Rotary Excavation Construction Problems And Countermeasures for Deep And Large Piles

Problems and countermeasures of deep pile construction

1, construction efficiency is low, the main reason is to lift down the drilling tool takes up too much time, the efficiency of the drill pipe to transfer the drilling pressure is low.

Countermeasures: 

(1) raise the length of the drill bit, so that the amount of drilling ballast per drill is increased; 

(2) the drill bit with ventilation holes, in order to raise the speed of drilling; 

(3) such as not rock, try to use the mooring rod, in order to save the time of unlocking the upper.

2, the drilling rod failure rate rises sharply, after the lengthening of the drill pipe, the slenderness ratio of the drill pipe is particularly unreasonable, the construction and have to withstand greater torque and pressure, especially the machine locking rod and have to be frequently on the unlocking, so the failure rate of the drilling rod will rise sharply.

Countermeasures: 

(1) work site as flat and solid as possible to reduce the swing of the rig; 

(2) often correct the leveling system, so that the drill pipe work vertically; 

(3) pressurized drilling is strictly prohibited to the top of the drilling rig up; 

(4) in the drilling pipe to add the righting device.

3, the pile hole skew, the main reason is the stratum of uneven hardness and softness, the drill pipe lengthening the overall steel reduces, the drilling tool longer cumulative gap increases the drill bit swing increases.

Countermeasures: 

(1) increase the height of the drilling tool; 

(2) add a support ring on the drill pipe; 

(3) add a counterweight device on the upper part of the drill bit, and pressurize the bottom of the hole, so that the drilling tool will have a self-sagging effect when drilling.

4, hole accidents occur frequently, mainly in the hole wall instability collapse buried drilling.

Countermeasures: 

(1) Due to the lengthening of the construction time of deep pile, if the effect of wall protection is not good, the hole wall will be destabilized, and high-quality mud should be prepared; 

(2) The drill bit comes with ventilation holes, which reduces the impact and suction of the hole wall when lifting and lowering the drill.

Problems and countermeasures of large pile construction

1、Construction efficiency will drop sharply

Countermeasures: 

(1) choose reasonable drill bit (according to the stratum); 

(2) develop reasonable drilling program, if the rig capacity is enough, the stratum is soft, it is best to one diameter to the end of the hole, such as the efficiency of the progress of the footage significantly reduced significantly, must be used in the grading of the drilling, but must follow two principles, one is to guide drilling until the bottom of the hole and then change the large diameter drill bit to expand the hole, and secondly, the first drilling diameter is selected reasonable, generally drilling area is not less than Half of the total area.

2、Pile holes are easy to incline drill bit straight and drill pipe diameter difference is large, the height of the drill bit is small, the stratum is not uniform.

Countermeasures: 

(1) the drill pipe plus the righting device; 

(2) in the rig lifting height and lifting capacity is enough, as far as possible to increase the height of the bit; 

(3) graded drilling can also prevent slanting, small diameter drilling hole slanting is good to control, and then expanding the hole will be drilled in accordance with the original guiding hole trajectory when the drill bit. 

(4) If encountered especially easy to slope stratum, try to make a large length of coring cylinder drilling transition.

3、Many accidents in the hole (drill pipe breakage, dropping drill bit, difficulty in pouring soil from drill bit)

Reason: due to the large diameter of the drill bit, the self-importance, the drill rod load will be broken, drill rod pin broken caused by falling drill bit, drill bit bottom plate weight plus full bucket ballast soil weight is very large, resulting in the drilling bucket open the door difficult.

Countermeasures: 

(1) strictly in accordance with the drilling rod is using the method of operation; 

(2) drilling rod and drilling bit is best to use double pins, and with the steel wire rope to the drilling bit and drilling rod square head above the tray, even if it is the pin and the square head is broken also is not to drop the drilling bit to the hole; 

(3) drilling bit to the ground and then open the door, or lifting the drilling bit away from the ground high-speed counter-rotation, so that the two layers of the bottom plate between the inlet opening, ballast soil automatically leaks down.

END