CN111254939A

CN111254939A - Foundation pit enclosure strengthening method for soft soil foundation

Info

Publication number: CN111254939A
Application number: CN201910568218.XA
Authority: CN
Inventors: 周兆弟
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-11-30
Filing date: 2019-06-27
Publication date: 2020-06-09

Abstract

The invention discloses a foundation pit enclosure strengthening method of a soft soil foundation, which is characterized in that an integral gapless strengthening area is formed at the edge of a foundation pit by filling a filler mixed with an adhesive and/or a curing agent and gravel aggregate and/or recycled aggregate in a region from the ground of a weak bearing layer at the edge of the foundation pit to the depth of the foundation pit. The foundation pit enclosure strengthening method of the soft soil foundation provided by the invention is characterized in that an integral type gapless strengthening region is arranged in a weak bearing layer at the edge of the foundation pit so as to improve the enclosure strength of the foundation pit, the earth retaining strength is improved after the strengthening region is hardened, and a waterproof curtain can be formed.

Description

Foundation pit enclosure strengthening method for soft soil foundation

Technical Field

The invention relates to the field of buildings, in particular to a method for strengthening the enclosure of a foundation pit of a soft soil foundation.

Background

China is wide in regions, different regions and different climates have profound influences on soil layers and soil texture, and therefore great attention needs to be paid to foundation treatment of the building body during construction of the building body.

With the development of industry, the demand of high-rise or super high-rise buildings for cities, particularly dense-population cities, is gradually increased, and the bearing capacity of foundations of the high-rise or super high-rise buildings is high. If the bearing capacity of the building foundation is insufficient, such as a soft soil foundation with soft soil, various construction measures are needed for reinforcing the foundation, and the influence of the soft soil is reduced to the minimum.

According to experience, soft soil foundations are mostly distributed in coastal cities of China, water areas are sufficient, soil is mostly a sand soil layer or a mucky soil layer, and pebbles, gravels and the like are contained. When the construction is carried out around rivers or lakes, soil layers need to be strictly managed, otherwise serious economic loss is brought. The soft soil foundation contains a great variety of soft soil substances including but not limited to silt, mucky soil, plain filling and other soft soil, plastic cohesive soil and other loose soil, medium dense fine sand and other slightly dense soil, medium dense fine soil and other loose soil, slightly dense medium coarse sand and gravel, loess and other soil layers, so that in a soft soil environment, the soil layers need to be deeply researched and analyzed to determine the bearing capacity of the corresponding soil substances, and various construction measures are taken to reinforce the foundation, so that the influence of a weak bearing layer is minimized.

The foundation pit refers to a space below the ground excavated during the construction of a building or a structure foundation or the construction of a basement. The foundation pit engineering provides necessary conditions for the construction of underground space, and is an important ring of the whole foundation engineering. Because the bearing capacity of the soft soil foundation is weak, the difficulty of excavating a foundation pit in a soft soil area is high, the main difficulty lies in low bearing capacity and poor stability of the soft soil, in order to ensure the stability of a foundation pit support system, a deeper support pile is usually arranged to achieve a better support effect, but the support system has a longer pile length, so the pile cost is high, and the pile driving cost is high.

Disclosure of Invention

In order to solve the technical problems, the invention provides a foundation pit bracing strengthening method of a soft soil foundation, wherein an integral gapless strengthening area is formed by mixing a filler in a weak bearing layer at the edge of a foundation pit, so that the bracing strength of the foundation pit is improved.

The invention provides a foundation pit bracing and reinforcing method of a soft soil foundation, which is characterized in that a filling agent mixed with an adhesive and/or a curing agent is filled in a region from the ground of a weak bearing layer at the edge of a foundation pit to the depth below the foundation pit so as to form an integral gapless reinforcing region at the edge of the foundation pit.

Furthermore, a rotary jet drill is adopted to spray the filler in a high-pressure rotary jet method in a preset area of the weak bearing layer to form an integral gapless reinforcing area.

Further, the spray forming radius of the rotary jet drill is larger than half of the center distance between two adjacent drilling holes; or the jet forming radius of the rotary jet drill is adjustable, and the rotary jet drill forms a gapless integral structure in the reinforced area formed by jet forming at any three adjacent drilling hole positions on the non-same straight line.

Further, drilling holes of the rotary jet drill are staggered on the ground;

or the drilling holes of the rotary jet drill are arranged in the ground in a row;

or the drilling holes of the rotary jet drill are continuously distributed on the ground along the boundary of the foundation pit.

The invention provides a foundation pit enclosure strengthening method of a soft soil foundation, which comprises the following steps:

the preparation method comprises the following steps: leveling a construction site and measuring and positioning the positions of all drilling holes according to a preset injection molding radius;

drilling operation: the pile machine moves to the right position, so that the rotary jet drill drills at a preset drilling hole position until a jet orifice of the rotary jet drill reaches a preset depth in the soft soil;

a spraying operation step: adjusting the jetting pressure and the drilling and withdrawing speeds of the pile machine according to the preset jetting forming radius until the preset jetting operation step is completed;

and (3) continuous operation steps: and moving the upper rotary jet drill to the next drilling position after the upper rotary jet drill is separated from the ground, and repeating the drilling operation step and the jet operation step.

Furthermore, the vertical section of the integral gapless reinforced area is I-shaped, L-shaped, bent or deformed.

Furthermore, the filler also comprises sand aggregate and/or recycled aggregate and/or an expanding agent.

Furthermore, a fender post with a precast pile or a cast-in-place pile structure is additionally arranged at the position, close to the foundation pit wall, of the integral type gapless reinforcing area, and the bottom end of the fender post is lower than the bottom of the foundation pit.

Furthermore, a stirring method is adopted to spray the filler at a preset depth of the weak bearing layer to form an integral gapless reinforcing area.

Furthermore, the bottom of the foundation pit is filled with a filler mixed with an adhesive and/or a curing agent to form an integral high-strength supporting area, and the integral high-strength supporting area and the integral gapless reinforcing area are connected into a whole.

The foundation pit enclosure strengthening method of the soft soil foundation provided by the invention is characterized in that an integral gapless strengthening region is additionally arranged in a weak bearing layer at the edge of the foundation pit to improve the enclosure strength of the foundation pit, as the strengthening region is filled with adhesive and/or curing agent, the adhesive and/or curing agent is mixed with soft soil to firmly glue the dispersed soil in the soft soil together, the strength is improved and the soil can resist corrosion to a certain degree after hardening, in addition, the strengthening region is in an integral gapless form, has stronger bearing capacity than a split strengthening region, greatly improves the enclosure strength of the foundation pit, improves the bending resistance, prevents the foundation pit wall from toppling, is suitable for weak bearing layers of various soil types and is suitable for the construction of various foundation pits.

When the foundation pit enclosure reinforcing area provided by the invention is used for a gravity type cement-soil wall, an expanded area can be established at the bottom of the foundation pit to form a composite sliding surface, so that the stability of the wall body is improved, and the buried depth of the wall body is reduced, thereby achieving the purposes of safety and economy.

The foundation pit enclosure strengthening method provided by the invention is matched with the enclosure piles to form the foundation pit enclosure structure, so that the water-stopping and soil-retaining effects are achieved, the pile length is reduced, the pile distance is increased, the pile cost and the pile driving cost are reduced on the basis of ensuring and even improving the enclosure strength of the foundation pit, the foundation pit engineering cost is reduced, the engineering applicability is improved, and the foundation pit enclosure strengthening method is easy to widely apply.

Drawings

Fig. 1 is a schematic longitudinal sectional view of an I-type foundation pit support of a soft soil foundation in examples 1 and 5;

FIG. 2 is a schematic longitudinal sectional view of the soft soil foundation of examples 1 and 5 showing the L-shaped foundation pit support;

FIG. 3 is a schematic longitudinal cross-sectional view of the support of the notch-type foundation pit of the soft soil foundation of examples 1 and 5;

FIG. 4 is a schematic longitudinal sectional view of the architectural protective structure for a soft soil foundation according to embodiments 1 and 5;

FIG. 5 is a schematic view of the embodiment 1-5 in which the drill holes have the same forming radius and the drill holes are arranged in a row;

FIG. 6 is a schematic view of the embodiment 1-5 in which the drill holes have the same forming radius and are arranged in a plurality of rows;

FIG. 7 is a schematic view of the embodiment 1-5 in which the drill holes have the same forming radius and the drill holes are arranged in a staggered manner;

FIG. 8 is a schematic view showing another arrangement in which the drill holes are formed with equal radii and the drill holes are staggered in examples 1 to 5;

FIG. 9 is a schematic view of the embodiment 1-5 in which the drill holes have the same radius and are arranged in a plurality of staggered rows;

FIG. 10 is a schematic view of the embodiment 1-5 in which the drill holes have the same radius and the drill holes are arranged continuously along the boundary of the foundation pit;

fig. 11 is a schematic longitudinal sectional view of the enclosure and fender post of the I-type foundation pit of the soft soil foundation in examples 2, 3 and 4;

fig. 12 is a schematic longitudinal sectional view of the enclosure and fender post of the L-shaped foundation pit of the soft soil foundation in examples 2, 3 and 4;

FIG. 13 is a schematic longitudinal sectional view of the seam-type foundation pit support and the retaining pile for the soft soil foundation of examples 2, 3 and 4;

FIG. 14 is a schematic longitudinal sectional view of the construction of a soft soil foundation support and fender post according to examples 2, 3 and 4;

fig. 15 is a schematic longitudinal sectional view of a foundation pit support of a soft soil foundation in example 6;

FIG. 16 is a schematic view showing an arrangement in which the drill holes are formed with equal radii and the drill holes are arranged in a row in example 6;

FIG. 17 is a schematic view of the embodiment 6 in which the drilled holes have the same radius and are staggered;

FIG. 18 is a schematic view showing an arrangement in which the drill holes are formed with equal radii and the drill holes are arranged in a regular polygon in example 6;

FIG. 19 is a schematic view showing an arrangement in which the drill holes are formed with equal radii and the drill holes are arranged in a random or continuous manner in example 6;

fig. 20 is a schematic longitudinal sectional view of a foundation pit support and a fender pile of the soft soil foundation according to embodiment 6.

Description of the drawings: 1-foundation pit, 2-weak bearing layer, 3-reinforcing area and 4-fender pile.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

In the method for reinforcing the foundation pit enclosure of the soft soil foundation provided by the embodiment, the weak bearing layer 2 at the edge of the foundation pit 1 is filled with the filler mixed with the adhesive and/or the curing agent and the gravel aggregate and/or the recycled aggregate to reinforce the weak bearing layer 2 so as to construct the foundation pit 1 with high firmness.

In the foundation pit enclosure strengthening method for the soft soil foundation provided by the embodiment, the foundation pit 1 edge weak bearing layer 2 is filled with the filler by adopting the high-pressure jet grouting method through the jet grouting drill to form the strengthening area 3 so as to strengthen the soil body. The strengthening method comprises the following steps:

1) the preparation method comprises the following steps: leveling a construction site, determining the edge reinforcement form of the foundation pit 1 and the distribution of drilled holes in the reinforcement area 3 by combining the soil quality of the foundation pit 1 obtained by a building construction drawing and a geological exploration report, and uniformly distributing the reinforcement area 3 along the side wall of the foundation pit 1. The vertical section of the reinforced area 3 is selected from I type (as shown in figure 1), L type (as shown in figure 2), seam type (as shown in figure 3) or construction type (as shown in figure 4) according to requirements, the reinforced area 3 is used for reinforcing the side edge and the bottom edge of the foundation pit 1, the reinforced area 3 comprises the soil facing surface of the foundation pit 1 and/or a part close to the wall of the foundation pit 1 below the bottom surface of the foundation pit 1, the bearing capacity is improved, and a waterproof curtain is formed. The depth of the reinforced area 3 should exceed the depth of the overall stable sliding surface of the weak bearing layer 2, and when a soft underlying layer is arranged below the foundation pit 1, a composite sliding surface should be tested to meet the reinforcement degree and bearing capacity of the reinforced area 3 on the foundation pit 1 and prevent toppling.

And determining the formula of the filling agent according to the soil texture of the foundation pit 1 and the strength requirement of the foundation pit 1. The filler is selected from corresponding adhesive and/or curing agent and sandstone aggregate and/or recycled aggregate according to the requirement. The filler is selected from a slurry filler (for a soil with a low water content) or a powder filler (for a soil with a high water content), as required.

2) Drilling and spraying operation steps: the jet grouting pile driver is moved to the position, so that a drill bit drills into the weak bearing layer 2 to a preset depth at a preset drilling position, the drill bit of the pile driver is placed on a designed hole position, the drill bit is aligned to the center of the hole position, and the longitudinal and transverse deviation is within an allowable range. In order to ensure that the drilled hole reaches the verticality deviation range required by the specification, the pile driver is horizontally aligned after being in place, so that the drill rod is axially and vertically aligned with the hole position, and the pile driver is fixed; the pile machine drills holes on the side of the pile machine and sprays the filler, so that the filler is uniformly mixed in the weak bearing layer 2 between the soil layer with the depth and the ground to form a reinforcing area 3, and the plurality of reinforcing areas 3 are overlapped in a crossed mode to form an integral gapless reinforcing area surrounding the edge of the side wall of the foundation pit. And adjusting the jet pressure and the drilling and withdrawing speeds of the pile machine according to the preset jet forming radius until the preset jet operation steps are completed.

The arrangement of the reinforcing area 3 on the weak bearing layer 2 at the edge of the foundation pit 1 is mainly three, namely, the reinforcing area is arranged in a row (as shown in fig. 5 and 6), is arranged in a staggered manner (as shown in fig. 7, 8 and 9) and is continuously arranged along the boundary of the foundation pit (as shown in fig. 10). The radius of the rotary spray molding is larger than half of the center distance between two adjacent drilling holes. Or the jet forming radius of the rotary jet drill is adjustable, and the rotary jet drill forms a gapless integral structure in the reinforcing area formed by jet forming at any three adjacent drilling hole positions on the non-same straight line, so that the integral structure strength of the reinforcing area is more reliable by the arrangement. 3) And (3) continuous operation steps: and lifting the drill rod to move to the next drilling position after the drill rod is separated from the ground, and repeating the drilling and spraying operation steps.

Because the integral gapless reinforced areas are formed, the drilling jet speed is ensured not to be too slow, so that the soil mixed with the filler in all the reinforced areas 3 forming the integral can be solidified at the same time or basically at the same time in the initial setting time, the retarder is added if necessary, the integrity of all the reinforced areas 3 is ensured, and the strength of the reinforced areas 3 is ensured.

During drilling and injection operations, the forming radii of the drill holes are preferably equal, and the following arrangements are exemplified in this embodiment, and other related injection forming radii and drilling hole arrangements are also included in this embodiment.

(1) When the forming radius of each drilling hole is equal and the drilling holes are arranged in line along the straight line direction, as shown in fig. 5, the reinforcing areas 3 formed by spraying in each drilling hole are overlapped with each other, so that the reinforcing areas 3 surrounding the edge of the foundation pit 1 are connected into a whole. When the range of the foundation pit 1 is large or the soil quality of the weak bearing layer 2 is weak or the water content is high and a stronger enclosure requirement is required, the transverse and longitudinal ranges of the reinforcing area 3 need to be enlarged, more than two rows of reinforcing areas 3 can be sprayed (a double-shaft drill rod or a multi-shaft drill rod can be used for simultaneous construction), and as shown in fig. 6, the reinforcing strength of the reinforcing area 3 is improved.

(2) When the forming radius of each drilling hole is equal and the drilling holes are arranged in a staggered manner along the straight line direction, as shown in fig. 7 and 8, the reinforcing areas 3 formed by spraying in each drilling hole are overlapped with each other, so that the reinforcing areas 3 surrounding the edge of the foundation pit 1 are connected into a whole. When the range of the foundation pit 1 is large or the soil quality of the weak bearing layer 2 is weak or the water content is high and a stronger enclosure requirement is required, the transverse and longitudinal ranges of the reinforcing area 3 need to be enlarged, more than two rows of reinforcing areas 3 can be sprayed (a double-shaft drill rod or a multi-shaft drill rod can be used for simultaneous construction), and as shown in fig. 9, the reinforcing strength of the reinforcing area 3 is improved.

(3) When the forming radius of each drilling hole is equal and the drilling holes are continuously arranged along the boundary of the foundation pit, as shown in the annular foundation pit shown in fig. 10, the reinforcing areas 3 formed by spraying in each drilling hole are mutually overlapped, so that the reinforcing areas 3 surrounding the edge of the foundation pit 1 are connected into a whole. When the range of the foundation pit 1 is large or the soil quality of the weak bearing layer 2 is weak or the water content is high and stronger enclosure requirements are required, the transverse range and the longitudinal range of the reinforcing area 3 are required to be enlarged, more than two rows of reinforcing areas 3 can be sprayed (a double-shaft drill rod or a multi-shaft drill rod can be used for simultaneous construction), and the reinforcing strength of the reinforcing area 3 is improved.

The drill rod moves up and down while the drilling jet is carried out, and a reinforcing area 3 with a preset thickness is formed in a preset area, so that the reinforcing area 3 can achieve enough bearing force.

The slurry filler is a slurry mainly comprising water, aggregate, an adhesive and/or a curing agent and/or an expanding agent, cement is used as the adhesive and the curing agent for bonding the aggregate and curing to form the enclosure reinforcing area 3 with certain strength, and in order to enable the slurry and the soil body to have better bonding viscosity, the slurry can be added with other components and an adhesive which can coexist with the cement and can act synergistically, such as an adhesive mainly comprising metakaolin and/or a resin material. And adjusting the components of the slurry according to the design requirements to meet the enclosure support requirements and the spraying requirements of the foundation pit 1, and spraying under the preset spraying conditions. In addition, other additives can be added into the slurry according to requirements, for example, a pumping agent can be properly added for improving the pumping performance of the slurry; in order to facilitate the formation of the integral foundation pit 1 for enclosing the reinforcement area 3, a retarder and the like can be properly added, and all the reinforcement areas 3 for enclosing the foundation pit 1 are solidified simultaneously or basically simultaneously within the initial setting time; in order to further prevent water and crack, an expanding agent can be added.

The aggregate is sand stone aggregate or recycled aggregate comprising fine aggregate and coarse aggregate, the sand stone aggregate comprises broken stone, sand, slag, pebble, tiles and the like, the recycled aggregate mainly refers to waste concrete or masonry material, for example, the recycled aggregate formed by crushing and screening construction waste is applied to the slurry preparation of the enclosure reinforcing area 3 of the foundation pit 1 after the recycled aggregate is selectively and intensively treated, and the method has the advantages of waste utilization, site cleaning and cost saving. And (3) blending fine aggregate and coarse aggregate in a proper proportion according to the requirement, preferably selecting continuous gradation for the aggregate, adjusting the content of the aggregate in the slurry according to the requirement, and controlling the maximum nominal particle size of the aggregate to be smaller than the caliber of the shotcrete pipe.

The powder filler is powder whose main components include aggregate, adhesive and/or curing agent and/or expanding agent, and the powder filler is different from the slurry filler mainly in that water is not added and the powder filler is sprayed in the weak bearing layer 2 in a powder form. The powder filler is suitable for reinforcing underground water or a weak bearing layer 2 with the water content of more than 25 percent. The ingredients of the powder filler are basically consistent with those of the slurry filler, and the ingredient proportion of the powder filler is properly adjusted compared with that of the slurry filler.

In order to ensure that the foundation pit 1 in the soft soil foundation is enclosed into an integral gapless reinforced area 3, after the injection construction operation is completed, the injection construction quality is also checked.

In order to adapt to complex soil conditions, the reinforced areas 3 are adjusted to different thicknesses according to geological conditions, and the reinforced areas 3 with different thicknesses can meet bearing requirements.

The reinforced area 3 manufactured by the foundation pit enclosure reinforcing method provided by the embodiment forms a waterproof curtain and a gravity type cement-soil wall, the enclosure strength of the foundation pit 1 is improved, in order to ensure the integrity of the whole foundation pit 1 enclosure reinforced area 3, the bottom of the reinforced area 3 can be properly expanded to form a composite sliding surface, the stability of the reinforced area 3 is improved, the depth of the reinforced area 3 is reduced, and the method has the advantages of safety and economy.

Example 2

The same portions as those in embodiment 1 are given the same reference numerals, and the same description is omitted.

In order to further improve the robustness of the foundation pit 1 enclosure and have stronger blocking and water stopping capabilities, the foundation pit enclosure strengthening method provided by the embodiment is to additionally arrange a fender post 4 with a precast pile structure at the position, close to the side wall of the foundation pit 1, of the integral type gapless strengthening area 3.

On the basis of the integral gapless foundation pit 1 enclosing and reinforcing area 3 built in the embodiment 1, the construction method for manufacturing the precast pile comprises the following steps:

A) the preparation method comprises the following steps: according to the pile bitmap of the fender pile 4 and the designated area of a designer, pile sites (arranged in the integral gapless reinforced area 3) are measured and placed on a construction site, the pile sinking sequence of each pile site is determined, the problems that a pile which is firstly driven into the pile and then driven into the pile and horizontally extruded causes deviation and displacement or is vertically extruded and pulled to cause floating pile in the pile group construction are solved, and the problem that the pile which is subsequently driven into the pile is difficult to reach the designed elevation or the soil penetration depth, so that the soil body is raised and extruded, the pile cutting is overlarge and the like are solved.

B) Pile sinking of the precast pile: before the initial setting of the reinforcing area 3 is finished, a pile machine clamping part with a static pressure, hammering or vibration group is used for hanging a precast pile to be vertically erected above the mixing pile to align with a pile site and to be sunk into the reinforcing area 3, wherein the pile sinking mode is a static pressure, hammering or vibration mode corresponding to the pile machine; then, the precast pile is sunk to the pile end of the precast pile to enter a preset area of the reinforcing area 3 through pile splicing; and (3) hoisting the precast pile to be vertical to the pile position, sinking and splicing the pile, wherein the vertical deviation of the precast pile meets the standard requirement until the pile end of the precast pile enters a preset area of the integral gapless reinforced area 3 to form a foundation pit 1 enclosure structure formed by combining the reinforced area 3 and the precast pile, as shown in a type I in figure 11, a type L in figure 12, a type notch in figure 13 and a type notch in figure 14. And determining the depth of the pile end of the precast pile entering the reinforced area 3 to be at least more than the bottom depth of the foundation pit 1 according to the soil property of the weak bearing layer 2, the density of the reinforced area 3 and other factors and the standard specification of the building foundation.

C) And (3) continuously sinking the pile: transferring the clamping part of the pile machine and aligning to the next pile site, and repeating the pile sinking steps of the precast piles until pile sinking of all the precast piles is completed. In order to ensure the quality and the progress and prevent the existing piles from being damaged, a proper piling sequence is selected according to the factors of the density of the piles, the specification and the length of the piles, whether the pile frame is convenient to move and the like before piling.

The area and depth of the precast pile entering the integral gapless reinforced area 3 are determined according to the soil quality of the weak bearing layer 2 and the soil property of the reinforced area 3. In this embodiment, the precast pile is close to foundation ditch 1 lateral wall setting, because the precast pile sinks in reinforcing district 3, has reinforcing district 3 as the basis of retaining soil stagnant water, and the distribution of precast pile can increase the interval setting, and the retaining formula foundation ditch 1 envelope that the precast pile formed can improve the bearing capacity of foundation ditch 1 lateral wall and bottom soil body, and the bending resistance reduces the pile length, increases the pile distance, reduces foundation ditch engineering construction cost.

The precast pile used in this embodiment includes, but is not limited to, a concrete solid precast pile, a concrete hollow precast pile, a steel pipe pile, an H-shaped steel pile, and other special-shaped steel piles.

In embodiment 1, the reinforcement area 3 is a concrete structure, and the weak bearing layer 2 at the edge of the foundation pit 1 is reinforced to improve the enclosure strength of the foundation pit 1, compared with embodiment 1, in this embodiment, a precast pile is additionally arranged on the basis of embodiment 1, so that the enclosure strength of the reinforcement area 3 is improved, and the foundation pit enclosure structure obtained by the foundation pit enclosure reinforcement method of this embodiment has a stronger enclosure effect, and is suitable for foundation pit construction under various soil conditions and foundation pit requirements.

Example 3

Compared with the embodiment 2, the foundation pit enclosure strengthening method provided by the embodiment is that the enclosure piles 4 of the cast-in-situ bored pile structure are additionally arranged at the integral type gapless reinforced area 3 close to the side wall of the foundation pit 1 to form a reinforced enclosure, as shown in fig. 11, 12, 13 and 14.

On the basis of the integrated gapless foundation pit 1 enclosing and reinforcing area 3 built in the embodiment 1, the construction method for manufacturing the cast-in-situ bored pile comprises the following steps:

A) the preparation method comprises the following steps: according to the pile bitmap of the fender pile 4 and the designated area of a designer, pile sites (arranged in the integral gapless reinforced area 3) are measured and placed on a construction site, and the pile sinking sequence of each pile site is determined.

B) Drilling: preferably selecting a pile machine with a drill rod, moving the pile machine in place, enabling the stirring drill rod to be vertically aligned with a pile site, and enabling the longitudinal and transverse deviation to be within a standard allowable range; in order to ensure that the drilled hole reaches the verticality deviation range required by the specification, the pile driver is horizontally aligned after being in place, the axis of a drill rod is vertically aligned with the hole position, and the pile driver is fixed; the pile machine drills a hole and takes out soil in the hole to form a pile hole, and the bottom of the pile hole exceeds the depth of the bottom of the foundation pit 1. In order to prevent the collapse of the hole wall or the occurrence of the sand running phenomenon during construction, wall protection measures can be added, and commonly used wall protection modes comprise slurry wall protection, casing wall protection and the like, which are properly selected according to requirements. When the pile hole is drilled, the hole drilling diameter is increased at intervals to enlarge the pile body, so that the contact area of the cast-in-place pile and the soil body is increased, and the stability of the cast-in-place pile in the soil body is improved.

C) And (3) perfusion: and placing a reinforcement cage in the pile hole, and pouring concrete for forming the pile to form the cast-in-place pile. In order to ensure the compactness and stability of the cast-in-place pile, certain concrete needs to be vibrated and compacted in time after being poured.

D) And (3) continuously sinking the pile: and (4) transferring the stirring drill of the pile machine to align to the next pile site, and repeating the drilling and pouring steps until pile sinking of all the cast-in-situ bored piles is completed. In order to ensure the quality and the progress and prevent the existing piles from being damaged, a proper piling sequence is selected according to the factors of the density of the piles, the specification and the length of the piles, whether the pile frame is convenient to move and the like before piling.

The cast-in-situ bored pile additionally arranged in the reinforced area 3 surrounded by the foundation pit 1 has the beneficial effect basically consistent with the precast pile, and is different from the precast pile in pile forming type and pile forming mode. And selecting according to design requirements and actual conditions of construction sites.

Example 4

Compared with the embodiment 2, the foundation pit enclosure strengthening method provided by the embodiment is that the enclosure pile 4 of the pipe-sinking cast-in-place pile structure is additionally arranged at the integral type gapless reinforced area 3 close to the side wall of the foundation pit 1 to form a reinforced enclosure, as shown in fig. 11, 12, 13 and 14.

B) Sinking the tube: the pile machine with a sleeve pile sinking assembly (a static pressure assembly, a hammering assembly or a vibration assembly is selected according to requirements) is preferred, and the corresponding pile sinking mode is a static pressure, hammering or vibration mode; moving the pile machine to a proper position, aligning the clamping part of the pile machine with a pile position point, hanging a sleeve pipe with a pile tip sleeved at the bottom or enabling an independent pile tip to be vertical to the pile position point, and sinking the pile, wherein the vertical deviation of a pile hole formed by the pile tip or the sleeve pipe meets the standard requirement until the depth of the bottom end of the pile tip is lower than that of the bottom of the foundation pit 1. In order to ensure that the pile hole reaches the verticality deviation range required by the specification, the pile driver is horizontally aligned after being in place, the axis of the pile tip is vertically aligned with the hole position, and the pile driver is fixed. And determining the area of the pile tip entering the reinforced area 3 according to various factors such as the soil quality of the weak bearing layer 2, the density of the reinforced area 3 and the like and the relevant standard specification of the building foundation. When the pile hole is drilled, the hole drilling diameter is increased at intervals to enlarge the pile body, so that the contact area of the cast-in-place pile and the soil body is increased, and the stability of the cast-in-place pile in the soil body is improved.

C) Tube drawing and filling: and placing a steel reinforcement cage in the pile hole, pouring concrete for forming the pile while vibrating or hammering and pulling the pipe, and compacting the concrete by using the vibration or hammering during pipe pulling to form the cast-in-place pile.

D) And (3) continuously sinking the pile: and transferring the stirring drill of the pile machine to align to the next pile site, and repeating the steps of pipe sinking and pipe drawing and pouring until pile sinking of all the cast-in-situ bored piles is completed. In order to ensure the quality and the progress and prevent the existing piles from being damaged, a proper piling sequence is selected according to the factors of the density of the piles, the specification and the length of the piles, whether the pile frame is convenient to move and the like before piling.

The pile sinking cast-in-place pile additionally arranged in the reinforcing area 3 of the foundation pit enclosure has the beneficial effect basically consistent with the precast pile, and the difference between the pile sinking cast-in-place pile and the precast pile is the pile forming type and the pile forming mode. And selecting according to design requirements and actual conditions of construction sites.

Example 5

Compared with the embodiment 1, the method for reinforcing the foundation pit enclosure of the embodiment adopts a stirring method to fill the filler into the weak bearing layer 2 at the edge of the foundation pit 1, and reinforces the soil body to form the reinforcing area 3. The strengthening method comprises the following steps:

1) the preparation method comprises the following steps: leveling a construction site, determining the edge reinforcement form of the foundation pit 1 and the distribution of drilling holes in a reinforcement area 3 according to the soil quality of the weak bearing layer 2 at the edge of the foundation pit 1 determined by a geological exploration report, and uniformly distributing the reinforcement area 3 along the side wall of the foundation pit 1. The vertical section of the reinforced area 3 is selected from I type (shown in figure 1), L type (shown in figure 2), seam type (shown in figure 3) or construction type (shown in figure 4) as required, the reinforced area 3 is used for reinforcing the side edge and the bottom edge of the foundation pit 1, the reinforced area 3 comprises the soil facing surface of the foundation pit 1 and/or a part close to the wall of the foundation pit 1 below the bottom surface of the foundation pit 1, so that the bearing capacity is improved, and a waterproof curtain is formed. The depth of the reinforced area 3 should exceed the depth of the overall stable sliding surface of the weak bearing layer 2, and when a soft underlayer is arranged below the foundation pit 1, a composite sliding surface should be tested to meet the reinforcement degree and bearing capacity of the reinforced area 3 to the foundation pit 1 and prevent toppling.

2) Drilling and spraying operation steps: the mixing pile machine is moved to the position, so that a drill bit drills to a preset depth in the weak bearing layer 2 at a preset drilling position, the drill bit of the pile machine is placed on a designed hole position, the drill bit is aligned to the center of the hole position, and the longitudinal deviation and the transverse deviation are within an allowable range. In order to ensure that the drilled hole reaches the verticality deviation range required by the specification, the pile driver is horizontally aligned after being in place, the axis of a drill rod is vertically aligned with the hole position, and the pile driver is fixed; the pile machine drills holes on the side of the pile machine and sprays the filler, so that the filler is uniformly mixed in the weak bearing layer 2 between the soil layer with the depth and the ground to form a reinforcing area 3, and the plurality of reinforcing areas 3 are overlapped in a crossed mode to form a gapless whole reinforcing area surrounding the edge of the side wall of the foundation pit. And adjusting the jet pressure and the drilling and withdrawing speeds of the pile machine according to the preset jet forming radius until the preset jet operation steps are completed.

There are three main arrangements of the reinforcing regions 3 on the weak bearing layer 2, which are arranged in a row (as shown in fig. 5 and 6), in a staggered arrangement (as shown in fig. 7, 8 and 9) and in a continuous arrangement along the boundary of the foundation pit (as shown in fig. 10). The radius of the rotary spray molding is larger than half of the center distance between two adjacent drilling holes. Or the jet forming radius of the rotary jet drill is adjustable, and the rotary jet drill forms a gapless integral structure in the reinforcing area formed by jet forming at any three adjacent drilling hole positions on the non-same straight line, so that the integral structure strength of the reinforcing area is more reliable by the arrangement. 3) And (3) continuous operation steps: and lifting the drill rod to move to the next drilling position after the drill rod is separated from the ground, and repeating the drilling, stirring and spraying operation steps.

Since the integral, gapless reinforcing zones 3 are to be formed, the drilling jet velocity must be guaranteed not to be so slow that the soil mixed with the filler in all the reinforcing zones 3 forming the integral can be solidified simultaneously or substantially simultaneously during the initial setting time, the retarder is added if necessary, the integrity of all the reinforcing zones 3 is guaranteed, and the strength of the reinforcing zones 3 is guaranteed.

The drilling holes, the stirring radius and the filler formulation of the integrated gapless reinforced zone 3 obtained by the stirring method of this example were set up in reference to example 1.

In order to ensure that the foundation pit 1 formed in the soft soil foundation is enclosed into an integral gapless reinforced area 3, the stirring construction quality is also checked after the stirring construction operation is completed.

The stirring strengthening method in this embodiment can be used in combination with guard piles of various structures, and pile foundation construction operations refer to

embodiments

2, 3, and 4.

Compared with the embodiment 1, the embodiment adopts different construction methods for the reinforcement area 3, the stirring method has the advantages of low equipment requirement, high mixing degree of soil and the filler and low cost compared with the rotary spraying method, and a user selects different construction methods according to design requirements, actual conditions of a construction site and requirements.

Example 6

In the method for reinforcing the foundation pit enclosure of the soft soil foundation provided by the embodiment, the weak bearing layer 2 mixed with the adhesive and/or the curing agent and the gravel aggregate and/or the recycled aggregate is filled in the weak bearing layer 2 at the edge of the foundation pit 1 and in the whole range of the bottom of the foundation pit 1 to reinforce the weak bearing layer 2 so as to construct the foundation pit 1 with high firmness. The bottom of the foundation pit 1 is filled with a filler mixed with an adhesive and/or a curing agent to form an integral high-strength supporting area, the edge of the foundation pit 1 is filled with the filler mixed with the adhesive and/or the curing agent to form an integral gapless reinforcing area, the integral high-strength supporting area and the integral gapless reinforcing area are connected into a whole, and the foundation pit 1 is reinforced and enclosed in an omnibearing manner.

In the foundation pit enclosure strengthening method for the soft soil foundation provided by the embodiment, a high-pressure jet grouting method is adopted to fill fillers into the weak bearing layer 2 at the edge of the foundation pit 1 and the weak bearing layer 2 at the bottom of the foundation pit 1 to form an integrated strengthening region 3 for strengthening the soil body. The strengthening method comprises the following steps:

1) the preparation method comprises the following steps: leveling a construction site, determining the reinforcing form and the hole drilling distribution of the edge of the foundation pit 1 and the bottom of the foundation pit 1 by combining the soil quality of the foundation pit 1 obtained by a building construction drawing and a geological exploration report, wherein the reinforcing form and the hole drilling distribution of the reinforcing area 3 are uniformly distributed on the edge of the foundation pit 1 along the side wall of the foundation pit 1, and the reinforcing area 3 at the bottom of the foundation pit 1 is uniformly distributed on the bottom surface of the foundation pit 1, as shown in fig. 15. The reinforcement area 3 reinforces both the side edge and the bottom edge of the foundation pit 1. Reinforced area 3 has included foundation ditch 1's the soil-facing side and foundation ditch 1's bottom surface, and 3 depths in reinforced area should exceed the overall stability glide plane degree of depth of weak bearer layer 2, when having weak subjacent layer under foundation ditch 1, still should check and calculate compound glide plane to satisfy reinforced area 3 and to foundation ditch 1's reinforcement and bearing capacity, prevent to empty simultaneously.

And determining the formula of the filling agent according to the requirements of the soil texture at the foundation pit and the strength of the foundation pit. The filler is selected from corresponding adhesive and/or curing agent and sandstone aggregate and/or recycled aggregate according to the requirement. The filler is selected from a slurry filler (for a soil with a low water content) or a powder filler (for a soil with a high water content), as required.

The arrangement of the reinforcement area 3 on the edge of the foundation pit 1 and the weak bearing layer 2 at the bottom of the foundation pit 1 is mainly four, which are respectively in the same-row arrangement (as shown in fig. 16), the staggered arrangement (as shown in fig. 17), the regular polygon arrangement (as shown in fig. 18) and the disordered or continuous arrangement (as shown in fig. 19), so that the boundary and the bottom of the foundation pit form an integral reinforcement area, including but not limited to a round, square and triangular whole. The radius of the rotary spray molding is larger than half of the center distance between two adjacent drilling holes. Or the jet forming radius of the rotary jet drill is adjustable, and the rotary jet drill forms a gapless integral structure in the reinforcing area formed by jet forming at any three adjacent drilling hole positions on the non-same straight line, so that the integral structure strength of the reinforcing area is more reliable by the arrangement.

3) And (3) continuous operation steps: and lifting the drill rod to move to the next drilling position after the drill rod is separated from the ground, and repeating the drilling and spraying operation steps.

The drilling holes, the stirring radius and the filler formulation of the integral gapless reinforced area 3 obtained by the rotary spraying method of this example were set up in reference to example 1.

In order to ensure that a foundation pit 1 formed in a soft soil foundation below a building or structure 1 is enclosed as an integral gapless reinforced area 3, after stirring construction operation is completed, the stirring construction quality is also checked.

The reinforced area 3 manufactured by the foundation pit enclosure reinforcing method provided by the embodiment is used for comprehensively reinforcing the side wall and the bottom of the foundation pit 1, the integrity of the whole foundation pit 1 enclosure reinforced area 3 is ensured, and the formed gravity type cement-soil wall has high wall stability, reduces the wall burial depth and has the advantages of safety and economy.

The foundation pit enclosure strengthening method in the embodiment may also be used in combination with guard piles of various structures, as shown in fig. 20.

In order to adapt to complex soil conditions, the reinforced areas 3 are adjusted to have different thicknesses according to geological conditions, and the reinforced areas 3 with different thicknesses all meet the bearing requirements, as shown in fig. 20.

Compared with the embodiment 1, the embodiment has stronger enclosure strengthening effect on the foundation pit 1, is particularly suitable for the condition that the foundation pit is used as a basement and other use spaces, and can be used for selecting different construction methods according to the actual condition and the requirement of a construction site.

In addition, the fender pile category used in the present invention also includes piles of related types of structures, including but not limited to long spiral cast-in-place piles, punched cast-in-place piles, drilled extruded cast-in-place piles, stiff core mixing piles, pre-drilled (static pressure) precast piles, etc., and the construction mode is slightly different from the above embodiments, but the above pile construction is within the protection scope of the present invention.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment includes only a single embodiment, and such description is for clarity only, and all embodiments may be combined with each other, or some embodiments may be combined with existing conventional techniques to form other embodiments as will be apparent to those skilled in the art without inventive faculty.

Claims

1. A foundation pit enclosure strengthening method of a soft soil foundation is characterized in that a region, from the ground of a weak bearing layer at the edge of the foundation pit to the position below the depth of the foundation pit, is filled with a filler mixed with an adhesive and/or a curing agent so as to form an integral gapless strengthening region at the edge of the foundation pit.

2. The method for reinforcing a foundation pit enclosure of a soft soil foundation according to claim 1, wherein a high pressure jet grouting method is used to spray a filler in a predetermined region of the weak bearing layer by using a jet grouting drill to form an integral gapless reinforcing region.

3. The foundation pit bracing reinforcing method of the soft soil foundation of claim 2, wherein the injection molding radius of the rotary jet drill is larger than half of the center distance between two adjacent drilling holes;

or the jet forming radius of the rotary jet drill is adjustable, and the rotary jet drill forms a gapless integral structure in the reinforced area formed by jet forming at any three adjacent drilling hole positions on the non-same straight line.

4. A soft soil foundation pit bracing reinforcement method according to claim 2 or 3, wherein the drilling holes of the rotary jet drill are staggered on the ground;

5. The method for reinforcing the enclosure of the foundation pit of the soft soil foundation according to claim 2, comprising the steps of:

6. A method for reinforcing a foundation pit support for a soft soil foundation as claimed in claim 1, wherein the vertical cross-section of the integral gapless reinforced area is I-shaped, L-shaped, crimped or deformed.

7. A method of strengthening a foundation pit envelope in a soft soil foundation as claimed in claim 1, wherein the filler further comprises sand aggregate and/or recycled aggregate and/or a swelling agent.

8. The method for reinforcing the enclosure of a foundation pit of a soft soil foundation according to claim 1, wherein a fender pile of a precast pile or a cast-in-place pile structure is additionally arranged at the integral gapless reinforced area close to the wall of the foundation pit, and the bottom end of the fender pile is lower than the bottom of the foundation pit.

9. The method for reinforcing a foundation pit support of a soft soil foundation according to claim 1, wherein a stirring method is adopted to spray the filler at a predetermined depth of the weak bearing layer to form an integral gapless reinforcing area.

10. The method of reinforcing a soft soil foundation pit envelope of claim 1, wherein the bottom of the pit is filled with a filler mixed with an adhesive and/or a curing agent to form an integral high strength support zone, and the integral high strength support zone is integrally connected with the integral gapless reinforcing zone.