Single-pile vertical compression resistance static load test device and test method

Abstract

The invention discloses a single-pile vertical compression resistance static load test device and a test method. The test device comprises a heavy object, a jack and a base plate which are sequentially stacked from top to bottom, and further comprises an extension cylinder pressed below the base plate, the bottom end of the extension cylinder is inserted into a pile head of an external cast-in-place pile, and a test load generated by the heavy object is vertically transmitted to the external cast-in-place pile through the jack, the base plate and the extension cylinder. The test method adopts the test device and comprises the steps of pore forming; an extension cylinder, an external reinforcement cage and an external pouring guide pipe are in place; grouting the pile; performing maintenance; placing a weight, a jack and a base plate in place, and carrying out a load test; and after the test is finished, the single-pile vertical compression resistance static load test device is removed, and the like. The extension cylinder fills the gap from the pile top of the external cast-in-place pile to the rock soil surface, so that the test load can be transmitted to the external cast-in-place pile, the pile head is not required to be exposed out of the ground by excavating ground soil or excessively pouring concrete, the test cost is greatly reduced, and the construction period is shortened.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of civil engineering tests, and particularly to the vertical compressive static load test of single piles. Background Art

[0002] In the field of construction engineering, as a common foundation form, the bearing capacity and stability of pile foundations are crucial for the safety of buildings. The vertical compressive static load test of single piles is the most direct and reliable method to determine the ultimate vertical compressive bearing capacity of single piles. This test simulates the stress conditions of pile foundations in actual use by applying vertical loads to the pile top, so as to determine the bearing capacity and deformation characteristics of pile foundations, and is widely used in the pile foundation detection of various construction projects.

[0003] When conducting the vertical compressive static load test of single piles, loads need to be piled on the pile top. However, since the pile top is usually below the ground surface, the test cannot be directly carried out. Based on the above actual situation, in the face of some special circumstances, the prior art can only adopt the method of excavating the ground soil or over-pouring concrete to expose the pile head to the ground. Both of these methods have obvious drawbacks: when using the method of excavating the ground soil until the pile head is exposed to the ground, the earthwork construction will have a serious impact on other processes or construction safety. When using the method of over-pouring concrete to make the pile head exposed to the ground, the lengthened pile will generate friction with the surrounding rock and soil, which will interfere with the test results. Moreover, the over-poured concrete and the pile head formed by breaking the over-poured concrete will increase the test cost and extend the construction period.

[0004] Therefore, it is necessary to improve the method of the vertical compressive static load test of single piles on the basis of the prior art in the face of special circumstances, and design a supporting test device according to the improved test method. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to save the expenses of excavating the ground soil or over-pouring concrete and obtain relatively accurate test results in the face of special circumstances.

[0006] To solve the above technical problem, the present invention adopts the following technical solutions: The vertical compressive static load test device for a single pile includes a heavy object, a jack, and a backing plate stacked in sequence from top to bottom. It also includes an extension cylinder pressed under the backing plate. The bottom end of the extension cylinder is inserted into the pile head of an external cast-in-place pile. The test load generated by the heavy object is vertically transmitted to the external cast-in-place pile through the jack, the backing plate, and the extension cylinder. The extension cylinder with openings at both the upper and lower ends is vertical, and its outer diameter is smaller than the pile diameter of the external cast-in-place pile, its inner diameter is larger than the outer diameter of the external casting conduit, and its length is the distance L from the pile top of the external cast-in-place pile to the rock-soil surface + (10 - 30) cm. By setting the extension cylinder, the gap from the pile top of the external cast-in-place pile to the rock-soil surface is filled, enabling the test load to be accurately and stably transmitted vertically downward to the external cast-in-place pile, effectively avoiding test errors caused by unclear or unstable load transmission paths, and improving the reliability of the test results. At the same time, by transmitting the load to the pile head through the extension cylinder, it is possible to avoid the method of excavating the ground soil or over-pouring concrete to expose the pile head above the ground, thus avoiding the impact of earthwork construction on other processes or construction safety, greatly reducing the costs of materials and pile head removal brought about by over-pouring concrete, shortening the construction period, and improving the test efficiency. Also, because the outer diameter of the extension cylinder is smaller than the pile diameter of the external cast-in-place pile, it can avoid friction between the extension cylinder and the pile hole wall, thereby improving the accuracy of the test. Moreover, since the inner diameter of the extension cylinder is larger than the outer diameter of the external casting conduit, the external casting conduit can pass through the extension cylinder to reach the bottom of the pile hole, thus avoiding interference with the concrete pouring using the external casting conduit due to the setting of the extension cylinder, ensuring that it will not affect the normal construction and structure of the cast-in-place pile. At the same time, since the length of the extension cylinder is the distance L from the pile top of the external cast-in-place pile to the rock-soil surface + (10 - 30) cm, it can ensure that the top of the extension cylinder protrudes above the rock-soil surface for the backing plate, the jack, and other instrument devices to be in place.

[0007] The central axis of the extension cylinder coincides with the central axis of the external cast-in-place pile. This setting can ensure that the test load acts on the cast-in-place pile evenly and vertically, avoiding uneven stress on the pile body caused by load eccentricity and affecting the accuracy of the test results. At the same time, this design with coincident axes is also beneficial to the tight connection between the extension cylinder and the pile head, reducing the load transmission loss caused by loose connection, and improving the overall stability and reliability of the test device.

[0008] The bottom of the extension cylinder gradually contracts, and the inner diameter of its end is larger than the outer diameter of the external perfusion catheter. The contracted bottom of the extension cylinder is the connecting part with the external cast-in-place pile. This contracted structure can reduce the adhesion between the two when the extension cylinder is pulled out from the external cast-in-place pile, making it easier to separate the two. At the same time, the inner diameter of the end of the extension cylinder after contraction is still larger than the outer diameter of the external perfusion catheter, so that the external perfusion catheter can pass through the extension cylinder and reach the bottom of the pile hole, thus avoiding interference with the concrete perfusion using the external perfusion catheter due to the setting of the extension cylinder and ensuring that it will not affect the normal construction and structure of the cast-in-place pile.

[0009] The extension cylinder includes several segments spliced end to end vertically, and adjacent segments are detachably connected. This detachable splicing design makes the extension cylinder more convenient and flexible during transportation and installation. Moreover, according to the distance from the pile top to the rock and soil surface in the actual project, the number of segments and the length of the extension cylinder can be flexibly selected, avoiding the problems of material waste or inability to meet the test requirements caused by the fixed length of the extension cylinder. At the same time, after the test is completed, it is also convenient to disassemble and recycle the extension cylinder, reducing the test cost and improving the reusability of the test device.

[0010] The single-pile vertical compressive static load test device further includes a casing sleeved outside the extension cylinder. The outer diameter of the casing is not larger than the outer diameter of the external cast-in-place pile, and its inner diameter is not smaller than the outer diameter of the extension cylinder. The casing is coaxially arranged with the extension cylinder. The casing can support the rock and soil around the extension cylinder and isolate the rock and soil from the extension cylinder, avoiding the collapse of the hole wall caused by the precipitation or loss of the mud in the hole and the extrusion and increased friction between the rock and soil and the extension cylinder, thereby improving the accuracy of the test.

[0011] The single-pile vertical compressive static load test device further includes a pile cap fixed on the upper section of the extension cylinder, and part of the pile cap is buried in the rock and soil. In case of an enlarged bearing platform, by setting a reinforced concrete pile cap, it can better fit the actual application scenario, thereby obtaining more real test data.

[0012] Then, the present invention discloses a single-pile vertical compressive static load test method, which uses the above single-pile vertical compressive static load test device, and the test method includes the following steps: Step S1, drilling a hole; Step S2, positioning the extension cylinder, the external steel reinforcement cage and the external perfusion catheter; Step S3, pouring concrete until the design elevation requirement is met; Step S4, curing the external cast-in-place pile until the specification requirement is met; Step S5, positioning the heavy object, the jack and the backing plate, and conducting a vertical compressive static load test; Step S6, after the test is completed, removing the single-pile vertical compressive static load test device.

[0013] By setting the extension cylinder, the gap between the top of the external cast-in-place pile and the rock-soil surface is filled, enabling the test load to be accurately and stably transmitted vertically downward to the external cast-in-place pile. This effectively avoids test errors caused by unclear or unstable load transmission paths and improves the reliability of test results. At the same time, by transmitting the load to the pile head through the extension cylinder, it is possible to avoid the method of excavating the ground soil or over-pouring concrete to expose the pile head above the ground, thereby avoiding the impact of earthwork construction on other processes or construction safety, greatly reducing the costs of materials and pile head removal caused by over-pouring concrete, shortening the construction period, and improving the test efficiency. Through reasonable step arrangements, this test method makes full use of the advantages of the above test device to achieve efficient and accurate detection of the vertical compressive bearing capacity of a single pile. Compared with the prior art, it avoids cumbersome construction processes such as excavating the ground soil or over-pouring concrete, reducing test costs and construction period. At the same time, through the reasonable use of devices such as the extension cylinder, it ensures the effective transmission of load and the stability of the pile body during the test, improves the reliability of test results, and provides a more scientific and reasonable method for the quality inspection of pile foundations in building projects.

[0014] Between the step S1 and the step S2, the following is further included: Step S1', the casing is in place.

[0015] When the casing is in place after hole formation, it can play a certain supporting and protecting role for the hole wall after hole formation, preventing the hole wall from collapsing or deforming during subsequent construction processes, and ensuring the quality and stability of the hole formation. At the same time, the casing can isolate the rock-soil from the extension cylinder, avoiding the collapse of the hole wall caused by the precipitation or loss of mud in the hole and the resulting extrusion and increased friction between the rock-soil and the extension cylinder, thereby improving the accuracy of the test. Description of the Drawings

[0016] Figure 1 is a schematic structural diagram of the test device in Embodiment 1; Figure 2 is a schematic structural diagram of the extension cylinder; Figure 3 is a schematic structural diagram of the test device in Embodiment 2.

[0017] In the figure, each label represents: 01, external cast-in-place pile; 1, heavy object; 2, jack; 3, backing plate; 4, extension cylinder; 41, section; 42, fixed ear; 43, weldable steel sleeve; 5, casing; 6, pile cap. Detailed Description of the Embodiment

[0018] The following will further elaborate on the present invention in detail with reference to the specification drawings and specific embodiments.

[0019] Embodiment 1 As Figure 1 and Figure 2 shown, in this embodiment, the single-pile vertical compressive static load test device includes a weight 1, a jack 2, and a backing plate 3 stacked in sequence from top to bottom. It further includes an extension cylinder 4 pressed under the backing plate 3. The bottom end of the extension cylinder 4 is inserted into the pile head of an external cast-in-place pile 01. The test load generated by the weight 1 is vertically transmitted to the external cast-in-place pile 01 through the jack 2, the backing plate 3, and the extension cylinder 4. The extension cylinder 4 with openings at both the upper and lower ends is vertical, and its outer diameter is smaller than the pile diameter of the external cast-in-place pile 01, its inner diameter is larger than the outer diameter of the external casting conduit, and its length is the distance L from the pile top of the external cast-in-place pile 01 to the rock and soil surface + (10 - 30) cm.

[0020] In this embodiment, the central axis of the extension cylinder 4 coincides with the central axis of the external cast-in-place pile 01. The bottom of the extension cylinder 4 gradually tapers, and the inner diameter of its end is larger than the outer diameter of the external casting conduit. The extension cylinder 4 includes a number of segments 41 spliced end to end in the vertical direction, and adjacent segments 41 are detachably connected. Specifically, adjacent segments 41 are connected in the form of a flange, that is, a wing plate is formed on the joint surface of adjacent two segments 41, and a number of bolt holes are evenly spaced on the wing plate, and bolts inserted into the bolt holes connect the two wing plates into one body. Further, four fixing ears 42 are evenly spaced along the circumferential direction at the top of the extension cylinder 4, and the fixing ears 42 can be fixed to the casting platform to prevent the extension cylinder 4 from moving during the casting process.

[0021] In this embodiment, the single-pile vertical compressive static load test device further includes a casing 5 sleeved outside the extension cylinder 4. The outer diameter of the casing 5 is not greater than the outer diameter of the external cast-in-place pile 01, and its inner diameter is not less than the outer diameter of the extension cylinder 4.

[0022] Embodiment 2 As Figure 3 shown, the second embodiment of the single-pile vertical compressive static load test device of the present invention is basically the same as Embodiment 1, except that: in this embodiment, for the case of an enlarged bearing platform, the single-pile vertical compressive static load test device further includes a pile cap 6 fixed to the upper section of the extension cylinder 4, and part of the pile cap 6 is buried in the rock and soil. Further, the pile cap 6 is a cast-in-place reinforced concrete structure, and a number of weldable steel sleeve 43 are welded at intervals on the upper section of the extension cylinder 4 to form a firm connection with the steel bar grid in the cast-in-place reinforced concrete pile cap 6.

[0023] Embodiment 3 Then, the present invention also discloses a single-pile vertical compressive static load test method. In one of its embodiments, the test method uses the above-mentioned single-pile vertical compressive static load test device, and the test method includes the following steps: Step S1, hole forming; Step S1', the casing 5 is in place.

[0024] Step S2, the extension cylinder 4, the external steel reinforcement cage and the external perfusion conduit are positioned; Step S3, concrete is poured until the design elevation requirement is met; Step S4, the external cast-in-place pile 01 is cured until the specification requirement is met; Step S5, the heavy object 1, the jack 2 and the backing plate 3 are positioned, and the vertical compressive static load test is carried out; Step S6, after the test is completed, the single-pile vertical compressive static load test device is removed.

[0025] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes, without departing from the scope of the technical solution of the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of the protection of the technical solution of the present invention.

Claims

1. A single pile vertical compressive static load test device, comprising a weight (1), a jack (2) and a pad (3) stacked in sequence from top to bottom, characterized in that: It also includes an extension tube (4) pressed under the pad (3), the bottom end of the extension tube (4) is inserted into the pile head of the external cast-in-place pile (01), and the test load generated by the weight (1) is vertically transmitted to the external cast-in-place pile (01) via the jack (2), the pad (3) and the extension tube (4); The extension tube (4) with openings at both ends is vertical, and its outer diameter is smaller than the pile diameter of the external cast-in-place pile (01), its inner diameter is larger than the outer diameter of the external cast-in-place pipe, and its length is the distance from the top of the external cast-in-place pile (01) to the rock and soil surface L+(10-30) cm.

2. The single pile vertical compressive static load test device according to claim 1 is characterized in that: The central axis of the extension tube (4) coincides with the central axis of the external cast-in-place pile (01).

3. The single pile vertical compressive static load test device according to claim 1 is characterized in that: The bottom of the extension tube (4) gradually shrinks, and the inner diameter of the end thereof is larger than the outer diameter of the external perfusion catheter.

4. The single pile vertical compressive static load test device according to claim 1 is characterized in that: The extension tube (4) comprises a plurality of segments (41) which are vertically spliced ​​end to end, and adjacent segments (41) are detachably connected.

5. The single pile vertical compressive static load test device according to claim 1 is characterized in that: The single pile vertical compressive static load test device also includes a sleeve (5) sleeved outside the extension tube (4), the outer diameter of the sleeve (5) is not greater than the outer diameter of the external cast-in-place pile (01), and the inner diameter is not less than the outer diameter of the extension tube (4).

6. The single pile vertical compressive static load test device according to claim 1 is characterized in that: The single pile vertical compressive static load test device also includes a pile cap (6) fixed to the upper section of the extension tube (4), and the pile cap (6) is partially buried in the rock soil.

7. Single pile vertical compressive static load test method, characterized in that: A single pile vertical compressive static load test device according to any one of claims 1 to 6 is used, and the test method comprises the following steps: Step S1, forming a hole; Step S2, the extension tube (4), the external steel cage and the external perfusion catheter are in place; Step S3, pouring concrete until the design elevation requirement is met; Step S4, maintaining the external cast-in-place pile (01) until it meets the specification requirements; Step S5, the weight (1), the jack (2) and the pad (3) are in place, and a vertical compressive static load test is performed; Step S6, after the test is completed, remove the single pile vertical compressive static load test device.

8. The single pile vertical compressive static load test method according to claim 7 is characterized in that: Between step S1 and step S2, the method further includes: Step S1', the sleeve (5) is in place.

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