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# Application of square pile machine in cutting of precast reinforced concrete square pile

In recent years, prefabricated reinforced concrete square piles have the advantages of convenient production and processing, fast sinking speed, and safe and reliable connection of piles. They are especially suitable for soft soil foundations mainly based on friction and supplemented by end bearing capacity. Duration. However, when the upper pile head is broken after sinking, it is often difficult to improve the efficiency. At present, the main treatment methods for pile heads are: air picks, hydraulic picks, breakers, etc., which mainly destroys the pile concrete through the impact of external forces, which easily affects the mother pile, and has low construction efficiency, high cost, and high noise. The environmental hazards during manual construction are complex and the safety risks are high.

This article takes the KP500S square pile machine produced by Jiangsu Taixin Machinery Technology Co., Ltd. and the supporting KPS15 hydraulic pump station as an example to construct a construction site in Suqian, Xuzhou. The structure, construction method and construction cost of the other pile pile machine are analyzed for square pile machine operation. The promotion of construction methods has accumulated some experience.

1, composition and introduction of square pile machine

The square pile machine (Figure 1), also known as a full-hydraulic pile cutter, is a type of high pressure hydraulic oil that is simultaneously supplied to multiple oil cylinders by a power source. The oil cylinder directly drives the drill rod and squeezes the pile body at the same time. Special shape equipment for crushing concrete. It is mainly composed of pile cutting frame, oil cylinder, drill rod, hanging chain, oil pipe and other components.

Figure 1 square pile machine

Figure 1 square pile machine

2, construction site profile

The construction site is located in the city of Suqian, Xuzhou. It is a second-phase project of a commercial house. There are a total of 8 buildings designed, which use reinforced concrete prefabricated square piles as the pile foundation, and the pile diameter is 400mm × 400mm. After the elevation of the sinking pile, the height of the cut-off pile is about 1.2 meters. There are about 120 sinking piles in each building, and there are 955 square piles in the whole project. Party A requires that each building be broken within 3 days after sinking. The first building uses artificial wind pickers to break piles, and the efficiency is not ideal. From the second building, the construction of the square pile machine began. figure 2

Figure 2 Construction site

Figure 2 Construction site

3. Pile cutting construction by square pile machine

1. Preparation for construction

1.1 KP500S square pile machine is used for pile cutting construction. The power source is KPS15 hydraulic pump station, and the equipment is moved by 50 tower cranes. The main parameters of KP500S square pile machine are shown in Table 1.

1.2 According to the size of the site, the cable of the hydraulic pump station is 60 meters. The hydraulic hose connected between the pumping station and the pile driver is 80 meters.

2. Construction process flow (see Figure 3)

Figure 3 Construction process

Figure 3 Construction process

3. Construction process

3.1 Device connection

The tower crane first lifts the KPS15 hydraulic pump station to the middle of the pile group. After checking the hydraulic oil level, connect the oil pipes and cables, turn on the machine and confirm that the oil pump is turning in the correct direction.

3.2 Pile cutting process

Lift the KP500S with a tower crane and use it as a moving vehicle. The construction crew will command the auxiliary pile driver to insert it into the pile body. When cutting the first section, cut it about 400mm from the upper end surface of the pile (Figure 4) In the future, it will be cut once every not more than 300mm. When cutting the last section, first clear the broken concrete falling around the pile body, and then cut the final line at the level line.

Figure 4 First nesting

3.3 Pile clearing

After cutting, transfer the pile cutter to the next pile and repeat the previous step. The remaining broken piles (Fig. 5) were cut by two construction workers using reinforcing bar pliers to cut the transverse bars, and the broken concrete was removed with an iron drill, and the scattered steel bars were recovered.

Figure 5 The broken pile after cutting

3.4 Special Pile

As a result, there were 6 long piles in a foundation pit. The length to be cut is above 3M. After using the method of slicing, the excess part of the main steel bar is cut by gas cutting, and finally the cut pile is lifted out of the foundation pit by a tower crane for processing (Figure 6), and the steel bar is recovered.

Figure 6 Lifting and cutting the broken pile

4. Economic analysis

The average height of each pile at this site is 1.2 meters. Party A provides power and tower cranes. The pile cutting fee is 35 yuan each. The cut steel bars are handled by Party B. The estimated value of the rebar cut by each pile is 5 yuan on site. We conduct economic analysis by comparing the two methods of manual pile cutting and equipment pile cutting:

4.1 Artificial broken pile (8 hours)

4.1.1 Pile cutting efficiency: one per hour, 8 cuttings per day, gross profit: 8 × (35 + 5) = 320 yuan.

4.1.2 Pile cutting costs:

4.1.2.1 Axle drill rod loss:

The cost of the drill rod is 20 yuan / piece. The air pick drill rod can be used repeatedly after grinding and repairing. Calculated by consuming 5 sticks per day. Loss of each pile: 5 × 20/8 = 1.25 yuan / root.

4.1.2.2 Equipment depreciation expense:

According to national regulations, the depreciation period of machinery is 10 years, and the residual value of fixed assets is 5%. We calculate it based on 5 years and the residual value rate is 5%.

购 Purchase cost of air compressor and air pick: 1500 + 250 = 1750 yuan

Leap year depreciation rate = (1-estimated net profit residual value rate) / estimated useful life × 100%

Leap year depreciation: 1750 × (1-0.05) /5=332.5 yuan

The next day's depreciation amount is: 332.5 / 365 ≈ 1 yuan / day

Other costs: 1 yuan per pile

Total cost: 1.25 + 1 + 1 = 3.25 yuan / root

日 The daily income of artificial pile cutting: 8 × (40-3.25) ≈294 yuan

4.2KP500S pile cutting: (8 hours)

Equipment preparation time: half an hour including: lifting the pump station, connecting cables and hydraulic hoses.

4.2.1 Pile-cutting efficiency: 7 minutes / root (Table 2), pile-cutting per day:

(8-0.5) × 60/7 = 64, gross income: 64 × 45 = 2880 yuan.

4.2.2 Pile cutting costs:

4.2.2.1 Drill rod loss: 340/2000 × 8 = 1.26 yuan / piece

340: Cost of drill rod. unit: yuan

2000: Drill rod life. Unit: root

8: Number of drill rods per device

4.2.2.2 Labor cost: 150 yuan per person per day, with three people as standard

人工 Labor cost per pile: 150 × 3 / 64≈7 yuan / root

4.2.2.3 Workers' lunch fee: 100 yuan. Converted into the cost of each root: 100/64 = 1.56 yuan / root

4.2.2.4 Equipment depreciation expense:

According to national regulations, the depreciation period of machinery is 10 years, and the residual value of fixed assets is 5%. We calculate it based on 5 years and the residual value rate is 5%.

Equipment procurement costs:

采购 KP500S square pile driver and KPS15 hydraulic pump station purchase cost: 150,000 yuan

Leap year depreciation rate = (1-estimated net profit residual value rate) / estimated useful life × 100%

Leap year depreciation: 150000 × (1-0.05) / 5 = 28500 yuan

The next day's depreciation amount is: 28500/365 ≈ 78 yuan

Cost per pile: 78 / 64≈1.22 yuan / root

Other costs: such as hydraulic oil loss, maintenance, repair costs, etc., we estimate 2 yuan each.

总 The total cost of each pile is: 1.26 + 7 + 1.56 + 1.22 + 2≈13 yuan

Next day's earnings: 64 × (40-13) = 1728 yuan

Through the analysis of the above data, the manual pile breaking tool is simple to use and the cost of cutting single roots is very low. However, the "human sea tactics" and the efficiency are very low, and it has been increasingly unable to meet the requirements of modern construction. In the cost structure of the square pile machine, the cost of workers also accounts for a large part, and there is a lot of room for subsequent improvement. Compared to manual pile breaking, the simple and efficient operation of the square pile machine also makes it possible to create better economic benefits.

5, concluding remarks

With the continuous increase of labor costs, the trend of replacing manual construction with machinery and equipment is becoming more and more obvious. Compared with other pile breaking methods through the construction case of a square pile machine in Suqian, the square pile machine has the following outstanding advantages.

1. Effectively reduce the number of construction personnel, improve construction efficiency, and reduce construction costs. During construction, a suitable working platform can be selected according to the site construction conditions;

2. The new pile cutting method has no effect on the mother pile and can effectively guarantee the construction quality of the project;

3. Strong adaptability to small and low-lying spaces. By choosing the matching of different platforms and adjusting the length of the hanging chain, it can adapt to different construction environments;

4. During the construction, the safety distance between the equipment and the pile head and the operator is large, and people do not need to enter the foundation pit, which can effectively prevent safety risks.

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