Prestress applying device for inclined strut of foundation pit

Abstract

The utility model discloses a prestress applying device for a foundation pit inclined strut. The prestress applying device comprises a top beam poured at the top of a fender post, a static pile driver fixedly installed on the top beam, and a locking structure for locking the inclined strut on the top beam. An anchoring hole for the inclined strut to penetrate through is formed in the top beam, the static pile driver is obliquely arranged towards the outer portion of the foundation pit, an annular space is formed between the inclined strut and the anchoring hole, the annular space is filled with annular bonding blocks formed by first concrete grouting materials, and the bonding blocks form a locking structure. According to the static pile driver, the static pile driver is installed on the top beam, and during pile pressing, counter force can be provided by the top beam for construction, so that the static pile driver with light self weight can be adopted for construction, the construction cost is reduced, and the construction convenience is improved. The static pile driver with the light dead weight is adopted for construction, the construction angle of the static pile driver can be conveniently adjusted, piles with the large inclination degree can be constructed, the larger horizontal supporting force is improved, and the stability of foundation pit support is guaranteed.

Description

Technical Field

[0001] The utility model relates to a prestress application device for a foundation pit inclined strut. Background Technique

[0002] Due to its large excavation area and fewer columns or column piles in the foundation pit, the inclined strut support is widely used in large foundation pits. At present, the inclined strut support mainly includes traditional inclined strut support, high-pressure jet grouting steel inclined support, pre-injected grouting steel pipe inclined strut, and static pressure precast pipe pile inclined support and other structures. Among them, the traditional inclined strut support adopts the middle soil basin type development, leaves a soil platform on the side, first pours the middle cushion and bottom plate, sets the inclined strut on the already poured bottom plate, and then excavates the soil under the inclined strut. Compared with the horizontal internal support support scheme, the support and column layout are less, and the cost is low, with obvious economic benefits. However, in this inclined strut support scheme, since the bottom plate is used as a reliable support force point and the inclined strut is constructed when the bottom plate reaches the design strength, it is difficult to excavate the soil under the inclined strut, and a post-cast strip needs to be set between the inner wall of the foundation pit and the bottom plate, resulting in a significant lag in the subsequent construction period.

[0003] For the high-pressure jet grouting steel inclined support, the inclined high-pressure jet grouting pile is constructed first, and then the steel section is inserted along the high-pressure jet grouting pile by using a vibratory hammer. This process has the functions of reinforcement and pilot hole during high-pressure jet grouting, with high bearing capacity, but it is difficult to control the insertion accuracy of the steel section, and the steel section is prone to deviate from the high-pressure jet grouting pile, resulting in the failure of the inclined pile support.

[0004] For the pre-injected grouting steel pipe inclined strut, small holes are opened around the steel pipe. First, the steel pipe inclined strut is driven in by using a vibratory hammer, and then high-pressure grouting is carried out to reinforce the surrounding soil through the small holes around the steel pipe. The diameter of the steel pipe is generally small, and for deep soft soil, the bearing capacity is insufficient. For inclined vibration pile sinking, the exciting force of the vibratory hammer is small, the pile sinking depth is limited, and the vibration has a large impact on the surrounding environment.

[0005] For the static pressure precast pipe pile inclined support, a special inclined static pressure pile driver is used to press the precast pipe pile into the soil section by section. This equipment uses its own weight to provide the reaction force, the equipment is relatively heavy, requires a relatively large space, and the angle between the pile body and the vertical direction generally does not exceed 20°. It is more difficult to construct large-angle inclined piles, resulting in limited horizontal support force provided by the pile.

[0006] The above problems of each inclined strut support limit its application in the foundation pit. Therefore, how to overcome the above problems to expand the application of the inclined strut support in the foundation pit, reduce the construction cost of the foundation pit, and improve the construction efficiency has great value. Content of the Utility Model

[0007] In order to overcome at least one of the above-mentioned problems in the diagonal brace support and to improve the application scope of the diagonal brace support, the utility model proposes a prestressing device for a foundation pit diagonal brace, which includes a crown beam cast on the top of the retaining pile, a static pile driver fixedly installed on the crown beam, and a locking structure for locking the diagonal brace on the crown beam; an anchor hole for the diagonal brace to pass through is provided on the crown beam, the static pile driver is inclined toward the outside of the foundation pit, and an annular gap is provided between the diagonal brace and the anchor hole, and the annular gap is filled with a ring-shaped bonding block formed by a first concrete grouting material, and the bonding block forms a locking structure.

[0008] In the present application, a static pile driver is installed on a crown beam, and when driving the pile, the crown beam can be used to provide a reaction force for construction, thereby enabling a static pile driver with a relatively light weight to be used for construction, reducing construction costs and improving construction convenience. Since a static pile driver with a relatively light weight can be used for construction, the construction angle of the static pile driver can be easily adjusted, and piles with large inclinations can be constructed to increase the horizontal support force and ensure the stability of the foundation pit enclosure. By using the present application, piles with an inclination angle of 15° can be constructed, that is, the angle between the pile and the vertical direction can reach 75°.

[0009] Furthermore, the anchor hole is in the shape of a cone with the small end tilted upward. This design can make the outer peripheral surface of the bonding block conical, so that the bonding block forms a ring-shaped wedge, which is more conducive to locking the steel pipe pile in the anchor hole.

[0010] Furthermore, the top of the diagonal brace is accommodated in the anchor hole, and there is a distance between the top end surface of the diagonal brace and the upper edge of the anchor hole, and an anchor block formed by the second concrete grouting material is poured in the anchor hole. The anchor block can form a sealing plug at the top of the anchor hole, and the top end of the diagonal brace is abutted against the sealing plug, further improving the external end connection between the diagonal brace and the crown beam.

[0011] Furthermore, in order to improve the connection strength between the diagonal brace and the crown beam, an embedded plate is provided on the inner wall of the anchor hole. After the anchor pile is cut, the connecting ribs are welded to the embedded plate, and then the second concrete grouting material is poured. The connecting ribs are located above the diagonal brace.

[0012] Furthermore, in order to improve the connection strength between the diagonal brace and the anchor block, a number of steel protrusions are fixedly installed on the outer peripheral surface of the top of the diagonal brace, at least one steel protrusion is cast in the bonding block, and the top end surface of the diagonal brace is wrapped in the anchor block.

[0013] Furthermore, in order to improve the connection strength between the static pile driver and the crown beam to ensure the reaction force during pile driving, anchor bars are pre-embedded in the crown beam, and the base of the static pile driver is detachably connected to the anchor bars.

[0014] Furthermore, the crown beam includes a main body and a reinforcement block arranged on the upper surface of the main body, and the static pile driver is at least partially installed on the reinforcement block. Since the installation area of ​​the base of the static pile driver is relatively large, if the main body of the crown beam is constructed based on the installation area of ​​the base, the construction cost of the crown beam will increase. The use of the reinforcement block to ensure the installation of the static pile driver can ensure the smooth installation of the static pile driver without significantly increasing the construction cost of the crown beam.

[0015] Furthermore, the static pile driver is supported on the ground by an adjustable bracket. Since the static pile driver is heavy, a crane or other lifting equipment is required during installation. It is not convenient to fine-tune the inclination angle of the static pile driver during installation. The adjustable bracket can conveniently fine-tune the inclination angle of the static pile driver, and after the adjustment is completed, it can also serve as a support frame for the static pile driver.

[0016] Furthermore, the diagonal brace includes a concrete pile and a steel pipe pile connected together, the steel pipe pile is located on the upper side of the concrete pile, and the top of the concrete pile does not exceed the set bottom surface of the foundation pit. Since the concrete pile is located below the underground structure, it is retained underground after the construction is completed and can be used as a foundation pile. The use of concrete piles can improve its bearing capacity and anti-corrosion performance, and the steel pipe pile located on the upper side of the concrete pile can be cut off and recycled after the construction is completed, thereby reducing construction costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural diagram of the static pile driver after installation.

[0018] Figure 2 yes Figure 1 Center AA view.

[0019] Figure 3 This is a state diagram of a static pile driver sinking a concrete pile.

[0020] Figure 4 It is a schematic diagram of the structure after the diagonal bracing construction is completed.

[0021] Figure 5 This is a schematic diagram after the underground structure construction is completed.

[0022] Figure 6 yes Figure 5 Magnified view of part B.

[0023] Figure 7 yes Figure 6 View of steel pipe piles.

[0024] Figure 8 This is a schematic diagram after the portion of the steel pipe pile that passes through the underground structure is cut away. DETAILED DESCRIPTION

[0025] See also Figure 1-Figure 8 , a prestressing device for a foundation pit diagonal brace, comprising a crown beam 11 cast on the top of a retaining pile 10, a static pile driver 16 fixedly mounted on the crown beam 11, and a locking structure for locking a diagonal brace 20 on the crown beam 11. There are no special requirements for the static pile driver, and the existing static pile drivers can meet the needs of this application and will not be described in detail. In the accompanying drawings, mark 100 represents the ground. In this embodiment, the retaining piles are concrete pipe piles.

[0026] In this embodiment, the crown beam adopts a reinforced concrete structure, and an anchor hole 15 for the diagonal brace 20 to pass through is arranged on the crown beam. In this embodiment, the crown beam 11 specifically includes a body 12 and a reinforcement block 13 arranged on the upper surface of the body. Corresponding to each anchor hole 15, a reinforcement block 13 is arranged. The reinforcement block and the body are cast at one time, that is, the reinforcement block is also a reinforced concrete structure. During construction, the reinforcement block and the crown beam are constructed as a whole. The reinforcement block has an inclined surface 130 away from the foundation pit 40, and the inclined surface is formed as the installation surface of the static pile driver 16. That is, in this embodiment, the static pile driver is completely installed on the reinforcement block. It can be understood that in other embodiments, the installation surface can also be extended to the body 12 of the crown beam, so that the static pile driver is only partially installed on the reinforcement block.

[0027] Several anchor bars 14 arranged in a rectangular shape are embedded in the crown beam. Corresponding to each mounting hole on the base of the static pile driver, an anchor bar 14 is provided. The anchor bar 14 is specifically made of finely rolled threaded steel bars. The upper end of the anchor bar passes through the inclined surface and is connected to the base 161 of the static pile driver through a nut, that is, the base of the static pile driver is detachably connected to the anchor bar. In the accompanying drawings, the nut on the anchor bar is not shown. In this embodiment, a static pile driver with patent number CN2020203306274 and the name of anchor static pile driver is specifically used. It can be understood that in other embodiments, other similar static pile drivers can also be used. The anchor hole passes through the inclined surface upward along its extension direction, that is, the anchor hole passes through the surface of the reinforcement block upward along its extension direction. In this embodiment, the diagonal brace specifically includes a concrete pile 18 and a steel pipe pile 19 welded together. The steel pipe pile is located on the upper side of the concrete pile, and the pile top of the concrete pile does not exceed the set bottom surface 49 of the foundation pit upward. The concrete piles are specifically PHC high-strength prestressed concrete pipe piles.

[0028] The static pile driver is installed obliquely on the inclined surface, so that the static pile driver is inclined toward the outside of the foundation pit. In this embodiment, the inclination angle of the static pile driver is 45°, so that the inclination angle of the diagonal brace 20 is also 45°. There is an annular gap 151 between the diagonal brace and the anchor hole, and the annular gap 151 is filled with a ring-shaped bonding block 31 formed by the first concrete grouting material, and the bonding block is formed into a locking structure. Specifically in this embodiment, the upper end inner diameter D1 of the anchor hole is smaller than the lower end inner diameter D2, that is, the anchor hole is a cone with the small end inclined upward, so that the outer peripheral surface of the formed bonding block is conical, causing the bonding block to form an annular wedge, that is, an annular wedge, which is more conducive to locking the diagonal brace in the anchor hole.

[0029] The top of the diagonal brace is accommodated in the anchor hole, and there is a distance between the top end surface of the diagonal brace and the upper end edge of the anchor hole. An anchor block 32 formed by the second concrete grouting material is poured in the anchor hole, and the top end surface of the diagonal brace is wrapped in the anchor block. In this application, the above-mentioned first concrete grouting material and the second concrete grouting material are only for the convenience of description. In specific construction, the first concrete grouting material and the second concrete grouting material can use the same type of concrete grouting material or different types of concrete grouting materials.

[0030] Since in this embodiment, the diagonal brace is composed of concrete piles 18 and steel pipe piles 19, and the steel pipe piles are located on the upper side of the concrete piles, so that the steel pipe piles are connected to the crown beam, when the strength of the bonding block 31 reaches the first set strength, the static pile driver is removed, and then the upper end of the steel pipe pile is cut, so that the top end surface of the steel pipe pile is accommodated in the anchor hole, and the steel pipe pile can be cut by a grinder or an oxy welding cutting tool or other cutting tools. In this embodiment, the first set strength is 30MPa. It can be understood that in other embodiments, the first set strength can also be set according to specific requirements.

[0031] In this embodiment, in order to further improve the connection strength between the diagonal brace and the crown beam, an embedded plate 131 is provided on the inner wall of the anchor hole. The embedded plate 131 can be constructed according to conventional methods, and the inner surface of the embedded plate 131 facing the inner side of the anchor hole is coplanar with the inner wall of the anchor hole. After the steel pipe pile is cut, the connecting rib 132 is welded to the embedded plate, and then the second concrete grouting material is poured. The connecting rib is located above the steel pipe pile. In the actual construction process, the inner surface of the embedded plate is sometimes bonded with concrete. Before welding the connecting rib, it is necessary to remove the concrete bonded to the inner surface of the embedded plate to facilitate the welding of the connecting rib 132 and the embedded plate 131. It can be understood that the embedded plate and the corresponding connecting rib are not necessary. When the second concrete grouting material can ensure the connection strength between the anchor pile and the crown beam, the embedded plate and the connecting rib can be eliminated.

[0032] In order to improve the anchoring effect, a plurality of steel protrusions 191 are welded on the outer peripheral surface of the top of the steel pipe pile, and each steel protrusion is cast in the bonding block. Specifically, in this embodiment, the steel protrusion is made of a steel bar, one end of which is welded on the outer peripheral surface of the steel pipe pile, and the other end of the steel bar extends obliquely toward the upper end of the steel pipe pile and away from the steel pipe pile.

[0033] Since the static pile driver 16 is tilted, it is inconvenient to install the static pile driver. Since the crown beam is a reinforced concrete structure, there is a certain deviation in construction accuracy. Therefore, an adjusting bracket 17 is used to support the upper part of the static pile driver. In this embodiment, the adjusting bracket 17 includes two adjusting rods arranged side by side. Each adjusting rod includes two steel rods 171 connected together by a threaded tube 172. Each steel rod is connected to the threaded tube by a threaded method. The spiral directions of the threads of the two steel rods are opposite. By screwing the threaded tube, the length of the adjusting rod can be adjusted, thereby fine-tuning the inclination angle of the static pile driver, thereby eliminating the deviation of the crown beam caused by the construction accuracy.

[0034] During construction of this embodiment, the following steps are followed:

[0035] (1) Please refer to Figure 1 and Figure 2 , sink the retaining piles along the edge of the foundation pit, and then construct the crown beam 11 on the top of the retaining piles. When constructing the crown beam 11, the main body 12 and the reinforcement block 13 are constructed simultaneously. To facilitate the construction of the crown beam, the surface soil in the foundation pit 40 area is excavated to reach the construction elevation of the crown beam. When constructing the crown beam, the embedded plate is embedded and the anchor hole is reserved simultaneously.

[0036] (2) Please continue reading Figure 1 and Figure 2 After the crown beam reaches the set strength, install the static pile driver on the crown beam, connect the base of the static pile driver to the anchor bar, and use the adjustment bracket to adjust the angle of the static pile driver.

[0037] (3) Please refer to Figure 3-Figure 7 , use a static pile driver to press the diagonal brace into the ground until it is completed. When constructing the diagonal brace, first complete the pressing of the concrete pile, then weld the steel pipe pile to the concrete pile, and continue the construction, wherein the top of the concrete pile does not exceed the upper surface of the bottom plate 41 of the underground structure 42. In order to facilitate the welding of the water-stop steel plate 21, in this embodiment, the lower end of the steel pipe pile is made to exceed the lower surface of the bottom plate of the underground structure by 10-200mm.

[0038] After the steel pipe pile is lowered, the first concrete grouting material is poured between the steel pipe pile and the anchor hole. The first concrete grouting material is only poured in the lower half of the anchor hole. The first concrete grouting material does not exceed the preset cutting line of the steel pipe pile upwards, so that when the steel pipe pile is cut later, the cut part of the steel pipe pile can be smoothly taken out from the anchor hole. When the strength of the bonding block 31 formed by the first concrete grouting material reaches the first set strength, the static pile driver is removed, and then the upper end of the steel pipe pile is cut, and the upper end face of the steel pipe pile after cutting is accommodated in the anchor hole.

[0039] The connecting ribs 132 are welded to the embedded plate, the connecting ribs are located above the anchor piles, and then the second grouting material is poured. After the second grouting concrete grouting material solidifies, it forms an anchor block 32 .

[0040] (4) Please continue reading Figure 5 , excavate the earth in the foundation pit until it is completed, then weld the water-stop steel plate 21, pour the bottom plate, and pour the water-stop steel plate in the bottom plate, and construct the underground structure until it is completed.

[0041] (5) Please refer to Figure 8 When the strength of the bottom plate reaches the set value, the portion of the steel pipe pile located at the upper portion of the bottom plate is cut off, and the inner cavity of the steel pipe pile remaining on the bottom plate is sealed with the third concrete grouting material 22. In this embodiment, the set value of the bottom plate strength is 80% of the bottom plate design strength.

Claims

1. A prestressing device for foundation pit diagonal bracing, characterized in that: It includes a crown beam cast on the top of the retaining pile, a static pile driver fixedly installed on the crown beam, and a locking structure for locking the diagonal brace on the crown beam; an anchor hole for the diagonal brace to pass through is arranged on the crown beam, the static pile driver is inclined toward the outside of the foundation pit, and an annular gap is provided between the diagonal brace and the anchor hole, and the annular gap is filled with a ring-shaped bonding block formed by a first concrete grouting material, and the bonding block forms a locking structure.

2. The prestressing device according to claim 1, characterized in that: The anchor hole is in a conical shape with a small end inclined upward.

3. The prestressing device according to claim 1 or 2, characterized in that: The top of the diagonal brace is accommodated in the anchor hole, and there is a distance between the top end surface of the diagonal brace and the upper end edge of the anchor hole. An anchor block formed by the second concrete grouting material is poured in the anchor hole, and the top end surface of the diagonal brace is wrapped in the anchor block.

4. The prestressing device according to claim 1, characterized in that: A plurality of steel protrusions are fixedly mounted on the outer peripheral surface of the top of the diagonal support, and at least one of the steel protrusions is cast in the bonding block.

5. The prestressing device according to claim 1, characterized in that: Anchor bars are pre-buried in the crown beam, and the base of the static pile driver is detachably connected to the anchor bars.

6. The prestressing device according to claim 1, characterized in that: The crown beam comprises a body and a reinforcement block arranged on the upper surface of the body, and the static pile driver is at least partially installed on the reinforcement block.

7. The prestressing device according to claim 1, characterized in that: The static pile driver is supported on the ground by an adjustable bracket.

8. The prestressing device according to claim 1, characterized in that: The diagonal brace includes a concrete pile and a steel pipe pile connected together, the steel pipe pile is located on the upper side of the concrete pile, and the top of the concrete pile does not exceed the set bottom surface of the foundation pit upward.

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