CN-122013757-A - Karst area pile foundation construction method and operation platform

CN122013757ACN 122013757 ACN122013757 ACN 122013757ACN-122013757-A

Abstract

The invention discloses a karst area pile foundation construction method and an operation platform, and relates to the field of pile foundation construction, wherein the method comprises the following steps of drilling a steel sleeve to bedrock by adopting a full-rotation sleeve drilling machine; the method comprises the steps of prefabricating a steel pile casing on the ground, respectively laying a first water-resisting layer and a second water-resisting layer on the inner wall and the outer wall of the steel pile casing, connecting a steel sling on the lower portion of the steel pile casing, hanging the composite pile casing into a steel sleeve, filling broken stone between the steel pile casing and the second water-resisting layer to form a broken stone layer, after the steel sleeve is pulled out, lowering a steel reinforcement cage, pouring pile body concrete, after the concrete is initially set, pulling out the steel pile casing through cooperation of the steel sling and lifting equipment, and finally grouting the two water-resisting layers. The operation platform comprises a bottom frame, an upper frame, a hydraulic lifting mechanism, a slewing mechanism and a prestress support, and the top of the steel casing is pulled out. The invention realizes the recycling of the steel pile casing, reduces the construction cost, forms a multiple permanent protection system at the periphery of the pile body, and improves the construction quality and durability of pile foundations in karst areas.

Inventors

CHANG ZHANHONG
DU RUIFENG
ZHAO NAN
CUI SHAOGUANG
You Zijia
LI BINGTAO
Jiao Jingxin
ZHANG LINHUI
ZHANG GUOBIN
Hou Shuaiwei
MA ZHENBIN
WEI YUEPEI
HOU WEIXIN
MA MING
Zhao Junpo
WANG LIFENG
Wei Yuekan
LIU LIQIANG
Qi Shuangjia
ZHOU JIE

Assignees

邢台路桥建设集团有限公司

Dates

Publication Date: 20260512
Application Date: 20260415

Claims (10)

1. The karst area pile foundation construction method is characterized by comprising the following steps of: S1, driving a full-rotation casing drilling machine to enable a steel sleeve (2) to rotationally cut a karst stratum (1) and drill downwards until a bedrock (10) is reached, and synchronously removing soil and crushed rock in the steel sleeve (2) in the drilling process; S2, prefabricating a steel pile casing (3) on the ground, laying a first water-resisting layer (4) on the inner wall of the steel pile casing (3), laying a second water-resisting layer (41) on the outer part of the steel pile casing (3), connecting the bottoms of the first water-resisting layer (4) and the second water-resisting layer (41), forming a composite pile casing structure by the steel pile casing (3), the first water-resisting layer (4) and the second water-resisting layer (41), connecting one end of a steel sling (8) on the outer wall of the lower part of the steel pile casing (3), and extending the other end of the steel sling (8) from the position between the steel pile casing (3) and the second water-resisting layer (41); S3, integrally hoisting the composite pile casing structure to enable the composite pile casing structure to be placed in the middle of the steel sleeve (2); S4, filling graded broken stone into a circumferential gap between the steel casing (3) and the second water-resisting layer (41) to form a broken stone layer (5); S5, after the crushed stone layer (5) is filled and compacted, starting a full-rotation sleeve drilling machine to rotationally pull out the steel sleeve (2); S6, placing a pile reinforcement cage (31) in the space surrounded by the first water-resisting layer (4), and pouring pile body concrete into the space; S7, when the pile body concrete reaches an initial setting state and volume expansion caused by hydration heat does not occur yet, the steel pile casing (3) is pulled out of the hole through the cooperation of the steel sling (8) and lifting equipment, and the first water-resisting layer (4), the second water-resisting layer (41) and the gravel layer (5) positioned between the two layers are all reserved in the hole; And S8, pouring cement paste into the space between the first water-resisting layer (4) and the second water-resisting layer (41), and solidifying the cement paste and the crushed stone layer (5) to form a crushed stone concrete composite layer.
2. The karst area pile foundation construction method according to claim 1, wherein the first water-proof layer (4) and the second water-proof layer (41) are made of PVC macromolecule waterproof coiled materials, a PVC base layer of the first water-proof layer (4) is contacted with the inner wall of the steel casing (3), an impervious crystallization layer of the first water-proof layer (4) faces to the inner side of a pile hole and is used for forming anchoring combination with pile body concrete, a PVC base layer of the second water-proof layer (41) faces to the inner wall of the steel sleeve (2), and an impervious crystallization layer of the second water-proof layer (41) faces to the inner side and is used for forming anchoring combination with the crushed stone concrete composite layer.
3. The karst area pile foundation construction method of claim 1, wherein: the bottom of the steel pile casing (3) is provided with a base (7), and the base (7) comprises an inner cylinder body (71), a bottom plate (72) and a plurality of plugboards (73); The outer diameter of the inner cylinder body (71) is smaller than the inner diameter of the steel protection cylinder (3), a plurality of vertical insertion holes (30) are formed in the bottom of the steel protection cylinder (3), the insertion plates (73) are horizontally arranged on the outer wall of the inner cylinder body (71) in a protruding mode, and the insertion plates (73) are in one-to-one corresponding insertion fit with the insertion holes (30); the bottom plate (72) is annular, is horizontally arranged on the outer edge of the bottom of the inner cylinder body (71) in a protruding mode and extends to the outer side of the steel protection cylinder (3), a plurality of positioning columns (74) are vertically arranged on the bottom plate (72), and all the positioning columns (74) are arranged at intervals on the outer side of the steel protection cylinder (3); The outer matching cover of reference column (74) is equipped with sheath (6), the bottom of sheath (6) with bottom plate (72) meets, just the length of sheath (6) with the length of second water barrier (41) equals, the outside of all sheaths (6) is located in second water barrier (41) around.
4. A karst region pile foundation construction method according to claim 3, wherein the sheath (6) is fixedly connected with the second water-resisting layer (41) through a plurality of hot-melt gaskets (62), one side of each hot-melt gasket (62) is fixedly connected with the inner wall of the second water-resisting layer (41), and the other side of each hot-melt gasket (62) is fixedly connected with the outer wall of the sheath (6).
5. A karst region pile foundation construction method according to claim 3, wherein the lower part of the steel casing (3) is provided with a plurality of sling supports (81), the sling supports (81) are matched with the inner wall of the sheath (6) and can vertically slide in the sheath (6), the sheath (6) is provided with a through groove (61) along the length direction, the through groove (61) penetrates through the side wall of the sheath (6), the insertion plate (73) is arranged between the inner cylinder (71) and the positioning column (74) and penetrates through the through groove (61), and when the sheath (6) is matched and sleeved on the positioning column (74), the notch of the through groove (61) is contacted with the outer wall of the steel casing (3); The connecting part of the sling support (81) and the steel pile casing (3) penetrates through the through groove (61), the sling support (81) is connected with the bottom end of the steel sling (8), and the rope body of the steel sling (8) is penetrated inside the sheath (6).
6. A karst region pile foundation construction method according to claim 3, wherein the bottom of the first water barrier (4) is disposed in an annular gap between the steel casing (3) and the inner cylinder (71), and the bottom of the second water barrier (41) bypasses the lower edge of the bottom plate (72) and is folded upwards to form lap seal with the first water barrier (4).
7. The karst area pile foundation construction method according to claim 1, wherein the crushed stone layer (5) is filled with pebbles, the pebbles are continuous gradations with the particle size of 5 mm-25 mm, the mass ratio of particles with the particle size of 5 mm-10 mm is 25% -35%, the mass ratio of particles with the particle size of 10 mm-20 mm is 40% -55%, the mass ratio of particles with the particle size of 20 mm-25 mm is 10% -20%, the pebbles are round or sub-round, the needle-shaped particle content is not more than 5%, the mud content is not more than 1%, and the mud content is not more than 0.5%.
8. Karst region pile foundation construction method according to claim 5, characterized in that the arrangement of the steel slings (8) satisfies: Wherein n is the number of steel slings, Allowing tension for a single steel sling, G being the dead weight of the steel casing, The pull-up force of the full-rotation casing pipe drilling machine to the steel casing pipe, Is the total friction force of the inner side of the steel protective cylinder, Is the total friction force of the outer side of the steel casing, Is the friction coefficient between the steel casing and the first water-resisting layer, Is the friction coefficient between the steel casing and the crushed stone layer, The effective lateral pressure during initial setting of concrete, the diameter of the steel pile casing, the pile length of the steel pile casing, the pressure transmission reduction coefficient of the crushed stone layer of the steel pile casing, the pressure transmission reduction coefficient of the crushed stone is 0.2-0.5, Is the static side pressure coefficient of the crushed stone layer, Is the crushed stone layer.
9. Karst area pile foundation operation platform is applied to the karst area pile foundation construction method of any one of claims 1 to 8, and is characterized by comprising: a bottom frame (91) placed on the ground; An upper frame (92) provided above the bottom frame (91); The hydraulic lifting mechanism (93) is connected between the bottom frame (91) and the upper frame (92) and is used for driving the upper frame (92) to lift relative to the bottom frame (91); The slewing mechanism (94) is arranged on the upper frame (92) and used for clamping the outer wall of the steel sleeve (2) or the steel casing (3) and driving the clamped steel sleeve (2) or the steel casing (3) to rotate; And a pre-stressing bracket (95) mounted on the upper frame (92) for fixing the upper end of the steel sling (8) and tensioning the steel sling (8).
10. Karst region pile handling platform according to claim 9, further comprising temporary fixing means provided to the bottom frame (91) or to the ground for temporarily fixing the steel casing (3) when the slewing mechanism (94) releases the steel casing (3) and the pre-stressing support (95) releases the steel slings (8).

Description

Karst area pile foundation construction method and operation platform Technical Field The invention relates to the field of pile foundation engineering construction. More particularly, the invention relates to a karst region pile foundation construction method and an operation platform. Background Karst areas are widely distributed with unfavorable geological phenomena such as karst cave, solution gap, fissure, underground river, etc., and the stratum structure is uneven and the stability is poor. When the bored pile is constructed in such areas, wall protection slurry can be lost instantaneously along cracks in the conventional pore-forming process, so that the hole wall is lost to be supported, collapse, burial and other accidents are easy to occur, meanwhile, the existence of a cavity of a karst cave can cause the excessive pouring and loss easily in the concrete pouring process, and even the quality defects of pile body mud clamping, pile breaking, pile bottom hollowed-out and the like occur, so that the bearing capacity and durability of a pile foundation are seriously affected. In order to ensure pile forming quality, a full sleeve follow-up process is commonly adopted in engineering, namely, a full-rotation sleeve drilling machine is utilized to drive a steel sleeve to drill in a rotating mode, so that the steel sleeve penetrates through a karst cave development area and is embedded into a lower stable bedrock, bad stratum is isolated by means of the rigid retaining wall effect of the steel sleeve, and a safe operation space is provided for subsequent construction. In the full casing follow-up process, there is a class of construction methods employing double casings (double casing) in addition to the conventional single casing process. Compared with a single casing process, the double-casing method has the advantages that when the situation of crack groups, plastic-flowing fillers or communicated bead string karst cave groups is met, the outer steel casing is recovered after drilling and rigid wall protection functions are carried out, the inner steel casing provides a closed forming space for concrete pouring, and the plastic-flowing fillers in the karst cave are prevented from rushing into holes and the concrete is prevented from being lost in a large amount. For example, chinese patent CN114673188a discloses a method for pile foundation construction in karst areas, which uses an outer casing to drill in a follow-up manner, installs an inner casing in the outer casing and pours concrete, and pulls out the outer casing after the concrete is coagulated, wherein the inner casing is permanently left in the pile hole. For another example, chinese patent CN113445498a discloses a construction process of a complex geological karst hole pile foundation, and the double steel casing full sleeve follow-up method also adopts the procedures of outer steel casing drilling, inner steel casing installation, and outer steel casing pulling out after concrete pouring. In practical operation, other similar double-casing construction processes are also practically applied. The construction method comprises the steps of rotationally pressing an outer layer steel sleeve to a designed depth by adopting a full-rotation sleeve drilling machine, meanwhile removing soil in the sleeve, then, placing a permanent steel pile casing with the inner diameter identical to the diameter of a designed pile in the outer layer steel sleeve, filling broken stone in a circumferential gap between the permanent steel pile casing and the outer layer steel sleeve, pulling out the outer layer steel sleeve after filling is finished, enabling the broken stone layer to wrap the periphery of the permanent steel pile casing, and finally, placing a reinforcement cage in the permanent steel pile casing and pouring pile body concrete. According to the construction method, poor stratum such as karst cave and the like are effectively isolated through the combined action of the permanent steel pile casing and the gravel layer, the concrete loss is prevented, and the pile body forming quality is ensured. However, the prior art solutions have a common problem that the inner steel casing in the double-sleeve method or the permanent steel casing in the method of 'steel sleeve + permanent steel casing' is not taken out after concrete casting, but is buried underground as a permanent structure. The pile foundation in karst area needs to penetrate karst cave to embed bedrock, so that pile body is generally deep and long, the contact area between steel pile casing and concrete is larger than that of conventional cast-in-place pile in steel sleeve form, and the pile body and the concrete form bonding effect after initial setting. If only rely on top play equipment after concrete sets, not only very easily lead to the tube drawing failure because of bonding resistance, the tube drawing power can pass through the bonding interface and transmit to the pile body moreov