Construction process of bridge pier bearing platform
Technical Field
The invention relates to a bridge construction process, in particular to a construction process of a bridge pier bearing platform.
Background
The bridge pier bearing platform is a supporting foundation at the lower part of the bridge pier, has large volume and large concrete pouring amount, and belongs to large-volume concrete construction. After the pouring of the large-volume concrete is finished, a large amount of hydration heat is generated inside, the release of the hydration heat is concentrated, and the internal temperature rise is quick. When the temperature difference between the inside and the outside of the concrete is large, the concrete can generate temperature cracks, and the structural safety and normal use are affected.
In order to control the internal temperature of the concrete, in the construction process, a temperature measuring element and a cooling water pipe are usually embedded in the concrete, and cooling water is introduced according to the detected temperature condition to reduce the internal temperature of the concrete so as to achieve the purpose of reducing the internal and external temperature difference of the concrete. In the prior art, a temperature measuring element and a connecting wire thereof are usually directly bound on a steel bar of a concrete framework, and are easy to shift or even damage and malfunction due to the impact of concrete or the touch of a vibrator in the process of casting concrete, so that the temperature measurement in the concrete is inaccurate. Also some pre-buried steel pipe in concrete, through setting up temperature measuring element and come the measurement temperature in the steel pipe, but because the steel pipe is inside relatively closed and the low thermal conductivity of air, lead to temperature measurement also inaccuracy to pre-buried steel pipe also has certain influence to the overall structure nature of concrete construction. If the temperature of each area inside the concrete cannot be accurately measured, the control of the water supply temperature and the flow of the cooling water pipe is necessarily inaccurate according to the inaccurate result, and better concrete maintenance is not facilitated.
Disclosure of Invention
The invention aims to overcome the defect that the temperature control in the concrete is inaccurate due to the fact that a temperature measuring element arranged in the prior art is easily interfered and even damaged by touch, and provides a construction process of a bridge pier bearing platform which is more beneficial to concrete maintenance.
The technical scheme adopted by the invention for solving the technical problems is as follows: after a concrete cushion layer is paved at the bottom of an excavated foundation pit, setting a template according to a defined bearing platform edge, binding bearing platform reinforcing steel bars on the inner side of the template and setting an embedded part, wherein the embedded part comprises a cooling water pipe and a temperature measuring element; after binding the steel bars, pouring concrete layer by layer and vibrating, curing until the concrete reaches the required strength after the whole bearing platform is poured, and then removing the template. When reinforcing steel bars of a bearing platform are bound, a plurality of temperature measuring element isolation bars which extend horizontally are arranged in the plane direction of the bearing platform every time reinforcing steel bars with a certain height are bound; the temperature measuring element isolation strip is provided with an upper wing plate which is horizontally arranged and used for protecting the temperature measuring element, one side of the lower end surface of the upper wing plate is provided with a side wing plate which is used for limiting the temperature measuring element and the connecting line position of the temperature measuring element and blocking concrete, and the other side of the upper wing plate is an open structure which can be used for allowing the concrete to flow below the upper wing plate; arranging the temperature measuring element and connecting wires thereof in an inner cavity of a semi-closed structure formed by the upper wing plate and the side wing plate, and thermally isolating the temperature measuring element from the upper wing plate and the side wing plate; in the process of binding the steel bars, a layer of cooling water pipes are arranged on the plane direction of the bearing platform every time a certain layer of temperature measuring element isolation strips are arranged, and the operation of arranging the temperature measuring element isolation strips and the cooling water pipes in the process of binding the steel bars is repeated until the steel bars of the bearing platform are bound.
In the layered and gradual concrete pouring process, each layer of cooling water pipe is covered by concrete, and water is introduced into the layer of cooling water pipe for cooling.
After the concrete pouring is finished, determining the internal temperature distribution of the concrete of the bearing platform according to the detection values of different temperature measuring elements, and adjusting the water passing temperatures and flow rates of different cooling water pipes according to the temperature distribution.
Comparing detection values of a plurality of temperature measuring elements in a region between two adjacent cooling water pipes, and when the temperature measuring element corresponding to the highest detection value is positioned in the middle of the region and the difference value between the highest detection value and the lowest detection value is larger than a set threshold value, increasing the water inlet temperature of the cooling water pipes and increasing the flow; when the highest temperature detection value is positioned at one side of the area, the water inlet temperature of the cooling water pipe at the side is reduced.
When the detected value of the temperature measuring element exceeds the set highest temperature value, the water inlet temperature of the cooling water pipe closest to the temperature measuring element is reduced, and the flow rate is increased.
The difference between the inlet and outlet water pipes of the cooling water pipe is controlled to be between 5 ℃ and 10 ℃ until the peak value of the hydration heat of the concrete is transited, and the flow of the cooling water pipe is halved after the peak value is transited.
The upper wing plate is provided with flow holes distributed along the length direction of the upper wing plate.
When laying the condenser tube, every layer all sets up a plurality of condenser tube that distribute side by side, and the water inlet of each condenser tube all is connected with the control valve of independent control.
The cooling water pipes adopt serpentine cooling pipes which are bent back and forth, and the water flowing directions of the cooling water pipes on the same layer are the same; in the upper and lower adjacent layers, the water flowing directions of the cooling water pipes corresponding to the vertical direction are opposite.
And (3) after curing until the concrete reaches the required strength, introducing cement slurry into the cooling water pipe to fill the cavity in the cooling water pipe.
The beneficial effects of the invention are as follows: the provided temperature measuring element isolating strip can effectively protect the temperature measuring element, and the upper wing plate can prevent the cast concrete from impacting the temperature measuring element and the connecting wire thereof from the upper part. In the transverse direction, due to the blocking effect of the side wing plate, the concrete can only flow laterally from the side without the side wing plate to push the temperature measuring element and the connecting line thereof, and the pushing direction only enables the temperature measuring element and the connecting line thereof to enter the protection range of the upper wing plate and the side wing plate more deeply. When the vibrator is used for vibrating concrete, no matter how an operator moves the vibrator, the temperature measuring element and the connecting wire thereof under the protection of the temperature measuring element isolating bar are not touched, so that the deviation or failure cannot be caused, the measuring accuracy is ensured, an accurate reference is provided for controlling the internal temperature of the concrete, and the accurate control of the temperature and the improvement of the quality of a bridge pier bearing platform are facilitated.
Drawings
FIG. 1 is a schematic diagram of the skeleton structure of a bridge pier cap of the present invention.
FIG. 2 is a schematic diagram of the arrangement of the insulating strips and connecting wires of the temperature measuring element according to the present invention.
FIG. 3 is a schematic cross-sectional view of a spacer for temperature sensing elements according to the present invention.
FIG. 4 is a schematic view of the arrangement of the flow holes of the spacer of the temperature measuring element according to the present invention.
FIG. 5 is a schematic view of the distribution of temperature measuring elements in a horizontal plane according to the present invention.
FIG. 6 is a schematic view of the cooling water pipe arrangement in a horizontal plane according to the present invention.
Fig. 7 is a schematic view of another horizontal cooling water pipe arrangement adjacent to fig. 6.
The marks in the figure: 1. the temperature measuring device comprises a template, 2, a reinforcement cage, 3, a temperature measuring element isolation strip, 301, an upper wing plate, 302, a side wing plate, 303, a flow hole, 4, a temperature measuring element, 5, a connecting wire, 6, a cooling water pipe, 601, a water inlet, 602, a water outlet, 7, concrete, 8 and a protection groove.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
The basic construction steps of the construction process of the bridge pier bearing platform are the same as those of the prior art, after a concrete cushion layer is paved at the bottom of an excavated foundation pit, templates are arranged according to the delimited bearing platform side lines, the templates 1 are usually steel structure templates, and reinforcement is assembled and arranged according to the delimited marked lines of a concrete building to be constructed. Binding bearing platform steel bars on the inner side of the template and arranging an embedded part, wherein the embedded part comprises a cooling water pipe and a temperature measuring element; after binding the steel bars, pouring concrete layer by layer and vibrating, curing until the concrete reaches the required strength after the whole bearing platform is poured, and then removing the template.
When the steel bars of the bearing platform are bound, a plurality of temperature measuring element isolation bars which extend horizontally are arranged in the plane direction of the bearing platform every time the steel bars of a certain height are bound. For example, a layer of temperature measuring element isolation strip is arranged when the temperature measuring element isolation strip is bound to the height of 20cm, and then a layer of temperature measuring element isolation strip is arranged every 30cm upwards. The temperature measuring element isolation strip 3 can be bound with the steel bars or welded and fixed.
As shown in fig. 3, the temperature measuring element isolation strip 3 is provided with an upper wing plate 301 which is horizontally arranged and used for protecting the temperature measuring element 4, one side of the lower end surface of the upper wing plate 301 is provided with a side wing plate 302 which is used for limiting the position of the temperature measuring element 4 and a connecting line 5 thereof and blocking concrete, and the other side is an open structure which can be used for allowing the concrete to flow below the upper wing plate.
The temperature measuring element 4 and the connecting line 5 thereof are arranged in an inner cavity of a semi-closed structure surrounded by the upper wing plate 301 and the side wing plate 302. The temperature measuring element 4 is thermally isolated from the upper wing plate and the side wing plate, so that the influence on the measuring precision due to heat conduction of the upper wing plate and the side wing plate is prevented. The specific thermal isolation mode can adopt the way of deflecting the temperature measuring element 4 away from the upper wing plate 301 and the side wing plate 302, and the temperature measuring element is naturally thermally isolated through a separated space. Or a heat insulation cushion layer is arranged between the temperature measuring element and the upper wing plate and the side wing plate. The upper wing plate 301 shields the upper part of the temperature measuring element 4 and the connecting wire 5 thereof, and is used for bearing the impact of falling concrete when in pouring.
In the process of binding reinforcing steel bars, every temperature measuring element isolating bar with a certain layer is arranged, a layer of cooling water pipes are arranged in the plane direction of the bearing platform, and when the cooling water pipes are arranged, each layer is provided with a plurality of cooling water pipes which are distributed side by side, and the water inlets of the cooling water pipes are connected with control valves which are independently controlled. And repeating the operation of arranging the temperature measuring element isolating bars and the cooling water pipes in the process of binding the reinforcing steel bars until the reinforcing steel bars of the bearing platform are bound.
When concrete is poured, a horizontal layered pouring mode is adopted, and the pouring thickness of each layer can be controlled to be about 30 cm. Each layer of casting is pushed from one side to the other side, and is vibrated while casting.
The poured concrete flows sideways due to its fluidity and vibrating action. In order to avoid that the flowing concrete pushes the temperature measuring element 4 and its connecting line 5 away from the shielding of the upper wing plate 301, a side wing plate 302 is arranged at the side below the upper wing plate 301. Since the upper wing plate 301 is shielded by the side wing plate 302 on one side and is open on the other side, the flowing concrete can only flow from the open side to below the upper wing plate. The concrete flowing in the direction only drives the temperature measuring element 4 and the connecting wire 5 thereof to be closer to the side wing plate 302 and deeper into the protection range of the upper wing plate and the side wing plate, so that the condition that the temperature measuring element 4 and the connecting wire 5 thereof are out of protection due to the lateral flow of the concrete can not occur.
In the layered and gradual concrete pouring process, each layer of cooling water pipe is covered by concrete, and water is introduced into the layer of cooling water pipe for cooling. After the concrete pouring is finished, determining the internal temperature distribution of the concrete of the bearing platform according to the detection values of different temperature measuring elements, and adjusting the water passing temperatures and flow rates of different cooling water pipes according to the temperature distribution. The water temperature difference between the inlet and the outlet of the cooling water pipe is controlled to be between 5 ℃ and 10 ℃ until the hydration heat peak value passes, the flow in the cooling water pipe is ensured to reach 3 square/hour in the period, the flow of the cooling water pipe after the peak value is halved, the cooling water after the temperature peak is controlled to be cooled within 2 ℃ every day in the later period, the cooling water is cooled by using circulating water (15 ℃ different from the highest temperature of a bearing platform), and the cooling water shock effect is reduced.
In the specific control cooling water pipe water-through cooling process, comparing detection values of a plurality of temperature measuring elements in an area between two adjacent cooling water pipes, and when the temperature measuring element corresponding to the highest detection value is positioned in the middle of the area and the difference value between the highest detection value and the lowest detection value is larger than a set threshold value, increasing the water inlet temperature of the cooling water pipe and increasing the flow; when the highest temperature detection value is positioned at one side of the area, the water inlet temperature of the cooling water pipe at the side is reduced. The set threshold reflects the temperature difference conditions of different areas, the size of the threshold can be determined according to the distance between temperature measuring elements, the influence of the temperature difference on the internal stress of the concrete and the like, and the threshold is set to be 5 ℃ for example. It should also be noted that the temperature difference between the concrete core and the surface layer, the surface layer and the environment should always be controlled at preferably not more than 20 ℃ and at most not more than 25 ℃. When the detected value of the temperature measuring element exceeds the set highest temperature value (for example, the difference from the surface temperature reaches 20 ℃), the water inlet temperature of the cooling water pipe closest to the temperature measuring element is reduced, and the flow rate is increased. In the method, the detection value of the detection element which is closer to the cooling water pipe is compared with the detection value which is farther from the cooling water pipe, and different control is carried out according to the comparison result, so that the defects that the local temperature in the concrete is too fast, the temperature of the introduced cooling water is blindly reduced due to the fact that the detection value of the temperature measurement element which is closer to the cooling water pipe is higher, the temperature difference of different areas is too large, internal cracks are avoided, and the like are avoided.
When the temperature measuring element isolating strips 3 are arranged, the temperature measuring element isolating strips 3 of each layer are arranged in parallel according to the same direction, so that the influence on the vibration operation of concrete caused by mutual staggering is avoided. As shown in FIG. 5, the temperature measuring elements 4 in the same temperature detecting layer are distributed in a staggered manner, and the number of the temperature measuring elements arranged in the center of the concrete is more than that of the peripheral area, so that the whole plane is covered as much as possible. As shown in fig. 1, the connecting wires 5 of the temperature measuring element 4 are collected on one side of the steel reinforcement cage 2, and extend upwards to the outer side of the steel reinforcement cage through the protection groove 8 arranged on the inner side of the template 1. The protection groove 8 can adopt a structure similar to a temperature measuring element isolation strip, the side wing plate faces the template, and the upper wing plate internally measures the protection connecting line 5.
Advantageously, as shown in fig. 3, the lower end surface of the upper wing 301 is configured as a slope with gradually decreasing horizontal height toward the side wing 302, and the slope is connected to the side wing 302 via a circular arc transition surface. The lower end surface of the upper wing plate 301 which is inclined downwards can accord with the flowing characteristic of concrete, so that the concrete flows towards the side wing plate along the lower end surface, and the arc transition surface at the corner can avoid the generation of gaps under the upper wing plate 301 and out of the bent angle of the concrete, thereby ensuring the integral quality of the concrete casting structure.
As shown in fig. 3 and 4, a plurality of flow holes 303 are distributed in the length direction of the upper wing plate 301, and the flow holes 303 can not only enable the concrete above to flow downwards, thereby being beneficial for the concrete to fill the space enclosed by the upper wing plate 301 and the side wing plate 302, but also limit the downward flowing amount of the concrete, and prevent the falling concrete from impacting the temperature measuring element 4 and the connecting wire 5 thereof.
As shown in fig. 6 and 7, the cooling water pipe 6 is a serpentine cooling pipe consisting of a plurality of straight pipe sections and elbow sections connected with the straight pipe sections. The cooling water pipe adopts a standard cast iron water pipe with nominal diameter of 42mm and wall thickness of 2.5mm, the cooling pipe joint adopts a matched joint, the plane position adopts U-shaped reinforcing steel bars to be welded and fixed with the reinforcing steel bars of the bearing platform, and if the cooling pipe collides with the reinforcing steel bars of the bearing platform, the cooling pipe should be properly moved. The cooling water pipe should ensure no slurry and water leakage, and after the installation, the water sealing inspection should be performed to ensure the smoothness of the pipeline during water injection. Straight pipe sections of cooling water pipes in the same water cooling layer are arranged in parallel, and the water flowing directions of the cooling water pipes are the same. After water is introduced and heat released by concrete is absorbed, the straight pipe section with the water temperature at the water outlet end of one cooling water pipe relatively increased is adjacent to the straight pipe section with the low-temperature cooling water just introduced into the other cooling water pipe, and the two are combined to make the cooling of each area of the whole water cooling layer more balanced.
Similarly, in the upper and lower adjacent water cooling layers, the water flowing directions of the corresponding cooling water pipes in the vertical direction are opposite, and the upper and lower cold and heat are complementary, so that the cooling balance of each region of the vertical layer is ensured.
And after the concrete is poured, covering a layer of geotextile to prevent the concrete surface from being subjected to dry shrinkage cracks due to wind blowing and water loss. And controlling the temperature of the concrete in the process, and after the concrete is initially set, adopting geotextile to cover the concrete integrally and sprinkling water in time, wherein the surface wetting area of the bearing platform is required to reach 100%. Before the concrete strength reaches 2.5Mpa, it is not necessary to bear the constructor or other load. After the compressive strength of the concrete reaches 2.5MPa, and when the surface and edges and corners of the concrete are not damaged due to demolding, cement slurry is introduced into the cooling water pipe to fill the cavity in the cooling water pipe, so that the side mold can be disassembled.