Pile planting construction method for deep and thick backfill foundation

Abstract

The invention provides a deep and thick backfill foundation pile planting construction method, and belongs to the technical field of backfill foundation pile construction, and the method comprises the following steps: S1, pre-drilling in a large-particle-size backfill layer by using a down-the-hole pile hammering machine, and synchronously burying a pile casing in the pre-drilling process; s2, the down-the-hole hammer construction equipment is moved away, and soil body backfilling is conducted in the pre-drilled hole; s3, a percussion drilling machine is adopted for percussion drilling in the hole with the soil body backfill; s4, after the hole deeply penetrates through the large-particle-size backfill layer, a special drilling machine with a grouting function is adopted to replace a percussion drilling machine to conduct drilling in a conventional soil layer in the hole; s5, after the special drilling machine drills a hole to a preset depth, the special drilling machine lifts a drill rod from the interior of the drill hole and injects curing slurry for stirring at the same time; and S6, before the solidification slurry in the hole is not solidified, the precast pile is implanted into the solidification slurry in the hole. The method has the beneficial effects that the precast pile construction efficiency and effect are improved, the pile forming quality is guaranteed, and many defects existing in a traditional construction technology are overcome.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pile construction, and relates to a deep backfill foundation pile construction method. BACKGROUND

[0002] With the rapid development of infrastructure construction in China, the demand for bridge, high-rise building, port terminal and other engineering projects in complex geological areas is increasing. Large boulders in the throw-fill area are a typical adverse geological condition, which widely exists in coastal backfill land, mine tailings accumulation, mountain road expansion and "mountain cutting for city building" engineering. The geological characteristics of such areas are that the block stones formed by artificial throw-fill have large diameter, large gap between block stones, loose structure and disordered distribution, and there are also characteristics such as high underground water level and strong permeability in coastal backfill land engineering. This leads to low pile construction efficiency, poor hole forming stability and difficult to guarantee pile quality.

[0003] In view of the above problems, the current industry mainly uses "down-the-hole hammer" hole forming process, "rotary drilling combined with down-the-hole hammer", "impact drill combined with ramming" and "down-the-hole hammer combined with rotary jet grouting" combined hole forming process for backfill foundation pile drilling construction.

[0004] However, the above traditional process still has many drawbacks in the actual construction process, such as in the construction process of down-the-hole hammer, the air pressure is insufficient due to the current air compressor power, which affects the chip removal effect; the impact hole forming efficiency is low and easy to get stuck, a large amount of mud is generated during construction, which seriously affects the surrounding environment, and the pile body verticality is difficult to control; the flowability of concrete after pile forming reduces the recovery of steel casing; and the strength of the pile body formed by down-the-hole hammer and rotary jet grouting cannot meet the demand of high bearing capacity. SUMMARY

[0005] The purpose of the present application is to solve the above problems existing in the prior art, and a deep backfill foundation pile construction method is proposed.

[0006] The purpose of the present application can be achieved by the following technical scheme: a deep backfill foundation pile construction method, comprising the following steps:

[0007] S1: first, use a down-the-hole hammer pile machine to pre-drill a hole in the large particle size backfill layer, and simultaneously bury a casing during the pre-drilling process;

[0008] S2: after the down-the-hole hammer pile machine pre-drills to the initial set depth, the soil in the pre-drilled hole is backfilled;

[0009] S3: use an impact drill to drill in the hole with soil backfill until the entire large particle size backfill layer is penetrated;

[0010] S4: After the hole depth passes through the large particle size backfill layer, a special drilling machine with grouting function is used to replace the impact drill to drill in the conventional soil layer in the hole;

[0011] S5: After the special drilling machine drills to the predetermined depth, the special drilling machine lifts the drill rod from the hole while injecting and stirring the solidified slurry;

[0012] S6: Before the solidified slurry in the hole is not consolidated, the precast pile is planted in the solidified slurry in the hole.

[0013] Preferably, in step S1, the down-the-hole hammer continuously breaks the large particle size backfill layer particles into small particle size particles by driving the hammer body with high pressure gas, and the small particle size particles are discharged outside the hole by high pressure gas.

[0014] Preferably, in step S3, the impact drill drilling machine has a hole diameter that is 5cm to 15cm smaller than the hole diameter of the down-the-hole hammer, ensuring the position of the steel casing in the hole.

[0015] Preferably, in step S5, the special drilling machine opens the pile end expansion wing of the drill bit to perform hole expansion operation, thereby forming a diameter expansion part at the bottom of the hole, then injecting pile end solidified slurry in the diameter expansion part, and after the injection of the pile end solidified slurry is completed, the pile peripheral solidified slurry is injected in the hole while the drill rod is pulled out.

[0016] Preferably, in step S5, a segmented grouting process is used, first, the drill bit remains stationary, and the pile end solidified slurry equivalent to one third of the volume of the diameter expansion part is injected; then, the remaining two-thirds volume of the pile end solidified slurry is injected by repeated up and down movement of the drill bit within the expansion height range.

[0017] Preferably, mud water exists in the diameter expansion part, the first injected pile end solidified slurry is deposited below the diameter expansion part, causing the mud water to rise, and then the pile end solidified slurry is injected in the expansion height range in an up and down stirring manner, forcing most of the mud water to completely leave the diameter expansion part.

[0018] Preferably, after the pile end solidified slurry injection is completed, the pile peripheral solidified slurry is injected while the drill rod is pulled out.

[0019] Preferably, the precast pile is any one or a combination of two pile segments of a pipe pile segment, a bamboo joint pile segment, and a composite reinforced pile segment.

[0020] Preferably, if the deep backfill foundation is located in an underground water flow area, the casing is a steel casing, and the pile end solidified slurry is a high-viscosity cement-soil slurry.

[0021] Preferably, it further includes step S7: pulling out the casing after a predetermined time interval after the precast pile is planted.

[0022] Compared with the prior art, the beneficial effects of the present application are:

[0023] 1. The method of hole formation using a combination of down-the-hole hammer, impact drill, and special single-axis drill combines the advantages of the down-the-hole hammer's high construction speed and the impact drill's drilling depth, enabling efficient penetration through thick backfill layers, improving the efficiency and effectiveness of precast pile construction, ensuring pile quality, and avoiding many drawbacks of traditional construction techniques.

[0024] 2. No mud discharge, avoiding the mud pollution problems of traditional rotary drilling rigs. It can effectively improve construction speed, provide high-precision pre-drilling for subsequent impact drilling rigs, ensure hole verticality, reduce the risk of deviation, and prevent drill bit burial. Step S1 solves the problem that conventional drilling rigs cannot drill holes in deep backfilled foundations.

[0025] 3. The impact drill impacts the pre-drilled hole of the down-the-hole hammer, and gradually breaks up the deep, large-diameter stones through automated drop control. The impact drill uses the principle of concentrated kinetic energy release to penetrate the dense backfill layer that the down-the-hole hammer cannot handle, thus solving the problem of insufficient hole depth of the down-the-hole hammer.

[0026] 4. Precast piles feature high-strength concrete, are factory-prefabricated, and reduce the impact of groundwater, thus solving the problems of unreliable quality in cast-in-place concrete piles and low strength in pure jet grouting piles. Specifically, standardized factory production of precast piles ensures higher quality and avoids issues such as diameter reduction and exposed reinforcement during cast-in-place pile construction, thereby guaranteeing construction quality.

[0027] 5. A segmented grouting process is adopted. The first injection of solidifying grout forms a dense layer at the bottom, while the mud water, due to its lower density, rises to the top of the grout. Then, the drill bit is pulled up and down to inject solidifying grout into the remaining area of ​​the enlarged section. During this process, the mud water is completely discharged from the enlarged section. This method can eliminate sediment, ensure the bearing capacity of the pile end is fully utilized, and after the mud water is completely discharged, there is no sediment-weakened layer at the pile end. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of step S1 of the present invention.

[0029] Figure 2 This is a schematic diagram of step S3 of the present invention.

[0030] Figure 3 This is a schematic diagram of step S4 of the present invention.

[0031] Figure 4 This is a schematic diagram of the special drilling machine drilling to a set depth in step S4 of the present invention.

[0032] Figure 5 This is a schematic diagram of step S5 of the present invention.

[0033] Figure 6 This is a schematic diagram of step S5 of the present invention, in which an enlarged diameter portion is formed at the bottom of the hole.

[0034] Figure 7 A schematic diagram for pulling out the drill pipe after step S5 of the present application is completed.

[0035] Figure 8 A schematic diagram for step S6 of the present application.

[0036] Figure 9 A schematic diagram for the precast pile after being implanted in place in step S6 of the present application.

[0037] Figure 10 A schematic diagram for step S7 of the present application.

[0038] Figure 11 A schematic diagram for removing the hole body of the precast pile in step S7 of the present application.

[0039] Figure 12 A schematic diagram for hoisting the precast pile of the present application.

[0040] In the figure, 100, large particle size backfill layer; 200, conventional soil layer; 300, down-the-hole hammer pile machine; 400, casing; 500, impact drill rig; 600, special drill rig; 610, enlarged wing; 700, precast pile; 800, diameter expansion part. DETAILED DESCRIPTION

[0041] The following is a specific embodiment of the present application and further describes the technical solutions of the present application in conjunction with the accompanying drawings, but the present application is not limited to these embodiments.

[0042] As shown in the figure, a pile planting construction method for deep thick backfill foundation, comprising the following steps: Figures 1 to 12

[0043] S1: first use the down-the-hole hammer pile machine 300 to pre-drill in the large particle size backfill layer 100, and simultaneously bury the casing 400 during the pre-drilling process to ensure the verticality of the hole;

[0044] S2: after the down-the-hole hammer pile machine 300 pre-drills to the initial set depth, remove the down-the-hole hammer construction equipment, and backfill the soil in the pre-drilled hole for subsequent impact drill rig 500 hole forming and mud wall protection;

[0045] S3: use the impact drill rig 500 to impact drill in the hole with soil backfill, improve the drilling depth, and punch through the entire large particle size backfill layer 100;

[0046] S4: after the hole depth penetrates the large particle size backfill layer 100, use the special drill rig 600 with grouting function to replace the impact drill rig 500 to drill in the conventional soil layer 200 in the hole, and improve the hole forming construction speed;

[0047] ​S5: After the special drilling rig 600 drills to the predetermined depth, the special drilling rig 600 lifts the drill rod from the borehole while injecting and mixing the curing slurry;

[0048] S6: Before the curing grout in the hole solidifies, the precast pile 700 is inserted into the curing grout in the hole.

[0049] Preferably, the method further includes step S7: after the precast pile 700 is implanted, the casing 400 is pulled out after a predetermined time interval, thereby recovering the steel casing 400.

[0050] This method employs a combination of a down-the-hole hammer, a 500mm impact drill, and a dedicated single-axis drill to create holes. It combines the high speed of a down-the-hole hammer with the deep drilling depth of a 500mm impact drill, enabling efficient penetration through thick backfill layers. The principle of this method is as follows:

[0051] like Figure 1 As shown, drilling is performed within a depth of 30 meters using a down-the-hole hammer and casing. In step S1, high-pressure gas drives the hammer head to impact at high frequency, breaking large-diameter backfill layer 100 (such as boulders or construction waste) into smaller particles. These particles are discharged from the hole with the airflow, achieving rapid hole formation. The casing is used to fix the hole wall and provide a sealed air chamber for the down-the-hole hammer, maintaining the efficiency of the high-pressure airflow. Step S1 involves no mud discharge, avoiding the mud pollution problems of traditional rotary drilling rigs. It effectively improves construction speed, provides high-precision pre-drilling for the subsequent impact drilling rig 500, ensures hole verticality, reduces the risk of deviation, and prevents drill bit burial. Step S2 is the process of backfill soil slurry wall protection, filling the voids in the hole wall with soil. Mud slurry wall protection reduces the risk of hole wall collapse during the impact drilling rig 500's operation. Step S1 solves the problem that conventional drilling rigs cannot form holes in deep backfill foundations.

[0052] like Figure 2 As shown, in the depth range below 30 meters, an impact drill rig 500 is used to form holes. In step S3, the impact drill rig 500 impacts within the pre-drilled hole of the down-the-hole hammer, gradually breaking up deep, large-diameter rocks through automated drop control. The impact drill rig 500 utilizes the principle of concentrated kinetic energy release to penetrate dense backfill layers that the down-the-hole hammer cannot handle, thus solving the problem of insufficient hole depth in down-the-hole hammer drilling. Figure 3 , Figure 4 As shown, step S4 uses a dedicated single-axis drilling rig to efficiently form holes, which greatly improves the construction speed in conventional soil layers.

[0053] like Figure 5 , Figure 6 , Figure 11As shown, the purpose of step S5 is to mechanically expand the hole bottom by the drill bit expansion wing 610, and to inject pile end solidifying slurry at the expansion section 800, which can eliminate the influence of sediment. The purpose of step S6 is to inject pile peripheral solidifying slurry, which can eliminate the disturbance to the surrounding soil during the hole forming process; and ensure the high bearing capacity.

[0054] As shown in Figure 7 , Figure 8 , Figure 9 Step S5 is to prepare for the implantation of the prefabricated pile 700 in step S6. The prefabricated pile 700 has high concrete strength grade and is factory prefabricated, which reduces the influence of underground water and solves the defects of the cast-in-place concrete pile forming quality being difficult to guarantee and the pure rotary jet grouting pile body strength being not high. Specifically, the prefabricated pile 700 is produced in a factory standardization manner, which is more guaranteed in quality and avoids problems such as shrinkage and exposed reinforcement in the construction process of the cast-in-place pile, thereby ensuring the construction quality. Step S7 is to recover the casing 400 after the construction is completed.

[0055] On the basis of the above embodiment, in step S1, the down-the-hole hammer continuously breaks the large-particle-diameter backfill layer 100 particles into small-particle-diameter particles by driving the hammer body by high-pressure gas, and discharges the small-particle-diameter particles outside the hole through high-pressure gas. The down-the-hole hammer does not discharge mud during the hole forming process.

[0056] The air compressor provides high-pressure gas to drive the piston of the down-the-hole hammer to reciprocate, form high-frequency impact energy, and generate stress waves by the hammer head impact, which propagate and superimpose in the backfill layer, resulting in micro-cracks in the large-particle-diameter boulders and concrete blocks, and finally disintegrating into debris. The high-pressure gas enters the hole bottom through the central passage of the drill rod, carries the debris back to the ground along the gap between the drill rod and the hole wall, and relies only on gas discharge throughout the process without mud discharge.

[0057] As shown in Figure 2 On the basis of the above embodiment, in step S3, the impact drill rig 500 has a hole forming diameter that is 5-15 cm smaller than the hole forming diameter of the down-the-hole hammer, thereby ensuring the position of the steel casing 400 in the hole.

[0058] On the basis of the above embodiment, in step S3, the impact drill rig 500 is an Ukas impact drill rig 500. The hammer head of the Ukas impact drill rig 500 is slender, which can play a good guiding role in the formed hole. The Ukas impact drill rig 500 adopts automatic control of the drop distance, and the drop distance is small first and then large—ensuring the verticality of the formed hole.

[0059] As shown in Figures 3 to 7As shown, based on the above implementation method, in step S4, during the drilling process of the dedicated drilling rig 600, the drill rods are spliced ​​together to reach the design elevation. The dedicated drilling rig 600 uses standard length drill rods (usually 3-6 meters), and each drill rod has high-precision threads or hydraulic quick couplings pre-installed at both ends, allowing connection to be completed within 10-30 seconds, reducing downtime.

[0060] like Figure 11 As shown, based on the above implementation method, in step S5, the special drilling rig 600 opens the pile end enlarging wing 610 of the drill bit to perform hole enlargement operation, thereby forming an enlarged diameter section 800 at the bottom of the hole. Then, pile end curing grout is injected into the enlarged diameter section 800. After the pile end curing grout is injected, pile perimeter curing grout is injected into the hole, and the drill rod is pulled out at the same time.

[0061] In step S5, a segmented grouting process is adopted. First, the drill bit is kept stationary, and one-third of the pile end curing grout equivalent to 800 mm of the enlarged diameter section is injected. Then, within the enlarged bottom height range, the remaining two-thirds of the pile end curing grout is injected by repeatedly moving the drill bit up and down.

[0062] Based on the above implementation method, the enlarged diameter section 800 contains mud and water. The first injected pile end curing grout is deposited below the enlarged diameter section 800, causing the mud and water to rise. Then, within the enlarged bottom height range, the pile end curing grout injected by up and down stirring forces most of the mud and water to completely leave the enlarged diameter section 800.

[0063] Step S5 employs a segmented grouting process. The first injected solidifying grout forms a dense layer at the bottom, while the low-density mud rises to the top. The drill bit is then pulled up and down to inject solidifying grout into the remaining area of ​​the enlarged diameter section 800. During this process, the mud is completely drained from the enlarged diameter section 800. This method eliminates sediment, ensuring the pile tip bearing capacity is fully utilized. After the mud is completely drained, there is no sediment-weakened layer at the pile tip.

[0064] After the pile end curing grout is injected, the pile perimeter curing grout is injected, and the drill rod is pulled out at the same time.

[0065] like Figure 9 As shown, based on the above implementation method, the precast pile 700 is an extended body composed of any one or a combination of two of the following pile segments: pipe pile segment, bamboo-joint pile segment, and composite reinforced pile segment. The precast pile 700 is manufactured in a standardized factory, ensuring higher pile quality and avoiding problems such as diameter reduction and exposed reinforcement during cast-in-place pile construction, thus guaranteeing construction quality.

[0066] like Figure 1 As shown, based on the above implementation method, if the deep backfill foundation is located in a groundwater circulation area, then the casing 400 is a steel casing 400, and the pile end curing grout is a high-viscosity cement-soil grout. This design can effectively reduce the impact of groundwater on construction.

[0067] As Figure 9 , Figure 10 shown, on the basis of the above embodiment, the pile periphery solidified slurry is a flow type cement soil. This design reduces the adhesion of the pile periphery solidified slurry to the casing 400, facilitating the recovery of the casing 400 in subsequent step S8.

[0068] It should be noted that all directional indications, such as upper, lower, left, right, front, back, and the like, are only used to explain the relative position relationship, movement condition, etc. between components in a certain specific posture (as shown in the drawings), and if the specific posture changes, the directional indications will also change accordingly.

[0069] In addition, the descriptions such as "first", "second", "one", etc. in the present application are only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first" and "second" can be explicitly or implicitly included at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0070] In the present application, unless otherwise specifically defined and limited, the terms "connection", "fixation" and the like should be understood broadly, for example, "fixation" can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection; can be directly connected, or indirectly connected through intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise specifically limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0071] In addition, the technical solutions of each embodiment of the present application can be combined with each other, but it must be based on the realization of the ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor within the scope of protection required by the present application.

Claims

1. A method for pile construction in deep backfill ground, characterized by, The steps include the following: S1: first use the down-the-hole hammer pile machine (300) to pre-drill in the large particle size backfill layer (100), and synchronously bury the casing (400) during the pre-drilling; S2: the down-the-hole hammer pile machine (300) drills to the initial set depth, and then fills the soil in the pre-drilled hole; S3: use the impact drill rig (500) to drill in the hole with soil filling until the entire large particle size backfill layer (100) is penetrated; S4: after the hole depth penetrates the large particle size backfill layer (100), use the special drill rig (600) with grouting function to replace the impact drill rig (500) to drill in the conventional soil layer (200) in the hole; S5: after the special drill rig (600) drills to the predetermined depth, the special drill rig (600) lifts the drill rod from the hole while mixing the solidified slurry; S6: before the solidified slurry in the hole is not consolidated, the precast pile (700) is planted in the solidified slurry in the hole.

2. The method of claim 1, wherein: In step S1, the down-the-hole hammer drives the hammer body to continuously crush the large particle size backfill layer (100) particles into small particle size particles, and the high-pressure gas is discharged outside the hole.

3. The method of claim 1, wherein: the pile is driven to a depth of at least 20 feet below the ground surface. In step S3, the impact drill rig (500) has a hole diameter that is 5cm to 15cm smaller than the hole diameter of the down-the-hole hammer, ensuring the position of the steel casing (400) in the hole.

4. The method for pile driving in deep backfill foundations as described in claim 1, characterized in that: In step S5, the special drill rig (600) opens the pile end expansion wings (610) of the drill bit at the lower end of the drill rod to perform hole expansion operations, thereby forming a diameter expansion part (800) at the bottom of the hole, then injecting pile end solidified slurry into the diameter expansion part (800), and after the pile end solidified slurry injection is completed, injecting pile peripheral solidified slurry in the hole while pulling out the drill rod.

5. The method of claim 4, wherein: In step S5, a segmented grouting process is used. First, the drill bit remains stationary, and the pile end solidified slurry equivalent to one-third of the volume of the diameter expansion part (800) is injected. Then, within the expansion height range, the pile end solidified slurry with the remaining two-thirds volume is injected by repeatedly moving the drill bit up and down.

6. The method of claim 5, wherein: The diameter expansion part (800) contains mud water. The first injected pile end solidified slurry is deposited below the diameter expansion part (800), causing the mud water to rise. Then, within the expansion height range, the pile end solidified slurry is injected in an up-and-down mixing manner, forcing most of the mud water to completely leave the diameter expansion part (800).

7. The method of claim 6, wherein: After the pile end solidified slurry injection is completed, the pile peripheral solidified slurry is injected, and the drill rod is pulled out at the same time.

8. The method for pile driving in deep backfill foundations as described in claim 1, characterized in that: The precast pile (700) is any one or a combination of pipe pile segments, bamboo joint pile segments, and composite reinforced pile segments.

9. The method for constructing piles in deep backfill foundations as described in claim 1, characterized in that: If the deep backfill foundation is located in an underground water flow area, the casing (400) is a steel casing (400), and the pile end solidified slurry is a high-viscosity cement-soil slurry.

10. The method for constructing piles in deep backfill foundations as described in claim 1, characterized in that: It also includes step S7: after the precast pile (700) is planted, the casing (400) is pulled out after a predetermined time interval.

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