CN112900468A - Bridge foundation construction method suitable for complex geological conditions - Google Patents
Bridge foundation construction method suitable for complex geological conditions Download PDFInfo
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- CN112900468A CN112900468A CN202110140002.0A CN202110140002A CN112900468A CN 112900468 A CN112900468 A CN 112900468A CN 202110140002 A CN202110140002 A CN 202110140002A CN 112900468 A CN112900468 A CN 112900468A
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/10—Deep foundations
- E02D27/12—Pile foundations
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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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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/10—Deep foundations
- E02D27/12—Pile foundations
- E02D27/14—Pile framings, i.e. piles assembled to form the substructure
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- 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
- E02D5/46—Concrete or concrete-like piles cast in position ; Apparatus for making same making in situ by forcing bonding agents into gravel fillings or the soil
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Abstract
The invention relates to the technical field of bridge foundation construction, in particular to a bridge foundation construction method suitable for complex geological conditions, which specifically comprises the following steps: excavating a foundation pit; draining the foundation pit and constructing a temporary support; supporting construction of a bearing platform deep foundation pit; the method specifically comprises the following steps: carrying out foundation pit supporting construction by adopting a jet grouting pile, a cement-soil wall and a steel sheet pile; constructing a bearing platform foundation pit; and (5) constructing a bearing platform. The method can effectively prevent the influence of complex geological conditions on the bridge foundation construction; construction quality is effectively improved, and construction progress is accelerated; the invention can effectively avoid the large-area collapse of the foundation pit caused by the complex geological condition in the construction process; the safety accident caused by collapse is avoided.
Description
Technical Field
The invention relates to the technical field of pile foundation construction, in particular to a bridge foundation construction method suitable for complex geological conditions.
Background
The bored pile is first produced in the united states in about the years after the manual hole digging, that is, in the early century, along with the successful development of a high-power drilling machine. With the economic resurgence and development around the world after the second world war, high-rise and super high-rise buildings and heavy structures are continuously built, and most of the buildings select cast-in-situ bored piles. Since the year, the bored pile has been developed vigorously worldwide, and the dosage thereof is increased year by year and is high. The cast-in-situ bored pile is applied to thousands of major and middle cities in provinces, cities and autonomous regions of China except for Tibet and is mainly applied to various foundations including special soils such as soft soil, loess, expansive soil and the like along with the improvement of pace-opening and acceleration of development and rapid development in the late era of the last century. It is estimated that the number of the cast-in-place piles used in China is the greatest worldwide in recent years, and the cast-in-place piles are developed rapidly even though they are started late.
The adoption of cast-in-place bored piles on highway bridges in China begins at the end of the century. At that time Henan province pioneered drilling with a manual rotary drill bit. And then, the drilling equipment gradually develops various equipment and drilling processes such as a percussion and grabbing cone, a percussion cone, a positive circulation rotary drill, a submerged drill, a rotary drill and the like all over the country, and the application scale is continuously enlarged. At present, cast-in-place bored piles occupy an important position in engineering construction, and develop towards large-diameter and diversification (variable interface piles, hollow piles and the like), the drilling level is continuously improved, and the drilling process is complete and mature. Especially, advanced high-power hydraulic drilling machines are produced in many western countries, so that the diameter of a drilled hole reaches more than 3m, the pile length exceeds 100m, the speed is high, the technology is safe and reliable, and the pile forming quality is high.
Constructing complex geological conditions that an underground drift sand layer is thick, rock cavern cracks develop strongly, and drift sand, underground water and the like exist more; if the treatment is carried out according to the traditional construction method, the treatment cannot be effectively and quickly carried out, the project construction period is limited, and the construction quality cannot be effectively ensured.
Disclosure of Invention
The invention aims to solve the technical problem of providing a bridge foundation construction method suitable for complex geological conditions.
The technical problem to be solved by the invention is as follows:
a bridge foundation construction method suitable for complex geological conditions specifically comprises the following steps:
excavating a foundation pit;
draining the foundation pit and constructing a temporary support;
supporting construction of a bearing platform deep foundation pit; the method specifically comprises the following steps: carrying out foundation pit supporting construction by adopting a jet grouting pile, a cement-soil wall and a steel sheet pile;
constructing a bearing platform foundation pit;
and (5) constructing a bearing platform.
In some possible embodiments, the shotcrete cemented soil wall described in the shoring construction of the bearing platform deep foundation pit specifically refers to:
after a drilling machine is used for drilling a grouting pipe to a preset position of a stratum, a high-pressure pulse pump is used for horizontally spraying cement slurry into a soil body at a high speed to the periphery through a spraying device at the lower end of a drill rod, the soil body in a jet flow range is damaged by cutting the soil layer by means of the impact force of fluid, meanwhile, one side of the drill rod rotates at a certain speed, and the other side of the drill rod slowly and slowly lifts, so that the soil body and cement slurry are fully stirred and mixed, and the cement is cemented and hardened;
the bottom of the cement-soil wall of the jet grouting pile is positioned on a weathered rock stratum;
the cement-soil wall of the rotary spraying pile is a multi-row lattice type high-pressure rotary spraying pile.
In some possible embodiments, after the construction of the jet grouting pile cement soil wall is completed, steel sheet pile construction is performed, which specifically includes the following steps:
construction measurement;
inspecting and hoisting the steel sheet piles;
driving a steel sheet pile;
and closing the corners of the steel sheet piles.
In some possible embodiments, the driving of the steel sheet pile specifically means:
arranging a guide frame;
inserting steel sheet piles into the guide frame in rows to form a screen, and then beating in batches;
when in driving, the steel sheet piles at two ends of the screen wall are driven to the designed elevation to form positioning sheet piles, and then the positioning sheet piles are driven into the middle of the screen wall in a step shape according to the heights of the sheet piles of l/3 and 1/2 in sequence.
In some possible embodiments, the closing of the corners of the steel sheet pile specifically includes the following steps:
stopping the driving along the long edge direction until eight steel sheet piles are arranged away from the corner pile, and measuring the total length and the increased length of the corner pile; the above method is also performed in the short side direction;
separating the purlin and the purlin pile in the short edge direction according to the length increased in the horizontal direction of the long side and the short side and the size of the corner pile, ejecting the purlin and the purlin pile outwards by using a jack, moving the axis outwards, and welding and fixing the purlin and the purlin pile again after checking the purlin and the purlin pile;
inserting piles into the purlin in the long edge direction, continuously driving, inserting and driving corner piles, turning, and inserting and driving two steel sheet piles in the short edge direction;
and continuously inserting and driving forwards along the short side direction according to the corrected axis, and arranging the last closed steel sheet pile at the position of the third steel sheet pile counted from the end part in the short side direction.
In some possible embodiments, the excavation of the bearing platform foundation pit specifically refers to layered excavation in a slope-releasing or vertical mode, and the excavation direction is excavation in a diagonal direction of the bearing platform.
In some possible embodiments, the foundation pit drainage is performed by well point dewatering and/or open trench drainage.
In some possible embodiments, the bearing platform construction specifically includes the following steps:
measuring and lofting;
installing a steel bar template and steel bars;
pouring and maintaining concrete;
and backfilling the foundation pit.
In some possible embodiments, the concrete casting is a layered casting.
In some possible embodiments, the foundation pit is backfilled by adopting layered construction, the thickness of each layer of backfilled soil is not more than 30cm after being compacted, the foundation is backfilled by outsourcing stone slag layer by layer, and the foundation is backfilled to 1.2m below the ground by adopting backfilled C15 plain concrete to the ground elevation.
Compared with the prior art, the invention has the beneficial effects that:
the method can effectively prevent the influence of complex geological conditions on the bridge foundation construction; construction quality is effectively improved, and construction progress is accelerated;
the invention can effectively avoid the large-area collapse of the foundation pit caused by the complex geological condition in the construction process; the safety accidents caused by collapse are avoided;
the invention realizes good soil layer reinforcement and water stop functions by the combination of the cement soil wall of the jet grouting pile and the steel sheet pile, and has good applicability in complex geological areas.
Drawings
FIG. 1 is a plan view of a construction employing the present invention;
FIG. 2 is a schematic cross-sectional view of the construction using the present invention;
FIG. 3 is a schematic structural view of a steel sheet pile according to the present invention;
wherein: 1. a cement-soil wall of the rotary jet grouting pile; 2. steel sheet piles; 21. a guide frame; 22. a steel sheet pile body; 3. intercepting a ditch; 4. and (7) a drainage ditch.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, embodiments of the present application. 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 application.
Reference herein to "first," "second," and similar words, does not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect.
In the implementation of the present application, "and/or" describes an association relationship of associated objects, which means that there may be three relationships, for example, a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone.
In the description of the embodiments of the present application, the meaning of "a plurality" means two or more unless otherwise specified. For example, the plurality of positioning posts refers to two or more positioning posts.
The invention is further illustrated with reference to the following figures and examples.
The invention is realized by the following technical scheme, as shown in figures 1 and 2,
a bridge foundation construction method suitable for complex geological conditions specifically comprises the following steps:
excavating a foundation pit;
draining the foundation pit and constructing a temporary support;
supporting construction of a bearing platform deep foundation pit; the method specifically comprises the following steps: carrying out foundation pit supporting construction by adopting a jet grouting pile cement soil wall 1 and combining a steel sheet pile 2;
constructing a bearing platform foundation pit;
and (5) constructing a bearing platform.
In some possible embodiments, the shotcrete cemented soil wall 1 described in the shoring construction of the bearing platform deep foundation pit specifically refers to:
after a drilling machine is used for drilling a grouting pipe to a preset position of a stratum, a high-pressure pulse pump is used for horizontally spraying cement slurry into a soil body at a high speed to the periphery through a spraying device at the lower end of a drill rod, the soil body in a jet flow range is damaged by cutting the soil layer by means of the impact force of fluid, meanwhile, one side of the drill rod rotates at a certain speed, and the other side of the drill rod slowly and slowly lifts, so that the soil body and cement slurry are fully stirred and mixed, and the cement is cemented and hardened;
the method specifically comprises the following steps:
construction preparation:
leveling a field, lofting a pile position, building a pollution discharge and mortar mixing system;
10-20% of slurry return amount can be generated in the construction process of the jet grouting pile, waste slurry is introduced into a sedimentation tank, and clear water after sedimentation can be discharged in a pollution-free manner according to site conditions. The deposited soil is transported away together when the foundation pit is excavated. The sediment and the sewage are uniformly brought into a whole sewage treatment system; the mortar mixing system is mainly arranged near cement, is convenient to operate and mainly comprises mortar mixing equipment, mortar storage equipment and mortar conveying equipment.
And (3) pile testing construction:
in order to ensure that the high-pressure jet grouting pile construction is standard, orderly and high-quality to develop comprehensive construction, pile test construction is firstly carried out. The geological condition is further-ascertained through pile testing, the time for reasonable mortar to reach the mortar spraying port of the mixer through the mortar conveying pipe is determined, the stirring subsidence, the lifting speed and the repeated stirring subsidence and lifting speed are determined, the cement mixing amount, the mortar consistency (water-cement ratio) and the working pressure are determined, and the construction equipment and the selected construction process are inspected. Operation requirements such as a high-pressure jet grouting pile construction method, a process flow, technical parameters, quality detection and the like are mastered by pile testing, and guidance is provided for construction of a full-scale high-pressure jet grouting pile. And testing 4 piles before formal construction of the jet grouting pile. The process test before construction mainly verifies the following aspects:
1) whether the test spraying result can meet the requirements of design;
2) constructing technological parameters of the jet grouting pile;
3) whether construction machines, equipment and construction processes selected according to the geological condition and the designed pile diameter meet the design requirements or not;
calculating the pulp quantity by the pulp quantity sprayed in unit time and the spraying duration, and calculating the pulp quantity by the following calculation formula: q ═ Hq (1+ β)/ν;
in the formula: q-amount of pulp (m)3)；
H-jet length (m);
q-amount of sprayed slurry per unit time (m)3/min)；
Beta-loss factor, typically 0.1 to 0.2;
v-lifting speed (m/min);
positioning a drilling machine:
2 MGJ-80 drilling machines are adopted to lead holes and form holes, after the drilling machines are in place, the pile machine is leveled and centered, the perpendicularity of the pile machine is adjusted, the drill rod is ensured to be consistent with the pile position, the deviation is within 10mm, and the error of the perpendicularity of the drilled holes is less than 1.5%; before drilling, an air compressor and a slurry pump are required to be debugged, so that the equipment can normally operate; and checking the length of the drill rod, and marking a depth line beside the drilling tower by using red paint to ensure that the elevation of the bottom of the hole meets the design depth.
Drilling a guide hole:
the drilling machine is moved to the drilling position, the machine platform level is controlled by aligning with the horizontal ruler for the hole position, the vertical shaft is vertical, the machine frame is firmly cushioned, the verticality of the drilling machine meets the precision requirement, and the drilling machine can be opened after the drilling machine is tested and tested by technicians to be qualified. If the drilling machine is inclined, stopping the machine for leveling and then opening the drilling machine. In the drilling process, the reason is found out in time when the drilling process encounters abnormal conditions, corresponding measures are taken, the formation change, the particle size, the hardness and the like are recorded in detail, after the drilling is finished, the quality inspection is carried out by technicians, and the next hole can be drilled in a shifting mode after the drilling is qualified. The diameter of the lead hole is 110mm, the deviation between the centering position and the design position of the lead hole is not more than 30mm, the vertical deviation is less than 1%, and double-pipe construction is adopted.
And (3) rotary spraying operation:
1) the method is characterized in that 2 XPB-900 spraying trolleys are adopted, the spraying trolleys are moved to a pore forming position, grout and gas are firstly sprayed on the ground in a trial mode, after all process parameters are checked to meet design requirements, the spraying pipes are lowered to the design depth, high-spraying grouting construction can be carried out after the spraying pipes are checked and approved by field quality inspection personnel, if special conditions such as overhigh grout pressure or nozzle blockage exist in the spraying process, the spraying pipes are lifted out of the ground to be processed, and construction is carried out after the processing is finished.
2) The rotary spraying machine frame is in place, the center of the spray pipe is aligned with the hole center when the spray pipe is in a natural suspension state, the deviation is not more than one-half of the hole diameter (hole forming hole diameter), and smooth operation of pipe descending, lifting and rotary spraying grouting is guaranteed.
3) Before the lower spray pipe, whether the spray nozzle and the guniting port are intact and unblocked is checked, then a guniting test is carried out, and the lower spray pipe can be arranged when the guniting pressure meets the design requirement.
4) When the spray pipe reaches the designed depth of 10cm, the cement slurry starts to be stirred and fed, then the high-pressure slurry is started, and after the design parameters are reached and the slurry outflow from the orifice is normal, the rotary spraying lifting is started.
5) When a fault and other special conditions occur in the injection process, the injection can be continued only by descending 10cm of the spray pipe, so that the vertical continuity of the rotary injection reinforced body is ensured.
6) During injection operation, the grouting and recharging operation of the adjacent sprayed piles is performed, the elevation of the reinforced pile top is ensured, and meanwhile, the waste slurry treatment operation must be performed in time during construction.
7) And (3) pressure control: the pressure of the cement slurry flow is not less than 20 MPa.
When the grouting pipe is placed into the drill hole, the nozzle reaches the designed elevation, and then grouting can be sprayed. And after the jet grouting parameters reach specified values, lifting the grouting pipe according to the process requirements of the jet grouting pile, and jet grouting from bottom to top. The drilling lifting speed is not more than 0.15 m/min. When abnormal conditions such as sudden pressure drop, pressure rise or slurry overflow occur in the high-pressure jet grouting process, the cause of the abnormal conditions is found out, and measures are taken in time. And when the high-pressure injection grouting is finished, quickly pulling out the grouting pipe.
Spraying a slurry material and pulping:
the cement is stirred and made into slurry by using 42.5R ordinary Portland cement, the cement is fresh and has no agglomeration, the screen allowance passing through a 0.08mm square hole sieve is less than or equal to 5 percent, the cement entering the site in each batch must have a product qualification certificate of a manufacturer, and the cement is checked according to relevant regulations. PO.42.5 cement is adopted for making the rotary jet grouting pile, the consumption of the cement per linear meter of the rotary jet grouting pile is about 265kg, and the specific consumption is determined according to field tests. The jet grouting pile must meet the technical specification of building foundation treatment (JGJ79-2002), the water for the jet grouting pile meets the requirements of water for concrete mixing (JGJ63-06), and the water-cement ratio is 1.1-1.3.
And stirring the slurry according to the designed proportion, measuring the specific gravity of the slurry at any time in the slurry preparation process, and counting the material dosage of each hole after the high-pressure spray grouting of each hole is finished. Stirring the slurry with a high-speed stirrer, wherein the stirring time of the slurry is not less than 30s, and the one-time stirring use time is controlled within 4 h.
And (3) injection lifting:
when the jet pipe is lowered to the designed depth, slurry and gas meeting the requirements are fed in, and when the injected slurry flows out of the orifice, the slurry is lifted from bottom to top according to the designed lifting mode and speed until the slurry is lifted to the designed final jet elevation. In the injection process, a technician on duty should check the operation condition of each link at any time, and take the following measures according to specific conditions:
1) the pipe is quickly connected and disconnected, and hole collapse and nozzle blockage are prevented;
2) injection due to fault interruption should be handled as appropriate:
(1) due to mechanical failure, the interruption time needs to be shortened as much as possible, and grouting needs to be recovered as soon as possible;
(2) if the interruption time exceeds 1 hour, remedial measures are taken;
(3) when the spraying is resumed, the spraying pipe needs to be at least 0.3m more, so as to ensure the continuity of the condensate.
Recharging:
after the injection is finished, static pressure filling grouting is carried out in the injection holes until the grout surface does not sink any more, the wall top elevation is ensured after the high-pressure injection impervious wall is solidified, and the refilling grout is generally filled by adopting the high-pressure injection grout bleeding of adjacent holes.
Recording:
the procedures of drilling and high-pressure grouting in construction are recorded in detail, timely and accurately, and all records need to use a unified form according to requirements.
And calculating the required guniting amount according to the test pile parameters to determine the using amount of the cement.
The bottom of the cement-soil wall 1 of the jet grouting pile is positioned on a weathered rock stratum;
the cement-soil wall 1 of the rotary spraying pile is a multi-row lattice type high-pressure rotary spraying pile.
In some possible embodiments, because the pile bottom of the jet grouting pile is connected with the limestone layer, the rock layers at the position of the bearing platform are uneven, and the pile bottom of part of the pile is higher than the excavation surface; for strengthening the overall stability of the cement-soil wall supporting structure, the balance stable state of the foundation pit is prevented from being unbalanced due to the load or sudden impact force of heavy machinery (such as a crane, a truck crane, a loader and the like) around the foundation pit in the excavation process and the later stage bearing platform construction, so that the foundation pit collapses in a large range, and therefore after the construction of the jet grouting pile cement-soil wall 1 is completed, the construction of a steel sheet pile 2 is carried out along the four inner walls of the jet grouting pile cement-soil wall, and the construction method specifically comprises the following steps:
construction measurement:
1) and carefully reviewing the construction drawing to grasp the design intention.
2) The position and elevation of the structure of each box culvert are determined according to a drawing, the coordinates and the axis direction of the piles in the culvert object are accurately calculated, then construction lofting is carried out according to the calculated specific position, and in order to facilitate inspection and check after excavation, the control piles of the basic axis line are extended out of the foundation pit to be fixed.
3) If the situation is found to be inconsistent with the site, the information is reported in time, after the information is determined by a manager and agreed by an owner, the corresponding adjustment can be carried out, after the lofting is finished, the sideline of the structural foundation is released according to the structural size of the foundation, the supervision engineer at the site is applied for rechecking, and after the confirmation, the foundation pit excavation can be carried out.
And (3) driving the steel sheet pile 2:
adopting a guide frame 21 screen type driving method;
(1) in order to ensure the driving precision of the steel sheet pile 2, a screen type driving method is adopted: the steel sheet pile 2 is driven and inserted by a DZ60 type vibration driving and pile pulling hammer. In the process of inserting and driving the steel sheet piles 2, the verticality of each row of piles is strictly controlled, rust at the lock catch positions of the steel sheet piles 2 is removed, and firm and close fit of the lock catch connection between every two adjacent piles is guaranteed.
(2) In order to ensure the plane position and the vertical degree of the steel sheet pile 2, a guide frame 21 is arranged, and the guide frame 21 is made of 45b I-shaped steel. As shown in fig. 3, the steel sheet pile 2 includes a guide frame 21 and a steel sheet pile body 22; the guide frames 21 are arranged in two groups and are arranged in parallel, a mounting cavity for mounting the plurality of steel sheet pile bodies 22 is formed between the two groups, and the plurality of steel sheet pile bodies 22 are mounted in the mounting cavity and are connected in sequence; the guide frame 21 is arranged in parallel with the inner side surface of the cement soil wall 1 of the jet grouting pile;
the 10 left and right steel sheet piles 2 are inserted into the guide frame in rows to form a screen shape and then are driven in batches.
When the positioning sheet pile is driven, the steel sheet piles 2 at two ends of the screen wall are driven to a designed elevation or a certain depth to form the positioning sheet pile, and then the positioning sheet pile is driven in the middle in a step shape according to the heights of the sheet piles of l/3 and 1/2 in sequence.
By adopting the method, the accumulation of inclination errors can be reduced, overlarge inclination is prevented, the closed folding is easy to realize, and the construction quality of the sheet pile wall can be ensured.
(3) In order to prevent the plane displacement of the central line of the fore shaft, a clamping plate can be arranged at the fore shaft of the steel sheet pile 2 in the piling proceeding direction to prevent the displacement of the steel sheet pile. Meanwhile, the position of each sheet pile is calculated in advance on the purlin so as to be convenient for checking and correcting at any time;
(4) the position and direction of the first and second steel sheet piles 2 which are initially driven should ensure the precision so as to play a role of sample plate guiding, so that the axial deviation of the steel sheet piles 2 is controlled within +/-10 cm, the pile top elevation +/-10 cm and the pile verticality within 1 percent when 1m is driven. And immediately welding and fixing the steel plate and the purlin surrounding bracket after the steel plate is punched to a preset depth.
And (3) corner and closed folding of the steel sheet pile 2:
(1) the length of the steel sheet pile wall 2 is not integral multiple of the standard width of the steel sheet pile wall 2, so that the final closed folding of the steel sheet pile wall is difficult, and the problem is solved by adopting an axis trimming method.
(2) The axis trimming method realizes closed closure by adjusting the designed length and position of the closed axis of the sheet pile wall, and the closed closure position is preferably selected at the corner of the short edge; the specific method comprises the following steps:
A. the steel plate pile driving method includes the steps that when the steel plate pile driving method is used for driving the steel plate pile to a position away from a corner pile along the long edge direction and about 8 steel plate piles 2 exist, the steel plate pile driving method is stopped temporarily, and the total length and the increased length of the steel plate pile driving method are measured; the above method is also performed in the short side direction;
B. separating the purlin and the purlin pile in the short edge direction according to the length increased in the horizontal direction of the long side and the short side and the size of the corner pile, ejecting the purlin and the purlin pile outwards by using a jack, moving the axis outwards, and welding and fixing the purlin and the purlin pile again after checking the purlin and the purlin pile;
C. inserting piles into the purlin in the long edge direction, continuously driving, inserting and driving corner piles, turning, and inserting and driving two steel sheet piles 2 in the short edge direction;
D. and continuously inserting and driving forwards along the short side direction according to the corrected axis, and arranging the last closed steel sheet pile 2 at the position of the third steel sheet pile from the end part in the short side direction.
In some possible embodiments, the closing of the corners of the steel sheet pile 2 specifically includes the following steps:
stopping the driving along the long side direction until eight steel sheet piles 2 are arranged away from the corner pile, and measuring the total length and the increased length of the corner pile; the above method is also performed in the short side direction;
separating the purlin and the purlin pile in the short edge direction according to the length increased in the horizontal direction of the long side and the short side and the size of the corner pile, ejecting the purlin and the purlin pile outwards by using a jack, moving the axis outwards, and welding and fixing the purlin and the purlin pile again after checking the purlin and the purlin pile;
inserting piles into the purlin in the long edge direction, continuously driving, inserting and driving corner piles, turning, and inserting and driving two steel sheet piles 2 in the short edge direction;
and continuously inserting and driving forwards along the short side direction according to the corrected axis, and arranging the last closed steel sheet pile 2 at the position of the third steel sheet pile from the end part in the short side direction.
In some possible embodiments, the excavation of the bearing platform foundation pit specifically refers to layered excavation in a slope-releasing or vertical mode, and the excavation direction is excavation in a diagonal direction of the bearing platform.
Preferably, slope excavation is adopted, and the slope excavation ratio is 1: 1.5; excavating in layers with the layer height of 1 m;
when the foundation pit is excavated to the designed elevation of the corresponding surrounding purlin, the surrounding is added immediately, the bolting is firm, the supporting is well done, and the surrounding purlin construction is carried out firstly under the condition of ensuring the requirement of the excavation working face;
c20 rubble concrete cushion bottom sealing measures are adopted for the over-excavated part, and manual excavation is adopted when excavation reaches 30cm above the designed elevation of the foundation pit.
In some possible implementation modes, in order to avoid the condition that a quicksand layer is possibly encountered in the excavation process, the quicksand layer is disturbed to inevitably cause large-area collapse of a foundation pit and bring unpredictable results, foundation pit dewatering and drainage are carried out before excavation; then excavating; and the foundation pit drainage adopts a well point dewatering and/or open trench drainage mode.
Preferably, a construction measure combining four-point well point dewatering and open drainage ditch is adopted in construction; water on the inner surface of the foundation pit is pumped by adopting an open drainage ditch and a water collecting well, and well points are arranged at two sides of a tie beam of a foundation pit bearing platform for dewatering.
For well point dewatering, a rotary drilling rig is adopted for drilling a hole, the aperture is phi 1500mm, the elevation of the hole bottom is required to be 5m lower than the elevation of the substrate, less than 5m of the hole bottom needs to penetrate through a quicksand layer, and the hole bottom is bordered by an limestone layer. And (3) putting a steel reinforcement cage with the diameter of 600mm in the dewatering well, wrapping the steel reinforcement cage with a double-layer filter screen, adopting brass wire cloth with meshes of 30-50 holes/cm, adopting iron wire cloth or nylon wire cloth or palm skin with meshes of 3-10 holes/cm, and binding a protective layer by using 8# iron wires outside the filter screen. And (5) backfilling 50cm of the hole bottom and gaps around the reinforcement cage by using graded broken stones.
The submersible pumps are adopted for pumping water at well points, and each dewatering well is provided with 1 WQ50-10-4 type submersible sewage pump. A steel pipe frame is erected at the orifice, a submersible pump is hung to a position 3m below the substrate, a power supply floating ball automatic water pumping switch is adopted, and a normally closed contact for low water level is connected in series on a contactor coil circuit; the normally open contact for high water level is connected in parallel to the start button to automatically control the elevation of the falling water level.
For surface drainage precipitation, the ground outside the periphery of the outer sides of all foundation pits is provided with a trapezoidal intercepting ditch 3 for intercepting and removing surface water around the foundation pits;
four corners in all foundation pits of the bearing platform are provided with water collecting wells, the water collecting wells are buried below the foundation pits by 1.5m in depth by adopting plastic pipes with the diameter of phi 500mm and are wrapped by geotextiles, and each water collecting well is provided with 1 WQ50-10-4 submersible sewage pump to uniformly pump accumulated water in the foundation pits and discharge the accumulated water after effective precipitation. Be equipped with many immersible pumps simultaneously reserve, prevent the freezing weather of heavy rain, be used for discharging the foundation ditch ponding fast when the foundation ditch ponding is serious, prevent that the foundation ditch from collapsing and other incident take place, ensure normal construction.
In some possible embodiments, the bearing platform construction specifically includes the following steps:
carrying out drainage construction on a foundation pit of the bearing platform; and arranging drainage ditches 4 at the periphery of the bottom of the foundation pit, namely the bottom of the cement soil wall, arranging water collecting wells at four corner points of the foundation pit respectively, and installing a WQ50-10-4 type sewage pump in each water collecting well. The outer side (the top end of the wall body) of the foundation pit is provided with a trapezoidal intercepting ditch 3, and the water is drained to a sedimentation tank for clarification and then is discharged.
Measuring and lofting;
installing a steel bar template and steel bars;
pouring and maintaining concrete;
and backfilling the foundation pit.
Preferably, in order to cool the bridge bearing platform, after the reinforcing steel bars are installed, cooling water pipes are installed, and a pre-buried cooling water pipe cooling measure is adopted to ensure the construction quality of mass concrete;
the cooling water pipe adopts a steel pipe with the diameter of 50 mm multiplied by 3mm, and the interlayer spacing is 50 cm. The multi-layer cooling water pipes can be arranged according to the size of the bearing platform, test operation is carried out after the cooling water pipes are arranged, whether leakage and water flow can meet requirements or not is checked, and meanwhile, a temperature measuring system is debugged. And the outside is connected with a water inlet and outlet main pipe and a water pump. During the concrete curing period, the cooling water pipe is continuously filled with water for 14 days, the water delivery amount is adjusted according to the water temperature, and the water temperature is controlled within 40 ℃. Meanwhile, the temperature difference of the inner surface of the concrete is controlled at 25 ℃.
In some possible embodiments, the concrete pouring adopts layered pouring, the thickness of each layer is not more than 30cm, and the interval time of the material distribution of each layer is not more than the initial setting time of the concrete.
In some possible embodiments, the foundation pit is backfilled by adopting layered construction, the thickness of each layer of backfilled soil is not more than 30cm after being compacted, the foundation is backfilled by outsourcing stone slag layer by layer, and the foundation is backfilled to 1.2m below the ground by adopting backfilled C15 plain concrete to the ground elevation.
The foregoing detailed description of the embodiments of the present application has been presented, and specific examples have been applied in the present application to explain the principles and implementations of the present application, and the above description of the embodiments is only used to help understand the method and the core ideas of the present application; meanwhile, for a person skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.
Claims (10)
1. A bridge foundation construction method suitable for complex geological conditions is characterized by comprising the following steps: the method specifically comprises the following steps:
excavating a foundation pit;
draining the foundation pit and constructing a temporary support;
supporting construction of a bearing platform deep foundation pit; the method specifically comprises the following steps: carrying out foundation pit supporting construction by adopting a jet grouting pile, a cement-soil wall and a steel sheet pile;
constructing a bearing platform foundation pit;
and (5) constructing a bearing platform.
2. The bridge foundation construction method suitable for complex geological conditions according to claim 1, characterized in that: the cement-soil wall of the jet grouting pile described in the pile cap deep foundation pit supporting construction specifically refers to:
after a drilling machine is used for drilling a grouting pipe to a preset position of a stratum, a high-pressure pulse pump is used for horizontally spraying cement slurry into a soil body at a high speed to the periphery through a spraying device at the lower end of a drill rod, the soil body in a jet flow range is damaged by cutting the soil layer by means of the impact force of fluid, meanwhile, one side of the drill rod rotates at a certain speed, and the other side of the drill rod slowly and slowly lifts, so that the soil body and cement slurry are fully stirred and mixed, and the cement is cemented and hardened;
the bottom of the cement-soil wall of the jet grouting pile is positioned on a weathered rock stratum;
the cement-soil wall of the rotary spraying pile is a multi-row lattice type high-pressure rotary spraying pile.
3. The bridge foundation construction method suitable for complex geological conditions according to claim 2, characterized in that: after the construction of the cement-soil wall of the jet grouting pile is completed, steel sheet pile construction is carried out, and the method specifically comprises the following steps:
construction measurement;
inspecting and hoisting the steel sheet piles;
driving a steel sheet pile;
and closing the corners of the steel sheet piles.
4. The bridge foundation construction method suitable for complex geological conditions according to claim 3, characterized in that: the steel sheet pile driving specifically comprises the following steps:
arranging a guide frame;
inserting steel sheet piles into the guide frame in rows to form a screen, and then beating in batches;
when in driving, the steel sheet piles at two ends of the screen wall are driven to the designed elevation to form positioning sheet piles, and then the positioning sheet piles are driven into the middle of the screen wall in a step shape according to the heights of the sheet piles of l/3 and 1/2 in sequence.
5. The bridge foundation construction method suitable for complex geological conditions according to claim 3, characterized in that: the corner closing of the steel sheet pile specifically comprises the following steps:
stopping the driving along the long edge direction until eight steel sheet piles are arranged away from the corner pile, and measuring the total length and the increased length of the corner pile; the method is carried out according to the method of a long side in the direction of a short side;
separating the purlin and the purlin pile in the short edge direction according to the length increased in the horizontal direction of the long side and the short side and the size of the corner pile, ejecting the purlin and the purlin pile outwards by using a jack, moving the axis outwards, and welding and fixing the purlin and the purlin pile again after checking the purlin and the purlin pile;
inserting piles into the purlin in the long edge direction, continuously driving, inserting and driving corner piles, turning, and inserting and driving two steel sheet piles in the short edge direction;
and continuously inserting and driving forwards along the short side direction according to the corrected axis, and arranging the last closed steel sheet pile at the position of the third steel sheet pile counted from the end part in the short side direction.
6. The bridge foundation construction method suitable for complex geological conditions according to claim 1, characterized in that: and excavating the bearing platform foundation pit, specifically adopting a slope-laying or vertical mode for layered excavation, wherein the excavation direction is the excavation in the diagonal direction of the bearing platform.
7. The bridge foundation construction method suitable for complex geological conditions according to claim 1, characterized in that: and the foundation pit drainage adopts a well point dewatering and/or open trench drainage mode.
8. The bridge foundation construction method suitable for complex geological conditions according to claim 1, characterized in that: the bearing platform construction method specifically comprises the following steps:
measuring and lofting;
installing a steel bar template and steel bars;
pouring and maintaining concrete;
and backfilling the foundation pit.
9. The bridge foundation construction method suitable for complex geological conditions according to claim 8, characterized in that: the concrete pouring adopts layered pouring.
10. The bridge foundation construction method suitable for complex geological conditions according to claim 1, characterized in that: and the foundation pit is backfilled by adopting layered construction, the thickness of each layer of backfilled soil is not more than 30cm after being compacted, the foundation is backfilled by outsourcing stone slag layer by layer, and the foundation is backfilled to 1.2m below the ground by backfilling C15 plain concrete to the ground elevation.
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Application publication date: 20210604 |