Bored pile construction technology

【China Deep Hole Rig Trading Network】

Bored pile construction technology

Chapter 1 Preparation before Drilling

Pre-drilling preparations mainly include stake placement, sorting and grading of sites, installation of access roads, installation of power supply and water supply systems, production and embedding of casings, preparation of drilling rigs, preparation of mud and preparation of drilling tools.

Section 1 Site Organizing

Before construction, the construction site will be treated according to different conditions. For the bored pile foundation in water, it is necessary to take the platform of the construction work. When the pile foundation is in the dry land, it can be compacted and compacted after removing the debris.

Section 2 explains

The bored piles of this tender section all use steel casing and are made of 3mm-5mm steel plates. In order to ensure its rigidity and prevent deformation, a stiffening rib is welded on the upper, lower and middle sides of the casing. The diameter of bored piles in this contract segment is Ñ„120cm and 100cm. According to the diameter of the bored pile, the diameter of the bushings we made is 145cm and 125cm. When the casing is buried, its axis is aligned with the center of the pile marked by the measurement. The casing around the casing and the bottom of the casing are in close contact to ensure that the position deviation is less than 5cm and the inclination is not more than 1%.

Section 3 Making of Mud

Before pulping, the clay should be broken as much as possible to make it easy to be slurried during stirring, shortening the pulping time and improving the quality of the mud. When pulping, the broken clay can be directly put into the casing and the impact cone can be used to impact the pulping. When the clay has been crushed into mud, drilling can be performed. Excess mud is piped into the mud pool outside the borehole for restocking.

Section 4 Rig in Place

After the casing is installed, the drilling rig can be placed in place. The drilling rig used in this bidding section is a traction hammer drill and a rush drill. When in place, as long as the center of the drill cone is aligned with the measured pile position when measuring and setting out, the centering error must not exceed 5cm.

Chapter 2 Drilling Process

Section 1 Impact Drilling Process

A. Matters needing attention before drilling

Before drilling, add some clay to the casing. When the surface soil layer is loose, mix a small amount of small pieces of rock, then inject mud and clean water, and use the bit's impact to squeeze the mud and stones into the hole wall to reinforce the angle of the protection barrel. In order to prevent shock and vibration from collapsing adjacent holes or affecting the solidification of the adjacent holes, it is necessary to wait until the adjacent holes are filled and reach a certain strength.

Drilling can start. It is recommended to use a small stroke when drilling a hole. When the hole bottom is 3-4m below the feet of the protective tube, the stroke can be appropriately increased according to the actual situation. In the upper mud section of the bored pile, the use of rush drills is considered: on the one hand, boring can be prevented, and on the other hand, construction progress can be appropriately accelerated.

B. The drilling rig installation is leveled and compacted beforehand to prevent the rig from tilting and sagging and affecting the quality of the hole during drilling. The rig must be firmly secured and it is strictly forbidden to shift the rig during the drilling process. When drilling, always look at the rebound condition of the wire rope, and listen to the impact sound of the drill cone to discriminate the situation at the bottom of the hole. Grasp the principle of frequent looseness and a little loose rope; the level of the cement slurry in the hole must be at least 0.5m above the foot of the protection tube. Above, in order to avoid mud surface rippling damage to the wall of the shield foot hole, but 0.3m lower than the top surface of the protective tube to prevent mud overflow; during the impact process twitching, diligently check the wire rope and drill bit wear, prevent safety and quality accidents.

C. Several issues that should be noted when twitching

(1) Timely replenish slurry or make up water in the hole, such as pouring clay into the hole to make pulp, and throwing clay with impact after convulsions. It is not advisable to pour in a lot at a time to prevent sticking.

(2) After the suction tube is placed on the bottom of the hole, it should be lifted several times on the bottom of the hole.

(3) The cutting edge of the drill bit is constantly worn in the drilling, and the diameter wear should not exceed 1.5 cm. Check the diameter of the drill bit before each drill, and repair welding in time. It should not be repaired in the middle to avoid sticking. Prepare spare drills for rotation and repair.

Section 2 Rotary Drilling Process

A. Drilling

Start the mud pump and turntable first, make it idling for a while, wait for the mud to input a certain quantity, just start drilling. The action of picking and unloading the drill pipe should be quick and safe, and strive to be completed within the time as soon as possible so as not to stop drilling for too long and increase the sedimentation at the bottom of the hole.

B. Operation points for drilling

a. At the beginning of drilling, the footage shall be properly controlled. At the edge of the bushing, slow drilling shall be performed at low speed, so that a firm mud wall will be provided at the cutting edge. After drilling to 1m under the cutting edge, it can be drilled at normal speed according to the soil quality. If the casing soil is loose and soil is found to be leaky, lift the drill cone, pour the clay into the hole, and then lower the drill cone to reverse, so that the cement squeezes into the hole wall to block the leakage of the slurry, stabilize the mud and continue drilling.

b. Drilling in clay, due to the large viscosity of the mud, the drilling cone is also subject to large resistance and easy to pour. Easy to use sharp-bottomed drill cone, medium speed, large pump capacity, and thin mud drilling.

c. Easy to empty holes when drilling in sand or soft soil. Easy to use flat-bottomed drill cone, to control the footage, light pressure, low-speed slow, large pump, thick mud drilling.

d. When drilling in the light sub-clay or sub-clay in the ovipositor and gravel layer, the soil layer is too hard, which will cause the drilling cone to pulsate, the drill rod to swing and the drill cone to deflect, etc. It is easy to overload the drilling rig. . It is advisable to use low-grade slow speed, high-quality mud, large pump volume, and two-step drilling.

e. During the drilling process, drill diameter and verticality shall be inspected for every 2 to 3 meters of the drilled hole. The inspection tool may use a round steel cage (outer diameter D equals the designed pile diameter and height of 3 to 5 meters) to hang into the hole. The center of the rebar cage coincides with the center of the drill hole, and there is no hanging resistance at the upper and lower points, which indicates that the borehole diameter and verticality meet the requirements.

Section 3 detects hole depth, inclination, diameter, and

After the drilling is completed, the hole depth, diameter and inclination must be measured. The hole diameter and hole depth must meet the design requirements and the inclination must not exceed 1%. The clear hole is to clean the stone rake and mud in the hole before lifting the cage, so that the mud content, the ram content and the bottom sediment meet the design and drawings requirements.

Chapter 3 Mud Emissions

The mud discharged during the process of drilling, purging and infusion shall be introduced into the appropriate location according to the site conditions to prevent contamination of rivers and surrounding environment.

Chapter 4 Making and hoisting reinforcement cages

Section 1 Material:

The type, model, and diameter of the steel bars used to make the cages are in accordance with the design drawings. The mechanical properties of Grade II steel bars are in accordance with the provisions of "Rolled Steel Bars for Hot Rolled Ribbed Bars" (GB1499-91); the mechanical properties of Grade I steel bars conform to the requirements of "Hot Rolled Light Bars for Reinforced Concrete" (GB13013-91). .

Section 2 Production of Rebar Cage

The rebar cages used in this bid section are installed as a whole, and no other lifting assembly is required. When making steel cages, the straightening, rust removal, cutting, bending and welding of steel bars shall be carried out according to the design drawings and technical specifications. The main reinforcement of the reinforcement cage should be a whole root. When it needs docking, it is advisable to use a lap joint. The length of the overlapping joint is not less than 5d, and the end is not provided with a hook. The finished reinforcement cage ensures its straight and accurate dimensions. The construction error of the diameter, the spacing of the main reinforcements, the spacing of the stirrups and the spacing between the reinforcement stirrups is not more than 20 mm.

Section 3 Installation of Rebar Cage

(1) In order to ensure that the thickness of the protective layer outside the reinforcement cage meets the design requirements, four reinforcing steel “earrings” are placed on the cross section of the upper and lower ends and in the middle every 2m.

(2) Before the reinforcement cage is hoisted, drill holes shall be tested first. The diameter of the probe used for testing is consistent with the diameter of the drilled hole. It mainly detects whether there is a collapse in the drilled hole and whether the hole wall has any influence on the installation of the reinforcing bar, such as protruding sharp stone, root, etc., to ensure the installation of the reinforcing cage.

(3) When the reinforcing cage is hoisted, align it with the hole position, try to put it gently and slowly. If it meets with obstacles, it can slow down and rotate forward and backward to make it fall. If it is invalid, immediately stop the drop. After checking the reason, install the cage. . It is not allowed to rise and fall violently, and forcefully lower it to prevent collapsing by collapsing the wall of the hole.

(4) After the hole is firmly positioned, the allowable deviation is not more than 5cm, and the steel cage is suspended.

Chapter 5 Infusion ç ¼

Section 1 Material Requirements and Conduits, Funnels,

(1) The gravel and sand that constitute the crucible are well-graded. The selection of the largest particle size is appropriate for the size of the structure, the spacing of the steel bars, and the mixing, loading and unloading, casting and operation of the crucible. The content of impurities in the aggregates meets the requirements of the specification. If necessary, it is cleaned and sieved to remove harmful impurities.

(2) Chemical analysis of the quality of water before mixing is conducted before mixing. The test is conducted in accordance with JTJ056-84.

(3) The cement used for concrete shall comply with the provisions of GB 175-85. All cements must be qualified by the qualified suppliers and purchased from the approved manufacturers. When the cement enters the site, it must be accompanied by the certificate of cement factory ex-factory, and it must be tested by this unit. The room (nationally recognized) is inspected.

(4) Preparation of Conduit, Funnel and Storage Hopper

The catheter is an important tool for infusion of hemorrhoids. It is made by rolling a 3mm thick steel plate. Its diameter is determined by the length of the pile, the diameter of the pile and the number of gills per hour that must be passed. It must not be less than 250mm. The length of the segment of the catheter should be easy to disassemble and transport, And less than the lifting height of the pipe Lifting Equipment, the middle section is generally about 2m long, the lower end section can be lengthened to 4-6m, and the upper end section of the funnel can be equipped with a length of about 1m to adjust the height of the funnel. The middle section is welded with flanges at both ends so that they can be connected to each other with bolts. The thickness of the flange is 10-12mm. The edge of the flange is 40-50mm larger than the outer wall of the pipe, 12-16mm in diameter and 6-8 bolt holes. A pair of small lugs is welded near one end flange, and the bolt is used to hang the wire rope. The upper and lower flanges of the upper and lower flanges are lapped with 4-5mm thick rubber mats. The outer width of the flange is equal to the edge of the flange, and the inner side is slightly narrower than the flange inner edge. .

The funnel is made of 2-3mm thick steel plate with a conical or pyramidal shape. Each of the rings is welded symmetrically on both sides of the funnel at a distance of 15cm. The upper diameter of the conical funnel is 800mm and the height is 900mm. The size of the funnel structure is 1000×1000×800 mm, and the general length of the insertion catheter is set at 15 cm.

The storage hopper is made of 3mm thick steel plates and stiffeners. The bottom is made as a ramp, the exit is set with a gate, the movable chute is located below the outlet of the storage hopper, and the chute is connected to the funnel.

According to calculations, the funnel and storage hopper used for all bored piles of this contract are considered as 2.5m3.

Section 2 Mixing

The number of boring plates used in bored piles in this contract section is 25, and the slump falls between 18 and 22 cm in the design of the mix ratio. The aggregate uses mechanism crushed stone, the particle size is 0.5-3cm, and the maximum is not more than 4cm. The water-cement ratio is used. 0.5-0.6. The amount of concrete per cubic meter of concrete meets the test requirements, and the actual assigned number is 10-15% higher than the design number.

Prior to mixing mash, the gravel material needed for each hopper is accurately weighed. The mixing water is weighed in volume, the bagged cement is calculated at 50kg per bag, and the bulk cement is replenished with a hopper. Mixing time from all the materials into the drum water to discharge, not less than 2 - 2.5 minutes, before the loading of the material in the lower plate, all the mixing material in the mixer is completely finished. If the mixer is deactivated for more than 30 minutes, the mixer must be thoroughly cleaned before mixing. In order to ensure the continuity of the infusion pot, an emergency mixer shall be used when filling the bored pile.

Section 3 Bored Pile Filling

After the beginning of the perfusion work, it must be carried out continuously and the interval between perfusion is to be as short as possible. The time taken to remove the catheter is strictly controlled, generally not exceeding 15 minutes, and the work can not be stopped halfway; in the process of perfusion, the height of the fistula is detected at any time. Remove or lift the catheter, pay attention to maintain a proper depth, the depth of the catheter is generally maintained at 2 - 4m, the maximum depth is not greater than

6m. Pay attention to several issues:

(1) The control of the lower end of the conduit from the bottom of the pile is 0.3-0.4m; when everything is ready and the sediment layer at the bottom of the measuring hole exceeds the standard, the shot (radio) pipe is used to shoot for 3-5 minutes.

(2) The depth at which the catheter is buried in the crucible is not less than 1.0 m at any time.

(3) The actual pile top elevation of underwater infusion concrete shall be higher than the design elevation of the pile top by approximately 0.5m.

(4) It is strictly forbidden to break the pile due to water leakage from the conduit or the water entering the bottom of the conduit (that is, the bottom of the conduit cannot be sealed), ensuring construction quality.

(5) After the concrete has been poured, the upper part of the pile shall be initially set and the fixing measures for the steel cage shall be lifted to ensure that the steel cage shrinks with the shrinkage of the concrete to avoid the loss of adhesive force.

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