阅读说明：本技术 一种潜孔钻配合冲击钻桩基成孔施工方法 (Down-the-hole drill and impact drill matched pile foundation pore-forming construction method ) 是由 惠鹏嘉 李秉强 杨映军 张恩健 刘章宝 胡九林 杨立君 杨树鹏 于 2020-06-02 设计创作，主要内容包括：本发明属于桥梁基础工程领域,是一种潜孔钻配合冲击钻桩基成孔施工方法,在冲击钻钻进前,首先采用潜孔钻在桩位处钻孔、松动爆破预裂,破坏岩层的整体性,增加岩石摩擦撞击面,在随后的冲击钻冲击成孔时增加破碎岩石间的摩擦、撞击,进而加快施工进度、缩短施工周期。本发明的有益效果：本法可操作性强,有效地解决了坚硬岩层区域灌注桩钻进困难的问题,缩短冲击钻成孔时间,缩短了桩基施工周期,降低了施工成本。(The invention belongs to the field of bridge foundation engineering, and relates to a down-the-hole drill and impact drill pile foundation pore-forming construction method. The invention has the beneficial effects that: the method has strong operability, effectively solves the problem of difficult drilling of the cast-in-place pile in the hard rock stratum area, shortens the hole forming time of impact drilling, shortens the construction period of the pile foundation and reduces the construction cost.)

1. A down-the-hole drill cooperation impact drill pile foundation pore-forming construction method is characterized in that: 1) preparing in advance, formulating a blasting construction scheme according to the rock stratum detection data and the bridge foundation design data, and determining the number, the interval, the hole depth and the dosage of the drilled holes; 2) repairing the drilling operation platform to expose the drilling operation surface of the down-the-hole drill; 3) determining the relative positions of a down-the-hole drill drilling point and an impact drilling point, arranging the down-the-hole drill drilling point around the center of the impact drilling hole, and uniformly distributing the down-the-hole drill drilling points along a circumference; 4) aligning the down-the-hole drill equipment with the drilling point of the down-the-hole drill, fixing the down-the-hole drill equipment after the alignment is finished, and correcting the verticality of the drill rod; 5) drilling is started, and the drilling depth is controlled to be more than 60cm of the designed elevation of the pile bottom; 6) after the down-the-hole drill is drilled, removing the down-the-hole drill, installing a PVC liner tube, filling explosives, detonators and connecting a detonating tube, and pre-cracking a hard rock layer by explosive blasting; 7) and (4) positioning and drilling the percussion drill, if the percussion drill does not drill smoothly, re-performing the steps of drilling and blasting of the down-the-hole drill, and finally completing the drilling of the pile foundation hole by the percussion drill.

2. The downhole drill and impact drill pile foundation hole forming construction method as claimed in claim 1, wherein the method comprises the following steps: when the aperture of the impact drill is 170cm, the distance between the drilling point of the down-the-hole drill and the center of the impact drill is 50cm, the aperture of the down-the-hole drill is 10cm, and the PVC liner tube is 8 cm.

3. The downhole drill and impact drill pile foundation hole forming construction method as claimed in claim 2, wherein the method comprises the following steps: the down-the-hole drill has three holes, and the connecting lines of the hole centers form an equilateral triangle.

4. The downhole drill and impact drill pile foundation hole forming construction method as claimed in claim 1, wherein the method comprises the following steps: and (4) controlling the hole site deviation of the down-the-hole drilling equipment and the down-the-hole drilling point in the step 4) to be within 20 mm.

5. The downhole drill and impact drill pile foundation hole forming construction method as claimed in claim 1, wherein the method comprises the following steps: multiple times of blasting are adopted, so that the influence of superblasting on the bearing capacity of the pile bottom is avoided; during the first blasting, the dosage of the single-hole long rice is controlled within 0.6 kg; according to the blasting effect, the dosage is increased or decreased and the number of the blasting holes is increased or decreased on the basis of the original blasting to continue blasting.

6. The downhole drill and impact drill pile foundation hole forming construction method as claimed in claim 1, wherein the method comprises the following steps: and 4) controlling the verticality deviation of the drill rod within 0.5%.

Technical Field

The invention belongs to the field of bridge foundation engineering, and relates to a pile foundation pore-forming technology of a hard rock stratum.

Background

With the rapid development of the traffic industry in China, the proportion of bridge engineering in highway construction is gradually increased, and a bored pile foundation is the most widely applied bridge foundation, and rotary drilling and impact drilling hole forming modes are mostly adopted. When a hard rock stratum is encountered, the rotary drilling hole-forming drill bit is fast worn, the requirement on the machine type is high, the construction cost is high, and the influence of natural conditions such as terrain is serious; the traditional impact drill has long hole forming period, fast abrasion of the drill bit, long time of welding hammer and serious waste of construction resources.

Disclosure of Invention

The invention aims to provide a pile foundation hole forming construction method by using a down-the-hole drill and an impact drill in a matched mode to improve the drilling efficiency.

The technical scheme of the invention is as follows: a down-the-hole drill cooperates with the pile foundation pore-forming construction method of the percussion drill, 1) prepare in advance, according to survey data of rock strata and basic design data of bridge, formulate the construction scheme of blasting, confirm drilling quantity, interval, hole depth and dosage; 2) repairing the drilling operation platform to expose the drilling operation surface of the down-the-hole drill; 3) determining the relative positions of a down-the-hole drill drilling point and an impact drilling point, arranging the down-the-hole drill drilling point around the center of the impact drilling hole, and uniformly distributing the down-the-hole drill drilling points along a circumference; 4) aligning the down-the-hole drill equipment with the drilling point of the down-the-hole drill, fixing the down-the-hole drill equipment after the alignment is finished, and correcting the verticality of the drill rod; 5) drilling is started, and the drilling depth is controlled to be more than 60cm of the designed elevation of the pile bottom; 6) after the down-the-hole drill is drilled, removing the down-the-hole drill, installing a PVC liner tube, filling explosives, detonators and connecting a detonating tube, and pre-cracking a hard rock layer by explosive blasting; 7) and (4) positioning and drilling the percussion drill, if the percussion drill does not drill smoothly, re-performing the steps of drilling and blasting of the down-the-hole drill, and finally completing the drilling of the pile foundation hole by the percussion drill.

Preferably: when the aperture of the impact drill is 170cm, the distance between the drilling point of the down-the-hole drill and the center of the impact drill is 50cm, the aperture of the down-the-hole drill is 10cm, and the inner diameter of the PVC liner tube is 8 cm.

Preferably: the down-the-hole drill has three holes, and the connecting lines of the hole centers form an equilateral triangle.

Preferably: and (4) controlling the hole site deviation of the down-the-hole drilling equipment and the down-the-hole drilling point in the step 4) to be within 20 mm.

Further: multiple times of blasting are adopted, so that the influence of superblasting on the bearing capacity of the pile bottom is avoided; during the first blasting, the dosage of the single-hole long rice is controlled within 0.6 kg; according to the blasting effect, the dosage is increased or decreased and the number of the blasting holes is increased or decreased on the basis of the original blasting to continue blasting.

Preferably: and 4) controlling the verticality deviation of the drill rod within 0.5%.

The process principle of the method is as follows: the down-the-hole drill has high efficiency of drilling small-aperture holes in a hard rock stratum; before the impact drill drills, a down-the-hole drill is firstly adopted to drill holes at a pile position, loosen and blast pre-splitting, the integrity of a rock stratum is damaged, a rock friction impact surface is increased, friction and impact among broken rocks are increased when the subsequent impact drill strikes a hole, the construction progress is accelerated, and the construction period is shortened.

The invention has the beneficial effects that: the method has strong operability, effectively solves the problem of difficult drilling of the cast-in-place pile in the hard rock stratum area, effectively shortens the hole forming time of the impact drill, further shortens the construction period of the pile foundation and reduces the construction cost.

Drawings

FIG. 1 is a process flow diagram of the present invention;

fig. 2 is a diagram of an example percussion drilling and blast drilling arrangement.

Detailed Description

A down-the-hole drill cooperates with the pile foundation pore-forming construction method of the percussion drill, 1) prepare in advance, according to survey data of rock strata and basic design data of bridge, formulate the construction scheme of blasting, confirm drilling quantity, interval, hole depth and dosage; 2) repairing the drilling operation platform to expose the drilling operation surface of the down-the-hole drill; 3) determining the relative positions of the down-the-hole drill drilling points and the impact drilling holes, arranging the down-the-hole drill drilling points around the center of the impact drilling holes, and uniformly distributing the down-the-hole drill drilling points (more than three in number) along one circumference; the aperture of the impact drilling hole is 170cm, and the distance between the drilling point of the down-the-hole drill and the center of the impact drilling hole is 50 cm; 4) aligning the down-the-hole drill equipment with the drilling point of the down-the-hole drill (the deviation of the hole position is controlled within 20 mm), fixing the down-the-hole drill equipment after the alignment is finished, and correcting the verticality of the drill rod (the deviation of the verticality is controlled within 0.5%); 5) drilling a hole with the aperture of 10cm by using a down-the-hole drill, and controlling the depth of the drilled hole to be more than 60cm of the designed elevation of the pile bottom; 6) after the down-the-hole drill is drilled, removing the down-the-hole drill, installing a PVC liner tube (the inner diameter is 8cm), filling explosives, detonators and connecting detonating tubes, and pre-cracking a hard rock stratum by explosive blasting; 7) and (4) positioning and drilling the percussion drill, if the percussion drill does not drill smoothly, re-performing the steps of drilling and blasting of the down-the-hole drill, and finally completing the drilling of the pile foundation hole by the percussion drill.

In order to avoid the influence of superexplosion on the bearing capacity of the pile bottom, multiple times of blasting are adopted. During the first blasting, the dosage of the single-hole long rice is controlled within 0.6 kg; according to the blasting effect, the dosage is increased or decreased and the number of the blasting holes is increased or decreased on the basis of the original blasting to continue blasting.

TABLE 1 Main materials

TABLE 2 Main construction Equipment

Serial number	Device name	Unit of
			1	Crawler-type down-the-hole drill	Table (Ref. Table)
2	Impact drill	Table (Ref. Table)

Benefit analysis of the method: compared with the traditional percussion drilling construction process, the construction period of each pile foundation (phi 1.7m, pile length 12m) can be shortened by half, the construction period is saved by about 22 days, the electricity consumption is saved by about 7750 degrees, and 22 manual and mechanical shifts are saved.

Economic benefit according to each pile foundation concrete calculation contrast (phi 1.7m, pile length 12m)

The construction cost accounting of the existing normal impact drill is as follows:

(1) labor cost: 12m/0.4 m/day 1.5 (welding hammer pause) 1 person 150 yuan/day 6750 yuan.

(2) Rig shift cost (including appurtenance, etc.): 12m/0.4 m/day 1.5 (welding hammer pause) 1 station 220 yuan/day 9900 yuan.

(3) Electric charge: (12m/0.4 m/day 10 hours/day 45KW/h +100 degrees/20 hammers) 0.6 yuan/degree 9300 yuan.

(4) Sporadic material costs (electrode, hammer, etc.): 2000 yuan.

Cost totalization: 6750+9900+9300+2000 as 27950 yuan.

The cost accounting of the construction method of combining the down-the-hole drill and the percussion drill for hole forming is as follows:

(1) the down-the-hole drill construction cost: 150 yuan/m 11 m/hole 3 hole 4950 yuan (including entrance and exit field cost, sporadic material cost).

(2) Explosive and service costs: 0.6 kg/well/m 11 m/well 3 well 15 yuan/kg +30000 yuan/50 equal to 897 yuan.

(3) Labor cost: 12m/0.8 m/day 1.5 (welding hammer pause) 1 person 150 yuan/day 3375 yuan.

(4) Rig shift cost (including appurtenance, etc.): 12m/0.8 m/day 1.5 (welding hammer pause) 1 station 220 yuan/day 4950 yuan.

(5) Electric charge: (12m/0.8 m/day 10 hours/day 45KW/h +100 degrees/time 10 hammers) 0.6 yuan/degree 4650 yuan.

(6) Sporadic material costs (electrode, hammer, etc.): 1000 yuan.

Cost totalization: 4950+897+3375+4950+4650+1000 ═ 19822 yuan.

Through the calculation, the down-the-hole drill is matched with the impact drill pile foundation to form a hole, and the construction method saves 8128 yuan per root compared with the normal impact drill construction.

Examples of the applications

The project name is as follows: LJ-10 contract segment of Shaanxi Ankang Pingli-Zhiping expressway

Engineering site: zhengqing county, Ankang city, Shanxi province

Construction period: 8 months in 2017 to 1 month in 2020

Construction cost: 3.31 billion yuan

Overview of the engineering: the high-speed LJ-10 contract segment of the Pingzheng is located in the town of the ox-head shop in Zhengchang county, Ankang city, and the line is laid along the south river, and the total length is 4.03 km. The main engineering quantities include: the foundation structure comprises 1822m/1 of a grand bridge, 1546m/7 of a grand bridge and 397m/5 of a middle bridge (comprising 559 cast-in-situ piles, 319 lanes of tie beams, 14 bearing platforms, 477 pillars, 28 rib plates, 8U-shaped bridge platforms, 252 capping beams (platform caps), 968 precast beam plates and 3 span/1 of cast-in-situ box girders). The project bridge pile foundation rock stratum is hard, especially bamboo gateway 1^#The design rock stratum of the pile foundation of the grand bridge is diabase, the intensity is between 30MPa-80 MPa; the construction progress of the traditional impact drill is 25cm-40 cm/day, and the construction progress is slow. In order to accelerate the construction progress of the pile foundation and shorten the overall project period, the project pile foundation construction method adopts the down-the-hole drill matched impact drill pile foundation pore-forming construction method, the pile foundation construction period is effectively saved by about 3 months, the direct cost is saved by more than 40 ten thousand yuan, and a good effect is obtained.