Monitoring device for bearing capacity of stiff composite pile

Abstract

The invention discloses a device for monitoring the bearing capacity of a stiff composite pile, and relates to the field of auxiliary engineering, the device comprises an optical fiber sensor, the stiff composite pile is formed by inserting a precast pile into unsolidified cement stirring soil, the surface of the precast pile is provided with a mounting groove, an optical fiber is arranged in the mounting groove, and the optical fiber sensor is arranged in the mounting groove. And a protection device for protecting the optical fiber is also arranged in the mounting groove. According to the monitoring device for the bearing capacity of the stiff composite pile, the fiber bragg grating is arranged in the mounting groove, and the protection device is arranged on the outer side of the mounting groove, so that the pile foundation of the stiff composite pile is pressed into an unsolidified cement mixing pile through pile pressing and piling; the fiber sensor is prevented from being damaged by the extrusion effect of the pile and cement stirring soil; and the survival rate of the fiber sensor is improved.

Description

Technical Field

[0001] The invention relates to the technical field of auxiliary engineering, in particular to a monitoring device for the bearing capacity of a rigid composite pile. Background Art

[0002] Rigid composite pile is a new type of pile foundation, which solves the multiple pain points of traditional pile foundation. The representative of rigid composite pile is MC rigid composite pile, among which flexible pile (M pile) is mainly a mixture of cement and soil, such as cement mixing pile, while rigid pile (C pile) is mostly prefabricated pipe pile, hollow pile or solid pile. This is a composite pile type that combines the advantages of flexible pile and rigid pile. Its construction method usually constructs cement mixing pile on soft soil foundation first, and inserts prefabricated column concentrically before cement mixing pile solidifies. This pile type combines the high strength pile body of prefabricated pile and the strong side friction resistance provided by large diameter cement soil pile, so that it performs well in vertical compression and pull-out resistance, and realizes complementary and enhanced performance. In actual engineering, it is necessary to test the bearing capacity and settlement of pile foundation, especially for a new type of pile, whether its actual performance and long-term performance are as good as expected and whether it meets the design requirements. Therefore, monitoring it can not only ensure the safety of the project, but also collect useful data. Existing monitoring methods often use pre-buried fiber optic sensors in pile foundations. However, rigid composite piles are different from ordinary pile foundations. They include precast piles and cement mixing piles. Sensors for precast piles can be deployed using existing technologies, but they can only monitor the conditions of precast piles. It is difficult to install optical fibers on the cement mixing piles outside the precast piles. If the optical fibers are set on the surface of the precast piles, they are easily squeezed during the pile sinking process, resulting in a low survival rate. Summary of the invention

[0003] In view of the above shortcomings, the object of the present invention is to provide a monitoring device capable of monitoring the interface between the precast pile and the cement mixing pile in the rigid composite pile or the stress of the cement mixing pile.

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

[0005] Furthermore, 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 cuts, and the cuts face the cement mixing 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: The present invention provides a monitoring device for the bearing capacity of a rigid composite pile. The device provides an installation groove around the precast pile, provides an optical fiber Bragg grating in the installation groove, and provides a protective device on the outside of the installation groove. This device prevents the rigid composite pile from damaging the optical fiber sensor due to the squeezing effect of the pile and the cement mixing soil during the process of pressing the pile foundation into the unsolidified cement mixing pile by pile pressing and piling. After the pile foundation reaches a predetermined position, the optical fiber sensor is connected to the cement mixing pile through the solidification of the cement mixing soil, so that the optical fiber sensor can monitor the stress of the cement mixing pile or the stress condition at the interface between the cement mixing pile and the precast pile, and improves the survival rate of the optical fiber sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of a rigid composite pile; Figure 2 It is a schematic diagram of the vertical slot and precast piles; Figure 3 is a schematic diagram of Example 1; Figure 4 It is a top view of the steel pipe and the C-shaped pipe of Example 1; Figure 5 is a schematic diagram of the annular groove; Figure 6 for Figure 5 A partial cross-sectional schematic diagram of Figure 7 is a schematic diagram of a spiral groove; Figure 8 Schematic diagram of the setup of precast pile reinforcement cage and optical fiber.

[0016] Explanation of the reference numerals in the accompanying drawings: 1. rigid composite pile; 2. cement mixing pile; 3. precast pile; 4. vertical groove; 5. optical fiber; 6. steel pipe; 601. mounting port; 602. annular hole; 7. C-shaped pipe; 8. bolt; 9. annular groove; 10. baffle; 11. structural adhesive; 12. support rod; 13. steel cage; 14. spiral groove. DETAILED DESCRIPTION

[0017] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0018] Reference Figures 1 to 8 As shown, a device for monitoring the bearing capacity of a rigid composite pile 1 of the present invention comprises an optical fiber sensor. The rigid composite pile 1 is formed by concentrically inserting a precast pile 3 into unsolidified cement mixed soil. A mounting groove is provided on the surface of the precast pile 3. An optical fiber 5 is arranged in the mounting groove. A protective device for protecting the optical fiber 5 is also provided in the mounting groove. Figures 2 to 4The specific embodiment 1 of the present invention is shown in the figure. A cutting machine is used to vertically groove the pile bodies on opposite sides of the precast pile 3. The depth and width of the groove are generally several centimeters. The anchoring components are buried in the corresponding positions of the installation grooves. The installation grooves can also be preformed when the concrete precast pile 3 is poured. In this case, embedded parts can be set at the corresponding positions of the installation grooves to cooperate with the fixing parts to fix the protective device. The fiber grating is pasted or fixed on the inner wall of the C-shaped tube 7, and the C-shaped tube 7 is placed in the steel tube 6. The C-shaped tube 7 is concentric with the steel tube 6. A fixing hole is provided on the back of the C-shaped tube 7. The steel tube 6 is provided with an annular hole 602 that matches the fixing hole. An installation port 601 is provided on the steel tube 6 facing the annular hole 602. After the optical fiber 5 is installed on the inner wall of the C-shaped tube 7, the steel tube 6 is sleeved on the outside of the C-shaped tube 7, and the relative position between the C-shaped tube 7 and the steel tube 6 is adjusted so that the installation port 601, the fixing hole, the annular hole 602 and the anchoring component form a straight line. The fixing bolt 8 is passed through the installation port 601, and the screw rod of the bolt passes through the installation port 601, the fixing hole and the annular hole 602 of the C-shaped tube 7 and is fixed to the anchoring component. The bolt head is stuck on the inner wall of the C-shaped tube around the fixing hole. Several of the above-mentioned components for fixing can be provided on the steel tube 6 and the C-shaped tube 7, and the steel tube 6 and the C-shaped tube 7 are fixed in the installation groove. A notch is provided on the steel pipe 6 at a position corresponding to the measuring point. Before the cement mixing pile 2 solidifies, a pile driver or pile driver is used to press the precast pile 3 into the cement mixing pile 2 so that the cement mixing pile 2 is concentric with the precast pile 3. After the precast pile 3 reaches the predetermined position, the notch of the steel pipe 6 is aligned with the opening of the C-shaped tube 7 by rotating the steel pipe 6, so that the cement mixing soil enters the C-shaped tube 7 through the notch and connects with the optical fiber 5. In order to prevent the cement mixing soil from damaging the optical fiber 5 during the falling process along the steel pipe 6, a baffle can be provided below the notch to prevent the cement mixing soil from falling along the steel pipe 6. Grouting can also be performed in the steel pipe 6 before the pile is pressed or driven, and the pile is pressed into the cement mixing pile 2 before it solidifies. After the steel pipe 6 is rotated, the cement mixing soil is in contact with the cement mortar in the steel pipe 6 under its own pressure, and forms a whole after solidification. During the pile sinking process, the notch of the steel pipe 6 is rotated to the outer wall of the C-shaped tube 7, so that the cement mixing soil cannot directly squeeze the optical fiber 5, and the bottom of the steel pipe 6 can be closed. Of course, the above-mentioned embodiment 1 can also only have a steel pipe 6, and the steel pipe 6 is provided with a plurality of incisions. The optical fiber 5 is inserted from one end of the steel pipe 6. The position of the incision is the measuring point, and the optical fiber 5 is pasted in the steel pipe 6 through the incision. Grouting can be performed in the steel pipe 6, and pile pressing can be performed before it solidifies.

[0019] Reference Figure 5 and Figure 6As shown, embodiment 2 adopts the method of arranging the optical fiber 5 along the cross section of the pile body, the installation groove includes a transversely arranged annular groove 9, a vertical groove 4 connected to the annular groove 9, and the optical fiber 5 is arranged in the annular groove 9 and the vertical groove 4. This embodiment cannot protect the optical fiber sensor in the manner of embodiment 1. One method is to arrange the optical fiber 5 in the vertical groove 4 and fill it with structural glue, and also arrange structural glue 11 in the annular groove 9. This method can monitor the stress condition at the interface between the prefabricated pile 3 and the cement mixing pile 2.

[0020] Reference Figure 6 As shown, structural glue 11 is arranged on both sides of the annular groove 9, an annular baffle 10 is arranged at the end of the annular groove 9 close to the ground, and the optical fiber 5 is arranged between the annular baffle 10 and the annular groove 9, and a predetermined spacing is reserved between the upper side of the annular baffle 10 and the upper structural glue 11, so that the cement mixing soil can enter the space between the annular baffle 10 and the annular groove 9 during the pile driving process, and form a whole with the optical fiber 5 after solidification. The baffle 10 prevents the cement mixing soil from directly squeezing the optical fiber 5 from below during the pile driving process of the rigid composite pile 1. Before the pile driving, the rigid composite pile 1 can also fill the annular groove 9 with cement mortar, and drive the pile before the cement mortar solidifies, so as to avoid damage to the optical fiber sensor during the pile driving process. The annular groove 9 can also be provided with structural glue 11 on three sides. The structural glue 11 has a certain elasticity, which reduces the force of the prefabricated pile 3 directly acting on the optical fiber 5. On the contrary, the cement mixing soil is directly fixed to the optical fiber 5, and the force of the cement mixing pile 2 can act more directly on the optical fiber sensor, so that the optical fiber sensor can mainly reflect the force of the cement mixing pile 2.

[0021] In the above embodiment, a plurality of support rods 12 are provided on the inner side of the baffle 10 to prevent the baffle 10 from bending in the direction of the annular groove 9 due to force during the pile sinking process. One end of the support rod 12 is fixed to the baffle 10, and the other end is not fixed to the mounting groove of the precast pile 3. The optical fiber 5 is fixed to the support rod 12 instead of being glued and fixed to the precast pile 3, thereby reducing the interaction between the optical fiber 5 and the precast pile 3, so that the optical fiber 5 sensor can more accurately monitor the force condition of the cement mixing pile 2.

[0022] Reference Figure 7 As shown, embodiment 3 of the present invention is basically the same as embodiment 2, and the only difference is that the installation groove is set as a spiral groove 14, and the adaptability is improved accordingly. The installation groove includes a spiral groove 14 spirally arranged on the pile body, and a spiral baffle 10 is provided on the lower side of the spiral groove 14, and a spiral upper baffle is also provided on the upper side of the spiral groove 14. The upper baffle and the baffle 10 have an overlapping part in the height direction, and a predetermined distance is provided between the upper baffle and the baffle 10 in the horizontal direction so that cement mixed soil can enter the spiral groove 14 through the gap. Of course, the installation groove can also be pre-injected with cement slurry. After the prefabricated pile 3 enters the predetermined position, the cement mixed soil and the cement slurry are solidified into one.

[0023] In the above-mentioned embodiments 1, 2 and 3, reference is made to Figure 8 As shown, an optical fiber 5 is pre-buried on the steel cage 13 of the precast pile 3, and the stress and other conditions of the precast pile 3 are monitored by the pre-buried optical fiber sensor.

[0024] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still 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 a protection device for protecting the optical fiber is also provided in the installation groove.

2. The device for monitoring the bearing capacity of a rigid composite pile according to claim 1, characterized in that: The installation groove is a vertical groove, the protection device comprises 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 cuts, and the cuts face the cement mixing soil side.

3. The device for monitoring the bearing capacity of a rigid composite pile according to claim 2, characterized in that: 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.

4. The device for monitoring the bearing capacity of a rigid composite pile according to claim 3, 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.

5. The device for monitoring the bearing capacity of a rigid composite pile according to claim 1, characterized in that: 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.

6. The device for monitoring the bearing capacity of a rigid composite pile according to claim 5, characterized in that: Structural adhesive is arranged on both sides of the annular groove, an annular baffle is arranged at the end of the annular groove close to the ground, and the optical fiber is arranged 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.

7. The device for monitoring the bearing capacity of a rigid composite pile according to claim 6, characterized in that: 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.

8. The device for monitoring the bearing capacity of a rigid composite pile according to claim 7, characterized in that: A plurality of support rods are arranged 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.

9. The device for monitoring the bearing capacity of a rigid composite pile according to claim 1, characterized in that: 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.

10. A device for monitoring the bearing capacity of a rigid composite pile according to any one of claims 1 to 9, characterized in that: An optical fiber sensor is pre-embedded on the steel cage of the prefabricated pile.

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