CN114232648B - PBA method pilot tunnel inner supporting and protecting structure and construction method thereof - Google Patents

PBA method pilot tunnel inner supporting and protecting structure and construction method thereof Download PDF

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Publication number
CN114232648B
CN114232648B CN202111487526.3A CN202111487526A CN114232648B CN 114232648 B CN114232648 B CN 114232648B CN 202111487526 A CN202111487526 A CN 202111487526A CN 114232648 B CN114232648 B CN 114232648B
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concrete
strength
low
aggregate
continuous wall
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CN114232648A (en
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张东
刘军
辛亮
王浩
刘硕
张志强
罗利娟
张恺伦
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Beijing University of Civil Engineering and Architecture
BCEG Civil Engineering Co Ltd
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Beijing University of Civil Engineering and Architecture
BCEG Civil Engineering Co Ltd
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D17/00—Excavations; Bordering of excavations; Making embankments
    • E02D17/06—Foundation trenches ditches or narrow shafts
    • E02D17/08—Bordering or stiffening the sides of ditches trenches or narrow shafts for foundations
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B14/02—Granular materials, e.g. microballoons
    • C04B14/04—Silica-rich materials; Silicates
    • C04B14/10—Clay
    • C04B14/104—Bentonite, e.g. montmorillonite
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B14/38—Fibrous materials; Whiskers
    • C04B14/46—Rock wool ; Ceramic or silicate fibres
    • C04B14/4643—Silicates other than zircon
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04—Waste materials; Refuse
    • C04B18/06—Combustion residues, e.g. purification products of smoke, fumes or exhaust gases
    • C04B18/08—Flue dust, i.e. fly ash
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04—Waste materials; Refuse
    • C04B18/16—Waste materials; Refuse from building or ceramic industry
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B22/00—Use of inorganic materials as active ingredients for mortars, concrete or artificial stone, e.g. accelerators, shrinkage compensating agents
    • C04B22/06—Oxides, Hydroxides
    • C04B22/062—Oxides, Hydroxides of the alkali or alkaline-earth metals
    • C04B22/064—Oxides, Hydroxides of the alkali or alkaline-earth metals of the alkaline-earth metals
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/24—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing alkyl, ammonium or metal silicates; containing silica sols
    • C04B28/26—Silicates of the alkali metals
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
    • E02D5/18—Bulkheads or similar walls made solely of concrete in situ
    • E02D5/187—Bulkheads or similar walls made solely of concrete in situ the bulkheads or walls being made continuously, e.g. excavating and constructing bulkheads or walls in the same process, without joints
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
    • E02D5/22—Piles
    • E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Abstract

The invention relates to a PBA method pilot tunnel inner supporting structure and a construction method thereof, belonging to the field of building construction. The low-strength recycled concrete with toughness adopts the additional components consisting of bentonite, fly ash and basalt fiber to replace synthetic fiber, and lime is added, so that the prepared concrete has low compressive strength, slow increase of the compressive strength, good toughness, large deformation without cracking under the action of water and soil pressure, capability of coordinately deforming with surrounding soil mass and meat piles with high rigidity, and guarantee of close adhesion. The water glass and the calcium chloride solution are used as additives, so that the impermeability of the concrete is improved. The supporting structure has the advantages of toughness, low strength, good waterproof performance and the like, is green, environment-friendly and low-carbon, and can be applied to waterproofing of underground engineering.

Description

PBA method pilot tunnel inner supporting and protecting structure and construction method thereof
Technical Field
The invention belongs to the field of building construction, and particularly relates to an internal supporting and protecting structure of a PBA method pilot tunnel and a construction method thereof.
Background
The PBA method is also called a hole pile method, namely, a small pilot hole is dug firstly, a pile body is constructed in the small pilot hole, a top structure is constructed after a beam column is finished, and then the follow-up construction is carried out under the protection of the top structure. The PBA method has a pile body of a soil-retaining structure, so that water cannot be stopped; in the case of underground water, although a precipitation method can be adopted, the PBA method is greatly limited in the case of underground water because the precipitation causes waste of underground water resources.
Some experts in recent years have proposed an embedded waterproof curtain of secant piles instead of pile bodies, but there are the following problems:
1) The pile body has high hole forming difficulty, and is easy to collapse in the process of drilling in a water-rich stratum, so that great difficulty is brought to hole forming quality and water stopping effect;
2) Perpendicularity of the vegetable pile and the meat pile of the occlusive pile is difficult to achieve coordination, and practice proves that: the vegetable pile and the meat pile are easy to be forked after reaching a certain depth, and particularly the vegetable pile and the meat pile cannot be closely attached in a sand pebble layer, so that a gap is generated, and the water-proof effect is difficult to guarantee.
3) The vegetable concrete pile and the meat pile are deformed and are not coordinated to generate a water leakage phenomenon;
4) The compressive strength of the plain concrete pile increases with time, which causes difficulty in drilling and cutting in the later period and is easy to crack during drilling and cutting, thereby a water flow channel is formed.
5) The plain concrete pile is easy to crack after being stressed, although synthetic fibers such as polypropylene fibers, polyester fibers, polyacrylonitrile fibers and the like are added, the synthetic fibers are not easy to diffuse and difficult to enhance toughness, and cannot be degraded so as to pollute the environment.
6) The plain concrete pile has high concrete bleeding rate, and water is easy to generate a channel in the concrete in the floating process, so that the anti-permeability capability of the pile body is reduced.
Therefore, the supporting structure with good soil retaining effect, toughness, low strength and good waterproof performance is designed, and the supporting structure has important significance.
Disclosure of Invention
The invention aims to provide a PBA method in-pilot tunnel supporting and protecting structure and a construction method thereof, so as to solve the technical problems.
Therefore, the invention provides a PBA method inner supporting and protecting structure of a pilot tunnel, which comprises a continuous wall body and bored piles arranged in the continuous wall body at intervals, wherein the bored piles are steel recycled concrete pile bodies, the continuous wall body is formed by tough low-strength recycled concrete, the diameter of the bored piles is smaller than the thickness of the continuous wall body, the compressive strength of the tough low-strength recycled concrete in 28 days is 1 to 6MPa, and the permeability coefficient is smaller than 1 x 10 -6 cm/s. The water stopping structure of the invention is formed on the continuous wall body, the hole collapse problem is thoroughly avoided, the hole forming efficiency is high, the quality is good, and the water stopping effect is greatly improved. The thickness of the continuous wall body is larger than the diameter of the bored pile, so that the problems of gaps and the like caused by construction errors of verticality can be effectively avoided, and the water-resisting effect can be ensured. The continuous wall body is low in compressive strength and slow in compressive strength increase, drilling and cutting at the later stage are facilitated, and the continuous wall body is not easy to crack.
Preferably, the elastic modulus of the tough low-strength recycled concrete is 500 to 1000MPa, and the ultimate strain is more than 0.6%. The elastic modulus is low, the pile is easy to plastically deform without cracking after being stressed, large deformation is generated under the action of water and soil pressure, and the adaptability to surrounding soil is strong, so that the pile is ensured to be closely attached to a meat pile with high rigidity; in addition, the method has the advantages of low cost, good wall integrity, uniform and continuous thickness and reliable quality.
Preferably, the tough low-strength recycled concrete consists of the following raw materials in amount: main gel material is 100 to 150kg/m 3 70 to 100kg/m as additional components 3 1200 to 1800kg/m of aggregate 3 10 to 20kg/m of additive 3 Wherein the water-cement ratio is 4:1 to 2:1, the additional components comprise bentonite, fly ash and basalt fiber, the dosage ratio of the bentonite to the fly ash to the basalt fiber is 1 (0.5-1.0) to (0.03-0.05), the admixture comprises water glass and calcium chloride, wherein the dosage ratio of the water glass to the calcium chloride is 1:1 to 1:1.2. the bentonite can reduce the compressive strength and can generate expansion, the compactness of concrete is ensured, the fly ash has activity and can fill gaps, the basalt fiber greatly improves the toughness of the fly ash, the main component of the basalt is silicon dioxide, the components of the basalt are similar to those of the main gel material, the compatibility of the basalt and the main gel material is good, the basalt can be easily dispersed during mixing, and the basalt is uniformly distributed in the concrete and can restrict the expansion of microcracks. And the basalt fiber can be degraded, which is beneficial to environmental protection. The sodium silicate and calcium chloride are subjected to chemical reaction to form flocculent substances which can be filled in the tiny cracks, so that the bleeding rate of the concrete is 0, free moisture is hardly generated, a channel generated by moisture movement is avoided, the porosity of the concrete is reduced, and the impermeability of the concrete is improved.
Preferably, the main gel material comprises cement and lime, wherein the mass ratio of the cement to the lime is 1:1 to 1:0.5. the addition of lime can reduce the strength of concrete and slow the strength increase of concrete.
Preferably, the bentonite is sodium bentonite, wherein the content of montmorillonite is 70 to 90 percent; the high montmorillonite content can increase the dispersibility and can ensure that the bentonite is uniformly diffused in the concrete; the particle size of the fly ash is 100-500 mu m, and the fly ash can be filled in a fine gap to avoid a water channel; the basalt fiber is monofilament fiber, the fiber length is 9mm, 12mm or 18mm, the monofilament fiber is easy to diffuse, and the monofilament fiber is too long, which is beneficial to crack resistance but not easy to diffuse.
Preferably, the aggregate is prepared by crushing waste concrete blocks, screening and mixing in a grading way, wherein the particle size of the coarse aggregate is 5-30mm, and the particle size of the fine aggregate is 0.1-5mm.
Preferably, the ratio of the amount of coarse aggregate to the amount of fine aggregate is 1:0.9 to 1:1.1, the dosage ratio can enable the aggregates to reach the optimal gradation, and ensure that gaps among the coarse aggregates can be effectively filled.
In addition, the invention also provides a construction method of the PBA method inner supporting and protecting structure of the pilot tunnel, which comprises the following steps:
s1, after primary support of the PBA small pilot tunnel is finished, paying off according to a designed position, and marking the position of the continuous wall body (1);
s2, chiseling the sprayed concrete of the bottom plate at the paying-off position, welding the steel grating of the bottom plate on each side in the longitudinal direction by adopting 2 steel bars, and connecting the steel grating of the bottom plate into a whole;
s3, cutting off sprayed concrete and steel gratings at the continuous wall;
s4, excavating soil at the continuous wall by using a drilling machine, and pouring tough low-strength recycled concrete to form the continuous wall after the soil reaches a designed elevation;
s5, paying off according to design requirements, and marking the position of the cast-in-situ bored pile;
s6, drilling the position of the bored pile at the marked position by using a drilling machine;
s7, placing a reinforcement cage at the hole position, and pouring rigid recycled concrete to form the cast-in-situ bored pile.
Preferably, the preparation method of the S4 moderate-toughness low-strength recycled concrete comprises the following steps:
s41, determining the dosage of a main gel material, additional components, aggregate and an admixture according to weight on the basis of determining the water-cement ratio;
s42, crushing the waste concrete blocks by using a crusher in a factory or a construction site, and sorting the crushed concrete blocks by using a vibrating screen to obtain aggregate with a specified particle size;
s43, preparing 3-6 samples according to the requirements, testing the compressive strength, the elastic modulus, the ultimate strain and the permeability coefficient, and preparing the mixture ratio after the requirements are met;
s44, mixing the materials according to a laboratory ratio, wherein the deviation of the material dosage is +/-2%, adding the additional components, the main gel material and the aggregate into water, and uniformly stirring;
s45, uniformly mixing the additives, adding the mixture into the mixture obtained in the S44 after floccules appear, and continuously stirring uniformly;
and S46, discharging and simultaneously reserving a sample as a sample for quality detection.
Preferably, in S45, water glass and calcium chloride solution are prepared respectively, then the water glass is added into the admixture barrel, then the calcium chloride solution is added, the two are mixed and stirred uniformly, and after floc appears, the mixture is immediately poured into the mixture obtained in S44. The water glass and the calcium chloride solution generate chemical reaction to generate floccule, and the floccule is insoluble in water; after the floccule is generated, the floccule is poured into the concrete and is uniformly stirred, so that the floccule can fully fill micro cracks and micro pores generated by various reasons, and the compactness of the concrete is ensured.
Compared with the prior art, the invention has the characteristics and beneficial effects that:
(1) The PBA method pilot tunnel internal supporting and protecting structure has supporting and water-resisting functions, wherein the supporting structure is a rigid recycled concrete pile body, the water-stopping structure is a continuous wall body formed by low-strength recycled concrete with toughness, the low-strength recycled concrete with toughness is obtained by mixing a main gel material, additional components, aggregate and an additive according to a certain proportion, and the additional components are formed by mixing bentonite, fly ash and basalt fiber according to a certain proportion. The rigid recycled concrete consists of common steel bars and recycled concrete. After the concrete continuous wall is constructed, a rigid concrete pile body is continuously constructed on the wall. The supporting structure provided by the invention has the advantages of good soil retaining effect, toughness, low strength, good waterproof performance and the like, is green, environment-friendly and low-carbon, and can be applied to waterproofing of underground engineering.
(2) The low-strength recycled concrete with toughness adopts the additional components consisting of bentonite, fly ash and basalt fiber to replace synthetic fiber, because the bentonite can reduce the compressive strength and can expand, the compactness of the concrete is ensured, the fly ash has activity and fills gaps, the basalt fiber greatly improves the toughness, the main component of the basalt is silicon dioxide, and is similar to the components of the main gel material, the compatibility of the two is good, the components are easy to disperse during mixing, and the components are uniformly distributed in the concrete, so that the micro-crack can be restrained from expanding. And the basalt fiber can be degraded, which is beneficial to environmental protection. Due to the addition of lime, the prepared concrete has low compressive strength, slow increase of the compressive strength and good toughness, can generate large deformation without cracking under the action of water and soil pressure, can be coordinately deformed with surrounding soil bodies and meat piles with higher rigidity, and ensures close contact.
(3) The concrete can shrink when being solidified so as to generate micro cracks, the sodium silicate and the calcium chloride generate chemical reaction to form flocculent substances which can be filled in the micro cracks, the bleeding rate of the concrete is 0, almost no free moisture is generated, channels generated by moisture movement are avoided, the porosity of the concrete is reduced, and the anti-permeability capability of the concrete is improved. After the concrete is solidified, the concrete is stressed to deform, cracks can still be generated even if the deformation is too large, and the basalt fibers pull the concrete to prevent the cracking; the bentonite is mainly used for reducing the strength and generating expansion, and the fly ash is used for reducing the strength on one hand and filling the micro-pores on the other hand. These materials work together to compensate for some of the defects.
(4) The concrete provided by the invention is comprehensive utilization of waste, such as waste concrete blocks, fly ash and the like, and the fly ash is main solid waste discharged by a coal-fired power plant, so that the concrete is low in manufacturing cost and has the advantages of greenness, environmental protection, resource saving and the like.
Drawings
FIG. 1 is a schematic plan view of a support structure in a PBA method pilot tunnel;
FIG. 2 is a schematic cross-sectional view of a support structure in a PBA method pilot tunnel;
FIG. 3 is a schematic diagram of reinforcement before the PBA method small pilot tunnel bottom plate is broken;
fig. 4 is a schematic diagram of a hole position after the continuous wall is poured.
The attached drawings are marked as follows: 1-continuous wall body and 2-cast-in-situ bored pile.
Detailed Description
In order to make the technical means, innovative features, objectives and functions realized by the present invention easy to understand, the present invention is further described below.
The embodiments described herein are specific embodiments of the present invention, and are intended to be illustrative and exemplary of the concepts of the present invention and should not be construed as limiting the scope of the embodiments of the present invention. In addition to the embodiments described herein, those skilled in the art will be able to employ other technical solutions which are obvious based on the disclosure of the claims and the specification of the present application, and these technical solutions include technical solutions which make any obvious replacement or modification for the embodiments described herein.
As shown in fig. 1 and 2, the PBA method tunnel internal supporting and protecting structure comprises a continuous wall 1 and cast-in-situ bored piles 2 arranged in the continuous wall 1 at intervals. The cast-in-situ bored pile 2 is a rigid recycled concrete pile body, and the continuous wall body 1 is formed by recycled concrete with low toughness and strength. The diameter of the cast-in-situ bored pile 2 is smaller than the thickness of the continuous wall body 1,
the compressive strength of the toughened low-strength recycled concrete in 28 days is 1-6 MPa, and the permeability coefficient is less than 1 x 10 -6 cm/s. The elastic modulus of the toughened low-strength recycled concrete is 500 to 1000MPa, and the ultimate strain is more than 0.6 percent.
The toughness low-strength recycled concrete is prepared from the following raw materials in parts by weight: 100 to 150kg/m of main gel material 3 70 to 100kg/m of additional components 3 1200 to 1800kg/m aggregate 3 10 to 20kg/m of admixture 3 Wherein the water-cement ratio is 4:1 to 2:1, the additional components comprise bentonite, fly ash and basalt fiber, the dosage ratio of the bentonite to the fly ash to the basalt fiber is 1 (0.5-1.0) to (0.03-0.05), the admixture comprises water glass and calcium chloride, wherein the dosage ratio of the water glass to the calcium chloride is 1:1 to 1:1.2.
the main gel material comprises cement and lime, wherein the mass ratio of the cement to the lime is 1:1 to 1:0.5. the bentonite is sodium bentonite, wherein the content of montmorillonite is 70 to 90 percent; the particle size of the fly ash is 100 to 500 mu m; the basalt fiber is monofilament fiber, and the fiber length is 9mm, 12mm or 18mm. The aggregate is prepared by crushing waste concrete blocks, screening and mixing in grades, wherein the particle size of the coarse aggregate is 5-30mm, and the particle size of the fine aggregate is 0.1-5mm. The dosage ratio of the coarse aggregate to the fine aggregate is 1:0.9 to 1:1.1.
the construction method of the PBA method inner support structure of the pilot tunnel comprises the following steps:
and S1, after the primary support of the PBA small pilot tunnel is finished, paying off according to a designed position, and marking the position of the continuous wall body 1.
And S2, chiseling the sprayed concrete of the bottom plate at the paying-off position, and welding the steel grating of the bottom plate on each side in the longitudinal direction by adopting 2 steel bars to connect the steel grating of the bottom plate into a whole.
And S3, cutting off the sprayed concrete and the steel grating at the continuous wall body.
And S4, excavating soil at the continuous wall by using a drilling machine, and pouring tough low-strength recycled concrete after the soil reaches a designed elevation to form the continuous wall 1.
And S5, paying off according to design requirements, and marking the position of the cast-in-situ bored pile 2.
And S6, drilling the position of the bored pile 2 at the marked position by using a drilling machine.
S7, placing a reinforcement cage at the hole position, and pouring rigid recycled concrete to form the cast-in-situ bored pile 2.
Specifically, the preparation method of the S4 medium-toughness low-strength recycled concrete comprises the following steps:
s41, on the basis of determining the water-cement ratio, determining the dosage of the main gel material, the additional components, the aggregate and the admixture according to weight.
S42, crushing the waste concrete blocks by using a crusher in a factory or a construction site, and sorting the crushed concrete blocks by using a vibrating screen to obtain aggregate with a specified particle size.
S43, preparing 3-6 samples according to the requirements, testing the compressive strength, the elastic modulus, the ultimate strain and the permeability coefficient, and preparing the mixture ratio after the requirements are met.
S44, mixing the materials according to the proportion in a laboratory, wherein the deviation of the material dosage is +/-2%, adding the additional components, the main gel material and the aggregate into water, and uniformly stirring.
S45, uniformly mixing the additives, adding the mixture into the mixture obtained in the S44 after floccules appear, and continuously and uniformly stirring. Specifically, water glass and a calcium chloride solution are prepared respectively, then the water glass is added into an additive barrel, then the calcium chloride solution is added, the two are mixed and stirred uniformly, and after floccule appears, the floccule is immediately poured into the mixture obtained in the step S44.
S46, reserving a sample while discharging, and taking the sample as a sample for quality detection.
The present invention will be described in further detail with reference to specific embodiments, but the scope of the present invention is not limited to the contents.
Example 1
After PBA small pilot tunnel primary support is completed, paying off according to a designed position, marking out the position of a continuous wall body 1 → chiseling concrete sprayed on the paying-off position, welding steel grids of the bottom plate longitudinally by 2 steel bars on each side, connecting the steel grids into a whole → cutting off the concrete sprayed and the steel grids on the continuous wall body → preparing low-strength recycled concrete for standby application → digging out the soil body on the continuous wall body by a drilling machine, pouring the low-strength recycled concrete with toughness after a designed elevation is achieved, forming the continuous wall body 1 → paying off according to design requirements, marking out the position of a bored pile 2 → drilling the position of the bored pile 2 marked by the drilling machine → placing a steel reinforcement cage at the hole position, and pouring the rigid recycled concrete to form the bored pile 2.
The preparation method of the low-strength recycled concrete with toughness comprises the following steps:
1) Determining the water-cement ratio as 4:1
2) Material preparation
(1) The raw materials such as main gel materials, bentonite, fly ash, basalt fibers and the like are accepted and meet the quality requirement; crushing waste concrete blocks by using a crusher in a factory or a construction site, and sorting the crushed concrete blocks by using a vibrating screen, wherein the size of a coarse aggregate particle is 5-30mm, and the coarse aggregate particle can be in any shape such as a circle, an edge angle and the like; the size of the fine aggregate is 0.1-5 mm.
(2) Determining the dosage of the main gel material, the additional components, the aggregate and the admixture by weight on the basis of determining the water-cement ratio, wherein the dosage of the main gel material is 100kg/m 3 Wherein the dosage ratio of cement to lime is 1:1, i.e. 50kg/m cement 3 Lime 50kg/m 3 The amount of the additional component is 76.5kg/m 3 . The dosage ratio of the bentonite, the fly ash and the basalt fiber is 1: 0.5: 0.03, namely the bentonite is 50kg/m 3 The fly ash is 25kg/m 3 Basalt fiber 1.5kg/m 3 . The dosage of the coarse aggregate is 800kg/m 3 Is thin and thinThe dosage of the aggregate is 720 kg/m 3 The admixture comprises water glass and calcium chloride, wherein the dosage of the water glass is 5kg/m 3 The dosage of calcium chloride is 5kg/m 3 。
3) Laboratory formulation
3-6 samples are prepared according to the requirements, the test of the compressive strength, the elastic modulus, the ultimate strain and the permeability coefficient is carried out, and the mixture ratio is prepared after the requirements are met.
4) Field preparation: the materials are mixed according to the proportion in a laboratory and are uniformly stirred, and the deviation of the material dosage is +/-2%.
(1) Firstly, putting bentonite, fly ash and basalt fiber into a stirrer, adding 20% of water, stirring for about 1 minute, then adding the rest water, cement, lime and fine aggregate, and stirring for about 2 minutes.
(2) Adding the coarse aggregate, and stirring for about 1 minute.
(3) Preparing sodium silicate into water glass according to the volume ratio of 5%, preparing calcium chloride aqueous solution according to the volume ratio of 5%, adding the water glass into an additive barrel, then adding the calcium chloride aqueous solution, mixing the calcium chloride aqueous solution and the water glass, uniformly stirring, immediately pouring the mixture into a concrete mixing barrel after floccules appear, and stirring for about 1 minute.
(4) The sample is left at the same time of discharging, 3/m 3 As a quality-approved sample.
Example 2
The difference from example 1 is that the method for producing the low-strength recycled concrete with toughness in this example is different, and the rest is the same as example 1.
The preparation method of the low-strength recycled concrete with toughness in the embodiment specifically comprises the following steps:
1) Determining the water-cement ratio as 3:1
2) Material preparation
(1) The raw materials such as main gel materials, bentonite, fly ash, basalt fibers and the like are accepted and meet the quality requirement; crushing waste concrete blocks by using a crusher in a factory or a construction site, and sorting the crushed concrete blocks by using a vibrating screen, wherein the size of a coarse aggregate particle is 5-30mm, and the coarse aggregate particle can be in any shape such as a circle, an edge angle and the like; the size of the fine aggregate is 0.1-5 mm.
(2) Determining the dosage of the main gel material, the additional components, the aggregate and the admixture by weight on the basis of determining the water-cement ratio, wherein the dosage of the gel material is 140kg/m 3 Wherein the dosage ratio of cement to lime is 1:0.75, i.e. cement 80kg/m 3 Lime 60kg/m 3 The amount of the additional component is 85.3kg/m 3 The dosage ratio of the bentonite, the fly ash and the basalt fiber is 1: 0.6: 0.04, namely the bentonite is 52 kg/m 3 The fly ash is 31.2 kg/m 3 Basalt fiber 2.08 kg/m 3 The dosage of the coarse aggregate is 740 kg/m 3 The amount of the fine aggregate is 740 kg/m 3 The admixture comprises water glass and calcium chloride, wherein the dosage of the water glass is 6.5kg/m 3 The dosage of calcium chloride is 6.8kg/m 3 。
3) Laboratory preparation
3-6 samples are prepared as required, and the test of the compressive strength, the elastic modulus, the ultimate strain and the permeability coefficient is carried out, so that the mixture ratio is prepared after the requirements are met.
4) Field preparation: the materials are mixed according to the proportion in a laboratory and are uniformly stirred, and the deviation of the material dosage is +/-2%.
(1) Firstly, putting bentonite, fly ash and basalt fiber into a stirrer, adding 20% of water, stirring for about 1 minute, then adding the rest water, cement, lime and fine aggregate, and stirring for about 2 minutes.
(2) Adding the coarse aggregate, and stirring for about 1 minute.
(3) Preparing sodium silicate into water glass according to the volume ratio of 6%, preparing calcium chloride aqueous solution according to the volume ratio of 6.6%, adding the water glass into an additive barrel, then adding the calcium chloride aqueous solution, mixing the calcium chloride aqueous solution and the water glass, uniformly stirring, immediately pouring the mixture into a concrete mixing barrel after floccules appear, and stirring for about 1 minute.
(4) The sample is left at the same time of discharging, 3/m 3 As a quality acceptance sample.
Example 3
The difference from example 1 is that the method for producing the low-strength recycled concrete with toughness in this example is different, and the rest is the same as example 1.
The preparation method of the low-strength recycled concrete with toughness in the embodiment specifically comprises the following steps:
1) Determining the water-cement ratio as 2:1
2) Material preparation
(1) The raw materials such as main gel materials, bentonite, fly ash, basalt fibers and the like are accepted and meet the quality requirement; crushing waste concrete blocks by using a crusher in a factory or a construction site, and sorting the crushed concrete blocks by using a vibrating screen, wherein the size of a coarse aggregate particle is 5-30mm, and the coarse aggregate particle can be in any shape such as a circle, an edge angle and the like; the size of the fine aggregate is 0.1-5 mm.
(2) Determining the dosage of the main gel material, the additional components, the aggregate and the admixture by weight on the basis of determining the water-cement ratio, wherein the dosage of the main gel material is 120kg/m 3 Wherein the dosage ratio of cement to lime is 1:0.5, i.e. 80kg/m cement 3 Lime 40kg/m 3 The amount of the additional component is 102.5kg/m 3 . The dosage ratio of the bentonite to the fly ash to the basalt fiber is 1: 1: 0.05, namely the bentonite is 50kg/m 3 50kg/m of fly ash 3 Basalt fiber 2.5kg/m 3 . The dosage of the coarse aggregate is 780 kg/m 3 The amount of the fine aggregate is 858 kg/m 3 The admixture comprises water glass and calcium chloride, wherein the dosage of the water glass is 9.5kg/m 3 The dosage of calcium chloride is 10.5kg/m 3 。
3) Laboratory preparation
3-6 samples are prepared according to the requirements, the test of the compressive strength, the elastic modulus, the ultimate strain and the permeability coefficient is carried out, and the mixture ratio is prepared after the requirements are met.
4) Field preparation: the materials are mixed according to the proportion in a laboratory and are uniformly stirred, and the deviation of the material dosage is +/-2%.
(1) Firstly, putting bentonite, fly ash and basalt fiber into a stirrer, adding 20% of water, stirring for about 1 minute, then adding the rest water, cement, lime and fine aggregate, and stirring for about 2 minutes.
(2) Adding the coarse aggregate, and stirring for about 1 minute.
(3) Preparing sodium silicate into water glass according to the volume ratio of 8%, preparing calcium chloride aqueous solution according to the volume ratio of 9.6%, adding the water glass into an additive barrel, then adding the calcium chloride aqueous solution, mixing the calcium chloride aqueous solution and the additive barrel, uniformly stirring, immediately pouring the mixture into a concrete mixing barrel after floccules appear, and stirring for about 1 minute.
(4) The sample is left at the same time of discharging, 3/m 3 As a quality-approved sample.
The performance of each example and each comparative example is tested by referring to ' standard of test method for common concrete mixture ' GBT50080-2016 ', ' test procedure for hydraulic plastic concrete ' DL/T5303-2013 ', ' test procedure for hydraulic concrete ' SL/T352-2020 ', and ' standard of test method for mechanical property of common concrete ' GB/T50081-2016, and the test results are shown in Table 1 and Table 2.
TABLE 1 Performance test results of the concrete of each example
Figure DEST_PATH_IMAGE002
The test result of the low-strength recycled concrete with toughness in the embodiment 1 meets the expected requirement, the strength is low, the elastic modulus is low, the permeability coefficient is low, the compressive strengths of 14d, 28d and 56d are respectively 2.5MPa, 4.1MPa and 4.6MPa, the strength is only increased by 12% from 28d to 56d, and the increase is slow; in addition, no cracks were observed in the test block before failure was achieved, and the concrete was able to develop large strains without cracking.
The recycled concrete with low toughness and strength in the example 2 also meets the requirement, compared with the example 1, the compression strength is increased due to the reduction of the water cement ratio and the large dosage of the main gel material, but the compression strength is not increased greatly due to the increase of the additional components, and is increased by about 24 percent. Because the basalt fibers in the additional components are increased by about 29 percent, the admixture is increased by about 20 percent, the ultimate strain is increased by 15 percent, and the permeability coefficient is reduced by 35 percent.
The recycled concrete with low toughness and strength in the embodiment 3 also meets the requirement, compared with the embodiment 1, the water cement ratio is reduced, the main gel material is used in a large amount, so that the compressive strength is increased, but the additional components are increased, so that the increase of the compressive strength is not large, and about 11 percent of increase is realized; the addition of the additional components simultaneously reduces the ultimate strain and the permeability coefficient, particularly the basalt fiber is increased by about 40 percent, the admixture is increased by 43 percent, the ultimate strain is increased by 23 percent, and the permeability coefficient is reduced by about 49 percent.
Example 3 compared with example 2, the water cement ratio was reduced, but the compressive strength was reduced due to the reduced amount of the main gel material and the increased amount of the additional component. Meanwhile, the increase of the additional components reduces the ultimate strain and the permeability coefficient, particularly increases about 17 percent of basalt fibers and about 22 percent of admixture, increases 10 percent of ultimate strain and reduces about 23 percent of permeability coefficient.
Comparative example 1
In this comparative example, water glass and calcium chloride were not contained, and the rest was the same as in example 1.
Comparative example 2
In the comparative example, the dosage ratio of bentonite to fly ash and basalt fiber is 1:2, the rest is the same as example 1.
TABLE 2 comparison of the results of the Performance test of the concrete of example 1 with those of comparative examples 1 and 2
Figure DEST_PATH_IMAGE004
From the test data, the comparative example 1 satisfies all the parameters except that the permeability coefficient does not satisfy the requirement, but the elastic modulus is slightly changed. The admixture may have a slight influence on the resisting pressure; the additive only improves the permeability of the concrete and hardly influences other properties of the concrete.
In comparative example 2, the amounts of bentonite, fly ash and basalt fiber were 3.3kg/m, respectively 3 ，66kg/m 3 ，6.6kg/m 3 . The test data shows that: the compressive strength and the elastic modulus are reduced, the increase range of the ultimate strain and the permeability coefficient is large, and the concrete can not meet the requirements. The bentonite has oneThe expansion property is determined, and in the hydration process, on one hand, the concrete aggregate is compacted by expansion, and on the other hand, a plurality of tiny holes, cracks and the like are generated, so that the fly ash can be filled; the bentonite is greatly reduced, so that the inert fly ash is difficult to fully exert the filling effect. The addition amount of the basalt is critical, the basalt is difficult to stir uniformly due to the increase of the addition amount, the basalt is easy to form clusters, concrete gaps are increased, formed concrete is not compact and uniform, a water flowing channel is easy to appear, and the impermeability is greatly reduced.
The above embodiments are merely illustrative and not intended to limit the scope of the claims, and other alternatives that may be suggested to one skilled in the art in light of the disclosure of this disclosure are to be included within the scope of the appended claims.

Claims (8)

1. The utility model provides a PBA method pilot tunnel internal support structure, includes continuous wall (1) and interval setting bored concrete pile (2) in continuous wall (1), its characterized in that: the cast-in-situ bored pile (2) is a rigid recycled concrete pile body, the continuous wall body (1) is formed by tough low-strength recycled concrete, the diameter of the cast-in-situ bored pile (2) is smaller than the thickness of the continuous wall body (1), the compressive strength of the tough low-strength recycled concrete in 28 days ranges from 1 to 6MPa, and the permeability coefficient of the tough low-strength recycled concrete is smaller than 1 x 10 -6 cm/s；
The toughness low-strength recycled concrete consists of the following raw materials in parts by weight: main gel material is 100 to 150kg/m 3 70 to 100kg/m of additional components 3 1200 to 1800kg/m aggregate 3 10 to 20kg/m of admixture 3 Wherein the water-cement ratio is 4:1 to 2:1, the additional components comprise bentonite, fly ash and basalt fiber, the dosage proportion of the bentonite to the fly ash to the basalt fiber is 1 (0.5-1.0) to (0.03-0.05), the admixture comprises water glass and calcium chloride, and the dosage proportion of the water glass to the calcium chloride is 1:1 to 1:1.2;
the main gel material comprises cement and lime, wherein the mass ratio of the cement to the lime is 1:1 to 1:0.5.
2. the structure of claim 1, in which the PBA method is used, characterized in that: the elastic modulus of the toughened low-strength recycled concrete is 500 to 1000MPa, and the ultimate strain is more than 0.6 percent.
3. The in-hole support structure based on the PBA method according to claim 1, characterized in that: the bentonite is sodium bentonite, wherein the content of montmorillonite is 70 to 90 percent; the particle size of the fly ash is 100 to 500 mu m; the basalt fiber is monofilament fiber, and the fiber length is 9mm, 12mm or 18mm.
4. The structure of claim 1, in which the PBA method is used, characterized in that: the aggregate is prepared by crushing waste concrete blocks, screening and mixing in grades, wherein the grain diameter of the coarse aggregate is 5 to 30mm, and the grain diameter of the fine aggregate is 0.1 to 5mm.
5. The structure of claim 1, in which the PBA method is used, characterized in that: the dosage ratio of the coarse aggregate to the fine aggregate is 1:0.9 to 1:1.1.
6. the construction method of the supporting structure in the PBA method pilot tunnel according to any one of claims 1 to 5, characterized by comprising the steps of:
s1, after primary support of a PBA small pilot tunnel is finished, paying off according to a designed position, and marking out the position of the continuous wall body (1);
s2, chiseling the sprayed concrete of the bottom plate at the paying-off position, adopting 2 steel bars at each side to weld the steel grating of the bottom plate in the longitudinal direction, and connecting the steel grating of the bottom plate into a whole;
s3, cutting off sprayed concrete and steel gratings at the continuous wall;
s4, excavating soil at the continuous wall by using a drilling machine, and pouring tough low-strength recycled concrete after the soil reaches a designed elevation to form the continuous wall (1);
s5, paying off according to design requirements, and marking the position of the cast-in-situ bored pile (2);
s6, drilling the position of the bored pile (2) at the marked position by using a drilling machine;
s7, placing a reinforcement cage at the hole position, and pouring rigid recycled concrete to form the cast-in-situ bored pile (2).
7. The construction method of the supporting structure in the PBA method pilot tunnel according to claim 6, characterized in that the preparation method of the recycled concrete with low toughness and strength in S4 comprises the following steps:
s41, determining the dosage of a main gel material, additional components, aggregate and an admixture according to weight on the basis of determining the water-cement ratio;
s42, crushing the waste concrete blocks by using a crusher in a factory or a construction site, and sorting the crushed concrete blocks by using a vibrating screen to obtain aggregate with a specified particle size;
s43, preparing 3-6 samples according to the requirements, testing the compressive strength, the elastic modulus, the ultimate strain and the permeability coefficient, and preparing the mixture ratio after the requirements are met;
s44, mixing the materials according to a laboratory ratio, wherein the deviation of the material dosage is +/-2%, adding the additional components, the main gel material and the aggregate into water, and uniformly stirring;
s45, uniformly mixing the additives, adding the mixture into the mixture obtained in the S44 after floccules appear, and continuously stirring uniformly;
and S46, discharging and simultaneously reserving a sample as a sample for quality detection.
8. The construction method of the supporting structure in the PBA method pilot tunnel according to claim 7, characterized in that: in S45, water glass and calcium chloride solution are prepared respectively, then the water glass is added into an additive barrel, then the calcium chloride solution is added, the water glass and the calcium chloride solution are mixed and stirred uniformly, and after floccule appears, the floccule is poured into the mixture obtained in S44 immediately.
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