The application of prestressed anchor cable for the mountainous area highway, subgrade excavation of large quantity, high cutting slope, geological weak section is generally using prestressed anchor cable ground beam, in order to ensure the stability of high side slope of roadbed. Prestressed anchor cable ground beam construction is a complex project, changes of the geological conditions of key construction technology of subtle and difficult special construction work, to arrange a professionally trained, with rich experience in the construction of professional construction team construction.
The main construction procedure is as follows:
In 1, anchor hole measuring discharge slope construction side digging edge reinforcement, namely excavation level, protection level, not an excavation on. According to the geological engineering elevation, according to design requirements, the anchor hole position accurately measure placed on the slope surface, hole position error should not exceed + 50mm. In case of both side of the brush surface irregularity or special sites, required by the design and supervision units authorized, in ensure slope stability and safety of the structure under the premise, relax appropriately positioning accuracy or adjust the anchor hole location.
In 2, drilling equipment drilling equipment choice, according to the anchoring formation categories, anchor hole diameter, hole depth, as well as the construction site conditions, selection of drilling equipment. Rock using down-the-hole percussive drilling in broken soft rock; or full water and so easy to collapse the hole and the drill drill formations using drilling technology with casing.
In 3, the rig anchor hole drilling construction, erection of meet the bearing capacity and the stability condition of the scaffold, according to the slope measuring discharge hole, accurately fixed rig, and strictly carry out seat adjustment, ensure that the anchor hole drilling in the vertical and horizontal error shall not exceed + 50mm, elevation error shall not exceed + 100mm, borehole inclination and direction comply with the design requirements, angle error bits + 1 degrees, + - 2 DEG azimuth error.
In 4, drilling. Drilling requirements stem drill, prohibiting the use of stones, to ensure that the anchor construction from deteriorating slope rock mass engineering geological condition and guarantee of hole wall adhesion. Drilling speed according to the use performance of drill and anchoring formation control strictly, prevent drill twisting and reducing, difficulties or other accidents caused by anchor.
5 in the process of drilling, drilling process for each hole in the stratum, drilling state ( drilling pressure, drilling), groundwater and some special cases for on-site construction records. If the collapse of hole shrinkage and other undesirable drilling phenomenon, must immediately stop drilling, timely solid wall treatment ( grouting pressure is 0.1 ~ 0.2MPa ), wait for cement mortar after initial set, to sweep the hole drilling.
In 6, the aperture hole drilling bore diameter, depth requirements shall not be less than the design #118alue. To ensure that the anchor hole diameter, actual use bit diameter shall not be less than the design aperture. To ensure that the hole depth, actual drilling depth greater than 0.2m above the depth of design.
In 7, the anchor hole cleaning drilling to reach design depth, not immediately stop drilling, the demand is steady drill 1 ~ 2 minutes, to prevent the bottom of the hole pinchout, can reach the designed aperture. Borehole wall without ballast and water viscosity, must be clean, in after drilling, the use of high pressure air ( wind pressure 0.2 ~ 0.4MPa ) will Kong Neiyan powder and water to remove all the holes, so as not to reduce the cement mortar and Kong Biyan bond strength of soil. Except for a relatively hard and complete the anchorage, may not be used in the high pressure water washing. If the anchor hole in the confined water outflow, the water pressure, water quantity is small before under an anchor and grouting, when necessary, in appropriate position around drainage hole processing. If the design requirements for processing anchor hole internal accumulation of water, usually by grouting and plugging the two drilling methods such as processing.
In 8, anchor hole drilling of an anchor hole after examination, shall be subject to supervision after passing the test, we can carry out the procedure. Bore diameter, deep checking the design, drill bit and drill rod in the standard aperture field standing-by supervisor under conditions of inspection hole, hole inspection requirements of bit smooth advance, no impact or vibration, drilling test send length meet design hole depth, back drilling requirements smoothly, with high pressure wind without obvious flying dust. Slag and water phenomenon. At the same time requirements review anchor hole hole, dip and azimuth, all anchor hole construction work item is eligible, can think drilling of an anchor hole inspection.
In 9, the production and installation of prestressed anchor cable body is composed of anchor beam, free section, anchoring and security section is composed of four parts. The pressure dispersed anchor cable, comprising three unit anchor cable component, each unit anchor cable is respectively composed of two unbonded strand anchor in steel bearing body, steel strand through a special extrusion spring and extrusion sleeve symmetrically anchorage in steel bearing body, a single connection strength is greater than 200KN requirements. Steel bearing body requires use of 45 steel processing production, its thickness not less than 2cm. Steel wire with diameter of j15.24mm and j12.7mm diameter high strength low relaxation prestressed steel strand. Before installation, to ensure that every steel strand straight, not twisted not fork, arranged evenly, rust, degreasing, the bending die, mechanical damage and rust pits out of. Steel strand anchor body along axis direction every 1 ~ 1.5m set a stringing ring, ensure the anchor body protection layer thickness not less than 20mm. Installation of cable anchor before again carefully check the anchor hole number, confirmation by the high pressure air blow hole, artificial slowly will anchor in the hole, using the ruler quantity hole exposed steel strand length, calculation of hole cable length ( error control in the 50mm range ), ensure the anchorage length.
In 10, anchoring and Grouting grouting using cement mortar, the test selection after determining the construction mixture ratio. The actual quantity of grouting is greater than the general theory of the grouting volume, or no longer exhaust and exhaust hole to anchor hole slurry overflow dense slurry grouting end as standard. As a note of dissatisfaction or settlement after grouting, grouting to supplement, until the fill. After the end of the grouting pipe grouting, grouting and grouting sleeve gun, clean, well grouting records.
In 11, ground beam beam using C25 concrete pouring. Based on 2cm mortar leveling layer to pave the way, then the steel production installation, steel joints to stagger, the same section reinforced joints shall not exceed the total number of reinforced root number 1 / 2, and the section of the distance between the welding joint shall not be less than 1m. Such as the anchor and the vertical beam stirrup phase disturbance, local adjustable stirrup spacing. The pouring of concrete, especially in the anchor holes around, reinforced more intensive, must carefully vibration, quality assurance.
In 12, anchor cable tensioning and locking, anchor sealing through the tensioning test, to determine a pulling the locking process. Cable tensioning and locking grading, in strict accordance with the operation procedures. In the design of a pulling 6 ~ 10d after a compensating tensioning, and then to be locked. Compensating tensioning, from anchorage volume, set aside 5 ~ 10cm strand, the rest must be amputated, using mechanical cutting, no electric arc flame cutting. Finally, the cement paste with anchor plate and the anchor head each part of space, and then the anchor head by not less than 20MPa concrete anchor sealing, preventing corrosion and beautiful balance.

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