Power transmission tower assembled retaining wall hand-dug pile construction method

Abstract

The present application belongs to the technical field of artificial hole digging pile construction of electric power engineering, and particularly relates to a transmission tower assembled retaining wall artificial hole digging pile construction method. The method comprises the following steps: step 1, pile hole positioning, and then installing lifting equipment; step 2, excavating soil, and installing the retaining wall with holes into the pile hole; step 3, using the lifting equipment to hoist the steel bars into the pile hole, binding the steel reinforcement cage, and installing the grouting pipe group on the steel reinforcement cage; and step 4, pouring concrete, and then performing pile bottom grouting. The construction method can reduce the weight of the retaining wall pipe piece, thereby reducing the difficulty of manual transportation and improving the transportation efficiency.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electric power engineering artificial hole digging pile construction, and particularly relates to a power transmission tower fabricated retaining wall artificial hole digging pile construction method. BACKGROUND

[0002] With the improvement of economic level and the rapid growth of power energy demand, more and more high-voltage transmission line projects are being constructed in China. The power transmission tower foundation is an indispensable part of the transmission line project. Due to the limitation of construction conditions and the particularity of geological environment, the traffic conditions of most tower sites in mountainous and hilly areas are poor, and construction machinery cannot reach, so artificial hole digging piles are mostly used as power transmission tower foundations.

[0003] During the artificial hole forming process, the collapse of the hole wall and the collapse of the soil body are prone to occur, and the construction operation risk is large, so a retaining wall needs to be set to ensure the safety of the operating personnel. At present, the artificial hole digging pile foundation generally adopts cast-in-place reinforced concrete retaining wall. This method has the following disadvantages: the construction process is relatively complex, and the construction process is long; the quality of the retaining wall concrete maintenance is not easy to guarantee, and the effect of the concrete retaining wall may be insufficient, which has safety hazards; the side friction resistance between the retaining wall and the soil body around the pile cannot be fully utilized, and it is difficult to better meet the design requirements of the bearing capacity. The fabricated retaining wall has the advantages of short construction period and higher safety, but the traffic conditions in some areas are poor, and the retaining wall pipe piece needs to be transported manually, which is difficult and inefficient. SUMMARY

[0004] The purpose of the present application is to provide a power transmission tower fabricated retaining wall artificial hole digging pile construction method, which can reduce the weight of the retaining wall pipe piece, thereby reducing the difficulty of manual transportation and improving the transportation efficiency.

[0005] To achieve the above purpose, the present application adopts the following technical scheme:

[0006] A power transmission tower fabricated retaining wall artificial hole digging pile construction method, comprising the following steps:

[0007] Step 1, pile hole positioning (including line laying, pile position and elevation), and then installing lifting equipment;

[0008] Step 2, excavate the soil body, and install the retaining wall with a hole into the pile hole;

[0009] Step 3, use the lifting equipment to hoist the steel bars into the pile hole to bind the steel reinforcement cage, and install the grouting pipe group on the steel reinforcement cage;

[0010] Step 4, pour concrete, and then perform pile bottom grouting.

[0011] Further, in step 2, the method for installing the retaining wall is that: the pipe piece with a hole is suspended into the pile hole through a steel wire rope, the pipe pieces are assembled into a closed loop retaining wall through bolts, and a steel nail is punched into the upper side of the hole of each pipe piece to fix the retaining wall to the soil body.

[0012] Further, the thickness of the pipe piece of the retaining wall is 50-60 mm, the weight of a single pipe piece is controlled to be 40-60 kg, the height of the pipe piece is 300-500 mm, and the convenience of construction is increased; the number of pieces of the retaining wall per ring is preferably 3-5; under the premise of not affecting the function of the fabricated retaining wall, the hole in the pipe piece is beneficial to reducing the weight of the pipe piece, the size of the hole can be designed according to the above constraints, and the form of the hole can be any polygon, and the arrangement form can also be parallel or staggered.

[0013] Further, the opening rate of the pipe piece is less than or equal to 52%; the hole in the pipe piece is provided with one or more, when the clay content of the soil body is high, the self-standing performance is good, the gravel particle size of the gravel soil is large, the weathering degree of the rock mass is low, and the integrity is good, the size of a single hole can be appropriately increased, otherwise, the size of a single hole should be appropriately reduced, when the condition of the rock-soil body is poor, a form of setting a large number of small holes can be used to ensure the opening rate and control the weight of a single piece, so that the height of the pipe piece, the number of pieces and other large schemes are not changed greatly.

[0014] Further, the grouting pipe group comprises two grouting pipes, and further comprises a grouting nozzle pipe connected to the bottom end of the grouting pipe, the grouting nozzle pipe is an annular structure arranged at the bottom end of the reinforcement cage, a hole is formed in the outer side of the grouting nozzle pipe, a waterproof packaging belt is wound on the grouting nozzle pipe to close the hole on the grouting nozzle pipe to prevent concrete from entering.

[0015] Further, the grouting nozzle pipe is a flexible high-pressure pipe with a steel wire.

[0016] Further, in step 2, a section of soil body is excavated, and a section of retaining wall is fixed to the soil body.

[0017] Further, in step 4, a guide pipe is used for continuous pouring when pouring concrete, and the depth of the guide pipe buried in the concrete is not less than 1 m; after the pouring of the concrete is completed, the guide pipe is slowly pulled out, and the guide pipe is repeatedly inserted and fixed before being lifted away from the concrete surface.

[0018] Further, 12-24 hours after the pouring of the concrete, a plug is opened, the grouting pipe is washed with clean water until the clean water overflows, then the grouting pipe is closed with a plug, the pile bottom grouting is performed within 3-14 days after the pile is formed, and the grouting is performed after ultrasonic detection.

[0019] Further, the guide pipe adopts a socket connection, and is sealed by a rubber ring or a rubber plate.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] 1. The assembled reinforced concrete retaining wall structure is prefabricated in a factory and assembled on site, and does not have the steps of formwork erection and pouring of cast-in-place retaining walls, can guarantee the continuity of construction, effectively shortens the construction period, the quality of the prefabricated retaining wall is easy to control, the structural strength is guaranteed, the safety of operating personnel is guaranteed, and the concrete mixing for on-site production of components is not required, has a small impact on the environment, is an environmentally friendly green construction method, and the lifting equipment facilitates the lowering and installation of the segment and the reinforcement.

[0022] 2. The use of the retaining wall with holes can reduce the weight of the segment and reduce the labor intensity of manual transportation; the hole rate of the segment is set to 52%, which can minimize the weight of the segment while guaranteeing the strength of the segment, facilitating transportation; during the pouring of the concrete, the concrete can flow into the holes and enter the space between the retaining wall and the soil, effectively connecting the retaining wall and the surrounding soil and increasing the bearing capacity of the pile.

[0023] 3. In mountainous and hilly areas, the traffic conditions of most tower sites are poor, construction machinery cannot reach, the length and diameter of the reinforcement cage are large, and the steel reinforcement processing site is relatively small, so it is difficult to bind the reinforcement cage first and then hoist it, and therefore the reinforcement is hoisted into the hole separately and the reinforcement cage is directly bound in the hole, which facilitates construction.

[0024] 4. The annular grouting nozzle pipe can uniformly grout at the bottom of the pile, two grouting pipes are provided, one grouting pipe can be used when the other grouting pipe fails, and stable grouting is guaranteed. The pressure grouting at the bottom of the pile can reinforce the pile end bearing layer, effectively fill the pores between the prefabricated retaining wall and the original hole wall, and make the grout and the soil around the pile side penetrate, compact and reinforce under pressure, improve the mechanical effect of the pile side wall, greatly increase the pile end resistance and pile side friction, and have a significant "root reinforcement effect"; compared with the traditional side wall grouting, the grouting effect is more obvious because the grout returns from the bottom under pressure, and the bottom of the pile is also well reinforced; the design requirements for bearing capacity can be better met. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a flowchart of embodiment 1 of the present application;

[0026] Figure 2 is a schematic diagram of the construction process of embodiment 1 of the present application;

[0027] Figure 3 is a schematic diagram of the complete retaining wall structure of embodiment 1 of the present application;

[0028] Figure 4 is a displacement nephogram of the segment of embodiment 1 of the present application;

[0029] Figure 5The load-displacement curve diagram of the pipe segment of the embodiment 1 of the application;

[0030] Figure 6 The schematic diagram of the grouting pipe group of the embodiment 1 of the application;

[0031] Figure 7 The schematic diagram of the grouting nozzle pipe of the embodiment 1 of the application;

[0032] Figure 8 The displacement nephogram of the pile body of the embodiment 1 of the application;

[0033] Figure 9 The load-displacement curve diagram of the pile body of the embodiment 1 of the application.

[0034] In the figure: pipe segment 1, hole 2, bolt 3, steel nail 4, lifting equipment 5, steel wire rope 6, soil body 7, retaining wall 8, steel reinforcement cage 9, grouting pipe group 10, concrete 11, grouting reinforcement body 12, grouting pipe 13, tee pipe 14, grouting nozzle pipe 15. DETAILED DESCRIPTION

[0035] Embodiment 1

[0036] A power transmission tower assembled retaining wall 8 manual hole digging pile construction method, as shown in the figure, comprising the following steps: Figures 1-9

[0037] Step one, pile hole positioning: before construction, carry out pile measurement positioning work, first, according to the coordinate relationship of the construction control point and the main control axis, measure and place the main control axis, then gradually encrypt the main control axis in turn, measure and place each axis, and finally, according to the coordinate position relationship of the pile core and the axis, measure and place the pile core control cross line; after the pile position is laid out, it should be repeatedly checked before entering the excavation stage.

[0038] Step two, install lifting equipment 5: install lifting equipment 5 in the construction site to facilitate the lowering and installation of pipe segment 1 and steel reinforcement, and the lifting equipment 5 is a SISINSING small gantry electric hoist, with a maximum lifting weight of 500 kg.

[0039] Step three, excavate soil body 7: as shown in the figure, excavate soil body 7 from top to bottom in sections, first excavate the middle part, then expand to the periphery, and pay attention to control the cross-sectional size during excavation; the pile diameter D of the manual hole digging pile of the embodiment is 1.2 m, the excavation depth h is 15 m, and the single excavation height is 500 mm. Figure 2 Step four, assemble retaining wall 8: after the nth section of soil body 7 is excavated, assemble the nth section of retaining wall 8, and suspend the pipe segment 1 of the assembled retaining wall 8 into the corresponding position in the pile hole through the steel wire rope 6, as shown in the figure.

[0040] Figure 3 ​​As shown, using 6.8 grade M16 bolt 3 in the pile hole assembled into a whole ring complete wall 8, at both sides of the middle hole 2 of each piece of pipe 1, 2 steel nails 4 are driven in to stabilize and fix the assembled wall 8 on the soil 7 around the pile; n = 1, 2, 3, 4, …, 30, sequentially increasing.

[0041] The pipe 1 opening rate selection method is as follows: as shown in Table 1, seven working conditions of pipe 1 with different opening rates are set, and the bending resistance experiment simulation of the pipe 1 of the seven working conditions is carried out, and the displacement nephogram of the pipe 1 is as shown in Figure 4

[0042] Table 1 Pipe size corresponding to seven working conditions

[0043]

[0044] The load-displacement values of the pipe 1 obtained by the experiment are shown in Table 2, and the load-displacement curve is as shown in Figure 5 According to the experimental results, when the opening rate is 52%, the pipe 1 is not damaged under the load of 8.5KN, which meets the design requirements, and the weight of the pipe 1 is low, which is convenient for transportation, so the pipe 1 with an opening rate of 52% is selected to assemble the wall 8.

[0045] Table 2 Load-displacement of pipe

[0046]

[0047] The pipe 1 of the assembled wall 8 is designed, the thickness of the wall 8, the height of the pipe 1, the number of pieces and the size of the hole 2 of the pipe 1 are as shown in Table 3. The hole 2 setting scheme in the table is not unique, and can be greatly adjusted according to the change of geological conditions. When the clay content of the soil 7 is high, the self-standing performance is good, the gravel particle size of the gravel soil is large, the weathering degree of the rock mass is low, and the integrity is good, the size of the single hole 2 can be appropriately increased, otherwise, the size of the single hole 2 should be appropriately reduced. When the condition of the rock-soil body 7 is poor, in order to avoid the soil 7 from leaking out of the hole 2, a small number of small holes 2 can be used to ensure the opening rate and control the weight of the single piece, so that the height of the pipe 1, the number of pieces and other large schemes do not change greatly. The thickness t of the assembled wall 8 is 60mm, the pile diameter D is 1.2m, the weight of the single piece is controlled within 40-60kg, the height of the pipe 1 is 500mm, and the number of pieces of the wall 8 per ring is 3. Considering the convenience of processing, the hole 2 adopts a rectangular cross section and a parallel arrangement.

[0048] Table 3 Pipe size corresponding to different pile diameters

[0049]

[0050] ​Step five, complete the construction of the retaining wall 8: repeat steps three and four, after each excavation of a section of soil 7, assemble a section of retaining wall 8, and ensure that each ring of retaining wall 8 is stable and fixed, until the design elevation.

[0051] Step six, tie the reinforcement cage 9, and simultaneously bury the grouting pipe set 10: use the lifting equipment 5 to lift and place the reinforcement into the pile hole for tying, and make the grouting pipe set 10 at the same time as tying the reinforcement cage 9, and install the grouting pipe set 10 on the reinforcement cage 9. As shown in Figures 6-7 , the grouting pipe set 10 includes two vertical grouting pipes 13, one is the main grouting pipe 13, and the other is the standby pipe, which is used when the main grouting pipe 13 fails unexpectedly, the grouting pipes 13 are arranged on both sides of the reinforcement cage 9, the bottom ends of the two grouting pipes 13 are connected to a flexible high-pressure pipe with an inner diameter of 25 mm and a steel wire as a grouting nozzle pipe 15 through a tee pipe 14, the grouting nozzle pipe 15 is arranged at the bottom end of the reinforcement cage 9, the grouting nozzle pipe 15 is processed into a ring shape, the outside of the grouting nozzle pipe 15 is perforated and sealed by wrapping waterproof packaging tape.

[0052] Step seven, pouring concrete 11: the pile core concrete 11 is continuously poured using a guide pipe, the guide pipe is connected using a socket, sealed with a rubber ring or rubber plate, the guide pipe is about 2m long per section, and the lowest section is 3m long. When pouring, the guide pipe needs to be lifted, and the depth of the guide pipe buried in the concrete 11 should be maintained at not less than 1m during the lifting process, the concrete 11 flows into the hole 2 and enters between the retaining wall 8 and the soil 7, connecting the retaining wall 8 and the surrounding soil 7; after the concrete 11 is poured, the guide pipe is slowly pulled out, and before the guide pipe is lifted away from the concrete surface, it is repeatedly inserted to avoid a hollow pile; the concrete 11 freely flows into the hole 2 of the pipe piece 1 and between the retaining wall 8 and the soil 7, effectively connecting the assembled retaining wall 8 and the surrounding soil 7.

[0053] Step eight, pile bottom grouting: open the plug 12h-24h after pouring the concrete 11, then flush the grouting pipe 13 with clean water until the clean water overflows, and then reseal the grouting pipe 13 with a plug. Pile bottom grouting is performed within 3d-14d of pile formation, and after ultrasonic testing; the grouting equipment is a GLZ-5 screw grouting machine, the pile bottom grouting pressure is 3Mpa-4Mpa, and the stress is maintained for not less than 5min after the pressure reaches the design value. Grouting can be terminated when one of the following conditions is met: (1) both the grouting amount and the grouting pressure meet the design requirements; (2) the grouting amount meets the design value, but the grouting pressure does not meet the design value, at this time intermittent grouting should be used, the intermittent time is 30 minutes-60 minutes, and the re-injection amount should not be less than 30% of the design grouting amount; (3) the grouting pressure exceeds the design value and maintains the pressure value for 5min, and the grouting amount reaches 80% of the design value to terminate the grouting. The grout penetrates, compacts, and reinforces the pile end bearing layer and the pile side soil 7, forming a grouting reinforced body 12, greatly enhancing the pile end resistance and pile side friction resistance.

[0054] The artificial excavated pile of the present application does not carry out pile bottom grouting, and when the pile bottom grouting is carried out, the displacement nephogram and load-displacement curve of the pile body are as shown in Figures 8-9 When the same uplift load is borne, the displacement of the pile bottom grouting pile is smaller than that of the pile without grouting, and it is more obvious with the increase of the load.

Claims

1. A method for constructing manually excavated bored piles for prefabricated retaining walls of transmission towers, characterized in that, Includes the following steps: Step 1: Locate the pile hole, and then install the lifting equipment; Step 2: Excavate the soil and install the perforated, equal-diameter retaining wall into the pile hole. The method is as follows: suspend the perforated segments into the pile hole using steel wire ropes, assemble the segments into a closed-loop retaining wall using bolts, and drive steel nails into the upper side of the perforation of each segment to fix the retaining wall to the soil; the perforation rate of the segments is less than or equal to 52%. Step 3: Use lifting equipment to hoist the reinforcing bars into the pile hole and tie the reinforcing cage, and install the grouting pipe assembly on the reinforcing cage; Step 4: Pour concrete and then perform grouting at the bottom of the pile.

2. The construction method as described in claim 1, characterized in that, The grouting pipe assembly includes two grouting pipes and a grouting nozzle pipe connected to the bottom end of the grouting pipes. The grouting nozzle pipe is a ring structure set at the bottom end of the reinforcing cage. The outer side of the grouting nozzle pipe has a hole and waterproof packaging tape is wrapped around the grouting nozzle pipe.

3. The construction method as described in claim 2, characterized in that, The grouting nozzle pipe is a flexible high-pressure pipe with steel wire.

4. The construction method as described in claim 1, characterized in that, In step 2, for each section of soil excavated, a section of retaining wall is fixed to the soil.

5. The construction method as described in claim 4, characterized in that, In step 4, a duct is used for continuous pouring of concrete, keeping the duct embedded in the concrete to a depth of not less than 1m. After the concrete is poured, the duct is slowly pulled out, and the duct is repeatedly inserted before being lifted from the concrete surface.

6. The construction method as described in claim 5, characterized in that, In step 4, the grouting pipe is opened 12 to 24 hours after the concrete is poured. After opening, the grouting pipe is flushed with clean water until clean water overflows. Then, the grouting pipe is sealed with a plug. Grouting is carried out at the bottom of the pile within 3 to 14 days after pile formation.

7. The construction method as described in claim 5, characterized in that, The conduit is connected by a socket and sealed with a rubber ring or rubber plate.

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