What Is an Impact Drill?

Impact drills rely on rotation and impact to work. A single impact is very slight, but an impact frequency of 40,000 times per minute can produce continuous forces. Can be used on natural stone or concrete. There are adjusting knobs on the drill chuck during impact drill work, which can be adjusted in two ways: ordinary electric drill and impact drill. However, the impact drill uses the gears on the inner shaft to beat each other to achieve the impact effect, and the impact force is far less than the electric hammer. It is not suitable for drilling reinforced concrete.

The impact mechanism of the impact drill has canine teeth and

Mainly applicable to

(1) Power switch.

(2) Reverse limit switch.

(3) Drill chuck.

(4) Power supply voltage regulation and clutch control torque.

(1) Special spare parts for electric drills.

(2) Super drill chuck.

(3) Dedicated drill chuck key.

(4) Adjustable auxiliary depth scale on the body.

(5) Diamond drill.

(6) Plug the power cable.

(7) Carbon brushes and terminals.

(8) Auxiliary handle and

(1) Attention must be paid when working, not only to keep a clear head, but also to operate the power tool rationally and be tired. Drinking or taking is strictly prohibited.

The impact drill has a double insulation design, which is safe and reliable in operation. It does not require a protective ground (zero connection) when used. It can be used with a single-phase two-pole plug. It can be used without wearing insulating gloves or shoes In order to make the operation convenient, flexible and powerful, the impact drill is usually equipped with an auxiliary handle. Due to the double insulation of the impact drill and no grounding (zero connection) protection, special care should be taken to protect the rubber-sheathed cable. When moving the drill by hand, you must hold the drill handle. Do not drag the rubber sheathed cable when moving. Rubber-sheathed cables do not allow wheels to roll and stand on feet; they prevent rat bites.

Impact drills cannot be used as electric drills in general:

1.Measurement and positioning

After leveling the site, the center position of the drill hole was determined according to the design pile position. And do a cross-shaped pile protection, in preparation for drilling and reinforcement cage positioning inspection of the pile position.

2.Buried steel protective cylinder

Underwater pier steel protection tube

Assemble the steel guard cylinder guide on the drilling platform, measure and set the pile position, butt the steel guard cylinder, hoist the steel guard cylinder into the water, adjust the tilt and position of the guard cylinder, and slowly enter the bed to stabilize the installation. Sinking Installation of drilling rigs to start the construction of bored piles on the water

During the vibration sinking of the steel protective cylinder, it is necessary to accurately locate, track, monitor and adjust to meet the requirements of the specification and ensure the construction of bored piles. The steel protective cylinder is rolled with A3 steel plate with a thickness of 4-12mm, and the inner diameter of the protective cylinder should be 40cm larger than the diameter of the pile. The steel protective tube is manufactured in sections in the workshop. After the platform is docked, it is sunk as a whole. At any time, the wooden wedge is used to adjust the deviation between the guide frame and the protective tube. The bottom of the protective tube is required to reach the top surface of the pebble layer. The top of the protection tube should be 2.0m higher than the construction water level or groundwater level.

Shoal and land bored pile steel jacket

An island should be built before the construction of piles in the river beach, and the height of the island should be 0.5m higher than the construction ground.

The steel protective cylinder is rolled with A3 steel plate with a thickness of 4-12mm, and the inner diameter should be greater than 40cm.

The buried depth of the protective cylinder shall meet the following requirements: the clay soil shall not be less than 1m, and the sandy soil shall not be less than 2m. When the surface soil is soft, the protective tube is buried in the harder and denser soil layer for at least 0.5m. A protection tube is buried on the shore, backfilled with clay around the protection tube and layered and compacted; the deviation between the top center of the protection tube and the design pile position is not more than 5cm, and the inclination is not more than 1%. To build islands in water, the protective tube should be buried 1m below the riverbed.

3.Making mud

Excavate the mud pool, select and prepare a good pulping clay or bentonite, the slurry volume is 2 times the concrete volume of the pile, and the mud specific gravity can be adjusted in time according to the drilling of different strata. The mud performance indicators are as follows:

Mud specific gravity: When drilling with a tubular drill, the specific gravity of the mud entering the pool can be 1.1 to 1.3; when drilling with a solid drill, the specific gravity of the mud at the bottom of the hole should not be greater than 1.3 when using clay or silt. In the pebble layer, the specific gravity of the mud at the bottom of the hole should not be greater than 1.4, and when it is rock, the specific gravity of the mud at the bottom of the hole should not be greater than 1.2.

Viscosity: General formations 18 to 24, loose and easily collapsed formations 22 to 30s.

Sand content: The fresh mud is not more than 4%.

Colloid ratio: not less than 95%.

PH value: should be greater than 11.5.

4.Drilling

Installing a rig

After the drilling platform is set up, move the drilling rig to the pile position and use the steel pillow as the machine base to stabilize the base. The base of the drilling rig is tightened cross-symmetrically with an inverted block to ensure that no displacement or subsidence occurs during drilling and operation. The frame and drill pipe should be vertical. The center of the drill bit, drill pipe, and drill diameter should be on a vertical line. The maximum deviation should not be greater than 50mm to ensure the correct hole position and straight drilling. Adjust the rig chassis to a horizontal state and stabilize it. Carefully align the drill with the design center, cover the sealing plate, test the rotation several times, and monitor the verticality of the drill pipe so that the lifting pulley on the top of the rig, the center of the turntable and the center of the pile hole are on the same vertical line. When the derrick is temporarily removed, a mark should be made to ensure the accurate position after resetting and realignment if necessary. The placement position of the drilling rig should be reasonably arranged in accordance with the platform's bearing conditions, and the drilling sequence should be uniformly arranged to avoid interference. In gravel soils, cross drills should be used in rock formations, and tubular drills should be used in clay and sandy soils.

Drilling

Pillars are drilled with impact drills. When drilling, open the hole into the bottom section of the protective cylinder, pour a small piece of stone-clay clay mixture (ratio about 1: 1) into the protective cylinder with a small stroke, and pay attention to maintaining the guidance of the hammer during construction to ensure the verticality of the hole. . The drilling operation should be continuous, and the drilling mud sampling test should also be performed frequently, and it should be adjusted in time if it does not meet the requirements. The purpose is to make a smooth and solid transition between the protective cylinder and the silt layer. After entering the pebble layer, add a high specific gravity ( = 1.3) high-quality mud and a small amount of cement. Using hammer-guided impact drilling to make the pebble layer a hard hole wall to prevent hole collapse until the design elevation.

When making holes by the impact method, small-stroke openings should be used to make the newly formed holes solid, straight, and round, which can play a guiding role and prevent the orifice from collapsing. After the drilling depth exceeds the full height and stroke of the drill bit, normal impact can be performed. Medium and large strokes should be used for hard drifting and pebble formations, and medium and small strokes should be used for loose formations.

Impact drilling, in order to prevent the shock vibration from causing the wall of the adjacent hole to collapse or affecting the solidification of the poured concrete of the adjacent hole, the drilling of the adjacent hole should be completed after the concrete has been poured and the compressive strength of 2.5 MPa is reached.

When drilling, there should be spare drill bits, which are used alternately. When the drill bit wear exceeds 1.5cm, it should be replaced and repaired in time.

When drilling in sandy soil or soft soil layer, it is easy to collapse the hole. Should use flat bottom drill cone, control the footage, light pressure, low gear slow speed, large pump capacity, thick mud drilling.

Mud replenishment and purification: A sufficient amount of mud should be prepared before the start. During drilling, if the mud is lost or missing, it should be replenished. And the mud index should be checked on time according to the mud inspection regulations. In case of soil layer changes, the number of inspections should be increased, and the mud index should be adjusted appropriately.

For drilling 2m or stratum change, drill slag samples should be taken in the mud tank, the soil quality should be identified and recorded, the drill slag should be removed in time and the mud should be replaced, so that the drill cone is often drilled into fresh formations. At the same time, pay attention to the changes of the soil layer. Slag samples should be taken at the changes of the rock and soil layers. The soil layer should be identified and recorded in the record table for checking with the geological profile.

terminal hole

When the borehole reaches the design elevation hole position, check the hole depth, hole diameter, hole position and hole shape, inclination, and the geological condition of the hole bottom, then fill in the final hole record, and promptly notify the supervision engineer to the site for inspection and acceptance. After passing, they are allowed to enter the next process. The hole depth, hole diameter, and inclination meet the following requirements: the hole depth is not less than the designed hole depth and enters the design soil layer; the hole diameter is not less than the designed hole diameter; the inclination is less than 1% of the hole depth; the hole position deviation is 100mm (50mm for passenger dedicated lines).

Clear hole

Impact drills generally use slag extraction to clear holes. The thickness of the bottom of the hole should meet the design requirements. When there is no design requirement, the thickness of the bottom of the column pile should be no more than 5cm for passenger transportation, and no more than 10cm for the passenger-cargo line. The thickness of sediment dedicated passenger line should be no more than 20cm, and the total passenger and freight line should be no more than 30cm.

The impact drill rig raises the bladed heavy drill (impact hammer) to a certain height through the frame and the hoist, and cuts the broken rock layer or the impact soil layer to form holes by the free-falling impact force.

Impact drills are cruciform, I-shaped, herringbone, etc. Cross-shaped impact drills are commonly used.

Before punching, a steel protective cylinder should be buried, and wall materials should be prepared.

After the percussion rig is in place, the center of the calibration hammer is aligned with the center of the protective cylinder. The stroke should be lifted in a range of 0.4 to 0.8m, and stones and mud should be added to protect the wall in time. After the protective cylinder sinks 3 to 4m, the stroke can be Raise to 1.5 2.0m, switch to normal impact, and measure and control the relative density of mud at any time.

During the construction, the damage of the wire rope should be checked frequently, and the tightness of the clamper and the flexibility of the steering device should be avoided to avoid drilling.

Percussion drilling is a drilling method that uses the kinetic energy of percussion drill motion to generate impacts and achieve drilling in broken rock formations. The forces that make the impact cone move are pneumatic, hydraulic and gravity. More than 2200 years ago, China has applied percussion drilling methods for drilling salt and water wells. In 280 AD, the deepest wells drilled by impact reached 200 feet. After the emergence of rotary drills, impact drills have also been used. The percussion drilling rig is simple, the equipment cost and use cost are low, the operation process is simple, and drilling in the gravel layer and the broken (or strongly weathered) bedrock is economical and effective. At present, it is still widely used in engineering geological drilling, sand ore drilling, farm water well drilling, and engineering construction drilling.