Construction method for backfill reinforcement of bored pile

Abstract

The application discloses a kind of bored pile empty pile backfill reinforcement construction method, including steps:1, the pile core area of the bored pile to be treated, i.e.empty pile, according to the additional load distribution of ground soil body, the pile core area is divided into main influence area, secondary influence area and no influence area;2, reinforce engineering slurry in pile core, form flocculation solidified filling area in no influence area;3, according to the load requirement in main influence area and secondary influence area, prepare first pile core solidified soil material and second pile core solidified soil material;4, first pile core solidified soil material is backfilled to secondary influence area, and form first high-strength solidified filler filling area;5, second pile core solidified soil material is backfilled to main influence area, and form second high-strength solidified filler filling area;6, maintenance, set up protective fence around pile foundation.The application relates to the technical field of building construction, can solve the problem that traditional backfill material cannot meet the requirement of foundation bearing capacity in prior art.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a method for backfilling and reinforcing bored cast-in-place piles. Background Technology

[0002] In building construction, bored piles are widely used as the main load-bearing components of the superstructure. With the continuous optimization of pile foundation design and construction technology, large-diameter bored piles are becoming increasingly common. During the foundation pit construction phase of building projects, the engineering piles are often constructed before the earthwork excavation to avoid the potential hazards that may arise from constructing the engineering piles after the foundation pit has been excavated to the bottom. This results in a section of empty piles from the ground to the bottom of the pit, which poses a significant construction safety hazard.

[0003] Traditional solutions involve backfilling the empty pile areas with miscellaneous soil and gravel, then excavating them along with the excavated soil during the foundation pit excavation phase. However, this approach is only suitable for situations where the empty pile areas do not bear the load from above. When construction site constraints prevent construction machinery from avoiding numerous empty pile areas, traditional backfill materials cannot meet the bearing capacity requirements of the foundation soil under the loads of the construction machinery, leading to significant construction safety hazards and reduced construction efficiency. While plain concrete backfilling can achieve the required strength, it significantly increases backfilling costs and consumes large amounts of natural resources such as sand, gravel, and cement, making it environmentally unfriendly and unsuitable for widespread application. Therefore, a method for backfilling and reinforcing bored piles is needed to address the problem that existing technologies using traditional backfill materials cannot meet the foundation bearing capacity requirements. Summary of the Invention

[0004] The purpose of this invention is to provide a construction method for backfilling and reinforcing bored cast-in-place piles, which can solve the problem that traditional backfill materials in the prior art cannot meet the bearing capacity requirements of the foundation.

[0005] This invention is implemented as follows:

[0006] A method for backfilling and reinforcing empty bored piles includes the following steps:

[0007] Step 1: Determine the core area of ​​the bored pile that needs to be treated, i.e., the empty pile, and divide the core area into the main influence zone I, the secondary influence zone II, and the no-influence zone III according to the distribution of additional loads on the foundation soil.

[0008] Step 2: Reinforce the engineering mud inside the pile core to form a flocculated and solidified filling zone in the unaffected area;

[0009] Step 3: Based on the load requirements in the main influence zone I and the secondary influence zone II, prepare the first pile core solidification soil material and the second pile core solidification soil material respectively;

[0010] Step 4: Backfill the first pile core solidified soil material into the secondary influence zone II of the pile core to form the first high-strength solidified filler filling zone;

[0011] Step 5: Backfill the second pile core solidified soil material into the main influence zone I of the pile core to form the second high-strength solidified filler filling zone;

[0012] Step 6: Curing is carried out on the surface of the solidified soil material of the second pile core, and a protective fence is set up around the pile foundation.

[0013] In step 1, based on the transmission law of additional load in the foundation soil in soil mechanics, the additional load distribution curve X of the foundation soil under the action of the upper construction machinery load is calculated; according to the distribution form of the additional load, the inflection point H on the additional load distribution curve X is used as the reference point. c And convergence value 0.1P zmax Using these as boundaries, the area affected by the additional load on the foundation soil is divided into three zones: the primary influence zone I, the secondary influence zone II, and the unaffected zone III.

[0014] The primary influence zone I, secondary influence zone II, and no-influence zone III are arranged sequentially from top to bottom, with the inflection point H. c This is the boundary point between the primary influence zone I and the secondary influence zone II, with a convergence value of 0.1P. zmax This is the dividing point between the secondary impact zone II and the unaffected zone III.

[0015] Step 2 includes the following sub-steps:

[0016] Step 2.1: Prepare the flocculant solution and determine the proportion of flocculant solution to be added through preliminary tests;

[0017] Step 2.2: Based on the volume of the engineering mud in the pile core, add flocculant solution and mix the flocculant with the engineering mud by stirring to separate the mud and water in the engineering mud.

[0018] Step 2.3: Drain the upper layer of clear liquid in the unaffected zone III of the pile core to form a flocculated and solidified filling zone. The soil on the side wall of the pile core after the upper layer of clear liquid is drained is supported by the steel casing that has been embedded during the construction of the bored pile.

[0019] In step 2.3, the embedment depth of the steel casing shall not be higher than the top surface of the unaffected zone III of the pile core.

[0020] In step 2.3, the height of the lower sediment after the upper clear liquid is discharged, i.e., the height of the flocculation and solidification filling zone, is consistent with the top surface height of the unaffected zone III of the pile core.

[0021] In step 3, the excavated soil from the pile foundation at the construction site is used as raw material. The moisture content of the excavated soil is measured. Industrial solid waste-based cementitious material is used as a curing agent. The excavated soil and the curing agent are mechanically mixed in a mixing tank according to the first and second water-solid ratios and the amount of curing agent, respectively, to prepare the first pile core solidified soil material and the second pile core solidified soil material. The industrial solid waste-based cementitious material is composed of steel slag powder, fly ash, and desulfurized gypsum.

[0022] In step 4, the volume of the first pile core solidified soil material filled into the secondary influence zone II is based on the difference between the filling elevation of the first pile core solidified soil material and the ground surface elevation.

[0023] In step 6, moist straw mats are laid on the surface of the second pile core solidified soil material for curing; protective fences are set around the pile foundation at a distance equal to one pile diameter.

[0024] The unconfined compressive strength of the first high-strength cured filler filling area reaches 1.0 MPa or more, and the unconfined compressive strength of the second high-strength cured filler filling area reaches 1.5 MPa or more.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. This invention segments large-diameter bored piles according to the additional load curve generated by the upper construction machinery on the foundation soil, dividing the large-diameter bored piles into a main influence zone, a secondary influence zone, and an unaffected zone from top to bottom. It adopts a segmented mud flocculation sedimentation combined with slag solidification backfilling process, and backfills the main influence zone, secondary influence zone, and unaffected zone in segments at a lower cost. This ingeniously solves the problem of insufficient bearing capacity of the foundation soil under load, which leads to large subsidence or overturning of construction machinery during operation, thus improving the efficiency of on-site construction operations and ensuring the safe operation of heavy construction machinery on the construction site.

[0027] 2. This invention utilizes flocculants to solidify engineering mud, thereby achieving the resource utilization of engineering mud in bored piles. This allows soil particles in the engineering mud to quickly settle and aggregate, becoming filling material in the non-affected zone of the pile core. This avoids pollution of the site and transportation of engineering mud, resulting in low construction costs and environmental friendliness.

[0028] 3. This invention fully utilizes the engineering waste soil generated on-site as the main raw material, and uses steel slag powder, fly ash, and desulfurized gypsum as multi-source industrial solid waste-based cementitious materials as solidifying agents. According to the load requirements of the main and secondary affected areas, the solidifying agent is mixed with the engineering waste soil in an appropriate proportion to form the first pile core solidified soil material and the second pile core solidified soil material, which are used as backfill materials for the main and secondary affected areas. This not only ensures the bearing capacity of the foundation soil, but also makes the strength of the material in the pile core backfill area match the distribution law of the additional load, giving full play to the characteristics of materials with different strengths, and taking into account the convenience and cost of construction, but also avoids the consumption of natural sand, gravel, cement and other materials, thus realizing green and low-carbon construction. Attached Figure Description

[0029] Figure 1 This is a construction flowchart of the hollow pile backfilling and reinforcement construction method of the present invention for bored cast-in-place piles;

[0030] Figure 2 This is a schematic diagram illustrating the design principle of the hollow pile backfilling and reinforcement construction method for bored cast-in-place piles according to the present invention.

[0031] In the figure, I represents the main affected area, II the secondary affected area, III the unaffected area, X the additional load distribution curve, 1 the flocculation and solidification filling area, 2 the first high-strength solidified filler filling area, 3 the second high-strength solidified filler filling area, 4 the steel casing, 5 the upper clear liquid, 6 the straw mat, 7 the protective fence, and 8 the engineering mud. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0033] Please see the appendix Figure 1 and attached Figure 2 A method for backfilling and reinforcing empty bored piles includes the following steps:

[0034] Step 1: Determine the core area of ​​the bored pile that needs to be treated, i.e., the empty pile, and divide the core area into the main influence zone I, the secondary influence zone II, and the no-influence zone III according to the distribution of additional loads on the foundation soil.

[0035] Specifically, based on the transmission law of additional load in foundation soil in soil mechanics, the additional load distribution curve X of the foundation soil under the action of the superstructure construction machinery load is calculated, as shown in the attached figure. Figure 2 As shown in the figure, P represents the load of the upper construction machinery. zmax The additional load on the foundation soil by the superstructure machinery; based on the distribution pattern of the additional load, the inflection point H on the additional load distribution curve X is used. c And convergence value 0.1P zmaxUsing these as boundaries, the area affected by the additional load on the foundation soil is divided into three zones: the primary influence zone I, the secondary influence zone II, and the unaffected zone III.

[0036] The primary influence zone I, secondary influence zone II, and no-influence zone III are arranged sequentially from top to bottom, with the inflection point H. c This is the boundary point between the primary influence zone I and the secondary influence zone II, with a convergence value of 0.1P. zmax This is the dividing point between the secondary impact zone II and the unaffected zone III.

[0037] The primary impact zone I is the area where the load from the upper construction machinery has the greatest impact on the foundation soil; the secondary impact zone II is the area where the load from the upper construction machinery has a relatively large impact on the foundation soil; and the unaffected zone III is the area where the load from the upper construction machinery has almost no impact on the foundation soil. Since the upper construction machinery operates on the ground surface, the impact of the load on the foundation soil gradually decreases from top to bottom. Therefore, it is divided into primary impact zone I, secondary impact zone II, and unaffected zone III from top to bottom.

[0038] Step 2: The engineering mud 8 inside the reinforced pile core forms a flocculated and solidified filling zone 1 in the unaffected zone III.

[0039] Step 2 includes the following sub-steps:

[0040] Step 2.1: Prepare a flocculant solution of a certain concentration and determine the reasonable addition ratio of the flocculant solution through preliminary experiments.

[0041] The solidification of engineering mud 8 using flocculants is a conventional construction process in this field. The composition, concentration, and dosage of the flocculant can be selected according to the actual working conditions, and will not be elaborated here. Directly flocculating and solidifying the engineering mud 8 inside the pile core eliminates the need to transport the engineering mud 8 externally, avoiding pollution to the construction site and making the construction more convenient, efficient, and environmentally friendly.

[0042] Step 2.2: Based on the volume of the engineering mud 8 in the pile core, add a certain amount of flocculant solution, and use a mixer to fully mix the flocculant with the engineering mud 8 so that the engineering mud 8 can quickly achieve mud-water separation.

[0043] Under the action of flocculant, water and soil particles in engineering mud 8 are separated to form lower sediment and upper clear liquid 5.

[0044] Step 2.3: Drain the upper layer of clear liquid 5 in the unaffected zone III of the pile core to form the flocculated solidification filling zone 1. After draining the upper layer of clear liquid 5, the soil on the side wall of the pile core is supported by the steel casing 4 that has been embedded during the construction of the bored pile.

[0045] Before solidification, the engineering mud 8 fills the entire pile core area. After the upper clear liquid 5 is discharged, the lower sediment fills the pile core unaffected zone III, forming the flocculated solidified filling zone 1. The area above the flocculated solidified filling zone 1 to the top of the pile is a cavity structure. Therefore, the embedment depth of the steel casing 4 is not higher than the top surface of the pile core unaffected zone III.

[0046] The height of the lower sediment after the upper clear liquid 5 is discharged, i.e. the height of the flocculation and solidification filling zone 1, is consistent with the top surface height of the pile core unaffected zone III, ensuring effective filling and reinforcement of the pile core unaffected zone III.

[0047] The soil particles in engineering mud 8 settle and self-compress rapidly. This sediment mainly serves as a filler in the unaffected zone III. Since the additional load generated by the upper construction machinery has virtually no impact on the foundation soil of the unaffected zone III, this sediment does not need to have high strength.

[0048] Step 3: Based on the load requirements in the main influence zone I and the secondary influence zone II, prepare the first pile core solidified soil material and the second pile core solidified soil material respectively.

[0049] Specifically, the excavated soil from the pile foundation at the construction site is used as raw material. The moisture content of the excavated soil is measured. Industrial solid waste-based cementitious material is used as a curing agent. The excavated soil and the curing agent are mechanically mixed in a mixing tank according to the first and second water-solid ratios and the amount of curing agent, respectively, to prepare the first pile core solidified soil material and the second pile core solidified soil material.

[0050] The industrial solid waste-based cementitious material is mainly composed of steel slag powder, fly ash, desulfurized gypsum, etc., which replaces cement-based cementitious materials and has low cost. The strength of the first pile core solidified soil material and the second pile core solidified soil material is controlled by the proportion of the solidifying agent added.

[0051] Solidification of construction waste soil is a conventional construction process in this field. Based on the moisture content of the construction waste soil at the construction site and the mixing ratio of the solidifying agent, a limited number of experiments can be conducted to obtain the first and second pile core solidified soil materials that meet the strength requirements, thereby resisting the additional load generated by the upper machinery on the foundation soil. The experimental process will not be described in detail here.

[0052] Step 4: Backfill the first pile core solidified soil material into the secondary influence zone II of the pile core to form the first high-strength solidified filler filling zone 2.

[0053] Since the first pile core solidified soil material will exert a certain degree of compression on the flocculation solidification filling zone 1, the volume of the first pile core solidified soil material filled into the secondary influence zone II is based on the difference between the filling elevation of the first pile core solidified soil material and the ground surface elevation.

[0054] The unconfined compressive strength of the first high-strength cured filler filling zone 2 reaches 1.0 MPa or more.

[0055] Step 5: Backfill the second pile core solidified soil material into the main influence zone I of the pile core to form the second high-strength solidified filler filling zone 3.

[0056] The unconfined compressive strength of the second high-strength cured filler filling zone 3 reaches more than 1.5 MPa.

[0057] Step 6: Curing the surface of the second pile core solidified soil material, and at the same time setting up a protective fence around the pile foundation 7.

[0058] Preferably, a moist straw mat 6 is laid on the surface of the second pile core solidified soil material for curing. A protective fence 7 is set around the pile foundation at a distance of one pile diameter to prevent surrounding construction activities from disturbing the strength formation of the pile core solidified soil.

[0059] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the invention. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for backfilling and reinforcing empty bored piles, characterized in that: Includes the following steps: Step 1: Determine the core area of ​​the bored pile that needs to be treated, i.e., the empty pile, and divide the core area into the main influence zone I, the secondary influence zone II, and the no-influence zone III according to the distribution of additional loads on the foundation soil. Step 2: Reinforce the engineering mud (8) inside the pile core to form a flocculated solidification filling zone (1) in the unaffected zone; Step 3: Based on the load requirements in the main influence zone I and the secondary influence zone II, prepare the first pile core solidification soil material and the second pile core solidification soil material respectively; Step 4: Backfill the first pile core solidified soil material into the secondary influence zone II of the pile core to form the first high-strength solidified filler filling zone (2). Step 5: Backfill the second pile core solidified soil material into the main influence zone I of the pile core to form the second high-strength solidified filler filling zone (3); Step 6: Curing the surface of the second pile core solidified soil material, and at the same time setting up a protective fence around the pile foundation (7); In step 1, based on the transmission law of additional load in the foundation soil in soil mechanics, the additional load distribution curve X of the foundation soil under the action of the superstructure construction machinery is calculated; based on the distribution form of the additional load, the inflection point Hc and the convergence value 0.1P on the additional load distribution curve X are used as the basis. zmax To define the boundaries, the area of ​​influence of the additional load on the foundation soil is divided into a primary influence zone I, a secondary influence zone II, and a non-influence zone III; these three zones are arranged sequentially from top to bottom, with the inflection point H. c This is the boundary point between the primary influence zone I and the secondary influence zone II, with a convergence value of 0.1P. zmax This is the dividing point between the secondary impact zone II and the unaffected zone III.

2. The method for backfilling and reinforcing empty piles of bored cast-in-place piles according to claim 1, characterized in that: Step 2 includes the following sub-steps: Step 2.1: Prepare the flocculant solution and determine the proportion of flocculant solution to be added through preliminary tests; Step 2.2: Based on the volume of the engineering mud (8) in the pile core, add the flocculant solution and mix the flocculant with the engineering mud (8) by stirring to separate the mud and water in the engineering mud (8); Step 2.3: The upper layer of clear liquid (5) in the unaffected zone III of the pile core is discharged to form a flocculated solidification filling zone (1). The soil on the side wall of the pile core after the upper layer of clear liquid (5) is discharged is supported by the steel casing (4) that has been embedded in the bored pile construction stage.

3. The method for backfilling and reinforcing empty piles of bored cast-in-place piles according to claim 2, characterized in that: In step 2.3, the embedment depth of the steel casing (4) is not higher than the top surface of the unaffected zone III of the pile core.

4. The method for backfilling and reinforcing empty piles of bored cast-in-place piles according to claim 2, characterized in that: In step 2.3, the height of the lower sediment after the upper clear liquid (5) is discharged, i.e. the height of the flocculation solidification filling area (1), is consistent with the top surface height of the pile core unaffected area III.

5. The method for backfilling and reinforcing empty piles of bored cast-in-place piles according to claim 1, characterized in that: In step 3, the excavated soil from the pile foundation at the construction site is used as raw material. The moisture content of the excavated soil is measured. Industrial solid waste-based cementitious material is used as a curing agent. The excavated soil and the curing agent are mechanically mixed in a mixing tank according to the first and second water-solid ratios and the amount of curing agent, respectively, to prepare the first pile core solidified soil material and the second pile core solidified soil material. The industrial solid waste-based cementitious material is composed of steel slag powder, fly ash, and desulfurized gypsum.

6. The method for backfilling and reinforcing empty piles of bored cast-in-place piles according to claim 1, characterized in that: In step 4, the volume of the first pile core solidified soil material filled into the secondary influence zone II is based on the difference between the filling elevation of the first pile core solidified soil material and the ground surface elevation.

7. The method for backfilling and reinforcing empty piles of bored cast-in-place piles according to claim 1, characterized in that: In step 6, a moist straw mat (6) is laid on the surface of the second pile core solidified soil material for curing; a protective fence (7) is set around the pile foundation at a distance equal to one pile diameter.

8. The method for backfilling and reinforcing empty piles of bored cast-in-place piles according to claim 1, characterized in that: The unconfined compressive strength of the first high-strength cured filler filling area (2) reaches 1.0 MPa or more, and the unconfined compressive strength of the second high-strength cured filler filling area (3) reaches 1.5 MPa or more.

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