Common Problems And Methods of Rotary Drilling Rigs in Construction

Rotary pile construction quality control points

1、Construction quality quality pre-control

(1) Piling machine performance check. After the pile set is installed, the construction unit should be urged to check the main performance of the pile machine. 

(2) Hole formation process evaluation. Through trial hole formation, determine the drilling speed of the drilling rig in different soil layers on the site, the specific gravity of wall mud, and the quality of hole formation for preliminary analysis, and provide reference data for the next step of construction.

(3) Review the construction organization design and advocate the advancement, feasibility, safety and reasonableness of the plan, and the effectiveness of the quality assurance measures. 

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

(5) Planning for key parts and control targets.

2、Quality control points of construction process

(1) Pile Measurement: Establish control piles and protect them properly; for each pile positioning, short steel bars with paint markings can be inserted at the end; before each pile sheath is buried, it is also necessary to repeat the measurement again, using two control piles on the axial network as base points, and reviewing the pile position by vector forward intersection method, so as to prevent the pile position deviation caused by the deflection during the construction period.

(2) Sheath burial: the center of the sheath should coincide with the center of the pile by cross-checking, and the soil around the sheath should be filled up to protect the stability of the sheath.

(3) Piling position adjustment: some models of rotary drilling rigs have automatic adjustment display, but the self-control system should be reviewed periodically.

(4) Hole formation: During the drilling process, the mud level in the hole should always be kept at about 2m above the groundwater level. Check the self-control instrument display, prevent the drill bit from deviating to appear hole slanting, take out the ballast should be transported out of the working surface in time.

(5) into the rock: in the drilling to into the rock, according to the last bucket out of the slag and standard rock samples comparison, determine into the rock interface. If the rock layer is hard, change the auger bit and drill to a depth of not less than the design requirement (the specific depth can be determined on site according to the elevation of the rock layer).

(6) Final hole checking: check the depth, diameter and verticality of the hole by using measuring rope and hole gauge (or hole gauge).

(7) clear hole: according to the experience of trial hole, can start to clear the hole after hoisting the reinforcing cage, which is good for reducing the thickness of sinking ballast. The hole depth should be measured immediately after clearing, and compared with the hole depth after conduit installation to determine the thickness of sub-ballast.

(8) Concrete underwater pouring: the concrete pouring process is the key stage of pile formation, and also the quality problem prone stage, hidden strong, difficult to remedy afterward.

Problems and solutions encountered by rotary drilling rig in construction Rotary drilling rig construction, as an emerging construction process, is a kind of construction machinery suitable for hole-forming operation in construction foundation engineering. In the construction industry is more and more widely used, the construction of problems encountered more and more, in order to ensure the quality of the pile, in order to lay the foundation for the later construction, we need to understand the problems encountered in the construction of the drilling rig, know how to solve the problem, now summarizes and analyzes the rotary drilling rig in the construction of a variety of bad causes and their prevention and control measures.

1, collapsed hole in the filling process, such as found in the borehole casing slurry slurry bit suddenly rise overflow casing, followed by a sudden drop and bubbles, should be suspected of collapsed hole signs, can be used to detect the depth of the hammer. If the depth hammer was originally suspended in the concrete surface is not taken out of the buried can not be lifted up, or depth hammer detection of the concrete surface can not reach the original depth, a lot of difference, can be confirmed as a collapsed hole. The reason for the collapse of the hole may be around the foot of the barrel leakage, water level in the hole to reduce or in the tidal river, when the high tide water level difference in the hole to reduce, can not maintain the original hydrostatic pressure, as well as due to the barrel around the stacking of heavy loads or vibration of the machine can be caused by the collapse of the hole. Collapse should be identified after the occurrence of the cause, take appropriate measures, such as maintaining or increasing the water head, remove heavy objects, exclude vibration, etc., to prevent the collapse of the hole to continue, and then use the suction mud machine to suck out the mud collapsed into the hole, such as not to continue to collapse the hole can be resumed to normal perfusion. If the collapsed hole is not serious, the hole can be backfilled to above the collapsed hole position, and take measures to improve the mud performance, increase the water head, bury the deep cylinder and other measures to continue drilling. When the collapse hole is serious, the hole should be immediately backfilled with sand or small gravel sandwiched with clay, and after suspending for a period of time to find out the cause of the collapse hole, take corresponding measures to redrill. When the collapsed hole part is not deep, it can take the method of deeply burying the shield, and tamp the soil around the shield to re-drill the hole.

2, the hole body skewed in the event of body skewing, bending should analyze the reasons, to deal with. Generally, you can hold the drilling cone at the skewed place and sweep the hole repeatedly to make the hole straight; when the skew is serious, you should backfill the skewed place with cohesive soil, and then drill the hole again after the deposition is compacted.

3. Expanded hole, shrinkage of the hole should be prevented from collapsing and preventing the drilling cone from swinging too much. Shrinkage hole is too much wear and tear of drill cone, weld patch is not timely or due to the formation of water swelling of soft soil, clay mudstone caused by the former should pay attention to timely weld patch drill cone, the latter should be used to lose water rate of small high-quality slurry wall protection. Shrinkage has occurred in the hole is appropriate to use the drill cone up and down repeatedly to expand the hole diameter.

4, paste drilling, buried drilling paste drilling, buried drilling often occurs in the positive cycle (including submersible drilling rig) rotary drilling and percussion drilling. In this case, the mud consistency, the import and export of drilling slag, the size of the inner diameter of the drill pipe, and the slag removal equipment should be checked and calculated, and the appropriate feed should be controlled; if the drilling has been seriously muddled, the drilling should be stopped to put forward the drilling cone, and to remove drilling slag.

5, jamming drill jamming often occurs in the impact drilling. It is not advisable to lift the drill after jamming, but only to lift it lightly, and when it is not possible to lift it lightly, the drill cone can be impacted by a small impact drill or the drill residue around the drill cone can be loosened by the method of flushing and sucking before putting it forward.

6、Dropping the drilling material to drop the drilling material should be quickly salvaged with salvage forks, hooks, rope sets and other tools, if the falling body has been buried by sediment, should be in accordance with the aforementioned articles, the first to remove the mud and sand, so that the salvage tool to contact the falling body and then salvage. In any case, it is strictly prohibited for construction personnel to enter the borehole without shields or other protective facilities to deal with faults. When it is necessary to go down the borehole of shroud or other protective facilities, it should be checked that there is no harmful gas in the borehole and all safety facilities such as anti-poisoning, anti-drowning and anti-collapsing and burial should be prepared before action is taken. For rotary drilling rig construction of this new process, we still need to accumulate more experience, especially for the construction of the various problems encountered, we need to seriously summarize, analyze, and ensure that the same situation will not be encountered in the future at a loss. I believe that with the deep promotion of rotary drilling rigs, we will learn more and more to deal with the problem will become more and more simple, the work will be more and more smooth.