Pile foundation construction structure

Abstract

The utility model discloses a pile foundation construction structure which is applied to a geological environment in which a soil layer, a rock layer and a geological cavity are sequentially formed from top to bottom, a pile casing is embedded in the soil layer, a rotary drilling hole for forming a hole by a rotary drilling rig is formed between the soil layer and the rock layer, and the rotary drilling hole is communicated with the pile casing; a rock stratum is penetrated, fluid slurry is poured into the geological cavity, and a hole-forming protection wall is formed by grouting the geological cavity; and an impact hole formed by a punching pile machine is formed in the hole-forming protection wall, the impact hole communicates with the rotary digging hole, the impact hole and the rotary digging hole jointly form a pile hole, a reinforcement cage is placed in the pile hole, and a pile foundation is formed by pouring the reinforcement cage. Compared with an existing pile foundation construction structure, rotary drilling and impact drilling are combined, and the advantages of different drilling modes are fully utilized; in addition, due to the formation of the pore-forming protection wall, ground collapse caused by soil layer loss in the construction process is avoided to a great extent, and the construction risk is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of infrastructure construction, in particular to a pile foundation construction structure. Background Art

[0002] During the engineering construction, the karst caves in some areas are more developed, and there are sparsely filled soil caves. It is preliminarily judged that during the pile foundation drilling process, the underground soil caves are touched or the thin roof above the karst caves is penetrated, resulting in the penetration of possible underground soil caves (karst caves). Karst caves, karst troughs or dissolution cracks are relatively developed, and thicker weak layers (silty silty clay) and sand layers (saturated medium and fine sand) are widely distributed, which are easy to lose and cause ground collapse. In the process of pile foundation drilling, mud is easy to lose and cause hole collapse.

[0003] At present, the process of drilling holes with a rotary drilling rig or punching holes with a punching pile machine is widely used in pile foundation cast-in-place pile construction projects. The drilling hole with a rotary drilling rig is not easy to form mud skin, and the wall protection is relatively poor, which is easy to shrink and collapse the hole; for the drilling of clay with high viscosity, the drilling rate is not high, the main clay is adsorbed on the wall of the bucket tube, which is not easy to remove, and the opening of the bottom plate of the bucket tube is prone to failure, and it is often necessary to vibrate the bucket tube or use manual help to clean it; the drill bit is more damaged when drilling to the rock layer; when the rotary punching machine is punched to the half-side rock or inclined rock, it is easy to cause the teeth to break, the drill rod to break, and the drill bit to be damaged due to uneven force; and the equipment cost is high, and the construction cost is higher than other hole-forming methods. The punching pile machine punches the pile once: when using a wire rope to pull the impact head for impact drilling, most of the operation time is consumed in lifting and lowering the drill bit and removing the slag soil, and the drilling speed is slow; as the pile body deepens, the slag removal time and the slag cleaning time at the bottom of the hole are relatively long, and the hole formation takes a long time.

[0004] Since the existing drilling technology and its construction structure have some inherent defects, the construction difficulty and cost of complex geological conditions have increased significantly. Therefore, it is necessary to improve the existing construction structure to optimize the construction conditions of the project. Utility Model Content

[0005] The utility model aims to provide a pile foundation construction structure to solve the technical problem that pile foundation pouring is difficult to construct in complex geology.

[0006] A pile foundation construction structure according to the first aspect of the embodiment of the utility model is applied to a geological environment with soil layers, rock layers and geological cavities formed in sequence from top to bottom, a casing is buried in the soil layer, a rotary drilling hole formed by a rotary drilling rig is formed from the soil layer to the rock layer, and the rotary drilling hole is connected to the casing; the rock layer is penetrated and fluid slurry is poured into the geological cavity, and a hole protective wall is formed by grouting the geological cavity; an impact hole formed by a punching pile driver is formed in the hole protective wall, the impact hole is connected to the rotary drilling hole, the impact hole and the rotary drilling hole together constitute a pile hole, a steel cage is placed in the pile hole, and a pile foundation is formed by pouring the steel cage.

[0007] A pile foundation construction structure according to an embodiment of the utility model has at least the following beneficial effects: compared with the existing pile foundation construction structure, since the utility model combines rotary drilling and impact drilling and fully utilizes the advantages of different drilling methods, it can significantly reduce the drilling cost and shorten the construction period, especially in areas with developed karst caves with thicker soil layers. In addition, the formation of the drilling protective wall can largely avoid ground collapse caused by soil loss during construction, thereby reducing construction risks.

[0008] According to some embodiments of the utility model, the distance between the rotary drilling hole and the surface of the rock formation is controlled within 1.5 meters, and the impact hole passes through the rock formation. Compared with the punching pile machine, since the rotary drilling rig has no advantage in rotary drilling of rock formations, the punching pile machine is used to punch holes in the rock formation. In order to avoid direct contact between the punching pile machine and the rock formation, thereby extending the service life of the punching pile machine, the rotary drilling rig stops drilling at a position within 1.5 meters from the surface of the rock formation to reserve a certain soil layer as a cushion between the punching pile machine and the rock formation.

[0009] According to some embodiments of the present invention, optionally, the distance between the rotary drilling hole and the rock formation surface is controlled to be 1 meter.

[0010] According to some embodiments of the present invention, if the geological cavity is a soil cave or a karst cave, the fluid slurry is selected to be a mixture of composite silicate cement slurry and water glass.

[0011] According to some embodiments of the present invention, optionally, the water-cement ratio of the composite silicate cement slurry is 0.5 to 1, and the Baume degree of the water glass is 35 to 40.

[0012] According to some embodiments of the utility model, in order to facilitate the circulation of mud, a slurry outlet is opened at the upper end of the casing.

[0013] According to some embodiments of the utility model, the rotary drilling hole has a liquid storage chamber to ensure the water head in the hole.

[0014] According to some embodiments of the present invention, in order to ensure the position accuracy of the pile foundation, the central axis of the steel cage coincides with the central axis of the pile hole.

[0015] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0017] Figure 1 It is a structural schematic diagram of the pile foundation construction structure of an embodiment of the utility model.

[0018] In the attached drawings: 100 - soil layer, 200 - rock layer, 300 - geological cavity, 400 - casing, 510 - rotary drilling hole, 310 - hole forming wall protection, 520 - impact hole, 500 - pile hole, 610 - steel cage, 600 - pile foundation. DETAILED DESCRIPTION

[0019] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0020] In the description of the present invention, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0021] In the description of the present utility model, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood to exclude the number itself, and "above", "below", "within" etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0022] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0023] like Figure 1 As shown, a pile foundation construction structure according to the first embodiment of the utility model is applied to a geological environment with soil layer 100, rock layer 200 and geological cavity 300 formed in sequence from top to bottom, that is, the utility model is applied to a geological environment with karst caves or soil caves. The underground of this terrain has complex and changeable conditions, and the construction is difficult. At present, the construction of pile foundation 600 for this terrain is generally done by a one-time hole forming by a rotary drilling rig or a punching pile driver. Although the rotary drilling rig is superior to the punching pile driver in terms of construction efficiency, it does not have an advantage when rotary drilling the rock layer 200. The rotary drilling rig has a large loss on the drill bit when rotary drilling to the rock layer 200, and when the rotary drilling rig is rotary drilling to the half-rock or inclined rock, the teeth will be broken, the drill rod will be broken, the drill bit will be damaged, etc. due to uneven force; compared with the rotary drilling rig, although the punching pile driver has a lower construction efficiency, it has more advantages in opening holes in the rock layer 200, and the construction cost is lower.

[0024] Combining the advantages and disadvantages of the above two hole-forming methods, the utility model proposes a rotary punching hole-forming method, whose construction structure is as follows: a casing 400 is buried in the soil layer 100, and a rotary drilling hole 510 is formed from the soil layer 100 to the rock layer 200 by a rotary drilling rig (not shown in the drawings), and the rotary drilling hole 510 is connected to the casing 400; the rock layer 200 is penetrated and a fluid slurry is poured into the geological cavity 300, and the geological cavity 300 is formed by drilling a hole 510 with a rotary drilling rig (not shown in the drawings). grouting to form a hole-forming protective wall 310; an impact hole 520 formed by a punching pile driver is formed in the hole-forming protective wall 310, the impact hole 520 is connected to the rotary drilling hole 510, the impact hole 520 and the rotary drilling hole 510 together constitute a pile hole 500, a steel cage 610 is placed in the pile hole 500, and a pile foundation 600 is formed by pouring the steel cage 610, and the casing 400 is no longer taken out after construction and becomes a part of the pile foundation 600.

[0025] By adopting the above-mentioned structure, compared with the existing pile foundation construction structure, since the utility model combines rotary drilling and impact drilling and fully utilizes the advantages of different drilling methods, it can significantly reduce the drilling cost and shorten the construction period, especially in the karst cave development areas with thicker soil layers 100. In addition, the formation of the drilling protective wall 310 largely avoids ground collapse caused by the loss of the soil layer 100 during the construction process, thereby reducing construction risks.

[0026] In order to facilitate the understanding of those skilled in the art, some specific construction methods of rotary punching are listed below. It should be noted that the construction methods listed below should not be understood as limiting the protection scope of the claims.

[0027] 1. Precautions for casing:

[0028] 1. Casing diameter and thickness: Casing 400 is a steel component, and its inner diameter should be 20cm to 40cm larger than the drill bit diameter of the rotary drilling rig; the thickness is guaranteed to be 1 / 130d to 1 / 150d, and not less than 10mm.

[0029] 2. Casing sinking: adopt the drilling follow-up sinking process. During the drilling process, appropriate wall protection measures need to be taken to ensure the stability of the overburden layer, such as increasing the mud specific gravity and strictly controlling the drilling footage. If the drilling reveals the existence of soil caves in the overburden layer or shallow karst caves with a rock layer of 200, pre-grouting treatment is appropriate.

[0030] 3. Casing depth: Passing through the silt layer, loose sand layer, and entering the clay layer 100 (hard plastic or plastic state) is not less than 2m. If the silt layer or sand layer is directly connected to the surface of the rock layer 200, the casing 400 should be sunk into the rock for about 0.5m.

[0031] 4. Protection of blade foot: For the casing 400 sunk to the surface of the rock layer 200, when the bottom reaches the rock surface, the blade foot of the casing is protected by throwing stone flakes, clay or pouring concrete to ensure the safety of the casing blade foot.

[0032] 2. Rotary digging into holes

[0033] According to the geological conditions provided in the advance drilling report, the construction drill reached the surface of the rock layer 200, and slow drilling was adopted at about 1.5 meters above the rock surface.

[0034] 1. Before the rotary drilling rig is put into place, all preparations for the rotary drilling rig should be checked. The base and top of the rotary drilling rig should be stable after installation. After the center is checked, the mud circulation system is connected, and the mud pump is started to circulate the mud for 2 to 3 minutes, and then the drilling is started. The drilling should be carried out at a low pressure and slow speed at the bottom of the casing 400, and normal drilling should be started after drilling to about 1 meter below the bottom of the casing 400. In order to facilitate the circulation of mud, a mud outlet is opened at the upper end of the casing 400 (not shown in the drawings).

[0035] 2. Rotary drilling rigs generally use a barrel drill bit. During construction, after the drill bit is lowered to a predetermined depth in the hole, the drill bit is turned and pressurized, and the rotated soil is squeezed into the drill barrel. After the drill barrel is filled with soil, the drill bit is reversed, the bottom of the drill bit is sealed and lifted out of the hole, and then the switch at the bottom of the drill bit is automatically turned on, and the abandoned soil is poured out to form a hole. During the drilling process or after the drill bit is lifted out of the borehole, grouting is injected into the hole, and the mud liquid level must not be lower than 400° at the bottom of the casing.

[0036] 3. Pre-grouting treatment

[0037] Pre-grouting is a pre-treatment measure taken before the construction of pile foundation 600 punching for the large-volume karst caves and earth caves that have been explored, when there is no filling or the filling is of poor quality. Grouting can solidify the filling in the karst and earth caves to form a better hole protection wall 310. At present, pre-grouting treatment is divided into two categories: static pressure grouting and karst cave grouting. For the situation where the earth caves in the overburden layer and the shallow karst caves on the rock surface need to be treated in this method, static pressure grouting should be used. The main methods are sleeve valve pipe grouting and flower pipe grouting.

[0038] The principles for developing pretreatment plans for different types of karst (soil) caves are shown in the following table:

[0039]

[0040]

[0041] Precautions for grouting using sleeve valve pipe:

[0042] 1. Use plum blossom-type drilling and grouting, the spacing between grouting holes shall not exceed 3m, and the plane error of the grouting holes shall not exceed 50mm.

[0043] 2. The sleeve valve tube must be extended into the bottom of the cave, and the lower tube position must be accurate, and it should be placed in the center of the borehole as much as possible. Deformed or thread-damaged flower tubes cannot be used to reduce the possibility of incomplete grouting or leakage in the cave.

[0044] 3. To fix the grouting of the pipe, it is necessary to ensure that the pipe will not move, deform, or leak grout around during the grouting process. Use cement slurry and add some glass water to speed up the solidification and increase the strength.

[0045] 4. The slurry should be prepared strictly according to the mix ratio. The slurry for grouting should be fully stirred and evenly stirred. Stir slowly during the grouting process. Use a hydrometer to measure the slurry concentration. The mix ratio error should be ≤5%. Determine the slurry volume according to the volume of the mixing barrel.

[0046] 5. Grouting should be carried out strictly according to the grouting pressure. When grouting starts, low pressure of 0.5Mpa to 0.8Mpa should be selected for pressure testing. Parameters such as drilling depth, grouting pressure of each round, grouting volume of each round, grouting time of each round and total grouting volume should be recorded in detail, so as to control the grouting speed during the grouting process. For multi-layer caves, fill them up step by step from bottom to top.

[0047] 6. During grouting, 3 to 5 leveling observation points should be set up on the ground surface for monitoring. Cracks and uplift are not allowed on the ground. Once they occur, the grouting pressure should be reduced in time. After analysis, corresponding measures should be taken, such as stopping grouting and waiting for solidification before grouting again, adding glass water to the grouting holes to allow it to emerge and accelerate the solidification of the cement slurry in the hole before grouting again.

[0048] 7. The grouting parameters in the actual construction of double-liquid grouting should be adjusted according to the specific actual situation. Especially when it comes to grouting in caves and soil caves, it is injected into the caves, soil caves, and soil gaps that have been filled with cement slurry. By using its rapid solidification characteristics, the slurry can be controlled to be poured within a certain range without loss, so that the cement slurry filled in the cave is fully squeezed and bonded into a whole, achieving the purpose of treating the caves, soil caves, and soil gaps.

[0049] 8. Use sleeve valve pipe grouting method. Control of problems in the process of cave treatment: For individual caves with excessive single grouting volume: When it is found that the single grouting volume of the first hole exceeds 100 tons of cement, it is necessary to stop grouting and clean the grouting pipe, and then grouting again after the injected cement slurry solidifies; if the second grouting exceeds 50 tons of cement, flush the grouting pipe again and stop grouting to allow the injected cement slurry to solidify again; the third grouting needs to be added with glass water according to the proportion of the plan, which can accelerate the rapid solidification of the injected cement slurry in the cave and reduce the fluidity of the cement slurry injected into the cave to achieve the effect of filling.

[0050] 9. When grouting, if grouting is found around, you need to reduce the grouting pressure or stop grouting. When the grouting area begins to shrink, add glass water to allow the grouting hole to solidify quickly to achieve the purpose of sealing, and then grouting again.

[0051] 10. When encountering holes in areas with large grouting volume, grouting should be done multiple times. The pipes need to be flushed clean after each grouting to prevent clogging of the sleeve valve pipe and affecting the effect of the next grouting.

[0052] 4. Impact Hole Forming

[0053] When the rotary drilling rig drills to about 1 meter from the rock surface, the punching pile machine is used to drill the hole. In the initial stage, a small stroke (5cm / h to 10cm / h) is used to break through the rock surface. Once it reaches the cave, water leakage and slurry leakage may occur. At this time, slurry should be replenished in time to ensure the water head in the hole. At the same time, the drill is lifted and a 1:1 stone-clay mixture is thrown and filled to 1 to 2 meters below the hole mouth, and the punching pile machine is used again to punch holes. In order to avoid direct contact between the punching pile machine and the rock layer 200, thereby extending the service life of the punching pile machine, the rotary drilling rig stops drilling at a position within 1 meter from the surface of the rock layer 200 to reserve a certain soil layer 100 as a cushion between the punching pile machine and the rock layer 200.

[0054] 5. Follow-up of casing

[0055] To ensure construction safety, the drilling is followed by casing. The casing 400 to the rock surface is processed with 10mm thick steel plate, and each section of casing 400 is 6 meters long. When the full casing is followed, the rock casing 400 is processed with 12mm thick steel plate to ensure the quality of the casing 400 after entering the rock. The inner diameter of the lowest casing 400 is designed according to the pile diameter, and the upper part is expanded with a modulus of 200mm according to the number of caves. The total length L of the casing 400 is calculated as follows:

[0056] L≥H+2n, where H is the designed pile length of the bored pile and n is the number of casings of different levels, indicating that casings of different levels overlap by 1m.

[0057] The processing size of the casing 400 must be strictly controlled. In addition to welding, a 10 cm wide reinforcing steel belt is welded at the joints of the upper and lower sections of the casing 400. The plane formed by the horizontal joints of the casing 400 is perpendicular to the vertical direction of the casing 400, so that the verticality of the entire casing 400 meets the requirements. The vibrating hammer is firmly welded to the top surface of the casing 400 without looseness. The vibrating hammer is required to be located in the top surface of the casing 400, and the verticality of each section of the sinking casing 400 must be strictly controlled.

[0058] When lowering the casing 400, its position must be accurate. After lowering, check its elevation, verticality, and horizontality of the top surface of the casing. If it exceeds the allowable error, correct it in time. When the impact passes through the top of the cave, the hammer should be lifted repeatedly, and slowly lowered and gently lifted within the top thickness range. The hammer is not obviously blocked. At this time, the inner casing is tied with a wire rope buckle, and the casing 400 is lowered into the open space with a crane. If necessary, it can be sunk with a vibrator. When using the impact drill to follow up the construction of the casing, the hole expansion performance of the impact drill should be fully utilized during construction so that the casing 400 can sink smoothly.

[0059] The casing 400 is followed to the bottom of the designed pile length, and the construction is continued according to the conventional pile construction process. After the pile is completed, the casing 400 is permanently buried in the side wall of the pile body.

[0060] 6. Installation and hoisting of steel cage

[0061] 1. The reinforcement of 610 steel cage must be arranged according to the design requirements. The joints of the main bars should be staggered to ensure that the number of joints does not exceed 50% of the total number of main bars in the same section. Welding should be used to extend the longitudinal steel bars. Steel bars with d < 22 are allowed to be overlapped with a lap length of 35d. The interfaces must be staggered according to the specifications. When welding is used, the steel bar joints should be sampled and sent for inspection.

[0062] 2. The joints of the main reinforcement of the steel cage 610 are single-sided lap welding. The number of joints on each section shall not exceed 50%, and the joints shall be staggered by more than 50cm. The connection between the reinforcement stirrups and the main reinforcement shall be fully welded. The materials, processing, joints and installation of the steel cage 610 meet the requirements. The density is set at one every 2 meters vertically, and each row shall be arranged along the circumference for no less than 3.

[0063] 3. For shorter pile foundations 600, the steel cage 610 should be made into an integral unit and hoisted into place at one time. For pile foundations 600 with larger hole depths, the steel cage 610 needs to be welded on site, and the length of the steel cage 610 segments should not be less than 6 meters to reduce the workload of on-site welding. In order to ensure that the frame does not deform during hoisting, for long frames, cross braces should be welded inside the reinforced frame before hoisting to increase its rigidity.

[0064] 4. The top end of the frame must be positioned. The length of the positioning bar must be calculated based on the measured hole elevation, and the positioning ring or fixing rod must be welded after repeated verification. A crosshair is drawn on the steel cage 610 to find the center of the steel cage 610, so that the central axis of the steel cage 610 coincides with the central axis of the pile hole 500, and the plane position deviation is no more than 5cm, and the bottom elevation deviation is no more than ±10cm.

[0065] 5. Insert two parallel I-beams or channel steels under the top lifting ring at the top of the positioning steel frame, place two parallel sleepers on both sides of the casing 400 (about 5 cm higher than the casing), and support the entire positioning frame on the sleepers.

[0066] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. A pile foundation construction structure, applied to a geological environment having a soil layer (100), a rock layer (200) and a geological cavity (300) formed in sequence from top to bottom, characterized in that: A casing (400) is buried in the soil layer (100), and a rotary drilling hole (510) is formed between the soil layer (100) and the rock layer (200) by a rotary drilling rig, and the rotary drilling hole (510) is connected to the casing (400); before the punching construction, the rock layer (200) is penetrated and a fluid slurry is poured into the geological cavity (300), and a hole is formed by grouting the geological cavity (300). A protective wall (310); an impact hole (520) formed by a punching pile driver is formed in the hole-forming protective wall (310); the impact hole (520) is connected to the rotary drilling hole (510); the impact hole (520) and the rotary drilling hole (510) together constitute a pile hole (500); a steel cage (610) is placed in the pile hole (500); and a pile foundation (600) is formed by pouring the steel cage (610).

2. A pile foundation construction structure according to claim 1, characterized in that: The distance between the rotary drilling hole (510) and the surface of the rock layer (200) is controlled within 1.5 meters, and the impact hole (520) passes through the rock layer (200).

3. A pile foundation construction structure according to claim 2, characterized in that: The distance between the rotary drilling hole (510) and the surface of the rock layer (200) is controlled to be 1 meter.

4. A pile foundation construction structure according to claim 1, characterized in that: The upper end of the casing (400) is provided with a slurry outlet.

5. A pile foundation construction structure according to claim 1, characterized in that: The rotary drilling hole (510) has a liquid storage cavity.

6. A pile foundation construction structure according to claim 1, characterized in that: The central axis of the steel cage (610) coincides with the central axis of the pile hole (500).

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