Construction steps of rotary drilling rig

A, rotary drilling rig construction process

Second, the control points of rotary excavation pile construction quality

1, construction quality quality precontrol

(1) performance inspection of pile driver. After the pile driver is assembled, the construction unit shall be urged to check the main performance of the pile driver.

(2) Evaluation of pore-forming process. Through the trial drilling, the drilling speed, the specific gravity of the wall protection mud and the hole-forming quality of the drilling rig in different soil layers of the site are determined, which provides reference data for the next construction.

(3) Review the construction organization design and advocate advanced, feasible, safe and reasonable schemes and effective quality assurance measures.

(4) Supervise the construction team to establish, improve and perfect the quality management system of the construction site according to the engineering requirements, and check the normal operation of the management system.

(5) Planning key parts and control targets.

2, the construction process quality control points

(1) Pile position measurement: control piles are established and properly protected; When each pile is positioned, short steel bars with paint marks on both ends can be inserted; Before each pile casing is buried, it needs to be retested. Based on the two control piles on the shaft network, the vector forward intersection method is used to check the pile position to prevent the deviation of pile position caused by deflection in the construction process.

(2) Embedding of the pile casing: use a cross to check that the center of the pile casing is coincident with the center of the pile, and the soil around the pile casing should be filled to ensure the stability of the pile casing.

(3) The pile driver is adjusted in place: some models of rotary drilling rigs have automatic adjustment display, but the automatic control system should be checked regularly.

(4) Hole-forming: During drilling, the mud level in the hole should always be about 2m higher than the groundwater level. Check the display of automatic control instrument, prevent the bit from deviating from the hole inclination, and remove the ballast soil on the working face in time.

(5) Rock entry: When drilling the rock, determine the rock entry interface according to the comparison between the slag taken out in the last bucket and the standard rock sample. If the rock stratum is hard, replace the auger bit and drill to a depth not less than the design requirements (the specific depth can be determined on site according to the elevation of the rock stratum).

(6) Final hole inspection: use measuring rope and hole gauge (or aperture gauge) to check the hole depth, aperture and verticality.

(7)? Hole cleaning: According to the experience of trial hole-forming, hole cleaning can be started after the reinforcing cage is hoisted, which is beneficial to reducing the thickness of ballast. After hole cleaning, the hole depth should be measured immediately and compared with the hole depth after conduit installation to determine the ballast thickness.

(8) Underwater concrete pouring: The concrete pouring process is a key stage of pile formation, and it is also a stage prone to quality problems, which is hidden and difficult to remedy afterwards.

Three. Problems and solutions of rotary drilling rig in construction

As a new construction technology, rotary drilling rig construction is a kind of construction machinery suitable for hole-forming operation of building foundation engineering. It is more and more widely used in the construction industry, and more and more problems are encountered in the construction. In order to ensure the pile quality and lay the foundation for the later construction, we need to know the problems encountered in the drilling rig construction and know how to solve them. This paper summarizes and analyzes the causes and preventive measures of various defects encountered in the construction of rotary drilling rig.

1, hole collapse

In the process of grouting, if it is found that the mud level in the drilling casing mud suddenly rises, overflows the casing, and then suddenly drops, and bubbles appear, it should be suspected to be a sign of hole collapse, which can be detected by sounding hammer. If the sounding hammer stopped hanging on the concrete surface and didn't take it out, it can't be lifted now, or the sounding hammer can't reach the original depth when detecting the concrete surface, and there are many differences, so it can be confirmed that it is indeed a hole collapse.

The hole collapse may be caused by water leakage around the bottom of the casing, and the water level in the hole decreases, or in tidal rivers, the water level difference in the hole decreases when the tide rises, and the original hydrostatic pressure cannot be maintained, and the hole collapse may be caused by the accumulation of heavy objects around the casing or the vibration of the machine.

After the hole collapse occurs, the reasons should be found out and corresponding measures should be taken, such as maintaining or increasing the water head, removing heavy objects and eliminating vibration. , to prevent the hole collapse from continuing, and then suck out the mud that has collapsed into the hole with a mud suction machine. If the hole collapse does not continue, normal grouting can be resumed. When the hole collapse is not serious, it can be backfilled above the hole collapse position, and measures such as improving mud performance, raising water head and burying casing can be taken to continue drilling. When the hole collapse is serious, all drilling holes should be immediately backfilled with sand or small gravel mixed with clay. After a period of suspension, find out the cause of hole collapse and take corresponding measures to re-drill. When the hole collapse position is not deep, the method of burying the casing can be used to tamp the soil around the casing and re-drill.

2. Well deviation

When the hole body is deviated and bent, the reasons should be analyzed and treated. Generally, a drill cone can be hung at the deviation to sweep the hole repeatedly to make the hole straight; When the deflection is serious, cohesive soil should be backfilled to the deflection, and drilling should be carried out after the deposition is dense.

3, reaming, shrinkage cavity

When reaming and reducing the diameter, measures should be taken to prevent hole collapse and excessive swing of the bit. Shrinkage is caused by excessive wear of drill bit, untimely welding repair or swelling of soft soil and clay mudstone in formation when it meets water. The former should pay attention to welding and repairing the drill bit in time, while the latter should adopt high-quality mud with low water loss rate to protect the wall. When shrinkage occurs, the drill should be used to sweep the hole up and down repeatedly to enlarge the aperture.

4. Paste drilling and buried drilling

Paste drilling and buried drilling often occur in rotary drilling and percussion drilling (including submersible drilling) in positive circulation. In this case, check and calculate mud consistency, drilling slag inlet and outlet, drill pipe inner diameter and slag discharge equipment, and control appropriate footage; If the drill bit is severely burned, stop drilling, take out the drill bit and remove the drill residue.

5. Stuck

Sticking often occurs in percussive drilling. After sticking, it is not advisable to lift the drill bit forcibly, but only gently. When the drill bit can't be lifted lightly, it can be lifted after being impacted or loosened by a small percussion drill cone.

6. Falling from the rig and falling objects

When drilling, tools such as harpoon, hook and noose should be used for quick fishing. If the falling objects have been buried by sediment, the sediment should be removed first, so that the fishing tools can contact the falling objects before fishing.

In any case, it is forbidden for construction personnel to enter the drilling hole without liners or other protective facilities to deal with faults. When it is necessary to drill holes in casing or other protective facilities, check that there is no harmful gas in the holes, and prepare safety facilities such as anti-virus, anti-drowning and anti-collapse.

We need to accumulate more experience for the new technology of rotary drilling rig construction, especially for all kinds of problems encountered in construction, we need to sum up and analyze carefully to ensure that we will not be at a loss when we encounter the same situation in the future. I believe that with the in-depth promotion of rotary drilling rig, we will learn more and more, handle problems more and more simply, and work more and more smoothly.

Fourth, the rotary excavator construction conditions

1. Scope of application: it is mainly suitable for the construction of sandy soil, cohesive soil, silt and other soil layers, and is widely used in the construction of various foundations such as cast-in-place piles, diaphragm walls and foundation reinforcement.

2. Equipment entry conditions: the road must be wide. Because the equipment will be transported to the construction site by large transport vehicles. ?

3. Site requirements: Because its own weight reaches 90 tons, the Wei bar of the frame is extremely high, and it is very difficult to walk the center of gravity. When walking, the guard bar must be tilted at a certain angle to ensure walking safety. If the vehicle rolls over, it will cause a large-scale accident, which may endanger casualties and the safety of surrounding areas, so site rolling and site leveling are very important.

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