A prestressed tendon anchorage construction process

Abstract

The application discloses a prestressed tendon anchorage block construction process, which solves the problem that the prestressed tendon anchorage head cannot be quickly constructed and the long construction time. The process comprises the following steps: S1, measuring and positioning, marking the center position of the prestressed tendon anchorage block and drawing the excavation range of the anchorage block; S2, excavating the anchorage block, excavating and forming the anchorage block according to the marked excavation contour range of the anchorage block; S3, spraying and backfilling, washing the excavation surface and then spraying concrete until the designed thickness is reached; S4, surface leveling, manually leveling the uneven parts of the surface after spraying; and S5, maintenance.

Description

TECHNICAL FIELD

[0001] The present application relates to the geological construction technical field, especially to a prestressed tendon anchor pier construction process. BACKGROUND

[0002] The side slope of the adverse geological section or the underground large-span deep foundation pit excavation engineering often needs to be reinforced by prestressed tendons due to the geological conditions and safety considerations, and the anchor pier as the supporting device for tensioning and locking of the prestressed tendons plays a crucial role in the success of the prestressed tensioning and locking. According to the prestressed tendon construction specification of water and hydropower, the prestressed tendon anchor pier construction process at the present stage is as follows: the anchor pier of the rock-soil body is divided into cast-in-place reinforced concrete anchor pier, prefabricated reinforced concrete anchor pier and steel anchor pier. The prestressed reinforced concrete structure anchor pier is divided into two types of external convex type and internal concave type according to its stress condition.

[0003] For the open-cut side slope and underground foundation pit engineering, the angle of the prestressed anchor rod is usually the elevation angle and the horizontal angle, and the cast-in-place reinforced concrete anchor pier method can be used for anchor pier construction, or the prefabricated reinforced concrete or steel anchor pier method can be used. For the prefabricated reinforced concrete or steel anchor pier method, the flatness requirement of the excavation surface is relatively high, and it is difficult to achieve the required flatness of the surface after blasting excavation of the relatively broken rock surface, which needs manual surface finishing, wasting a lot of manpower. For the cast-in-place reinforced concrete anchor pier, manual steel binding and formwork erection are needed, the formwork is not easy to fix due to the small pouring space, and pouring and vibrating need to be done manually, wasting a lot of time and manpower. The cast-in-place reinforced concrete generally needs to wait until it reaches a certain design strength before allowing blasting nearby, which affects the excavation progress of the lower layer.

[0004] For the top of the underground large-span structure engineering, the angle of the prestressed tendon is the downward angle (the angle is downward). It is difficult to use the cast-in-place reinforced concrete anchor pier method for anchor pier construction, and the steel anchor pier and prefabricated reinforced concrete anchor pier method requires the hole opening part to be flat. For the blasting excavation surface of the relatively broken rock, the flatness after blasting is difficult to meet the installation requirement, and manual hole opening leveling is needed in the later period, wasting a lot of manpower and time. SUMMARY

[0005] In view of the above situation, in order to overcome the defects of the prior art, the present application provides a prestressed tendon anchor pier construction process, which effectively solves the problem of long construction time of the prestressed tendon anchor head.

[0006] To solve the above problems, a prestressed tendon anchor pier construction process comprises the following steps:

[0007] S1, measuring and positioning, marking the center position of the prestressed tendon anchor pier, and drawing the excavation range of the anchor pier;

[0008] S2, anchor excavation, excavate the anchor according to the indicated anchor excavation profile range;

[0009] S3, anchor backfilling, flush the excavation surface, then spray concrete until the designed thickness is reached;

[0010] S4, surface leveling, manually level the uneven parts of the sprayed surface;

[0011] S5, maintenance.

[0012] Preferably, the specific steps of S1 are as follows: the surveyor uses a total station to mark the center position of the prestressed tendon anchor in the position where the prestressed tendon anchor needs to be excavated in the factory building, and the surveyor assists the site technician to paint the excavation range of the anchor with paint.

[0013] Preferably, the specific steps of S2 are as follows: use a hydraulic hammer or a milling machine to excavate the anchor according to the indicated anchor excavation profile range, and after the excavation is completed, the surveyor checks the excavated anchor profile line, and if it meets the requirements, the next process can be performed, if it does not meet the requirements, it needs to be excavated to the designed profile line.

[0014] Preferably, the specific steps of S3 are as follows: after the anchor excavation profile line is measured and accepted, use a wet spraying trolley to flush the excavation surface with high-pressure water, until there is no rock slag, debris and other impurities in the hole, and after the rock surface is accepted, spray C25 steel fiber concrete in layers until the designed thickness is reached.

[0015] Preferably, the specific steps of S4 are as follows: after the steel fiber concrete is sprayed, immediately send someone to use an iron trowel to manually level the uneven parts of the sprayed surface.

[0016] Preferably, the specific steps of S5 are as follows: after the anchor construction is completed, send a special person to water conservation, keep the anchor surface wet during the maintenance period, and the maintenance time is 28 days.

[0017] The present application has the following advantages: 1) fewer procedures and faster construction speed, the present application only needs to perform anchor head excavation and shotcrete construction, so fewer procedures and easier process quality control; due to full mechanized operation, high construction efficiency, 10-15 minutes can complete the construction of an anchor pier; 2) wide application range, the new anchor pier can be applied to prestressed anchor pier construction of any angle, while cast-in-place reinforced concrete is only applicable to anchor pier construction of upward angle and horizontal hole; 3) low operation requirement, the present device has no requirement for the flatness of the hole, while prefabricated reinforced concrete and steel anchor pier need hole flatness; 4) high equipment utilization rate, the present device can utilize the rock slope support shotcrete platform, and complete the shotcrete backfilling of the anchor pier simultaneously with the rock slope shotcrete support; 5) small construction influence, the present device uses C25 / 30 shotcrete added with accelerator, which has fast early strength development and does not affect the blasting excavation of the lower layer, while the cast-in-place reinforced concrete generally needs to wait for 3d or more to perform blasting excavation nearby. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Fig. 1 is a schematic diagram of the anchor pier structure of the present application. DETAILED DESCRIPTION

[0019] The present application will be further described in detail in combination with the drawings. The drawings are simplified schematic diagrams, which only schematically show the basic structure of the present application, and thus only show the components related to the present application.

[0020] Please refer to Figure 1 The prestressed anchor pier of the present application has a concave stress mode, which can be applied to prestressed tendon anchor pier operation of any angle without special requirement for the hole site. The anchor pier excavation section is trapezoidal or other section form (specifically according to the design), the excavation depth is 30-50 cm, and the C25 steel fiber shotcrete fills the excavation area (the specific strength is confirmed according to the design requirement), that is, the prestressed tendon anchor pier construction is completed. The C25 steel fiber shotcrete is sprayed after mixing with accelerator by the shotcrete platform, which is fast, quick and simple in construction. Moreover, it is well combined with the bedrock surface, densely filled, and has fast early strength growth, which does not affect the blasting excavation progress of the lower part.

[0021] For underground large-span top arch prestressed tendon construction, the prestressed tendon design angle is downward angle (angle downward), the hydraulic hammer or milling excavator is used to excavate the trapezoidal anchor head at the designed prestressed tendon position, the shotcrete platform is used to clean the rock debris, debris and other sundries in the trapezoidal anchor head after the excavation is completed, the shotcrete platform is used to spray the C25 steel fiber shotcrete added with accelerator layer by layer after the cleaning is completed, and the anchor head is manually quickly leveled after the spraying is completed.

[0022] In rock slope and foundation pit operation, the design angle of prestressed tendon is elevation angle and horizontal angle. In the position of designed prestressed tendon, hydraulic hammer or milling excavator can be used to excavate trapezoidal anchor head. After excavation, anchor platform car is used to clean the rock debris, debris and other sundries in trapezoidal anchor head. After cleaning, anchor platform car is used to spray C25 steel fiber shotcrete added with accelerator. After spraying, anchor head is leveled manually.

[0023] Nepal Tanahu Hydropower Project is located on the south side of the national highway from Kathmandu to Pokhara, close to Damu City. The second bid section of the project is underground water diversion system and permanent equipment. The total installed capacity of the project is 146.4MW (2x73.2MW) hydro-generator unit and 1.79MW ecological flow power plant.

[0024] The prestressed anchor rod is applied to the permanent support system of the underground powerhouse. The length, width and height of the underground powerhouse are 89m, 22m and 50.8m respectively. The designed prestressed anchor rod has a diameter of 47mm and a strength grade of st 950 / 1050 high-strength steel. The single designed length is divided into three types of 10m, 20m and 25m. The top arch of the underground powerhouse adopts 10m long prestressed anchor rod with a design angle of downward inclination (downward) and a design number of 220. The south and north side end walls adopt 20m long prestressed anchor rod with a design angle of horizontal and upward inclination (upward) and a design number of 158. The upstream and downstream side end walls adopt 25m long prestressed anchor rod with a design angle of horizontal and a design number of 644. The total design number is 1022. The rock of the underground powerhouse is thin-medium thick and medium-hard slate. The structural fissure is developed. According to the design requirement, the support of one section needs to be completed before the excavation of the next section. The key process affecting the excavation progress of the underground powerhouse is the prestressed tendon construction. The key affecting the prestressed tendon construction progress is the anchor pier construction. How to efficiently, simply and quickly construct the prestressed tendon anchor pier is the problem to be solved by the present application.

[0025] Construction procedure, measurement and positioning → anchor pier excavation → anchor spraying and backfilling → surface leveling → maintenance.

[0026] Construction method:

[0027] 1) Measurement and positioning

[0028] The measurement personnel use the total station to mark the center position of the prestressed anchor pier at the position of the prestressed anchor pier to be excavated in the powerhouse. The measurement personnel assist the on-site technical personnel to draw the excavation range of the anchor pier by spraying paint.

[0029] 2) Anchor pier excavation

[0030] The anchor pier is excavated according to the indicated anchor pier excavation contour range by using a hydraulic hammer or a milling excavator. After the excavation is completed, the excavated anchor pier contour line is checked by surveyors. If the contour line meets the requirements, the next step can be performed. If the contour line does not meet the requirements, the excavation needs to be continued until the design contour line is reached.

[0031] 3) Backfilling of the anchor

[0032] After the anchor pier excavation contour line is measured and accepted, the excavated surface is washed by using a wet spraying trolley with high-pressure water and air until there is no rock slag, debris and other impurities in the hole. After the rock surface is accepted, the C25 steel fiber concrete is sprayed in layers until the design thickness is reached.

[0033] 4) Surface leveling

[0034] After the steel fiber concrete is sprayed, a person is immediately sent to use an iron trowel to manually level the uneven parts of the surface after spraying.

[0035] 5) Maintenance

[0036] After the anchor pier construction is completed, a special person is sent to perform water spraying maintenance. During the maintenance period, the surface of the anchor pier is kept wet. The maintenance time is 28 days.

[0037] The embodiments are merely examples for clearly illustrating the present application and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. All the embodiments do not need to be exhausted and cannot be exhausted. The changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A prestressed tendon anchor pier construction process, characterized in that: Applied to the top of underground large-span structures; the prestressed anchor pier is concave in its load-bearing mode; the anchor pier excavation section is trapezoidal, with an excavation depth of 30-50cm. C25 steel fiber shotcrete is then filled into the excavated area, completing the prestressed anchor pier construction. C25 steel fiber shotcrete is mixed with an accelerator and sprayed out using a shotcrete trolley, making construction quick, rapid, and simple. Furthermore, it bonds well with the bedrock surface, densely filling the ground and achieving rapid initial strength growth without affecting the progress of the underlying blasting excavation. The steps include: S1, measure and locate, mark the center position of the prestressed tendon anchor pier, and draw the excavation range of the anchor pier; S2, anchor pier excavation, excavate and shape the anchor pier according to the marked anchor pier excavation outline range; S3, spray anchor backfill, flush the excavation surface, and then spray concrete until the designed thickness is reached; S4, surface leveling, manual leveling of uneven surfaces after spraying; S5, maintenance; The specific steps of S3 are as follows: after the anchor pier excavation outline is measured and accepted, the excavation surface is washed with high-pressure wind and water using a wet spraying trolley until there is no rock slag or debris in the hole; after the rock surface is accepted, C25 steel fiber concrete is sprayed layer by layer until the designed thickness is reached; The specific steps of S4 are as follows: after the spraying of steel fiber concrete is completed, a person is immediately sent to use an iron trowel to manually level the uneven parts of the sprayed surface; The specific steps of S5 are: after the construction of the anchor pier is completed, a special person is assigned to carry out watering maintenance, and the surface of the anchor pier is kept moist during the maintenance period. The maintenance time is 28 days.

2. A prestressed tendon anchor pier construction process according to claim 1, characterized in that: The specific steps of S1 are: the surveyor uses a total station to mark the center position of the prestressed tendon anchor pier at the location of the prestressed tendon anchor pier that needs to be excavated in the factory building, and the surveyor assists the on-site technician to draw the excavation range of the anchor pier with spray paint.

3. A prestressed tendon anchor pier construction process according to claim 1, characterized in that: The specific steps of S2 are: using a hydraulic hammer or a milling machine to excavate and shape the anchor pier according to the marked anchor pier excavation contour range, and after the excavation is completed, the surveyor verifies the excavated anchor pier contour line, and only proceeds to the next step after it meets the requirements; If the requirements are not met, excavation needs to continue to the designed contour line.

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