A construction method for cast-in-situ bored pile to form a hole in soft soil layer to pebble layer

Abstract

A construction method for cast-in-place pile in soft soil layer to pebble layer, comprising a multifunctional drilling machine, a rotary drilling machine and a required excavated soil layer, the soil layer comprising a pebble layer and a soft soil layer on the surface of the pebble layer; compared with the prior art, through the combined application of the multifunctional drilling machine and the rotary drilling machine in the large-diameter super-thick pebble layer, the advantages of the multifunctional drilling machine in the large-torque steel casing and the upper soft soil taken in the steel casing are exerted, and the function of the rotary drilling machine in stabilizing the construction of the pebble layer is utilized, so that the difficulty problem of the cast-in-place pile drilling in the super-thick pebble layer is solved. And the use of mud protection wall is reduced as much as possible, the dependence on the construction site is reduced, the overall construction period is shortened, and the comprehensive economic benefit is improved.

Description

Technical Field

[0001] This invention relates to the field of bored pile technology, and specifically to a construction method for drilling bored piles in soft soil to gravel layers. Background Technology

[0002] Drilled cast-in-place piles are piles made by forming pile holes in the foundation soil through mechanical drilling, steel pipe extrusion, or manual excavation on the engineering site, placing a steel cage inside, and pouring concrete. Depending on the hole-forming method, cast-in-place piles can be divided into several categories such as driven cast-in-place piles, drilled cast-in-place piles, and excavated cast-in-place piles.

[0003] The mud wall construction method can be used for percussion drilling, grab drilling, and rotary drilling. The process of this construction method is as follows: leveling the site → mud preparation → embedding the casing → laying the working platform → installing and positioning the drilling rig → drilling → cleaning the hole and checking the hole quality → lowering the reinforcing cage → pouring underwater concrete → pulling out the casing → checking the quality.

[0004] When drilling and grouting piles using a hydraulic full-casing multi-functional drilling rig, drilling efficiency is generally higher in soft soil layers. However, if an extremely thick layer of pebbles is encountered at the bottom, construction becomes more difficult, especially with frequent hole collapses.

[0005] Compared with ordinary geological conditions, construction in ultra-thick pebble layers presents technical challenges such as high technical difficulty and hole collapse and necking. Traditional GPS-rotary drilling rigs or impact hammer pile drivers cannot meet the requirements, resulting in technical problems such as long construction period, low efficiency and high overall cost.

[0006] Chinese Patent No. CN107386963A discloses a method for drilling large-diameter pebbles in rotary cast-in-place piles and a boulder, including the following steps: Step 1) Setting out and positioning; Step 2) Drilling to obtain particle samples, and judging the properties and geological structure of the strata and soil based on the obtained particle samples; Step 3) Rotating the boulder to the pebble layer until it is impossible to drill further; Step 4) Replacing the boulder with a boulder to remove the large pebbles from the ground; Step 5) After the large pebbles are removed, switching back to a conventional boulder for rotary drilling; Step 6) Repeating steps 3 to 5 until the pebble layer is drilled through.

[0007] The aforementioned drilling method involves replacing the rotary bucket drill with a bouldering bucket drill, which uses the bouldering bucket drill to bring large pebbles to the ground. This process is repeated until all the pebbles are drilled. However, this method is difficult to implement when drilling is required in a pebble layer. Furthermore, this method suffers from technical problems such as long construction period, low efficiency, and high overall cost. Summary of the Invention

[0008] The present invention aims to overcome the defects in the prior art and provide a construction method that is efficient, safe and reliable for drilling and grouting piles in soft soil to gravel layers.

[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a construction method for drilling bored piles in soft soil to gravel layers, comprising a multi-functional drilling rig, a rotary drilling rig, and the soil layer to be excavated, the soil layer including a gravel layer and a soft soil layer located on the surface of the gravel layer; comprising the following steps:

[0010] Step A: Measure the depth of the soft soil layer and customize steel sleeves of appropriate length according to the depth of the soft soil layer;

[0011] Step B: Load the steel casing and auger bit onto the multi-functional drilling rig, and drill the steel casing and auger bit into the soft soil layer simultaneously;

[0012] Step C: Until the bottom of the steel casing is pressed to the bottom of the soft soil layer, loosen the connection between the steel casing and the multi-functional drilling rig, and move the multi-functional drilling rig to a new location;

[0013] Step D: Inject mud slurry into the bottom of the steel casing for wall protection;

[0014] Step E: Move the rotary drilling rig to the steel casing and position the rotary drilling rig in the hole;

[0015] Step F: The rotary drilling rig performs hole drilling in the gravel layer;

[0016] Step G: After the hole is formed, the steel cage is hoisted in and installed, and the concrete guide pipe is lowered for underwater concrete pouring.

[0017] Step H: After the grouting is completed, remove the steel sleeve.

[0018] As a preferred embodiment of the present invention, the multi-functional drilling rig is equipped with a hydraulic press for loading steel casing, and the hydraulic press is sleeved on the auger drill bit.

[0019] As a preferred embodiment of the present invention, before the steel casing construction in step B, the location of the required steel casing to be erected is determined by pile core positioning, and the multi-functional drilling rig is positioned and adjusted.

[0020] In a preferred embodiment of the present invention, when the steel casing and the auger drill bit are simultaneously drilling into the soft soil layer in step B, the auger drill bit performs soil extraction operations inside the steel casing.

[0021] In a preferred embodiment of the present invention, the length of the steel casing is not less than the depth of the soft soil layer.

[0022] In a preferred embodiment of the present invention, in step C, after loosening the connection between the steel casing and the multi-functional drilling rig, the steel casing is fixedly buried in the soft soil layer.

[0023] In a preferred embodiment of the present invention, after the rotary drilling rig positions the hole in step E, the rotary drilling bit of the rotary drilling rig moves downward along the steel casing.

[0024] As a preferred embodiment of the present invention, after the hole-forming process in step F, the hole is inspected and the first hole cleaning operation is performed.

[0025] In a preferred embodiment of the present invention, after the concrete guide pipe is lowered in step G, a second hole cleaning operation is performed.

[0026] As a preferred embodiment of the present invention, the multi-functional drilling rig is used for construction operations on soft soil layers, and the rotary drilling rig is used for construction operations on gravel layers.

[0027] Compared with existing technologies, the beneficial effects of this invention are as follows: By combining the multi-functional drilling rig and the rotary drilling rig in the application of large-diameter ultra-thick gravel layers, the advantages of the multi-functional drilling rig in high torque under steel casing and extracting soft soil from the upper part of the casing are utilized. In addition, the rotary drilling rig's function of stabilizing the gravel layer is employed, thus solving the problem of difficult drilling of bored piles in ultra-thick gravel layers. Furthermore, the use of mud slurry for wall protection is minimized, reducing dependence on the construction site; the overall construction period is accelerated, and comprehensive economic benefits are improved. Attached Figure Description

[0028] Figure 1 This is a flowchart of the present invention;

[0029] Figure 2 These are construction operation diagrams for a multi-functional drilling rig;

[0030] Figure 3 These are construction operation diagrams for rotary drilling rigs;

[0031] Reference numerals: 1. Multi-functional drilling rig; 11. Spiral drill bit; 12. Steel casing; 13. Mud wall protection; 2. Rotary drilling rig; 21. Rotary drill bit; 3. Soft soil layer; 4. Gravel layer. Detailed Implementation

[0032] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] like Figures 1-3 As shown,

[0034] Example: A construction method for drilling bored piles in soft soil to gravel layers, including a multi-functional drilling rig 1, a rotary drilling rig 2, and the soil layer to be excavated. The soil layer includes a gravel layer 4 and a soft soil layer 3 located on the surface of the gravel layer 4. The multi-functional drilling rig 1 is equipped with a hydraulic press for loading a steel casing 12. The hydraulic press is sleeved on a spiral drill bit 11. The hydraulic press moves up and down along the height direction of the multi-functional drilling rig 1, and the hydraulic press drives the steel casing 12 to rotate synchronously during the lifting and lowering process.

[0035] The model of the multi-functional drilling rig 1 can be SWSD6638W walking dual-power head high-power multi-functional drilling rig.

[0036] In practical use, the following steps are included:

[0037] Step A: Measure the depth of the soft soil layer 3, and customize a steel sleeve 12 of the appropriate length according to the depth of the soft soil layer 3. The length of the steel sleeve 12 is not less than the depth of the soft soil layer 3, ensuring that the bottom of the steel sleeve 12 can be pressed to the bottom of the soft soil layer 3, and that the bottom of the steel sleeve 12 can abut against the surface of the gravel layer 4.

[0038] Step B: Load the steel casing 12 and the auger drill bit 11 onto the multi-functional drilling rig 1, and drill the steel casing 12 and the auger drill bit 11 into the soft soil layer 3 at the same time. Before the construction of the steel casing 12, locate the pile core of the required steel casing 12 and adjust the positioning of the multi-functional drilling rig 1 to ensure the downward pressure position of the steel casing 12. The position of the steel casing 12 is determined according to the actual required position of the cast-in-place pile.

[0039] When the steel casing 12 and the auger drill bit 11 are simultaneously drilling into the soft soil layer 3, the auger drill bit 11 performs soil removal operations inside the steel casing 12. As the hydraulic press tightens and lowers the steel casing 12, the auger drill bit 11 is located inside the steel casing 12. Through the rotation of the auger drill bit 11, the soft soil layer 3 inside the steel casing 12 is transported upward under the action of the auger drill bit 11's thread until the soil of the soft soil layer 3 is removed from the ground under the action of the auger drill bit 11's thread, thereby realizing the hollow structure of the steel casing 12.

[0040] Step C: Until the bottom of the steel casing 12 is pressed to the bottom of the soft soil layer 3, loosen the connection between the steel casing 12 and the multi-functional drilling rig 1, and move the multi-functional drilling rig 1. After loosening the connection between the steel casing 12 and the multi-functional drilling rig 1, fix the steel casing 12 in the soft soil layer 3.

[0041] Step D: Inject mud slurry 13 into the bottom of the steel casing 12 for wall protection.

[0042] Step E: Move the rotary drilling rig 2 to the steel casing 12 and position the rotary drilling rig 2 in the hole. After the rotary drilling rig 2 is positioned in the hole, the rotary drilling bit 21 of the rotary drilling rig 2 moves downward along the steel casing 12.

[0043] Step F: Rotary drilling rig 2 performs hole drilling in the gravel layer 4. After hole drilling, the hole is inspected and the first hole cleaning operation is carried out.

[0044] Step G: After the hole is formed, the steel cage is hoisted in and installed, and the concrete guide pipe is lowered to carry out the second hole cleaning operation and underwater concrete pouring.

[0045] Step H: After the grouting is completed, remove the steel sleeve 12.

[0046] Using this method, rotary drilling rig 2 can reach the pile bottom elevation in an average of 1 to 1.5 hours, and the hole is not prone to collapse. The average hole-forming time for a set of mechanical equipment is 3.6 hours (not including the time for subsequent guide pipe installation, secondary hole cleaning, and concrete pouring). In addition, while rotary drilling rig 2 is operating, multi-functional drilling rig 1 can continuously construct the next pile hole.

[0047] Multi-functional drilling rig 1 + rotary drilling rig 2 joint construction statistics table

[0048]

[0049] Comparative Example 1: One long spiral drilling and grouting machine was deployed. This equipment is equipped with a double spiral thick-bladed bullet-shaped alloy cutting tooth drill bit, which can drill holes in layers of large-diameter pebbles and boulder. Its features include entirely dry operation; the high-torque, high-strength drill bit drills to the bottom in one continuous stroke; when the drill rod is lifted, the excavated soil is carried out of the hole, and concrete is simultaneously poured while the drill rod is being lifted. The entire process is free of cavities and hole collapse. After pouring, a reinforcing cage is inserted. The hole-forming time for a single unit is less than 1 hour.

[0050] Long spiral bored piles have significant advantages, mainly reflected in: ① fast construction speed and high pile formation efficiency; ② use of pump-pressed super-fluid concrete flow; ③ no loose soil at the pile tip, no broken piles, diameter reduction, or hole collapse; ④ strong ability to penetrate hard soil layers and high single pile bearing capacity; ⑤ low noise, no need for mud, no sewage discharge, and no soil displacement; ⑥ high comprehensive benefits and relatively low project cost compared with other pile types.

[0051] Construction statistics table of long spiral drilling and grouting pile machine

[0052]

[0053]

[0054] Actual measurements showed that while the long spiral grouting machine was highly efficient in drilling, during subsequent construction, when injecting super-fluid concrete using a pump, the cap at the bottom of the guide pipe often failed to open. The presumed cause was the high groundwater pressure. After several failed attempts, the machine was discontinued.

[0055] Comparative Example 2:

[0056] Fifteen impact drills (including diesel generators) were deployed for construction, prioritizing the work on Ф600 engineering piles. Two shifts were implemented for continuous operation, with a theoretical efficiency of approximately 30 hours per hole per drill. Impact drilling utilizes free-fall impact on rock and soil, offering advantages such as simple structure, low cost, ease of operation, fewer mechanical failures, and convenience, effectively breaking relatively hard rock. However, because impact drills use a suction cylinder to remove drill cuttings, the cuttings removal method is outdated. Furthermore, the drill's performance parameters limit its stroke and lifting capacity, resulting in relatively low drilling power.

[0057] When drilling through gravel layers, percussion drilling rigs are an economical and effective drilling tool. Because the combined construction of full-casing drilling rigs and rotary drilling rigs used in this project is costly and cannot be fully implemented, percussion hammer drills will be used as a supplement on the remaining working faces, provided there is space to prepare drilling mud.

[0058] Impact Drilling Construction Statistics Table

[0059]

[0060] In summary, three different processes were employed for engineering piles of varying diameters during construction. Field tests revealed that the long auger drilling and grouting machine achieved the fastest hole-forming speed, but subsequent concrete grouting encountered problems, hindering its stable operation. A single impact drill took approximately 30 hours to complete the hole, offering high economic efficiency but low overall efficiency. The combined operation of a multi-functional drilling rig 1 and a rotary drilling rig 2 leveraged the advantages of each, reducing the hole-forming time to 3.6 hours with stable efficiency. Therefore, the combined operation of a multi-functional drilling rig 1 and a rotary drilling rig 2 for engineering pile construction is the optimal solution.

[0061] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention; therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0062] Although this document frequently uses reference numerals from the figures, such as "multi-functional drilling rig 1," "auger bit 11," "steel casing 12," "mud wall protection 13," "rotary drilling rig 2," "rotary drilling bit 21," "soft soil layer 3," and "pebble layer 4," the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A construction method for drilling cast-in-place piles in a soft soil layer to a gravel layer, wherein the soft soil layer is located on the surface of the gravel layer; characterized in that, Includes the following steps: Step A: Measure the depth of the soft soil layer (3) and customize a steel sleeve (12) of the appropriate length according to the depth of the soft soil layer (3). Step B: Load the steel casing (12) and the auger bit (11) onto the multi-functional drilling rig (1), and drill the steel casing (12) and the auger bit (11) into the soft soil layer (3) at the same time. The multi-functional drilling rig (1) is equipped with a hydraulic press for loading the steel casing (12). The hydraulic press is sleeved on the auger bit (11). The hydraulic press moves up and down along the height direction of the multi-functional drilling rig (1), and the hydraulic press drives the steel casing (12) to rotate synchronously during the lifting and lowering process. Step C: Until the bottom of the steel casing (12) is pressed to the bottom of the soft soil layer (3), loosen the connection between the steel casing (12) and the multi-functional drilling rig (1), and move the multi-functional drilling rig (1); Step D: Inject mud slurry into the bottom of the steel casing (12) for wall protection (13); Step E: Move the rotary drilling rig (2) to the steel casing (12) and position the rotary drilling rig (2) in the hole; Step F: The rotary drilling rig (2) performs hole drilling in the gravel layer (4); Step G: After the hole is formed, the steel cage is hoisted in and installed, and the concrete guide pipe is lowered for underwater concrete pouring. Step H: After the grouting is completed, remove the steel sleeve (12). While the rotary drilling rig (2) is operating, the multi-functional drilling rig (1) can continuously construct the next pile hole.

2. The construction method for drilling cast-in-place piles in soft soil to gravel layers according to claim 1, characterized in that, Before the construction of the steel casing (12) in step B, the location of the steel casing (12) to be erected is determined by the pile core positioning, and the multi-functional drilling rig (1) is positioned and adjusted.

3. A construction method for drilling bored piles in soft soil to gravel layers according to claim 2, characterized in that, In step B, when the steel casing (12) and the auger drill bit (11) are simultaneously drilling into the soft soil layer (3), the auger drill bit (11) performs soil removal operations inside the steel casing (12).

4. A construction method for drilling cast-in-place piles in soft soil to gravel layers according to claim 3, characterized in that, The length of the steel casing (12) is not less than the depth of the soft soil layer (3).

5. A construction method for drilling cast-in-place piles in soft soil to gravel layers according to claim 1, characterized in that, In step C, after loosening the connection between the steel casing (12) and the multi-functional drilling rig (1), the steel casing (12) is fixedly buried in the soft soil layer (3).

6. A construction method for drilling cast-in-place piles in soft soil to gravel layers according to claim 1, characterized in that, After the rotary drilling rig (2) positions the hole in step E, the rotary drilling bit (21) of the rotary drilling rig (2) moves downward along the steel casing (12).

7. A construction method for drilling cast-in-place piles in soft soil to gravel layers according to claim 1, characterized in that, After the hole-forming process in step F, the hole is inspected and the first hole cleaning operation is carried out.

8. A construction method for drilling cast-in-place piles in soft soil to gravel layers according to claim 1, characterized in that, After the concrete guide pipe below step G is installed, a second hole cleaning operation is performed.

9. A construction method for drilling and grouting piles in soft soil to gravel layers according to claim 1, characterized in that, The multi-functional drilling rig (1) performs construction work on the soft soil layer (3), and the rotary drilling rig (2) performs construction work on the gravel layer (4).

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