete; d. Maintenance of upper raft concrete: The maintenance method is the same as that of lower raft concrete.