Composite hole forming method for pile foundation of bridge adjacent cliff section

Abstract

The invention discloses a bridge adjacent cliff section pile foundation composite hole forming method in the field of pile foundation trepanning construction, which comprises the following steps: S1, fore shaft construction: after a hole digging position is selected in an adjacent cliff section, anchor rods are applied to the peripheral side of the hole digging position, grouting is carried out, and fore shaft construction is carried out after the slurry strength is qualified; s2, after manual hole digging is completed, a footage with a preset depth is dug at the hole digging position, after digging of one footage is completed, a protection wall is installed on the inner wall of the footage, one manual hole digging period is completed, and multiple manual hole digging periods are repeated; s3, mechanical drilling is carried out, and when the total drilling footage depth after multiple manual hole digging periods reaches a preset value, mechanical drilling and grouting are carried out till a hole is formed; manual hole digging is combined with the percussion drill, so that the quality of a drilled pile is well controlled, the phenomena of cliff collapse and pile foundation perforation are avoided to the maximum extent, and the stability of the construction process is improved.

Description

Technical Field

[0001] The invention relates to the technical field of pile foundation construction, and in particular to a composite hole forming method for pile foundations in a cliff-adjacent section of a bridge. Background Art

[0002] With the continuous expansion of the scale and speed of road traffic construction in my country, bridge engineering has become a very important construction link. During the construction process, pile foundation is the foundation of the entire bridge project, and the completion rate of pile foundation determines the quality and progress of the entire bridge project.

[0003] At present, the construction method of bridge pile foundation is generally based on mechanical drilling. Mechanical drilling has relatively high construction efficiency and high safety and controllability in the construction process. However, it is inconvenient to enter the site in a complex environment. In addition, for pile foundations that are longer in areas adjacent to cliffs, if the thickness of the pile side cover in the upper half of the pile foundation is too thin, mechanical drilling alone will cause great disturbance to the lateral cover, which can easily cause defects such as soil breakage and poor self-stabilization ability, posing a safety risk. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the technical problem to be solved by the present invention is: how to reduce the stability and safety of pile foundation drilling in the cliff-adjacent section.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] The composite hole forming method for pile foundation in the cliff section of a bridge comprises the following steps:

[0007] S1: Locking construction: After selecting the hole location in the cliff section, anchor rods are placed around the hole location and grouting is performed. After the grout strength is qualified, locking construction is carried out;

[0008] S2: Manual digging. After the locking construction is completed, a preset depth of excavation is carried out at the digging position. After the excavation of one depth is completed, a retaining wall is poured on the inner wall of the above-mentioned depth to complete a manual digging cycle. Multiple manual digging cycles are repeated;

[0009] S3: Mechanical drilling. When the total depth after multiple manual digging cycles reaches the preset value, mechanical drilling and grouting are carried out until the hole is completed.

[0010] Furthermore, in step S1, it specifically includes setting a cylindrical inner mold at the selected hole digging position, multiple anchor rods are set on the periphery of the inner mold, and the multiple anchor rods are connected by steel bars to form a casting array, an outer mold is set around the outside of the casting array, concrete is poured at the casting array between the outer mold and the inner mold, and the outer mold and the inner mold are removed after the concrete strength reaches the requirement, and the locking construction is completed.

[0011] Furthermore, the plurality of anchor rods are evenly spaced between the inner mold and the outer mold.

[0012] Furthermore, the depth of excavation in each manual hole digging cycle is determined based on the self-stabilizing capacity of the excavated soil layer combined with the construction advancement speed.

[0013] Furthermore, the drilling depth in each manual boring cycle does not exceed 1m.

[0014] Furthermore, in step S2, the installation process of the above-mentioned protective wall includes: in any of the above-mentioned manual digging cycles, an annular steel bar support is installed around the outer wall of the excavated hole, a cylindrical formwork is set on the inner side between the above-mentioned annular steel bars, and concrete is poured between the outer wall of the excavated hole and the cylindrical formwork.

[0015] Furthermore, the inner diameter of the upper end of the cylindrical template is smaller than the inner diameter of the lower end.

[0016] Furthermore, in step S3, when the total depth of the footage after multiple manual digging cycles reaches a preset value, the preset value is designed based on whether the lateral cover thickness meets the requirements of mechanical drilling.

[0017] The beneficial effects of the present invention are:

[0018] Manual digging causes little disturbance to the lateral cover soil, so the thinner lateral cover soil thickness of the pile foundation in the cliff-adjacent area can be constructed. When the lateral cover soil thickness meets the requirements, impact drilling can be used to punch holes, and the construction speed is faster than manual digging. During the construction process, the combination of manual digging and impact drilling can well control the quality of bored piles, avoid the occurrence of cliff collapse and pile foundation perforation to the greatest extent, improve the stability of the construction process, and meet the requirements of safe, efficient, cost-effective and green construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the composite hole forming of the pile foundation of the present invention;

[0020] Figure 2 It is a schematic diagram of the lock construction structure of the present invention;

[0021] Figure 3 It is a schematic diagram of a vertical cross section of the artificial hole-digging wall protection of the present invention;

[0022] Marked in the figure, 1-pile foundation, 2-locking mouth, 3-protective wall. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with the accompanying drawings.

[0024] according to Figure 1-3 As shown, the embodiment of the present application proposes a composite hole forming method for pile foundation in a cliff section of a bridge, comprising the following steps: Figure 1 Section a in the middle represents the manual digging section, and section b represents the mechanical digging section):

[0025] S1: Locking construction. After selecting the hole digging position in the cliff-adjacent area, anchor rods are installed around the hole digging position and grouting is performed. After the slurry strength meets the requirements, the locking construction is carried out. Specifically, a cylindrical inner mold is set at the selected hole digging position, and multiple anchor rods are set around the inner mold. The multiple anchor rods are connected by steel bars to form a casting array. An outer mold is set around the outer side of the casting array, and concrete is poured at the casting array between the outer mold and the inner mold. After the concrete strength reaches the requirements, the outer mold and the inner mold are removed to complete the locking 2 construction.

[0026] Among them, the hole digging location is selected in the area adjacent to the cliff. In order to ensure the stability of the pile foundation drilling process, the entire lock mouth 2 construction position is larger, and in order to facilitate construction, the above-mentioned casting array is set to a rectangle, which is convenient for the setting and installation of the external mold and improves efficiency.

[0027] S2: Manual excavation. After the construction of the lock 2 is completed, a preset depth of footage is excavated at the excavation position. After one footage of excavation is completed, a retaining wall 3 is poured on the inner wall of the footage to complete a manual excavation cycle, and multiple manual excavation cycles are repeated; wherein, the footage depth in each manual excavation cycle is determined according to the self-stabilizing capacity of the excavated soil layer combined with the construction footage speed, that is, the footage depth in each manual excavation cycle is limited by judging the self-stabilizing capacity of the soil layer, ensuring that the soil layer will not collapse at a single reasonable footage depth, and by dividing the preset total depth of manual excavation footage into multiple manual excavation cycles, ensuring that one section of excavation is reinforced and one section is reinforced to avoid instability during the excavation process.

[0028] Specifically, the depth of each shift of earthwork excavation is determined according to the self-stabilizing capacity of the excavated soil layer combined with the construction advancement speed. However, in any case, a single advancement cycle shall not exceed 1 meter; if the soil layer is broken and the self-stabilizing capacity is poor, a depth of 0.5 meters can be taken as one advancement cycle; but in the actual excavation process, when encountering soil layer changes and sliding surfaces, the wall protection sections shall not be set, and the wall protection sections shall be adjusted to stagger the parts to ensure that the soil layer changes and sliding surfaces can ensure sufficient protection measures to avoid subsequent unstable conditions.

[0029] The construction process of the above-mentioned protective wall 3 includes: in any of the above-mentioned manual digging cycles, an annular steel bar support is installed around the outer wall of the excavated hole, a cylindrical formwork is set on the inner side between the above-mentioned annular steel bars, and concrete is poured between the outer wall of the excavated hole and the cylindrical formwork. The above-mentioned steel bar support is composed of a plurality of vertical steel bars arranged axially along the outer wall of the hole and a plurality of horizontal annular steel rings from top to bottom which are sequentially connected to the plurality of the above-mentioned vertical steel bars to form a stable supporting structure, and the annular steel bar support is cast and buried in the concrete supporting wall to form a complete protective wall 3, thereby improving stability and supporting strength.

[0030] The lower end of the above-mentioned annular steel bar support is provided with a hook-shaped connecting part for connecting to the upper end of the annular steel bar support for the next manual excavation cycle, which can facilitate the connection of the annular steel bar support, and the inner diameter of the upper end of the above-mentioned cylindrical template is smaller than the inner diameter of the lower end, that is, the inner diameter of the lower end of the concrete retaining wall after pouring is larger than the inner diameter of the upper end, forming a truncated cone-shaped inner hole, which can ensure that subsequent excavation has a larger excavation space and improve efficiency.

[0031] S3: Mechanical drilling. When the total depth after multiple manual digging cycles reaches a preset value, mechanical drilling and grouting are performed until a hole is formed and a pile foundation 1 is set.

[0032] Among them, when the total depth of footage after multiple manual digging cycles reaches the preset value, the design is based on whether the lateral cover thickness meets the requirements of mechanical drilling. That is, after excavating to a certain total depth of footage, the lateral cover thickness is detected, and the lateral cover thickness is analyzed to see whether it has achieved sufficient stability and can stably withstand the impact of mechanical drilling without slipping and collapse. Then mechanical digging is carried out to ensure stability.

[0033] When encountering special geological layers such as silt, loose fine sand and other soft soil layers, clay blocks can be added with small stone pieces to repeatedly impact the hole wall to ensure the stability of the hole wall. In addition, the supply of mud must be guaranteed during the drilling process to stabilize the slurry in the hole.

[0034] Moreover, different geological layers may appear during the mechanical drilling process using an impact drill. At this time, it is necessary to follow the mechanical drilling points of the corresponding geological layers, such as replacing a reasonable drill bit or adjusting the drilling power, etc., to ensure the stability and efficiency of the mechanical drilling process.

[0035] In summary, manual digging causes little disturbance to the lateral covering soil, and the thinner section of the lateral covering soil thickness of the pile foundation 1 in the cliff-adjacent section can be constructed. When the lateral covering soil thickness meets the requirements, an impact drill can be used to punch holes, and the construction speed is faster than manual digging. During the construction process, the combination of manual digging and impact drilling can well control the drilling quality, avoid the occurrence of cliff collapse and pile foundation 1 perforation to the greatest extent, and improve the stability of the construction process. Moreover, the use of this technology can minimize the safety risks of construction operations, ensure the safety and stability of the bridge during the construction and operation and maintenance of the cliff-adjacent section, meet the requirements of the owner and related parties, ensure safety and reduce costs.

Claims

1. A composite hole forming method for pile foundations in a bridge adjacent to a cliff, characterized in that: The following steps are involved: S1: Locking construction: After selecting the hole location in the cliff section, anchor rods are placed around the hole location and grouting is performed. After the grout strength is qualified, locking construction is carried out; S2: Manual digging. After the locking construction is completed, a preset depth of excavation is carried out at the digging position. After the excavation of one depth is completed, a retaining wall is poured on the inner wall of the depth to complete a manual digging cycle. Multiple manual digging cycles are repeated; S3: Mechanical drilling. When the total depth after multiple manual digging cycles reaches the preset value, mechanical drilling and grouting are carried out until the hole is completed.

2. The composite hole forming method for pile foundation in the cliff section of a bridge according to claim 1 is characterized in that: In step S1, it specifically includes setting a cylindrical inner mold at the selected hole digging position, multiple anchor rods are set on the periphery of the inner mold, and the multiple anchor rods are connected by steel bars to form a casting array, an outer mold is set around the outside of the casting array, concrete is poured at the casting array between the outer mold and the inner mold, and the outer mold and the inner mold are removed after the concrete strength reaches the requirement, and the locking construction is completed.

3. The composite hole forming method for pile foundation in the cliff section of a bridge according to claim 2 is characterized in that: A plurality of anchor rods are evenly spaced and arranged between the inner mold and the outer mold.

4. The composite hole forming method for pile foundation in a cliff section of a bridge according to claim 1 is characterized in that: In step S2, the depth of the excavation in each manual hole digging cycle is determined according to the self-stabilizing capacity of the excavated soil layer and the construction advancement speed.

5. The composite hole forming method for pile foundation in the cliff section of a bridge according to claim 4 is characterized in that: The drilling depth in each manual digging cycle shall not exceed 1m.

6. The composite hole forming method for pile foundation in the cliff section of a bridge according to claim 1 is characterized in that: In step S2, the installation process of the protective wall includes: in any of the manual digging cycles, an annular steel bar support is installed around the outer wall of the dug hole, a cylindrical formwork is set inside between the annular steel bars, and concrete is poured between the outer wall of the dug hole and the cylindrical formwork.

7. The composite hole forming method for pile foundation in the cliff section of a bridge according to claim 6 is characterized in that: The inner diameter of the upper end of the cylindrical template is smaller than the inner diameter of the lower end.

8. The composite hole forming method for pile foundation in the cliff section of a bridge according to claim 1 is characterized in that: In step S3, when the total depth of the footage after multiple manual digging cycles reaches a preset value, it is designed based on whether the lateral cover thickness meets the requirements of mechanical drilling.

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