A monitoring device for the bearing capacity of a rigid composite pile

Abstract

The present invention discloses a monitoring device for the bearing capacity of a rigid composite pile, which relates to the field of auxiliary engineering. The device includes an optical fiber sensor. The rigid composite pile is formed by inserting a precast pile into the unhardened cement-soil mixture. An installation groove is provided on the surface of the precast pile, and the optical fiber is arranged in the installation groove. A protection device for protecting the optical fiber is also provided in the installation groove. In the monitoring device for the bearing capacity of a rigid composite pile of the present invention, an optical fiber grating is arranged in the installation groove, and a protection device is arranged outside the installation groove, so that during the process of pressing and driving the pile foundation into the unhardened cement mixing pile by the rigid composite pile, the extrusion effect between the pile and the cement-soil mixture can be avoided from damaging the optical fiber sensor and the survival rate of the optical fiber sensor can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of auxiliary projects, and particularly to a monitoring device for the bearing capacity of a rigid-flexible composite pile. Background Art

[0002] The rigid-flexible composite pile is a new type of pile foundation, which solves multiple pain points of traditional pile foundations. A representative type of rigid-flexible composite pile is the MC rigid-flexible composite pile. Among them, the flexible pile (M pile) is mainly composed of a mixture of cement and other cementitious materials and soil, such as a cement mixing pile, while the rigid pile (C pile) mostly uses precast pipe piles, hollow piles or solid piles. This is a composite pile type that combines the advantages of flexible piles and rigid piles. Its construction method usually involves first constructing a cement mixing pile on a soft soil foundation, and inserting a precast column concentrically before the cement mixing pile solidifies. This pile type combines the high-strength pile body of the precast pile and the strong side friction resistance provided by the large-diameter cement-soil pile, making it perform excellently in both vertical compression and uplift, achieving complementary and enhanced performance. In actual projects, it is necessary to detect the bearing performance and settlement of the pile foundation. Especially for a new pile type, whether its actual performance and long-term performance are as excellent as expected and whether it meets the design requirements. Therefore, monitoring it can not only ensure project safety but also collect useful data. Existing monitoring methods often use embedded optical fiber sensors in the pile foundation. However, the rigid-flexible composite pile is different from ordinary pile foundations. It includes a precast pile and a cement mixing pile. The sensors of the precast pile can be arranged using existing technologies, but it can only monitor the condition of the precast pile. It is difficult to install optical fibers in the cement mixing pile outside the precast pile. When the optical fiber is set on the surface of the precast pile, during the pile sinking process, the optical fiber is easily subjected to extrusion forces, resulting in a low survival rate. Summary of the Invention

[0003] Aiming at the above deficiencies, the purpose of the present invention is to provide a monitoring device that can monitor the interface between the precast pile and the cement mixing pile or the force on the cement mixing pile in a rigid-flexible composite pile.

[0004] To this end, a monitoring device for the bearing capacity of a rigid-flexible composite pile of the present invention includes an optical fiber sensor. The rigid-flexible composite pile is formed by inserting a precast pile into unfrozen cement-mixed soil. An installation groove is provided on the surface of the precast pile, and the optical fiber is arranged in the installation groove. A protection device for protecting the optical fiber is also provided in the installation groove.

[0005] Further, the installation groove is a vertical groove. The protection device includes a steel pipe. The steel pipe is arranged in the installation groove, the optical fiber is fixed in the steel pipe, and the steel pipe is provided with a plurality of cutouts, and the cutouts face the cement-mixed soil side.

[0006] Furthermore, a concentric C-shaped tube is provided inside the steel tube, the optical fiber is fixed on the inner wall of the C-shaped tube, the C-shaped tube is fixed in the mounting groove, and the steel tube can rotate relative to the C-shaped tube so that the steel tube blocks the optical fiber in the C-shaped tube or makes the incision opposite to the optical fiber in the C-shaped tube.

[0007] Furthermore, a fixing hole is provided on the back of the C-shaped tube, and an annular hole and an installation port matching the fixing hole are provided on the steel tube. After the optical fiber is installed on the inner wall of the C-shaped tube, the steel tube is sleeved on the outside of the C-shaped tube, and the C-shaped tube is fixed in the installation groove with a fixing piece through the installation port. The fixing piece passes through the annular hole so that the steel tube can rotate relative to the C-shaped tube.

[0008] The installation groove comprises a transversely arranged annular groove and a vertical groove connected to the annular groove. The optical fiber is arranged in the vertical groove and then filled with structural adhesive. The annular groove comprises structural adhesive.

[0009] Furthermore, structural adhesive is provided on both sides of the annular groove, an annular baffle is provided at the end of the annular groove close to the underground, and the optical fiber is provided between the annular baffle and the annular groove, so as to prevent cement soil from squeezing the optical fiber from below during the sinking process of the rigid composite pile.

[0010] Furthermore, the reinforced composite pile is filled with cement mortar in the annular groove before the pile is sunk, and the pile is sunk before the cement mortar solidifies.

[0011] Furthermore, a plurality of support rods are provided on the inner side of the annular baffle to prevent the baffle from bending in the direction of the annular groove due to force during the pile sinking process, and the optical fiber is fixed on the support rods.

[0012] The installation groove includes a spiral groove spirally arranged on the pile body, a spiral baffle is provided on the lower side of the spiral groove, and a spiral upper baffle is also provided on the upper side of the spiral groove. The upper baffle and the baffle have overlapping parts in the height direction, and a predetermined distance is provided between the upper baffle and the baffle in the horizontal direction so that cement soil can enter the spiral groove through the gap.

[0013] Furthermore, an optical fiber sensor is pre-embedded on the steel cage of the precast pile.

[0014] The beneficial technical effects of the present invention are:

[0015] A monitoring device for the bearing capacity of a rigid composite pile. By setting an installation groove around the precast pile, arranging a fiber Bragg grating in the installation groove, and setting a protection device outside the installation groove, during the process of pressing the pile foundation into the unhardened cement mixing pile by pile pressing or pile driving, the extrusion effect between the pile and the cement mixing soil is avoided from damaging the fiber optic sensor. After the pile foundation reaches the predetermined position, the fiber optic sensor is connected to the cement mixing pile through the solidification of the cement mixing soil, enabling the fiber optic sensor to monitor the force on the cement mixing pile or the force between the interface of the cement mixing pile and the precast pile, and improving the survival rate of the fiber optic sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the rigid composite pile;

[0017] Figure 2 Schematic diagram of the vertical groove and the precast pile;

[0018] Figure 3 Schematic diagram of Embodiment 1;

[0019] Figure 4 Top view of the steel pipe and the C-shaped pipe in Embodiment 1;

[0020] Figure 5 Schematic diagram of the annular groove;

[0021] Figure 6 For Figure 5 Partial cross-sectional view;

[0022] Figure 7 Schematic diagram of the spiral groove;

[0023] Figure 8 Schematic diagram of the setting of the precast pile steel cage and the optical fiber.

[0024] Explanation of the reference numerals: 1, rigid composite pile; 2, cement mixing pile; 3, precast pile; 4, vertical groove; 5, optical fiber; 6, steel pipe; 601, installation port; 602, annular hole; 7, C-shaped pipe; 8, bolt; 9, annular groove; 10, retaining piece; 11, structural adhesive; 12, support rod; 13, steel cage; 14, spiral groove. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following, in conjunction with the drawings and preferred embodiments, details the specific implementation manners, structures, features and their effects of the present invention as follows.

[0026] Refer to Figures 1 to 8As shown in the figure, a monitoring device for the bearing capacity of a composite stiff pile 1 of the present invention includes an optical fiber sensor. The composite stiff pile 1 is formed by concentrically inserting a precast pile 3 into the unhardened cement-soil mixture. An installation groove is provided on the surface of the precast pile 3, and an optical fiber 5 is arranged in the installation groove. A protection device for protecting the optical fiber 5 is also provided in the installation groove. Figures 2 to 4 The specific embodiment 1 of the present invention is shown as follows. Vertical grooves are cut on the pile bodies on the opposite sides of the precast pile 3 with a cutting machine. The depth and width of the grooves are generally several centimeters. Anchor components are buried by drilling holes at corresponding positions of the installation grooves. The installation grooves can also be preformed together during the casting of the concrete precast pile 3. At this time, embedded parts can be provided at corresponding positions of the installation grooves for cooperating with fixing parts to fix the protection device. The fiber grating is pasted or fixed on the inner wall of the C-shaped tube 7. The C-shaped tube 7 is placed in the steel pipe 6. The C-shaped tube 7 and the steel pipe 6 are concentric. A fixing hole is provided on the back of the C-shaped tube 7. The steel pipe 6 is provided with an annular hole 602 that cooperates with the fixing hole. An installation port 601 is provided on the steel pipe 6 opposite to the annular hole 602. After the optical fiber 5 is installed on the inner wall of the C-shaped tube 7, the steel pipe 6 is sleeved outside the C-shaped tube 7, and the relative positions between the C-shaped tube 7 and the steel pipe 6 are adjusted so that the installation port 601, the fixing hole, the annular hole 602 and the anchor component form a straight line. The fixing bolt 8 passes through the installation port 601, and the screw rod of the bolt passes through the installation port 601, the fixing hole of the C-shaped tube 7, the annular hole 602 and is fixed to the anchor component. The bolt head is stuck on the inner wall of the C-shaped tube around the fixing hole. Several sets of the above-mentioned fixing components can be provided on the steel pipe 6 and the C-shaped tube 7 to fix the steel pipe 6 and the C-shaped tube 7 in the installation groove. Cuts are provided at the positions corresponding to the measuring points on the steel pipe 6. Before the cement mixing pile 2 hardens, the precast pile 3 is pressed into the cement mixing pile 2 by a pile press or a pile driver so that the cement mixing pile 2 and the precast pile 3 are concentric. After the precast pile 3 reaches the predetermined position, the steel pipe 6 is rotated to align the cut of the steel pipe 6 with the opening of the C-shaped tube 7, so that the cement-soil mixture enters the C-shaped tube 7 through the cut and is connected to the optical fiber 5. In order to prevent the cement-soil mixture from damaging the optical fiber 5 during the falling process along the steel pipe 6, a baffle can be provided below the cut to block the cement-soil mixture from falling along the steel pipe 6. Or before pile pressing or pile driving, grout can be injected into the steel pipe 6, and the pile is pressed into the cement mixing pile 2 before it hardens. After the steel pipe 6 is rotated, the cement-soil mixture contacts the cement mortar in the steel pipe 6 under its own pressure and forms an integral body after hardening. During the pile sinking process of the steel pipe 6, the cut rotates to the outer wall of the C-shaped tube 7, so that the cement-soil mixture cannot directly extrude the optical fiber 5. The bottom of the steel pipe 6 can be closed. Of course, in the above-mentioned embodiment 1, only the steel pipe 6 can be provided. Several cuts are provided on the steel pipe 6. The optical fiber 5 is inserted from one end of the steel pipe 6. The positions of the cuts are the measuring points, and the optical fiber 5 is pasted in the steel pipe 6 through the cuts. Grout can be injected into the steel pipe 6, and pile pressing is carried out before it hardens.

[0027] Refer to Figure 5 and Figure 6As shown, in Embodiment 2, the optical fiber 5 is arranged along the cross-section of the pile body. The installation groove includes a horizontally arranged annular groove 9 and a vertical groove 4 connected to the annular groove 9. The optical fiber 5 is arranged in the annular groove 9 and the vertical groove 4. In this embodiment, the method of Embodiment 1 cannot be used to protect the optical fiber sensor. One method is to fill the vertical groove 4 with structural adhesive after the optical fiber 5 is arranged, and structural adhesive 11 is also arranged in the annular groove 9. This method can monitor the stress condition on the interface between the precast pile 3 and the cement mixing pile 2.

[0028] Referring to Figure 6 As shown, structural adhesive 11 is arranged on both sides of the annular groove 9. An annular retaining piece 10 is arranged at the underground end of the annular groove 9, and the optical fiber 5 is arranged between the annular retaining piece 10 and the annular groove 9. A predetermined distance is reserved between the upper side of the annular retaining piece 10 and the upper-side structural adhesive 11, so that the cement mixing soil can enter the space between the annular retaining piece 10 and the annular groove 9 during the pile pressing process and form an integral body with the optical fiber 5 after solidification. The retaining piece 10 prevents the cement mixing soil from directly extruding the optical fiber 5 from below during the pile sinking process of the stiffened composite pile 1. Before the stiffened composite pile 1 is sunk, cement mortar can also be filled into the annular groove 9 and the pile sinking can be carried out before the cement mortar solidifies, so as to avoid damaging the optical fiber sensor during the pile pressing process. The annular groove 9 can also be provided with structural adhesive 11 on three sides. The structural adhesive 11 has a certain elasticity, reducing the direct action of the force on the precast pile 3 on the optical fiber 5. On the contrary, the cement mixing soil is directly fixed to the optical fiber 5, and the force on the cement mixing pile 2 can act more directly on the optical fiber sensor, so that the optical fiber sensor can mainly reflect the stress condition of the cement mixing pile 2.

[0029] In the above embodiment, several support rods 12 are arranged on the inner side of the retaining piece 10 to prevent the retaining piece 10 from bending towards the annular groove 9 under force during the pile sinking process. One end of the support rod 12 is fixed to the retaining piece 10, and the other side is not fixed to the installation groove of the precast pile 3. The optical fiber 5 is fixed on the support rod 12 instead of being adhesively fixed to the precast pile 3, reducing the interaction between the optical fiber 5 and the precast pile 3 and enabling the optical fiber 5 sensor to more accurately monitor the stress condition of the cement mixing pile 2.

[0030] Referring to Figure 7 As shown, Embodiment 3 of the present invention is basically the same as Embodiment 2, except that the installation groove is set as a spiral groove 14 and corresponding adaptive improvements are made. The installation groove includes a spiral groove 14 spirally arranged on the pile body. A spiral retaining piece 10 is arranged on the lower side of the spiral groove 14, and a spiral upper retaining piece is also arranged on the upper side of the spiral groove 14. The upper retaining piece and the retaining piece 10 have an overlapping part in the height direction, and a predetermined distance is provided between the upper retaining piece and the retaining piece 10 in the horizontal direction so that the cement mixing soil can enter the spiral groove 14 through this gap. Of course, the installation groove can also be pre-injected with cement slurry. After the precast pile 3 enters the predetermined position, the cement mixing soil and the cement slurry solidify into an integral body.

[0031] In the above-described Embodiments 1, 2, and 3, with reference to Figure 8 as shown, an optical fiber 5 is embedded in the steel reinforcement cage 13 of the precast pile 3, and the force and other conditions of the precast pile 3 are monitored through the embedded fiber optic sensor.

[0032] The above is only a preferred embodiment of the present invention and does not impose any form of limitation on the present invention. 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 some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A monitoring device for the bearing capacity of a rigid composite pile, comprising an optical fiber sensor, wherein the rigid composite pile is formed by inserting a prefabricated pile into unsolidified cement-mixed soil, and wherein: The surface of the prefabricated pile is provided with an installation groove, the optical fiber is arranged in the installation groove, and the installation groove is also provided with a protection device for protecting the optical fiber; The installation groove is a vertical groove, the protection device includes a steel pipe, the steel pipe is arranged in the installation groove, the optical fiber is fixed in the steel pipe, the steel pipe is provided with a plurality of cutouts, and the cutouts face the cement mixing soil side; A concentric C-shaped tube is provided inside the steel tube, the optical fiber is fixed on the inner wall of the C-shaped tube, the C-shaped tube is fixed in the installation groove, and the steel tube can rotate relative to the C-shaped tube so that the steel tube blocks the optical fiber in the C-shaped tube or makes the incision opposite to the optical fiber in the C-shaped tube.

2. The device for monitoring the bearing capacity of a rigid composite pile according to claim 1, characterized in that: A fixing hole is provided on the back of the C-shaped tube, and an annular hole and an installation port are provided on the steel tube to match the fixing hole. After the optical fiber is installed on the inner wall of the C-shaped tube, the steel tube is sleeved on the outside of the C-shaped tube, and the C-shaped tube is fixed in the installation groove with a fixing piece through the installation port. The fixing piece passes through the annular hole so that the steel tube can rotate relative to the C-shaped tube.

3. A monitoring device for the bearing capacity of a rigid composite pile according to claim 1 or 2, characterized in that: An optical fiber sensor is pre-embedded on the steel cage of the prefabricated pile.

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