Soil taking and precast pile planting method under karst cave geology
By dividing the pile holes into upper diameter holes and lower diameter holes under the geological conditions of the cave, and using the prefabricated pile planting method of ring baffles, the quality problems and uncertainties of traditional drilled cast-in-place piles in the construction of cave geological conditions are solved, and a more efficient and controllable pile foundation construction is achieved.
Patent Information
- Application Number
- CN202510029366.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-08
- Publication Date
- 2025-04-11
AI Technical Summary
Under the geological conditions of the cave, traditional drilling and cast-injected pile construction is prone to quality problems such as bottom sediment, broken piles, neck shrinkage, exposed tendons, mud clamping, concrete separation, and leakage of slurry. The construction period is long and the cost is high, and there is uncertainty.
The prefabricated pile method of soil extraction and planting under the cave geology is used to divide the pile holes into upper diameter holes and lower diameter holes. Combined with a circular baffle with a suitable diameter, the integrity of the bedrock at the end of the pile is judged through two concrete liquid level measurements, and the second concrete pouring is carried out after determining the foundation pile holding layer.
It effectively solved the problem of pile side slurry leakage in the pile planting method under the cave geology, improved the stability of the pile foundation and the controllability of construction, reduced construction costs and construction periods, and reduced uncertainty in construction.
Smart Images
Figure CN119800996A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of pile foundation engineering, and in particular to a method for taking soil and planting prefabricated piles under karst geology. Background Art
[0002] Karst geology is an inevitable problem encountered in pile foundation construction. The karst geological conditions are extremely complex. Unfavorable geological conditions such as karst caves, karst grooves and karst troughs of various shapes and sizes are widely distributed in the strata. The existence of these geological structures significantly increases the difficulty of pile foundation construction. Under karst geological conditions, the traditional bored cast-in-place pile construction technology is more likely to have common quality problems such as sediment at the bottom of the hole, broken piles, neck shrinkage, exposed reinforcement, mud inclusions, concrete segregation, leakage, over-pouring, etc., especially the over-pouring of bored piles can reach more than 5 times the theoretical value, and there is a possibility of slow leakage after pouring, resulting in the loss of pile body concrete and the possibility of becoming a waste pile. Not only is the construction period long and the cost high, but the construction is also full of uncertainty. Summary of the invention
[0003] In view of the deficiencies in the prior art, the present invention provides a method for taking soil from karst caves and planting prefabricated columns. The method effectively solves the problem of pile side leakage in the pile planting method in karst caves by dividing the pile hole into an upper diameter hole and a lower diameter hole and using a circular baffle of appropriate diameter.
[0004] The present invention achieves the above technical objectives through the following technical means.
[0005] A method for taking soil and planting prefabricated piles under karst geology comprises the following steps:
[0006] Step 1: Select an interface 0 to 5 m above the rock surface elevation, drill a large diameter hole above the interface, and drill a small diameter hole below the interface;
[0007] Step 2: Calculate the volume of the concrete to be poured under the cave according to the height difference between the cave bottom elevation and the pile bottom elevation, perform the first concrete pouring, and record the concrete liquid level elevation at this time;
[0008] Step 3: Within a certain period of time, measure the concrete liquid level again and compare it with the concrete liquid level in step 2. If the depth changes, it proves that there is leakage, and continue to drill down until the complete rock layer is found. If the depth does not change during the two measurements, it proves that there is no leakage, indicating that the lower part of the cave to the pile end is complete bedrock, which meets the requirements of being a bearing layer for the foundation pile.
[0009] Step 4: After determining the bearing layer of the foundation pile, the precast pile is pressed into the bottom of the hole from the center pile position, and the annular baffle is installed so that the annular baffle is located at the junction of the large diameter hole and the small diameter hole, and the second concrete pouring is carried out.
[0010] In the above solution, the outer diameter of the annular baffle is smaller than the inner diameter of the large-diameter hole, and larger than the inner diameter of the small-diameter hole.
[0011] In the above solution, the inner diameter of the annular baffle is 5 to 10 mm larger than the outer diameter of the precast pile.
[0012] In the above solution, the annular baffle is an integral structure. After the prefabricated pile is pressed into the bottom of the hole, the annular baffle is directly inserted from the top of the pile.
[0013] In the above scheme, the annular baffle is a two-half structure, which is clamped in the set position of the precast pile, connected by bolts, and enters the pile hole together with the precast pile.
[0014] In the above scheme, in step 2, before the first concrete pouring, a conduit is set in the small diameter hole, the conduit is 0.3 to 0.5 m away from the bottom of the lower hole, and the conduit is retracted after the first concrete pouring.
[0015] In the above scheme, in step 3, the certain period of time is 10 minutes to 40 minutes.
[0016] In the above scheme, before construction, excavation and burying of casing are carried out.
[0017] In the above scheme, in step 4, after the precast pile is pressed into the bottom of the hole, slurry or solidified soil with a specific gravity less than that of concrete is first poured to completely fill the cave, and then the annular baffle is installed.
[0018] In the above scheme, in step 1, drilling a large diameter hole and a small diameter hole corresponds to drill bits of different diameters, respectively.
[0019] Beneficial effects:
[0020] 1. Make full use of the natural advantages of precast piles with good pile body quality and high bearing capacity, and organically combine precast piles with concrete through pile planting method. The precast piles bear the load of the upper building, and the concrete wraps and fixes the precast piles. This can effectively solve the problems of broken piles, neck shrinkage, exposed reinforcement, mud inclusions, concrete segregation, etc. that are common in pile foundations under karst geology at this stage.
[0021] 2. The traditional bored piles are constructed under karst geology. They are affected by the debris generated when penetrating the top of the cave and the filling materials in the cave when passing through. The sediment at the bottom of the hole is completely uncontrollable. However, with the advantages of the pile driving method, the precast piles are pressed into the piles densely using a hammer pile driver or a static pressure pile driver. The penetration rate or final pressure meets the design requirements, which means that the precast piles have begun to play a bearing capacity effect without fear of the adverse effects of the sediment at the bottom of the hole.
[0022] 3. Compared with traditional bored cast-in-place piles, due to the continuous pouring of concrete, which must also be maintained continuously in the cave, its filling coefficient is often more than 5 times. This construction process makes full use of the integrity of the precast piles, does not process or grout the caves, and bypasses the caves for pile construction, solving the problem of over-pouring of concrete in bored piles under karst geology, resulting in completely uncontrollable costs.
[0023] 4. At present, for pile foundation construction in karst areas, national standards have clear requirements for construction surveys, but the drill diameter of the construction survey is generally 75mm-110mm, while the diameter of the foundation pile is generally above 800mm. Therefore, there is a large error in the construction survey, and it cannot be determined whether the pile end is located in the complete bedrock. This process pours part of the concrete at the pile end, and by measuring the change of the concrete liquid level twice at an interval of 10-40 minutes, it can be determined whether the bedrock at the pile end is complete.
[0024] 5. The construction is simple and convenient. There is no need for long casing to follow up the construction. When encountering a cave during drilling, just be careful not to bury the drill. For the cave, just handle it normally and backfill it with stone or clay.
[0025] 6. In order to solve the problem of concrete leakage, it is only necessary to change two drill bits of different diameters during the drilling process, divide the pile hole into an upper hole and a lower hole, and use a ring of appropriate diameter to effectively solve the problem of pile side leakage in the pile construction method under karst geology. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 This is a schematic diagram of drilling the upper hole in the method of taking soil and planting prefabricated columns in karst geology;
[0027] Figure 2 This is a schematic diagram of drilling the lower hole in the method of taking soil and planting prefabricated columns in karst geology;
[0028] Figure 3 This is a schematic diagram of the first prefabricated soil pouring hole in the method of taking soil and planting prefabricated columns under karst geology;
[0029] Figure 4 This is a schematic diagram of the first pouring of prefabricated soil in the method of taking soil and planting prefabricated columns under karst geology;
[0030] Figure 5 This is a schematic diagram of the set of circular baffles in the method of taking soil and planting prefabricated columns under karst geology;
[0031] Figure 6 This is a schematic diagram of the second prefabricated soil pouring hole in the method of taking soil and planting prefabricated columns under karst geology;
[0032] Figure 7 It is a schematic diagram of the structure of two half-type circular baffles assembled on the pile.
[0033] The reference numerals are as follows:
[0034] 1-upper hole; 2-lower hole; 3-cavity; 4-conduit; 5-precast pile; 6-circular baffle; 7-first pouring of concrete; 8-second pouring of concrete; 9-pile. DETAILED DESCRIPTION
[0035] Embodiments of the present invention are described in detail below, examples of which 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 intended to be used to explain the present invention, and should not be construed as limiting the present invention.
[0036] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.
[0037] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0038] Example 1
[0039] A method for taking soil and planting prefabricated piles under karst geology comprises the following steps:
[0040] (1) Before construction, clear obstacles at the pile location and level and harden the site to facilitate stability of the equipment during construction and smooth construction roads;
[0041] (2) Measure and place the pile position according to the drawings, put the drilling machine in place, excavate and bury the casing, and the casing can be a conventional height of 1m-2m;
[0042] (3) Select an interface 0-5m above the rock surface elevation of the exploration hole, start the equipment and start drilling. First, use a large-diameter drill bit for construction. Detailed records of elevation data during the drilling process, such as the rock surface elevation, the cave roof elevation, the elevation when the cave is penetrated, the cave bottom elevation, the pile end elevation, etc. At the rock surface elevation, replace the small-diameter drill bit and construct to the pile end elevation. Based on the rock surface elevation, divide the pile hole into upper hole 1 and lower hole 2. The upper hole 1 is a large-diameter hole, and the lower hole 2 is a small-diameter hole. The diameter of the upper hole is larger than that of the lower hole. , the diameter of the lower hole is larger than the diameter of the prefabricated pile. At this time, the upper hole 1 is in the soil layer, and the lower hole 2 is in the rock layer. The purpose of opening the upper hole and the lower hole in this step is: to solve the problem of concrete leakage, two drill bits with different diameters are replaced during the drilling process, and the pile hole is divided into an upper hole and a lower hole. With a ring of appropriate diameter, the problem of pile side leakage in the pile planting method under cave geology can be effectively solved; the bottom end of the large-diameter hole can be exactly at the rock surface, or slightly higher than the rock surface. With the rock surface as the boundary, the bottom end of the large-diameter hole is 0 to 5 meters away from the rock surface.
[0043] (4) Construction to the pile end elevation, the pile hole acceptance meets the specification requirements, the next step is to install the conduit 4, the volume of the cave can be calculated according to the height difference between the bottom of the cave and the bottom of the pile, the bottom of the conduit is 0.3m-0.5m away from the bottom of the hole during pouring, to ensure that the conduit is inserted into the bottom of the cave, and then the first concrete is poured. After the pouring is completed, the conduit 4 is retracted, and then the measuring rope is lowered to record the concrete liquid level at this time; the purpose of setting the conduit in this step is to ensure accurate pouring and prevent leakage or re-pouring;
[0044] (5) After waiting for 30 minutes, continue to lower the measuring rope to measure the concrete liquid level elevation, and analyze the two measurements. If there is a change in the depth of the two measurements, it proves that there is leakage, which means that there are still karst fissures such as karst grooves and karst troughs from the lower part of the cave to the pile end. At this time, the drilling rig should be transferred back and continue to drill downward until the complete rock layer is found. If there is no change in the depth of the two measurements, it proves that there is no leakage, which means that the bedrock from the lower part of the cave to the pile end is complete and meets the requirements for the bearing layer of the foundation pile;
[0045] (6) After the bearing layer of the foundation pile is determined, the precast pile is pressed into the bottom of the hole from the center pile position, and then hammered with a pile hammer or statically pressed with a static pile driver. The penetration rate or final pressure is recorded. After meeting the design requirements, the special circular baffle is taken out. The outer diameter of the circular baffle is smaller than that of the upper hole, but larger than that of the lower hole. The inner diameter of the circular baffle is 5 mm to 10 mm larger than the outer diameter of the precast pile. The circular ring is inserted from the top of the precast pile and lowered. The circular baffle will fall freely along the precast pile to the junction of the upper hole 1 and the lower hole 2. Because the circular baffle 6 is located at the boundary between soil and rock, above the top plate of the cave, the second concrete is poured at this time. The second concrete pouring will not be missed. After the pouring is completed, the single pile is completed.
[0046] The annular baffle 6 can be divided into two structures. The annular baffle 6 is a two-half structure, which is stuck in the set position of the prefabricated pile and connected by bolts to enter the pile hole together with the prefabricated pile. When the annular baffle is a two-half structure, its specific structure is as follows: Figure 7 As shown, the annular baffle is a two-piece structure, and a heightened rib is provided on the side where the baffle contacts the pile body and the position where the baffle is connected, so as to increase the contact area between the baffle and the pile and facilitate the locking of the baffle.
[0047] The annular baffle 2 can also be an integral structure. After the prefabricated pile is pressed into the bottom of the hole, the annular baffle 6 is directly inserted from the pile top. The annular baffle falls freely to the junction of the small diameter hole and the large diameter hole and then supports on the small diameter hole. The annular baffle with such an integral structure is more convenient and flexible to construct, and the cost is low. The ring only needs to be processed and formed in the factory and can be directly used after being transported to the site. No other equipment or tools are required to assist in placement or positioning. It is not restricted by production, equipment and other conditions when in use. The integral annular baffle and the two-half annular baffle can be selected according to the construction requirements to meet the needs of on-site construction.
[0048] The annular baffle is made of iron sheet or other metal material or non-metal material. The bearing capacity of the annular baffle must meet the weight of the second pouring of concrete to prevent the baffle from being damaged and deformed during the pouring of concrete.
[0049] (7) Move the drilling equipment, hammering equipment and construction materials to the next pile hole and continue to construct other foundation piles according to steps (1) to (5).
[0050] Example 2
[0051] The difference between Example 2 and Example 1 is that after the bearing layer of the foundation pile is determined and the precast pile is pressed into the bottom of the hole, slurry or solidified soil with a specific gravity less than that of concrete is first poured to completely fill the cave, and then an annular baffle is installed for the second concrete pouring.
[0052] For areas where the soil layer above the bedrock surface is shallow and the karst caves are large, deep and unfilled, once the karst cave collapses, not only will safety accidents occur during construction, but also irreparable losses will be caused to the subsequent use of the building. The method of the present invention can be adjusted according to the actual construction situation. After the piles are sunk into place, slurry or solidified soil with a specific gravity less than that of concrete is poured to completely fill the karst cave and enhance the stability of the pile body. Then the ring is lowered and the second concrete is poured, thereby achieving the effect of pile foundation construction + foundation treatment.
[0053] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.
[0054] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.
Claims
1. A method for taking soil and planting prefabricated piles in karst geology, characterized in that: The steps include: Step 1: Select an interface 0 to 5 m above the rock surface elevation, drill a large diameter hole above the interface, and drill a small diameter hole below the interface; Step 2: Calculate the volume of the concrete to be poured under the cave according to the height difference between the cave bottom elevation and the pile bottom elevation, perform the first concrete pouring, and record the concrete liquid level elevation at this time; Step 3: Within a certain period of time, measure the concrete liquid level again and compare it with the concrete liquid level in step 2. If the depth changes, it proves that there is leakage, and continue to drill down until the complete rock layer is found. If the depth does not change during the two measurements, it proves that there is no leakage, indicating that the lower part of the cave to the pile end is complete bedrock, which meets the requirements of being a bearing layer for the foundation pile. Step 4: After determining the bearing layer of the foundation pile, the precast pile is pressed into the bottom of the hole from the center pile position, and the annular baffle is installed so that the annular baffle is located at the junction of the large diameter hole and the small diameter hole, and the second concrete pouring is carried out.
2. The method for taking soil and planting prefabricated piles under karst geology according to claim 1 is characterized in that: The outer diameter of the annular baffle is smaller than the inner diameter of the large-diameter hole, and larger than the inner diameter of the small-diameter hole.
3. The method for taking soil and planting prefabricated piles under karst geology according to claim 2 is characterized in that: The inner diameter of the annular baffle is 5 to 10 mm larger than the outer diameter of the prefabricated pile.
4. The method for taking soil and planting prefabricated piles under karst geology according to claim 3 is characterized in that: The annular baffle is an integral structure. After the prefabricated pile is pressed into the bottom of the hole, the annular baffle is directly inserted from the top of the pile.
5. The method for taking soil and planting prefabricated piles under karst geology according to claim 1 is characterized in that: The annular baffle is a two-half structure, which is clamped in a set position of the precast pile, connected by bolts, and enters the pile hole together with the precast pile.
6. The method for taking soil and planting prefabricated piles under karst geology according to claim 1 is characterized in that: In step 2, before the first concrete pouring, a conduit is set in the small diameter hole, the conduit being 0.3 to 0.5 m away from the bottom of the lower hole, and the conduit is retracted after the first concrete pouring.
7. The method for taking soil and planting prefabricated piles under karst geology according to claim 1 is characterized in that: In step 3, the certain period of time is 10 minutes to 40 minutes.
8. The method for taking soil and planting prefabricated piles under karst geology according to claim 1 is characterized in that: Before construction, excavation and burying of casing.
9. The method for taking soil and planting prefabricated piles under karst geology according to claim 1 is characterized in that: In step 4, after the precast pile is pressed into the bottom of the hole, slurry or solidified soil with a specific gravity less than that of concrete is first poured to completely fill the cave, and then the annular baffle is installed.
10. The method for taking soil and planting prefabricated piles in karst geology according to claim 8, characterized in that: In step one, large diameter holes and small diameter holes are drilled, corresponding to drill bits of different diameters.