CN113293773A - Foundation pit supporting system and construction method thereof - Google Patents
Foundation pit supporting system and construction method thereof Download PDFInfo
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- CN113293773A CN113293773A CN202110738571.5A CN202110738571A CN113293773A CN 113293773 A CN113293773 A CN 113293773A CN 202110738571 A CN202110738571 A CN 202110738571A CN 113293773 A CN113293773 A CN 113293773A
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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
- E02D17/02—Foundation pits
- E02D17/04—Bordering surfacing or stiffening the sides of foundation pits
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- 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
- C04B28/02—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 hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/06—Restraining of underground water
- E02D19/12—Restraining of underground water by damming or interrupting the passage of underground water
- E02D19/16—Restraining of underground water by damming or interrupting the passage of underground water by placing or applying sealing substances
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00034—Physico-chemical characteristics of the mixtures
- C04B2111/00146—Sprayable or pumpable mixtures
- C04B2111/00155—Sprayable, i.e. concrete-like, materials able to be shaped by spraying instead of by casting, e.g. gunite
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- 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
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/20—Resistance against chemical, physical or biological attack
- C04B2111/27—Water resistance, i.e. waterproof or water-repellent materials
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Abstract
The invention relates to a foundation pit supporting system and a construction method thereof, wherein the supporting system comprises a water stop pile layer, a supporting pile layer, a concrete bottom sealing layer and a grouting bottom sealing layer; the supporting pile layer and the water stopping pile layer are sequentially arranged on the side face of the foundation pit from inside to outside; the concrete bottom sealing layer and the grouting bottom sealing layer are sequentially arranged on the bottom surface of the foundation pit from top to bottom. The support system is strong in waterproofness and good in stability, and can meet the requirement of small deformation of a foundation pit and guarantee the safety operation in the foundation pit for a long time when facing the foundation pit with the strong permeable stratum. The construction method comprises the steps of marking the position of a foundation pit, constructing a water stopping pile layer and a supporting pile layer at the periphery of the foundation pit, forming a grouting bottom sealing layer at the designed depth in the marked foundation pit range in a drilling and grouting mode, excavating the foundation pit, and pouring a concrete bottom sealing layer, so that the efficiency and the safety are high, and the construction requirement of a complex environment can be met.
Description
Technical Field
The invention belongs to the technical field of foundation pit supporting engineering, particularly relates to a foundation pit supporting system and a construction method thereof, and particularly relates to a deep foundation pit water-stopping supporting system which is close to a railway business line, a highway or other external load influence range and needs to be constructed for a long time and a construction method thereof.
Background
With the rapid development of society, in the road network construction of cities, more and more bridges spanning railway lines are provided, so that when the proposed bridge is close to a railway business line, a highway or other external load influence ranges, a safe, reliable and stable support system is adopted for a foundation pit, so as to reduce and avoid the disturbance to the surrounding foundation during foundation pit construction. In particular, in the construction process of a foundation pit in a strongly permeable stratum, a supporting system of the foundation pit is particularly important, on one hand, the stability of the walls around the foundation pit is ensured, and the collapse of the surrounding soil body or the infiltration of surrounding underground water is avoided, and on the other hand, the underground water is prevented from entering the foundation pit, so that the problems of side slope collapse, the sinking of the surrounding foundation and the like are avoided.
The deep foundation pit close to the external load and influence the ground is more sensitive to the deformation of a supporting system, the supporting system commonly used for the current deep foundation pit is difficult to simultaneously meet the characteristics that the deformation of the foundation pit is small, the disturbance to the surrounding ground is small, the underground water is prevented from permeating into the foundation pit, the safe operation time in the foundation pit is ensured to be long and the like, such as a steel sheet pile system and an underground continuous wall system.
Therefore, the foundation pit supporting system which has strong waterproofness and good stability, can meet the requirement of small deformation of the foundation pit and can ensure long-time safe construction has very important significance.
Disclosure of Invention
The invention aims to: aiming at the problems of poor waterproofness, low stability, difficulty in meeting the requirements of small deformation of a foundation pit and guarantee of long-time safe operation in the foundation pit of the foundation pit supporting system in the prior art, the foundation pit supporting system and the construction method thereof are provided.
In order to achieve the purpose, the invention adopts the technical scheme that:
a foundation pit supporting system comprises a water stop pile layer, a supporting pile layer, a concrete bottom sealing layer and a grouting bottom sealing layer;
the supporting pile layer and the water stopping pile layer are sequentially arranged on the side face of the foundation pit from inside to outside; the concrete bottom sealing layer and the grouting bottom sealing layer are sequentially arranged on the bottom surface of the foundation pit from top to bottom.
The foundation pit supporting system mainly comprises a water stopping system and a supporting system, wherein the peripheral wall of a foundation pit adopts a water stopping pile layer, and the bottom of the foundation pit adopts a grouting sealing bottom layer and a concrete sealing bottom layer to jointly form a complete water stopping system; the perisporium of foundation ditch has effectively blockked foundation ditch soil pressure all around through the setting on stagnant water stake layer and support stake layer, has guaranteed the good wholeness and the stability of foundation ditch, when facing strong permeable stratum foundation ditch, should strut the system and can satisfy the little demand of foundation ditch deformation, can guarantee the problem of the interior safe operation of long-time foundation ditch simultaneously.
Furthermore, the depth of the foundation pit is more than 3 m. Preferably, the depth of the foundation pit is more than 6 m.
Furthermore, the foundation pit is located in a water-rich area, and the stratum has strong water permeability.
Furthermore, the surface water content of the designed depth of the foundation pit is higher, and groundwater can infiltrate into the foundation pit when the foundation pit is directly excavated to the designed depth of the foundation pit.
Further, the depth of the water stop pile layer is greater than or equal to that of the foundation pit; the depth of the support pile layer is greater than or equal to that of the water stop pile layer.
Furthermore, the areas of the concrete bottom sealing layer and the grouting bottom sealing layer are larger than or equal to the bottom area of the foundation pit.
Furthermore, the upper surface of the concrete bottom sealing layer is the bottom surface of the foundation pit.
Furthermore, one side of the supporting layer, which is close to the foundation pit, forms the inner peripheral wall of the foundation pit.
Further, stagnant water stake layer is including double interlock stagnant water stake, double interlock stagnant water stake has formed confined waterproof curtain. The double-row meshed water-stopping piles are composed of a plurality of water-stopping piles arranged in double rows, and every two adjacent water-stopping piles or every two adjacent water-stopping piles are mutually meshed and sealed.
Further, the double-row occlusive water stop pile is a high-pressure jet grouting pile. The disturbance to the surrounding environment is small during construction, and the influence on the surrounding buildings is reduced.
Furthermore, the double-row occlusion water stop pile is mainly prepared from cement slurry and water glass. The cement slurry and the water glass are matched, so that the mixture can be condensed in a proper time, and in the water stop pile preparation process, the grouting construction and the drilling construction can be matched with each other in time and effect.
Further, the water-cement ratio of the cement slurry is 0.8-1; the baume degree of the water glass is 35 Be-40 Be; the mass ratio of the cement slurry to the water glass is 0.9-1.2: 1. In the whole process of preparing the water-stopping pile by grouting, the proportion of the materials is very important for the water-stopping effect and the construction effect of the water-stopping pile, the baume degree of proper water glass controls the condensation time of slurry, and the proportion of the amount of cement, water and water glass not only controls whether the water-stopping pile can be successfully formed, the water-stopping effect and the condensation effect. The water glass is too much, or baume degree is too big, causes the rapid setting, has great influence to the quality that stagnant water stake formed, and cement thick liquid water-cement ratio too big undersize all can cause harmful effects to stagnant water effect and construction effect.
Furthermore, the supporting pile layer comprises a plurality of supporting piles arranged at intervals, the supporting piles are reinforced concrete piles, and the compressive strength of the supporting piles is more than 30 MPa. The arrangement of the supporting piles can effectively play a role in stable supporting, the reinforced concrete piles with certain strength can be obtained from local materials, and the compressive strength of 30MPa can guarantee the integrity of the foundation pit.
Further, the distance between the adjacent supporting piles is 10 cm-35 cm. The interval between the stake of support can not the undersize, and the undersize not only brings inconvenience for the construction, and has also caused the waste of material when can reaching the supporting effect, has increased some unnecessary costs, but the interval is too big, and not only the supporting effect variation also can not form mutual cooperation with stagnant water stake layer, can not guarantee the stability of foundation ditch. However, in the actual construction process, the water content and the area of the foundation pit are selected according to the water content of the stratum and the area of the foundation pit, the water content is large, the foundation pit is large, the distance between the supporting piles can be selected to be larger, the distance between the supporting piles can be selected to be smaller, and specific problems can be analyzed specifically. Preferably, the distance between adjacent support piles is 15 cm-30 cm. More preferably, the distance between adjacent support piles is 20cm to 30 cm.
Furthermore, the diameter of the support pile is 1 m-1.5 m.
Further, the concrete bottom sealing layer is of a reinforced concrete pouring structure, and the thickness of the concrete bottom sealing layer is 0.8-1 m.
Furthermore, the grouting sealing bottom layer is mainly formed by cement grout and water glass grouting. The grouting bottom sealing layer is formed by drilling and grouting at the top of a foundation pit to be excavated, the selection of materials is very important for the effect influence of the grouting bottom sealing layer, the mixture can be condensed at a proper time under the matching action of cement slurry and water glass, and the grouting construction can be matched with the drilling construction in time and effect in the preparation process of the water stop pile.
Further, the water-cement ratio of the cement slurry is 0.8-1; the baume degree of the water glass is 35 Be-40 Be; the mass ratio of the cement slurry to the water glass is 0.9-1.2: 1. The proper baume degree of the water glass controls the setting time of the grout, and the proportion of the cement, the water and the water glass not only controls whether the water-stopping pile can be successfully formed, the water-stopping effect and the setting effect, but also influences the diffusion condition of the grout in the deep position. The water glass is too much or the baume degree is too large, so that the rapid condensation is caused, the quality of the grouting bottom sealing layer can be greatly influenced, and the water-cement ratio of the cement slurry is too large or too small, so that the water stopping effect and the construction effect can be adversely affected.
Further, the thickness of the grouting bottom sealing layer is 1-5 m. The thickness setting of slip casting back cover layer is also very important, and thickness undersize can not effectively prevent during groundwater gets into the foundation ditch, brings unnecessary trouble for the work progress simultaneously, but is too thick, has not only reduced the efficiency of construction, and can not effectively guarantee back cover layer efficient completion construction in the work progress, brings the difficulty for the stagnant water effect. Preferably, the thickness of the grouting bottom sealing layer is 3 m-5 m.
Further, the foundation pit supporting system further comprises a crown beam and at least two steel pipe supporting pieces, wherein the crown beam is fixedly connected to the top of the supporting pile layer; and two ends of the steel pipe supporting piece are respectively connected with the crown beams on the adjacent sides. Through the combination of the supporting piles, the crown beams, the steel pipe supports and the suspended net spray anchors, the rigidity and the stability of the foundation pit support are effectively improved, and therefore collapse of the side wall of the foundation pit is avoided.
The invention also aims to provide a construction method of the foundation pit supporting system.
A construction method of the foundation pit supporting system comprises the following steps:
step 2, constructing the water stop pile layer on the periphery of the marked foundation pit excavation area;
The construction method of the foundation pit supporting system provided by the invention has the advantages that the position of the foundation pit is marked, then the water stop pile layer and the support pile layer at the peripheral position of the foundation pit are constructed, then the grouting back cover layer is formed at the designed depth within the marked foundation pit by means of drilling and grouting, then the foundation pit is excavated, and the concrete back cover layer is poured, so that the construction of the foundation pit supporting system is completed.
Further, in the step 2, in the process of constructing the water stop pile layer, a high-pressure jet grouting pile is used to form a double-row occluded water stop pile. Further, in the step 2, during the process of constructing the waterproof pile layer, drilling holes, then using a grouting apparatus to respectively spray out cement paste and water glass with high pressure to replace the cement paste with foundation soil or partially mix and solidify the cement paste and the water glass with soil to form a solidified pile body, and enabling parts of the pile bodies to be mutually occluded to form a complete waterproof curtain.
Further, in the step 3, after the water stop pile layer is cured, a support pile layer is constructed, and in the construction process of the support pile layer, the support pile layer is formed by drilling and pouring reinforced concrete into support piles arranged at intervals.
Further, in the step 4, the drill holes are uniformly arranged at intervals.
Further, in the step 4, holes are drilled in the foundation pit excavation area from outside to inside, the drill holes are uniformly arranged at intervals, and the distance between every two adjacent drill holes is 0.8-1.2 m.
Furthermore, in the step 4, in the drilling process, the deviation between the position of the drilling machine opening and the designed pile position is controlled within 50mm during drilling, the grouting pipe is inserted after the drilling machine is drilled to the designed specified elevation, in order to prevent the nozzle from being blocked, the pipe needs to be inserted while spraying water, and the water spraying pressure is not over 1 MPa.
Furthermore, in the step 4, during the drilling process, the drilling should be performed at a slow speed so as to understand and grasp the formation conditions and drilling parameters. Closely pay attention to the overflow condition in the drilling process, if large-area overflow or underground water is sprayed out from the drill rod in a large quantity, the drilling is stopped immediately, and the construction can be continued after the reason is analyzed and found out. When the water overflow amount is large when a certain hole is drilled, or grouting fails, jumping and hitting the hole by using the separation hole, and constructing the hole again after grouting is completed.
Further, in the step 4, the pressure of grouting is 1 to 1.5MPa in the grouting process.
Further, in the step 4, two grouting pumps are used for grouting in the grouting process, and cement slurry and water glass are respectively pumped.
Further, in the step 4, the drill rod can be lifted only after the drill rod is held under 2MPa, and the lifting of the drill rod is not more than 50cm each time.
Further, in the step 5, after the grouting bottom sealing layer is cured and before the foundation pit is excavated, a circle of crown beams are arranged at the top of the supporting pile layer, and steel supporting pieces are arranged on the inner sides of the crown beams. Through the combination of the supporting piles, the crown beams and the steel pipe supports, the rigidity and the stability of the foundation pit support are effectively improved, and therefore collapse of the side wall of the foundation pit is avoided.
Further, in the step 5, when excavation is performed within the range of the marked foundation pit, net hanging and anchor spraying are performed on the periphery of the foundation pit. Through carrying out the net that hangs on the wall around the foundation ditch and spouting the anchor, guaranteed the stability of the wall soil body around the foundation ditch, when avoiding the foundation ditch operation, the soil body appears collapsing around, also more effectual infiltration that prevents groundwater simultaneously.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
1. the foundation pit supporting system provided by the invention has the advantages of strong waterproofness and good stability, and can meet the requirement of small deformation of the foundation pit and simultaneously ensure the safe operation in the foundation pit for a long time when facing the foundation pit with a strong permeable stratum.
2. The foundation pit supporting system provided by the invention mainly comprises a water stopping system and a supporting system, wherein the peripheral wall of the foundation pit adopts a water stopping pile layer, and the bottom of the foundation pit adopts a grouting sealing bottom layer and a concrete sealing bottom layer to jointly form a perfect water stopping system; the perisporium of foundation ditch has effectively blockked foundation ditch soil pressure all around through the setting on stagnant water stake layer and support stake layer, has guaranteed the good wholeness and the stability of foundation ditch, when facing strong permeable stratum foundation ditch, should strut the system and can satisfy the little demand of foundation ditch deformation, can guarantee the problem of the interior safe operation of long-time foundation ditch simultaneously.
3. The construction method of the foundation pit supporting system provided by the invention has the advantages that the position of the foundation pit is marked, then the water stop pile layer and the support pile layer at the peripheral position of the foundation pit are constructed, then the grouting back cover layer is formed at the designed depth within the marked foundation pit by means of drilling and grouting, then the foundation pit is excavated, and the concrete back cover layer is poured, so that the construction of the foundation pit supporting system is completed.
Drawings
Fig. 1 is a schematic structural view of an excavation supporting system in example 1.
Fig. 2 is a schematic structural view of the foundation pit support system formed in step 3 in example 2.
Fig. 3 is a schematic structural view of the foundation pit support system formed in step 4 in example 2.
Fig. 4 is a schematic structural view of the foundation pit support system formed in step 5 of example 2.
Icon: 1-water stop pile layer; 2-supporting the pile layer; 21-supporting piles; 22-a crown beam; 221-steel tube support; 3-concrete sealing bottom layer; 4-grouting a bottom sealing layer; 41-drilling holes; and 5, foundation pit.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
The main bridge deck of a certain civil aviation road overpass project is integrally arranged, and the full width of the bridge is 34.4 m; the span is arranged to be (95+162+95) m continuous box girders, and large-section cast-in-place and swivel construction is adopted. 7. No. 8 pier is the main bridge main pier, closes on existing railway line, and place groundwater is higher. The water level burial depth is about 3.8-4.4 m during reconnaissance, and the railway traffic safety is greatly harmed if a general precipitation mode is adopted. A foundation pit support is needed, the difficult problem that the foundation pit close to the railway and the highway is difficult to prevent and drain is solved, the construction risk is reduced, and the construction cost is reduced.
As shown in fig. 1, a foundation pit supporting system comprises a water stop pile layer 1, a support pile layer 2, a concrete bottom sealing layer 3 and a grouting bottom sealing layer 4;
the supporting pile layer 2 and the water stopping pile layer 1 are sequentially arranged along the inner wall of the periphery of the foundation pit 5 outwards; the concrete bottom sealing layer 3 and the grouting bottom sealing layer 4 are sequentially arranged downwards along the bottom surface of the foundation pit 5. The depth of the water stop pile layer 1 is equal to that of the foundation pit 5; the depth of the support pile layer 2 is greater than that of the water stop pile layer 1. The areas of the concrete bottom sealing layer 3 and the grouting bottom sealing layer 4 are equal to the area of the bottom surface of the foundation pit 5. The upper surface of the concrete bottom sealing layer 3 is the bottom surface of the foundation pit 5. One layer of the supporting layer close to the foundation pit 5 forms the inner peripheral wall of the foundation pit 5.
The waterproof pile layer 1 is composed of double rows of occlusive waterproof piles, and the double rows of occlusive waterproof piles form a closed waterproof curtain. The support pile layer 2 is composed of a plurality of support piles 21 arranged at intervals, the support piles 21 are reinforced concrete piles, and the compressive strength of the support piles 21 is 35 MPa. The distance between adjacent support piles is 25 cm. The diameter of the support pile is 1.25m, and the thickness of the concrete bottom sealing layer 3 is 0.8 m. The thickness of the grouting bottom sealing layer 4 is 4.6 m. The foundation pit 5 supporting system further comprises a crown beam 22 and 4 steel pipe supporting pieces 221, wherein the crown beam 22 is fixedly connected to the top of the supporting pile layer 2; the two ends of the steel pipe supporting member 221 are respectively connected to the crown beams 22 of the adjacent sides.
Above-mentioned foundation ditch 5 is strutted system waterproof nature is strong, and stability is good, when facing strong permeable stratum foundation ditch 5, should strut the system and can satisfy the little demand of foundation ditch 5 deformation, can guarantee the problem of the interior safe operation of long-time foundation ditch 5 simultaneously.
Example 2
The embodiment provides a construction method of the foundation pit 5 supporting system.
The method comprises the following steps:
step 2, constructing a water stop pile layer 1 around the marked foundation pit 5;
the method comprises the steps of forming double-row occlusive waterproof piles by using high-pressure jet grouting piles, drilling holes, respectively spraying cement paste and water glass with high pressure by using a grouting instrument to replace foundation soil or partially mix and solidify the cement paste and the water glass with soil to form solidified pile bodies, and enabling parts of the pile bodies to be mutually occluded to form a complete waterproof curtain.
The specific remarks are as follows:
after the construction site is leveled, the high-pressure jet grouting pile drilling machine enters the field and moves to the designed specified hole site, then the horizontal correction is carried out by using the horizontal ruler, and the drill rod is straightened by using the vertical ball so as to ensure that the verticality of the drill hole meets the standard and the design requirement. The drilling machine starts to drill after positioning is finished, deviation between the position of a drilling machine opening and a designed pile position is controlled within 50mm during drilling, a grouting pipe is inserted after the drilling machine is drilled to a designed designated elevation, water spraying and pipe inserting are needed while preventing nozzles from being blocked in the pipe inserting process, and the water spraying pressure is not over 1 MPa. Preparation of cement slurry can begin while drilling. The bagged cement is delivered and inspected according to one batch when 200 tons of bagged cement is not enough, and the specification, variety and leaving time of the bagged cement meet the design requirements through laboratory inspection and have quality certification. The water used for pulping is clean and the acid and the alkali are moderate. The engineering adopts a double-pipe method for operation, the water cement ratio of cement slurry is 0.8, the baume degree of water glass is 35Be, and the cement slurry and the water glass strictly follow the following steps of 1: 1, the slurry can enter a high-pressure slurry pump after being stirred and filtered. The grouting pipe is inserted into a specified depth, then compressed air is pumped, then grouting is carried out, soil is cut by high-pressure airflow to form a large gap, and then cement slurry is injected for filling. The construction sequence should follow that the guniting is firstly carried out and then the rotary lifting is carried out, the rotating speed and the lifting speed of the drill rod need to be controlled during the rotary lifting, the whole rotary lifting process needs to be ensured to be continuous and uninterrupted, and if the construction is interrupted due to other reasons, the drill rod needs to be used for penetrating into the original pile body to be not less than 0.5m so as to ensure that the pile body is lapped continuously and tightly. After the construction is finished, the equipment such as the pipeline and the like needs to be washed clean, no cement paste remains in the pipe, and after the washing is finished, the equipment such as a drilling machine and the like is moved to a new hole position.
The method mainly comprises the following operation key points:
the construction is carried out by adopting a ZLJ-350 drilling machine, and the drilling machine is not provided with a leveling device, so that the site is leveled as much as possible when being erected. The leveling adjustment can be performed by using crossties and the like. The LJ-350 drilling machine mainly utilizes a hydraulic device to control drilling, so that before the drilling machine is constructed, whether an oil pipe of the drilling machine is full or not needs to be checked, and if the oil pipe is not full, hydraulic oil needs to be added. 46# anti-wear hydraulic oil is adopted as the hydraulic oil, and during construction in winter, the anti-freeze hydraulic oil is considered to be utilized, and the best hydraulic oil is added to a position 1cm away from the oil port. After an operator connects a power supply to start the machine, whether the rotation direction of the motor is consistent with the indication direction or not is checked. The drilling angle of the drilling machine is controlled by the rotary disc, and an operator can adjust the drilling angle according to actual conditions. During drilling, particularly the first hole, the drilling should be slow to understand the formation conditions and drilling parameters. Closely pay attention to the overflow condition in the drilling process, if large-area overflow or underground water is sprayed out from the drill rod in a large quantity, the drilling is stopped immediately, and the construction can be continued after the reason is analyzed and found out. And the hole is drilled by adopting hole-separating jumping, when a certain hole is drilled, the overflow amount is large, or grouting fails, the hole is constructed again after grouting is finished by utilizing the hole-separating jumping, and the success rate is greatly improved. The depth of the formed hole is required to be 50cm larger than the designed depth, and the record is made after the hole is formed. And grouting can be carried out after the hole position is drilled to the designed elevation. Grouting from the outside to the inside and from the bottom of the hole to the top. P.O 42.5 cement is adopted as grouting liquid, and the water cement ratio is 1. And water glass with the Baume degree of 40 is also arranged, the Baume degree of the water glass can Be customized according to geological conditions and design requirements, 35 Be-40 Be is adopted, the mass ratio of cement paste to the water glass is 1: 1. the grouting amount is controlled by the cement dosage, the grouting pressure is generally between 1.5MPa, and the specific numerical value can be adjusted according to the test of a field soil layer. During grouting, one pipeline of the grouting pump pumps cement, and the other pump pumps water glass to the drill rod for fusion. During the slip casting, the numerical value of a pressure gauge and the condition of overflowing grout are closely concerned, during general primary construction, the slip casting amount is large, the pressure value is low, the underground soil layer is loose, a large amount of grout is required to be filled, and after about 5 common constructions, the phenomenon can be reduced. Generally, the drill rod can be lifted only after the pressure is kept at 2MPa, and the lifting of the drill rod does not exceed 50cm each time. The distance between adjacent boreholes 41 is 1 m.
Wherein, at the slip casting in-process, because the gel time is short, the pipeline is at two kinds of thick liquids mixing process, and the inevitable emergence is solidified and blocking phenomenon, and the slip casting pump can improve pressure because of the pipeline trouble this moment, and the machine sends unusual sound, and the manometer instructs pressure to rise, if not handle in time and can produce the high pressure and injure people's dangerous accident. At this time, the pump must be stopped, the grouting high-pressure hose is detached, the cleaning pipeline is washed, or the mixer is cleaned, the fault part is checked and treated, the grouting high-pressure hose is washed clean, and then the operation is continued. In the grouting process, the change conditions of the earth surface and the roadbed of the adjacent business line need to be observed at any time, the stratum changes due to the entering of the grout, the grout may emerge at the place with lower sealing strength, the grout needs to be blocked at the grout-emerging place, and an intermittent grouting mode is adopted if necessary to ensure that the grout is effectively injected into the stratum.
After the drilling and grouting in step 4 is completed, the support system is shown in fig. 3.
And 5, after the grouting bottom sealing layer 4 is solidified, arranging a circle of crown beams 22 at the top of the support pile layer 2, arranging steel support pieces on the inner sides of the crown beams 22, and carrying out net hanging and anchor spraying on the periphery of the foundation pit 5. And then, excavating to the grouting bottom sealing layer 4 within the range of the marked foundation pit 5, and then pouring reinforced concrete on the upper surface of the grouting bottom sealing layer 4 to form a concrete bottom sealing layer 3 through construction, thereby completing the construction of a foundation pit 5 supporting system. As shown in fig. 4, the foundation pit 5 supporting system completed in example 2 is schematically structured.
The whole construction process is high in efficiency and safety, disturbance to surrounding buildings and foundations during precipitation in the pit and operation in the pit can be greatly reduced, construction requirements of complex environments can be met, and the method has popularization significance.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A foundation pit supporting system is characterized by comprising a water stop pile layer (1), a supporting pile layer (2), a concrete bottom sealing layer (3) and a grouting bottom sealing layer (4);
the supporting pile layer (2) and the water stopping pile layer (1) are sequentially arranged on the side face of the foundation pit (5) from inside to outside;
and the concrete bottom sealing layer (3) and the grouting bottom sealing layer (4) are sequentially arranged on the bottom surface of the foundation pit (5) from top to bottom.
2. The foundation pit support system according to claim 1, characterized in that the depth of the water stop pile layer (1) is greater than or equal to the depth of the foundation pit (5); the depth of the support pile layer (2) is greater than or equal to that of the water stop pile layer (1); the areas of the concrete bottom sealing layer (3) and the grouting bottom sealing layer (4) are larger than or equal to the bottom area of the foundation pit (5).
3. The foundation pit support system according to claim 1, characterized in that the waterproof pile layer (1) comprises double rows of occlusive waterproof piles which form a closed waterproof curtain.
4. The foundation pit supporting system according to claim 1, wherein the supporting pile layer (2) comprises a plurality of supporting piles (21) arranged at intervals, the supporting piles (21) are reinforced concrete piles, and the compressive strength of the supporting piles (21) is more than 30 MPa.
5. The foundation pit support system according to claim 1, characterized in that the concrete bottom sealing layer (3) is a reinforced concrete pouring structure, and the thickness of the concrete bottom sealing layer (3) is 0.8-1 m.
6. The foundation pit support system according to claim 1, characterized in that the grouting back cover layer (4) is prepared by grouting cement grout and water glass.
7. The foundation pit supporting system according to claim 6, wherein the cement slurry has a water cement ratio of 0.8-1; the baume degree of the water glass is 35 Be-40 Be; the mass ratio of the cement slurry to the water glass is 0.9-1.2: 1.
8. The foundation pit support system according to any one of claims 1-7, characterized by further comprising a crown beam (22) and at least two steel pipe supports (221), wherein the crown beam (22) is fixedly connected to the top of the support pile layer (2); and two ends of the steel pipe supporting piece (221) are respectively connected with the crown beams (22) on the adjacent sides.
9. A method of constructing an excavation supporting system as claimed in any one of claims 1 to 8, including the steps of:
step 1, marking a foundation pit excavation area;
step 2, constructing the water stop pile layer (1) on the periphery of the marked foundation pit excavation area;
step 3, constructing the support pile layer (2) on one side of the water stop pile layer (1) close to the foundation pit excavation area;
step 4, drilling and grouting construction is carried out at a plurality of positions in the foundation pit excavation area to form the grouting sealing bottom layer (4);
and 5, after the grouting sealing bottom layer (4) is solidified, excavating the foundation pit excavation region to the grouting sealing bottom layer (4), then building reinforcing steel bars on the upper surface of the grouting sealing bottom layer (4) and pouring concrete, and constructing to form the concrete sealing bottom layer (3), so that the construction of a foundation pit (5) supporting system is completed.
10. The construction method of the foundation pit supporting system according to claim 9, wherein in the step 4, holes are drilled from outside to inside in the foundation pit excavation area, the drilling holes (41) are uniformly arranged at intervals, and the distance between every two adjacent drilling holes (41) is 0.8-1.2 m.
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Application publication date: 20210824 |