CN111576499A - Self-balancing static load test operation method for building foundation pile - Google Patents
Self-balancing static load test operation method for building foundation pile Download PDFInfo
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- CN111576499A CN111576499A CN202010397277.8A CN202010397277A CN111576499A CN 111576499 A CN111576499 A CN 111576499A CN 202010397277 A CN202010397277 A CN 202010397277A CN 111576499 A CN111576499 A CN 111576499A
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- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D33/00—Testing foundations or foundation structures
Abstract
The invention discloses an operation method of a self-balancing static load test of a building foundation pile, which comprises a preparation stage, an installation stage and a detection stage; in the preparation stage, production and transportation work of concrete, a reinforcement cage and a load box is completed, and a proper load box, a self-balancing balance point and a load box embedding position are calculated in advance; the installation stage completes the installation work of the load box and comprises the steps of precast concrete of the load box, welding the load box and the reinforcement cage, lowering the welded reinforcement cage, pouring pile body concrete and protecting a pile head pipeline; the detection stage at least comprises the steps of building a reference beam and a reference pile, building a tent, carrying out on-site detection and grouting on the broken surface of the load box; the operation method is clear in thought and strong in operability, the tasks required to be completed in each stage and step are defined, the time of the whole test period can be saved, the construction standardization can be achieved, the human errors can be reduced, and the test accuracy can be improved.
Description
Technical Field
The invention relates to the technical field of foundation pile static load engineering tests, in particular to an operation method of a self-balancing static load test of a building foundation pile.
Background
The traditional static load test is carried out by applying a certain load on the pile top, and two methods of pile loading and pile anchoring are generally available. The pile loading method applies load on the pile top by adopting an oil pressure jack, the counter force of the jack is balanced with the pile weight on the counter-force frame, and the pile weight can be selected from sand bags, concrete counterweights, steel ingots and the like. The anchor pile method also adopts an oil pressure jack to apply load on the pile top, and the counter force of the jack is transmitted to the anchor pile through a counter-force frame. However, the two methods also have some problems, such as the stacking method needs to solve the problems of loading source, transportation and stacking of hundreds of tons and even thousands of tons. The anchor pile method needs to arrange a plurality of anchor piles and a counterforce crossbeam to balance counterforce, and load centering is not easy to control in installation, so that not only can relevant cost and time be increased, but also the limit of a construction site is realized. Therefore, the progress of some special and complicated construction sites is severely restricted.
The test is carried out in a self-balancing static load test mode, but the operation steps of selecting, setting and welding a load box, butting and putting down the load box and the reinforcement cage are not systematic and standard, so that the accuracy of the test is influenced; and the setting and the protection of pipeline are not good enough in operation process, have the potential safety hazard, influence the operation of pouring after the experiment, can not ensure that the test pile can both be changed into qualified engineering stake.
Disclosure of Invention
The invention aims to provide an operation method for a self-balancing static load test of a building foundation pile, aiming at the problems in the prior art.
In order to achieve the purpose, the invention adopts the technical scheme that:
the self-balancing static load test operation method of the building foundation pile is characterized by comprising a preparation stage, an installation stage and a detection stage;
the preparation stage is used for completing production and transportation work of concrete, a reinforcement cage and a load box, and selecting the load box with a matched type according to a construction site, and pre-calculating a self-balancing balance point and a load box embedding position;
the installation stage completes the installation work of the load box and comprises the steps of precast concrete of the load box, welding the load box and the reinforcement cage, lowering the welded reinforcement cage, pouring pile body concrete and protecting a pile head pipeline;
in the step of welding the load box and the reinforcement cage, the poured load box is laterally hung by a crane to complete the following welding work: welding a load box stirrup, butting the load box with the reinforcement cage, arranging a displacement pipeline and an oil pipe, and reinforcing the reinforcement cage by using a coil reinforcement;
in the step of putting the welded reinforcement cage and pouring the pile body concrete, when the elevation of the pile top is lower than the ground, the pile top is put on the ground to place the simple reinforcement cage for guiding and protecting the displacement pipeline and the oil pipe;
the detection stage at least comprises the steps of building a reference beam and a reference pile, building a tent, carrying out on-site detection and grouting on the broken surface of the load box.
The operation method has clear thought and strong operability, and by the arrangement of each stage, the tasks to be completed in each stage and step are defined, so that the time of the whole test period can be saved, the construction standardization can be realized, the human errors can be reduced, and the test accuracy can be improved;
the device used in the operation method is simple, the occupied space is small, hundreds of tons or thousands of tons of materials do not need to be transported, a heavy reaction frame does not need to be constructed, a plurality of test piles can be tested simultaneously, and the test preparation work is time-saving, labor-saving and safe;
after the test, the test pile can still be used as an engineering pile, pressure grouting can be carried out on the load box by utilizing a pre-buried pipeline, and the test pile can be ensured to reach the performance of the engineering pile.
The operation method is suitable for vertical compression static load tests and vertical pulling static load tests of bored piles, manual hole digging piles and tubular piles in soft soil, cohesive soil, silt, sandy soil, gravel soil, rock stratum and special rock soil.
The working principle is that a load box is placed at the position or the bottom of a balance point of a test pile, a pressure applying oil pipe and a displacement measuring device are connected to the top of the pile, after concrete is maintained to a standard age or reaches a designed strength, the load box is pressed towards an upper-jacking pile body through a top pressure pump, simultaneously, the bottom of the pile is pressed downwards, the frictional resistance and the end resistance of the pile are mutually opposite, a load-displacement curve is respectively obtained, and a bearing capacity of the pile top and a Q-s curve of displacement are obtained after superposition; the self-balancing method is a static load test method based on seeking loading counter force in a pile foundation, and can determine the limit bearing capacity, the pile side resistance sharing condition, the pile end resistance sharing condition and the like of a foundation pile by measuring two Q-S curves of an upper pile section and a lower pile section and corresponding S-lgt curves and adopting a corresponding test data equivalent conversion method and a corresponding bearing capacity determination method.
Selecting a load box: the integral (round full hydraulic cross section) load box is used for the test of an end bearing pile, meets the requirement of a small pile diameter test, and is generally used for friction piles with the diameter of 1.2 meters or less than 1.2 meters; the combined load box meets the requirements of large pile diameter and large tonnage tests, is generally used for friction piles with the diameter of more than 1.2 meters, and can be flexibly combined according to the requirements of loading tonnage.
Further, collecting geological exploration data of a construction site, and calculating a self-balancing balance point according to the type of rock and soil and combining with the on-site working condition; when the limit end resistance of the test pile is smaller than the limit side friction resistance, placing the load box at a balance point; when the resistance of the limit end of the test pile is larger than the limit side friction resistance, the load box is arranged at the pile end; when the test pile is an uplift pile, the load box is arranged at the pile end; the embedding position of the load box meets the requirement that the balance coefficient of the pile side resistance of the upper pile section, the pile side resistance of the lower pile section and the end resistance is between 1.2 and 1.5; the position of the pile load box is not less than 0.5m from the pile bottom.
In the preparation stage, the concrete, the reinforcement cage and the load box are manufactured in advance and transported to a test site, and meanwhile, the balance point is calculated and the installation position of the load box is determined according to a geological survey report, so that the time of the installation stage and the detection stage can be effectively saved, and the construction period is shortened.
Because the load box is a disposable embedded device, 100% of reliability is the premise of successful test, before the load box leaves a factory, the load box is subjected to rating pressure test (the rated load is 1.3 times of the required maximum loading force) and calibration, so that sufficient and accurate loading force is ensured to be generated, and test failure is avoided.
Further, in the step of welding the load box and the reinforcement cage, the welding of the load box stirrup is as follows: welding a stirrup at the bottom side of the load box, wherein the outer diameter of the stirrup is consistent with the inner diameter of the reinforcement cage;
the method for butting the load box and the reinforcement cage comprises the following steps: firstly, a load box is respectively welded with a reinforcement cage and a stirrup, the reinforcement cage and the load box must be ensured to be vertical during welding, and the eccentricity is controlled within 5 degrees; welding an upper horn-shaped guide rib and a lower horn-shaped guide rib, wherein the diameter of the guide rib is not less than phi 16mm, and the included angle between the guide rib and the load box is more than 60 degrees; one end of each guide rib is welded on the inner wall of the hole in the upper panel of the load box or the edge of the guide pipe hole, and the other end of each guide rib is welded with the corresponding main rib of the reinforcement cage; the number of the guide ribs is not less than that of the main ribs of the reinforcement cage, and the distance between the guide ribs is less than the caliber of the concrete guide pipe; by adopting the welding mode, enough connection strength can be ensured, welding workload is reduced, and the concrete guide pipe can be guided to carry out secondary hole cleaning and pouring through the central hole of the load box;
the method for encrypting the reinforcing cage coil bars comprises the following steps: and within 2 meters of the upper and lower ranges of the load box, the transverse stirrups of the reinforcement cage are encrypted, so that the distance between the transverse stirrups is less than 10 cm. The compression strength of the upper surface and the lower surface of the load box can be obviously improved.
Further, in the method for butting the load box and the reinforcement cage, for the annular load box: manufacturing an L-shaped rib, welding one end of the L-shaped rib with the main rib of the upper reinforcement cage, welding the other end of the L-shaped rib with the upper cover plate of the load box, wherein the specification of the L-shaped rib is consistent with that of the main rib of the reinforcement cage, the length of the welding part of the L-shaped rib and the load box is 5cm less than the annular width of the load box, and the L-shaped rib is connected with the main rib of the reinforcement cage to ensure that the L-shaped rib and the main; for a modular load box: the load box is respectively welded with the main reinforcements of the reinforcement cage at the upper and lower surfaces and the stirrups at the upper and lower surfaces; for an integral load box: and the main reinforcement of the reinforcement cage is welded with the stirrup additionally welded on the upper surface of the load box. The arrangement of the L-shaped ribs can further improve the connection strength.
Further, in the method for arranging the displacement pipeline and the oil pipe, the displacement pipeline comprises a displacement rod and a displacement protection pipe, the outer diameter of the displacement rod is larger than or equal to 16mm, the wall thickness of the displacement rod is larger than or equal to 1.5mm, the outer diameter of the displacement protection pipe is larger than or equal to 32mm, the wall thickness of the displacement protection pipe is larger than or equal to 2.0mm, the displacement protection pipe is connected to the ground along a reinforcement cage according to the designed length of the hole depth, the displacement protection pipe is connected through screw threads, a raw material belt is wound when the displacement protection pipe. The measuring device is arranged at 90 degrees and is respectively used for measuring the up-and-down displacement of the pile body. The displacement pillar that the size is great is convenient for on the one hand the interlude of displacement pole and circuit is laid, and on the other hand can regard as the slip casting pipe to use, to crack department slip casting after experimental completion.
Further, in the method for arranging the displacement pipeline and the oil pipe, the oil pipe is coiled at the load box in advance, and is continuously unfolded when the reinforcement cage is put down and is bound to the ground along the guide rib; the oil pipe is a high-pressure hose, is connected with the oil pipe after the load box and the reinforcement cage are welded for at least half an hour, is provided with protective guide reinforcements, and is hidden under the protective guide reinforcements to be led to the reinforcement cage. The arrangement mode can prevent the sealing ring in the oil pipe joint from being scalded by high temperature during welding, and reduce the damage of the oil pipe; the oil pipe can also be damaged for preventing the poured concrete.
Furthermore, in the step of putting down the welded steel reinforcement cage and pouring the pile body concrete, two lifting hooks are used for lifting, a main hook is connected with the upper part of the steel reinforcement cage, an auxiliary hook is connected with the middle lower part of the steel reinforcement cage, and the main hook and the auxiliary hook simultaneously lift and horizontally lift the steel reinforcement cage; receive the main messenger of colluding the upper portion of steel reinforcement cage is hoisted gradually, puts simultaneously vice colluding makes the lower part of steel reinforcement cage descends gradually, until the steel reinforcement cage is vertical state, removes vice colluding, through the main colluding with vertical the steel reinforcement cage is transferred downtheholely, carries out the ligature to displacement pipeline and oil pipe at the in-process of transferring.
Adopt this kind of mode of lifting by crane can be quick erect load case and steel reinforcement cage that the level was placed, labour saving and time saving to can prevent that the load case from receiving the bending.
Further, the pile head pipeline protection is carried out in a rest period between the completion of the placement of the reinforcement cage and the start of detection on site, and warning marks are arranged on the pile head to protect the displacement pipeline and the oil pipe. Prevent that grout from leaking into, guarantee that the pipeline is not destroyed, prevent that personnel from missing the stake hole, the security is good.
And in the detection stage, the normal use of a data acquisition system and an oil hydraulic pump is ensured, and a three-phase uninterrupted four-wire system distribution box with stable voltage is required to be equipped on site. The distribution box has leakage protection, two power supplies of 380V and 220V, and the capacity is not less than 10 kilowatts.
Furthermore, in the installation stage, various pipelines which are detected in the test need to be protected before and after installation; the scheme of protection before installation is that the engineering piles around the test pile are constructed preferentially by adopting a U-shaped route by taking the test pile as a center, and the engineering pile construction at the opening of the U-shaped route is finally completed; the construction is carried out according to the sequence, so that the test pile detection facility is not damaged by the construction of peripheral engineering piles when the engineering piles are constructed, and a construction site is not required to be paved (a test pile construction channel is reserved);
the protection scheme after installation is as follows: the test pile adopts a full reinforcement cage, and the main reinforcement and the reinforcing hoop reinforcement of the reinforcement cage at the hollow part are consistent with the reinforcement of the reinforcement cage at the upper end of the effective pile length; the spiral stirrup is phi 8 multiplied by 200 mm.
The engineering pile has deep holes (about 18m on average), and a full cage can be adopted to bind a displacement rod, a displacement protective pipe and other auxiliary detection pipes/lines for self-balancing detection on the main reinforcement of the reinforcement cage, so that bending caused by over deep holes and no attachment of the detection pipes/lines is avoided; because the hole wall of the engineering pile is easy to collapse under the unprotected condition, the full cage has a certain supporting effect on the hole wall, and the damage to the detection pipe/line caused by the collapse of the hole wall is avoided. The protection scheme comprehensively considers factors such as cost, construction period and operability and the like so as to ensure that various pipelines to be detected are not damaged after test piles are formed.
Further, the grouting step of the broken surface of the load box comprises the following steps: after the test is finished, the displacement rod and the detection line are taken out, and cement paste with the strength not lower than that of the pile body is injected into the position where the concrete at the load box is pulled open by a grouting pump through the displacement protective pipe; grouting is alternately carried out on the pipe by the pipe or a plurality of pipes, and the grouting pressure and the grouting amount are controlled according to double requirements.
During the test, the concrete at the load box is pulled open (the gap width is equal to the sum of the upward and downward residual displacements after unloading), but other parts of the pile body are not damaged, the upper pile and the lower pile are still connected together by the load box, after the test, the left-over displacement protective pipe is fully utilized for grouting, the tested pile can still be used as an engineering pile after grouting, and the cost and the time are saved.
Compared with the prior art, the invention has the beneficial effects that: 1. the operation method has clear thought and strong operability, and by the arrangement of each stage, the tasks to be completed in each stage and step are defined, so that the time of the whole test period can be saved, the construction standardization can be realized, the human errors can be reduced, and the test accuracy can be improved; 2. the welding structure of the reinforcement cage and the load box is reasonable and stable, the welding mode is simple and effective, and the bearing capacity of the load box is ensured; 3. the horizontally placed load box and the reinforcement cage can be quickly erected in a downward hoisting mode of the reinforcement cage, time and labor are saved, and the load box can be prevented from being bent; 4. in the whole operation process, the pipeline protection measures used for detection are good, and test failure or engineering delay caused by pipeline damage is avoided; and the pipelines can be reasonably utilized for final grouting work.
Drawings
FIG. 1 is a schematic structural view of an annular load box used in an operation method of a self-balancing static load test of a building foundation pile according to the present invention;
FIG. 2 is a schematic diagram of a butt joint of an annular load box and a reinforcement cage used in the operation method of the self-balancing static load test of the building foundation pile of the invention;
FIG. 3 is a schematic diagram of the arrangement of ground detection equipment in the self-balancing static test operation method of the building foundation pile of the present invention;
FIG. 4 is a schematic structural view of a combined load box used in a self-balancing static test operation method of a building foundation pile according to the present invention;
FIG. 5 is a schematic diagram of the positions of a test pile and an engineering pile in the operation method of the self-balancing static load test of the building foundation pile of the present invention;
FIG. 6 is a schematic diagram of pouring a cross section of a load box in the operation method of the self-balancing static load test of the building foundation pile of the present invention;
in the figure: 1. an annular load box; 2. a pressure unit; 3. a flow conductor; 4. an oil pipe; 5. hooping; 6. a reinforcement cage; 7. a main rib; 8. a guide rib; 9. l-shaped ribs; 10. a displacement rod; 11. a displacement protective pipe; 12. a displacement sensor; 13. a reference beam; 14. a support; 15. a data line; 16. a reference pile; 17. a data recorder; 18. a display; 19. pile testing; 20. engineering piles; 21. a pump truck.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The self-balancing static load test operation method of the building foundation pile is characterized by comprising a preparation stage, an installation stage and a detection stage;
the preparation stage is used for completing production and transportation work of concrete, a reinforcement cage and a load box, and selecting the load box with a matched type according to a construction site, and pre-calculating a self-balancing balance point and a load box embedding position;
the installation stage completes the installation work of the load box and comprises the steps of precast concrete of the load box, welding the load box and the reinforcement cage, lowering the welded reinforcement cage, pouring pile body concrete and protecting a pile head pipeline;
in the step of welding the load box and the reinforcement cage, the poured load box is laterally hung by a crane to complete the following welding work: welding a load box stirrup, butting the load box with the reinforcement cage, arranging a displacement pipeline and an oil pipe, and reinforcing the reinforcement cage by using a coil reinforcement;
in the step of putting the welded reinforcement cage and pouring the pile body concrete, when the elevation of the pile top is lower than the ground, the pile top is put on the ground to place the simple reinforcement cage for guiding and protecting the displacement pipeline and the oil pipe;
the detection stage at least comprises the steps of building a reference beam and a reference pile, building a tent, carrying out on-site detection and grouting on the broken surface of the load box.
The operation method has clear thought and strong operability, and by the arrangement of each stage, the tasks to be completed in each stage and step are defined, so that the time of the whole test period can be saved, the construction standardization can be realized, the personal errors can be reduced, and the test accuracy can be improved.
The working principle is that a load box is placed at the position or the bottom of a balance point of a test pile, a pressure applying oil pipe and a displacement measuring device are connected to the top of the pile, after concrete is maintained to a standard age or reaches a designed strength, the load box is pressed towards an upper-jacking pile body through a top pressure pump, simultaneously, the bottom of the pile is pressed downwards, the frictional resistance and the end resistance of the pile are mutually opposite, a load-displacement curve is respectively obtained, and a bearing capacity of the pile top and a Q-s curve of displacement are obtained after superposition; the self-balancing method is a static load test method based on seeking loading counter force in a pile foundation, and can determine the limit bearing capacity, the pile side resistance sharing condition, the pile end resistance sharing condition and the like of a foundation pile by measuring two Q-S curves of an upper pile section and a lower pile section and corresponding S-lgt curves and adopting a corresponding test data equivalent conversion method and a corresponding bearing capacity determination method.
The first embodiment is as follows:
the embodiment selects an annular load box, and the annular load box is arranged at a balance point.
As shown in fig. 1, the annular load box 1 and related accessories are transported to the site, and when unloading, the annular load box and the related accessories are lightly carried and lightly placed to prevent the pipelines from being collided and damaged; when in storage, the rain-proof and dust-proof are well achieved.
Annular load box precast concrete: the flow guide body 3 of the annular load box 1 faces upwards and is placed on the flat ground, and an oil pipe, a grouting joint, a displacement rod and the like on the other side are well protected; pouring concrete into the flow guide body 3, fully tamping the concrete by using a vibrating rod, wherein the concrete strength is not lower than that of the pile body, and commercial concrete is adopted; within 10 hours of completion of the filling, the annular load chamber 1 must not be moved.
The annular load box 1 is welded with the reinforcement cage 6 (the reinforcement cage 6 is divided into an upper reinforcement cage and a lower reinforcement cage which are respectively welded on the upper side and the lower side of the annular load box 1):
(1) the annular load box is welded with lower stirrups: and a circle of stirrups 5 are welded at the bottom side of the annular load box 1, and the outer diameter of each stirrup 5 is consistent with the inner diameter of the reinforcement cage 6.
(2) The annular load box is butted with the upper reinforcement cage: manufacturing an L-shaped rib 9, welding one end of the L-shaped rib 9 with a main rib 7 of an upper reinforcement cage, welding the other end of the L-shaped rib with an upper cover plate of an annular load box 1, wherein the specification of the L-shaped rib 9 is consistent with that of the main rib 7 of the reinforcement cage, the length of the welding part of the L-shaped rib 9 and the annular load box is 5cm less than the annular width of the annular load box, and the connecting part of the L-shaped rib 9 and the annular load box is connected with the main rib 7 of the reinforcement cage to ensure that the L; during welding, the reinforcement cage 6 and the annular load box 1 must be coaxial, and the eccentricity is controlled within 5 degrees;
the L-shaped ribs 9 are arranged in a central symmetry mode in an annular mode, so that the sealing device of the annular load box 1 is prevented from being burnt out due to overhigh local temperature during welding, and the oil pipe 4 and the joint of the oil pipe are protected.
(3) The annular load box is butted with the lower reinforcement cage: the annular load box 1 and the main reinforcement 7 of the lower reinforcement cage are welded with the stirrup 5 below or connected by L-shaped reinforcements, the reinforcement cage 6 and the annular load box 1 must ensure the coaxial line during welding, and the eccentricity is controlled within 5 degrees.
(4) Then welding an upper horn-shaped guide rib 8 and a lower horn-shaped guide rib 8, wherein the diameter of each guide rib 8 is not less than phi 16mm, and the included angle between each guide rib 8 and the annular load box 1 is more than 60 degrees; one end of each guide rib 8 is welded on the inner wall of the middle hole of the upper cover plate of the annular load box 1, and the other end of each guide rib is welded with the corresponding main rib 7 (corresponding to at least one reinforcing cage one by one); the number of the guide ribs 8 is not less than that of the main ribs 7 of the reinforcement cage, and the distance is less than the caliber of the concrete guide pipe; adopt such welding mode can guarantee sufficient joint strength, reduce welding work volume simultaneously, can guide the concrete pipe moreover to carry out the secondary through load box center hole and clear the hole and pour.
(5) Arranging a displacement pipeline and an oil pipe: the displacement pipeline comprises a displacement rod 10 and a displacement protection pipe 11, the outer diameter of the displacement rod 10 is larger than or equal to 16mm, the wall thickness of the displacement protection pipe 11 is larger than or equal to 1.5mm, the outer diameter of the displacement protection pipe 11 is larger than or equal to 32mm, the wall thickness of the displacement protection pipe is larger than or equal to 2.0mm, the displacement protection pipe is connected to the ground along a reinforcement cage 6 according to the designed length of the hole depth, the displacement protection pipe is connected through screw threads, a raw material belt is wound when the displacement. The displacement rod 10 protects the upper displacement rod and the lower displacement rod, is arranged on the annular surface at 90 degrees and is respectively used for measuring the vertical displacement of the pile body. The displacement protective pipe 11 with large size is convenient for the insertion and arrangement of the displacement rod 10 and the circuit on the one hand, and can be used as a grouting pipe on the other hand to perform grouting on a crack after the test is completed.
The oil pipe 4 is coiled on the annular load box 1 in advance, and is continuously unfolded when the reinforcement cage 6 is put down and is bound to the ground along the guide rib 8; the oil pipe 4 is a high-pressure hose, the connection of the oil pipe 4 is carried out after the annular load box 1 and the reinforcement cage 6 are welded for at least half an hour, protective guide reinforcements are arranged, and the oil pipe 4 is hidden under the protective guide reinforcements and led to the reinforcement cage 6. The arrangement mode can prevent the sealing ring in the oil pipe joint from being scalded by high temperature during welding, and reduce the damage of the oil pipe; the damage to the oil pipe can be prevented when concrete is poured; the oil pipe joint is a 24-degree cone M14x1.5, the oil pipe joint cannot be over-stressed when being screwed down, and the torque is controlled to be 25-35 Nm.
(6) The method for encrypting the reinforcing cage coil bars comprises the following steps: and within 2 meters of the upper and lower sides of the annular load box 1, the transverse stirrups of the reinforcement cage 6 are encrypted, so that the distance between the transverse stirrups is less than 10 cm. The compression strength of the upper surface and the lower surface of the annular load box 1 and the connection strength of the reinforcement cage after the butt joint is completed can be obviously improved.
Further, a welded reinforcement cage 6 is placed downwards, two lifting hooks are used for lifting, a main hook is connected with the upper portion of the reinforcement cage 6, an auxiliary hook is connected with the middle lower portion of the reinforcement cage 6, and the main hook and the auxiliary hook are lifted up and horizontally lifted up at the same time; receive the main messenger of colluding the upper portion of steel reinforcement cage 6 is hoisted gradually, puts simultaneously vice colluding the messenger the lower part of steel reinforcement cage 6 descends gradually, until steel reinforcement cage 6 is vertical state, removes vice colluding, through the main colluding with vertical the stake is downthehole to 6 transfers of steel reinforcement cage, further ligatures displacement pipeline and oil pipe 4 under the in-process of putting.
Adopt this kind of mode of lifting by crane can be quick erect load case and steel reinforcement cage that the level was placed, labour saving and time saving to can prevent that the load case from receiving the bending.
In the lowering process, the displacement pipeline and the oil pipe need to be bound, the displacement pipeline is bound by binding wires every 0.5m, and the oil pipe is bound by binding wires every 1 m; when the displacement inhaul cable is adopted, 4 main ribs are required to be added on the outer side of the steel reinforcement cage and used for guiding the displacement inhaul cable to be bound to the ground all the time so as to ensure the verticality and effective protection of the displacement inhaul cable; when the elevation of the pile top is lower than the ground, a simple reinforcement cage (8 main reinforcements, one reinforcement hoop per 3 meters) is required to be placed from the pile top to the ground for guiding and protecting pipelines.
Pouring pile body concrete: the guide pipe reaches the pile end through the annular load box and is poured with concrete, when the concrete approaches the annular load box, the speed of pulling the guide pipe is slowed down, and when the height of the concrete at the upper part of the annular load box is more than 2.5m, the bottom end of the guide pipe can be pulled through the annular load box and the concrete is poured to the pile top; the concrete slump of the lower part of the annular load box is preferably more than 200mm, so that the concrete can be conveniently turned up at the annular load box;
further, the pile head pipeline protection is carried out in a rest period between the completion of the placement of the reinforcement cage and the start of detection on site, and warning marks are arranged on the pile head to protect the displacement pipeline and the oil pipe. Prevent that grout from leaking into, guarantee that the pipeline is not destroyed, prevent that personnel from missing the stake hole, the security is good.
A detection step:
in order to ensure that the detection result of the self-balancing pile foundation is reliable and accurate, the following process is adopted: the method comprises the steps of early preparation, erection of a reference beam and a reference pile, erection of a tent, preparation of a power supply, starting detection, finishing detection and grouting on the disconnected surface of a load box.
As shown in fig. 3, the reference beam 13 and the reference pile 16 are set up: one end of the reference beam 13 is hinged with one reference pile 16, and the other end of the reference beam is welded with the other reference pile 16; the length of the reference beam 13 is not less than 6 times of the pile diameter of the test pile (the total length is not less than 2 meters), the pile center is taken as the center, and 3 times of the pile diameter of each side is erected right above the test pile; the reference pile 16 should be driven to a sufficient depth, typically not less than 1.5 meters.
When the reference beam 13 and the reference pile 16 are erected, connecting a plurality of displacement sensors 12 with a displacement rod 10 respectively, and fixing each displacement sensor 12 with the reference beam 13 through a support 14 respectively; the data line of each displacement sensor 12 is pulled to a data recorder 17, and a plurality of data lines 15 are bound and combed to avoid mutual winding; the data recorder 17 is connected with the display 18 and is used for displaying the detection data and the structure in real time.
Erecting a tent: during testing, in order to reduce the influence of external factors such as temperature, rainwater and wind as much as possible, the windproof tent frame is erected, so that the testing equipment, the reference beam 13, the reference pile 16, the displacement sensor 12, the displacement rod 10 and the like are not influenced by the external environment during detection, errors are reduced, and the detection accuracy is improved.
Preparing a power supply: the normal use of a data acquisition system and an oil hydraulic pump is ensured, and a three-phase uninterrupted four-wire system distribution box with stable voltage is required to be equipped on site. The distribution box has leakage protection, two power supplies of 380V and 220V, and the capacity is not less than 10 kilowatts.
And (3) starting detection: the loading process and time are required to meet the regulations of relevant specifications, such as the regulations of the building foundation pile self-balancing static test technical regulation (JGJ/T403-2017), the foundation pile static test self-balancing method (JT/T738-2009) and other standards.
And (4) finishing detection: after the detection is finished, storing the recorded data; and (4) recovering detection equipment, sensors, circuits and the like, wiping the detection equipment, the loading equipment and the like, and boxing and putting the detection equipment, the sensors, the circuits and the like.
Grouting on the broken surface of the load box: after the test is finished, taking out the line or the displacement rod, and injecting cement paste with the strength not lower than that of the pile body into the position where the concrete at the load box is pulled open by using a grouting pump through a displacement protective pipe; grouting is alternately carried out on the pipe by the pipe or a plurality of pipes, and the grouting pressure and the grouting amount are controlled according to double requirements.
During the test, the concrete at the load box is pulled open (the gap width is equal to the sum of the upward and downward residual displacements after unloading), but other parts of the pile body are not damaged, the upper pile and the lower pile are still connected together by the load box, after the test, the left-over displacement protective pipe is fully utilized for grouting, the tested pile can still be used as an engineering pile after grouting, and the cost and the time are saved.
Example two:
the difference between the embodiment and the first embodiment is that an integral load box is selected; accordingly, there are differences in the installation stage, and specifically, there are the following points.
Pouring concrete at the bottom of the integral load box, pouring the concrete into the bottom space, and then fully tamping by using a vibrating rod;
during welding, a stirrup is welded on the upper surface of the integral load box; the main reinforcement of the reinforcement cage is welded with the stirrup additionally welded on the upper surface of the integral load box; the process of butt joint of the integral load box and the reinforcement cage is simpler, the operation is easier, and the time can be saved.
Example three:
the difference between the embodiment and the first embodiment is that a combined load box is selected; accordingly, there are differences in the installation stage, and specifically, there are the following points.
As shown in fig. 4, when the concrete is precast, the lower flow conductor is poured first, and then the upper flow conductor is poured; when the upper diversion body is poured, the oil pipes 4 are respectively dragged out from the small holes on the side wall of the upper diversion body 3; and finally fully tamping by using a vibrating rod after pouring. And stirrups 5 are respectively welded on the upper side and the lower side of the combined load box.
Need not to set up L shape muscle when the welding, directly through welding loudspeaker muscle direction muscle and stirrup and combination formula load case fixed can.
Example four:
the embodiment provides a scheme for protecting various pipelines for detection.
In the detection process, various pipelines related to detection in the test need to be protected before installation and protected after installation.
As shown in fig. 5, the scheme of protection before installation is that, taking a test pile 19 as a center, construction is preferentially carried out on the engineering piles 20 (such as A, B, C, D, E, F, H) around the test pile by adopting a 'U' -shaped route, and finally construction of the engineering pile G at the opening of the 'U' -shaped route is completed; the construction is carried out according to the sequence, so that the test pile detection facility is not damaged by the construction of peripheral engineering piles when the engineering piles are constructed, and a construction site is not required to be paved (a test pile construction channel is reserved);
the protection scheme after installation is as follows: the test pile adopts a full reinforcement cage, and the main reinforcement and the reinforcing hoop reinforcement of the reinforcement cage at the hollow part are consistent with the reinforcement of the reinforcement cage at the upper end of the effective pile length; the spiral stirrup is phi 8 multiplied by 200 mm.
The engineering pile has deep holes (about 18m on average), and a full cage can be adopted to bind a displacement rod, a displacement protective pipe and other auxiliary detection pipes/lines for self-balancing detection on the main reinforcement of the reinforcement cage, so that bending caused by over deep holes and no attachment of the detection pipes/lines is avoided; because the hole wall of the engineering pile is easy to collapse under the unprotected condition, the full cage has a certain supporting effect on the hole wall, and the damage to the detection pipe/line caused by the collapse of the hole wall is avoided. The protection scheme comprehensively considers factors such as cost, construction period and operability and the like so as to ensure that various pipelines to be detected are not damaged after test piles are formed.
Example five:
the embodiment provides a scheme for grouting the broken surface of the load box.
As shown in fig. 6, the displacement sheath 11 that has been provided is used as a grouting pipe. In order to ensure the safety of the test pile after the test converted into the engineering pile, the test pile (foundation pile) is grouted, so that the completeness and smoothness of the displacement protective pipe 11 during installation are ensured, and the requirement on the displacement protective pipe 11 is met on the pressure resistance and the reliability.
The displacement protective pipe 11 is made of a steel pipe, the displacement protective pipe 11 is connected by adopting screw thread connection or sleeve welding, slurry leakage is avoided, the upper end of the displacement protective pipe is covered, and no foreign matter exists in the pipe. The displacement protective pipe 11 can bear hydrostatic pressure of more than 3MPa after connection. The number of the displacement protective pipes 11 is not less than two.
The grouting material is preferably low-alkali portland cement which is fresh, stable in performance and not lower than Po52.5 in strength grade, the water-cement ratio of the slurry is preferably 0.5-0.65, and 7% of expanding agent and 1% of water reducing agent are added to ensure that the slurry strength meets the pile body strength requirement and does not shrink.
The cement slurry can be injected by pressure after being fully and uniformly stirred by the pump truck 21, the slurry is continuously and slowly stirred in the grouting process, and the slurry is filtered by a mesh screen before being pumped. The grouting steps are as follows:
a) before grouting, a water pressing test is carried out to confirm whether a grouting pipe is blocked or not and determine a grouting initial pressure value. Therefore, the mud sucked by negative pressure and the dust in the grouting pipe can be washed clean when the load box is opened, and the grouting effect is ensured. The water pressing time is generally 1-2min, the pump pressure obviously decreases during the pressure opening on the basis of the pressure opening, and then water pressing is continued until the water flow returned by the adjacent grouting pipes becomes clear, so that grouting can be performed.
b) The grout is added to be pressed in from one grouting pipe, and fresh grout is blown out from the other grouting pipe. The pipe head can be sealed by adopting pressure slurry supplement, the pressure is more than 2MPa, and the duration is recommended to be 1 hour. And replacing one pipe with another pipe, and alternately performing grouting. The total pressure is about 0.8 to 1.5t (controlled by the grouting pressure and grouting amount)
c) When the grouting pressure is lower than the normal value for a long time or the grout is blown out from the ground, the intermittent grouting or the grout water-cement ratio reduction is required. In the intermittent grouting, the intermittent time is preferably 30-60 min.
d) In order to ensure the effect of pressure filling treatment, the pile is fully filled after normal grouting, sealing and pressure maintaining are carried out on the grouting pipe orifice, the pressure maintaining time is not less than 15min, and the grouting amount is recorded.
e) The grouting flow rate can not exceed 75L/min.
f) And (3) observing the pressure meter and the injection condition of the slurry during grouting, and recording: pile number, pile diameter, pile forming time, grouting pressure, termination pressure, water cement ratio, grouting amount and termination time.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. The self-balancing static load test operation method of the building foundation pile is characterized by comprising a preparation stage, an installation stage and a detection stage;
the preparation stage is used for completing production and transportation work of concrete, a reinforcement cage and a load box, and selecting the load box with a matched type according to a construction site, and pre-calculating a self-balancing balance point and a load box embedding position;
the installation stage completes the installation work of the load box and comprises the steps of precast concrete of the load box, welding the load box and the reinforcement cage, lowering the welded reinforcement cage, pouring pile body concrete and protecting a pile head pipeline;
in the step of welding the load box and the reinforcement cage, the poured load box is laterally hung by a crane to complete the following welding work: welding a load box stirrup, butting the load box with the reinforcement cage, arranging a displacement pipeline and an oil pipe, and reinforcing the reinforcement cage by using a coil reinforcement;
in the step of putting the welded reinforcement cage and pouring the pile body concrete, when the elevation of the pile top is lower than the ground, the pile top is put on the ground to place the simple reinforcement cage for guiding and protecting the displacement pipeline and the oil pipe;
the detection stage at least comprises the steps of building a reference beam and a reference pile, building a tent, carrying out on-site detection and grouting on the broken surface of the load box.
2. The operation method for the self-balancing static test of the building foundation pile according to claim 1, wherein geological exploration data of a construction site is collected, and self-balancing balance points are calculated according to rock-soil types and site working conditions; when the limit end resistance of the test pile is smaller than the limit side friction resistance, placing the load box at a balance point; when the resistance of the limit end of the test pile is larger than the limit side friction resistance, the load box is arranged at the pile end; when the test pile is an uplift pile, the load box is arranged at the pile end; the embedding position of the load box meets the requirement that the balance coefficient of the pile side resistance of the upper pile section, the pile side resistance of the lower pile section and the end resistance is between 1.2 and 1.5; the position of the pile load box is not less than 0.5m from the pile bottom.
3. The operation method for self-balancing static load test of the building foundation pile as claimed in claim 1, wherein in the step of welding the load box and the reinforcement cage, the load box stirrup is welded by: welding a stirrup at the bottom side of the load box, wherein the outer diameter of the stirrup is consistent with the inner diameter of the reinforcement cage;
the method for butting the load box and the reinforcement cage comprises the following steps: firstly, a load box is respectively welded with a reinforcement cage and a stirrup, the reinforcement cage and the load box must be ensured to be vertical during welding, and the eccentricity is controlled within 5 degrees; welding an upper horn-shaped guide rib and a lower horn-shaped guide rib, wherein the diameter of the guide rib is not less than phi 16mm, and the included angle between the guide rib and the load box is more than 60 degrees; one end of each guide rib is welded on the inner wall of the hole in the upper panel of the load box or the edge of the guide pipe hole, and the other end of each guide rib is welded with the corresponding main rib of the reinforcement cage; the number of the guide ribs is not less than that of the main ribs of the reinforcement cage, and the distance between the guide ribs is less than the caliber of the concrete guide pipe;
the method for encrypting the reinforcing cage coil bars comprises the following steps: and within 2 meters of the upper and lower ranges of the load box, the transverse stirrups of the reinforcement cage are encrypted, so that the distance between the transverse stirrups is less than 10 cm.
4. The method of operation of a self-balancing static test of a construction foundation pile as claimed in claim 1 or 3, wherein in the method of interfacing the load box with the reinforcement cage, for an annular load box: manufacturing an L-shaped rib, welding one end of the L-shaped rib with the main rib of the upper reinforcement cage, welding the other end of the L-shaped rib with the upper cover plate of the load box, wherein the specification of the L-shaped rib is consistent with that of the main rib of the reinforcement cage, the length of the welding part of the L-shaped rib and the load box is 5cm less than the annular width of the load box, and the L-shaped rib is connected with the main rib of the reinforcement cage to ensure that the L-shaped rib and the main; for a modular load box: the load box is respectively welded with the main reinforcements of the reinforcement cage at the upper and lower surfaces and the stirrups at the upper and lower surfaces; for an integral load box: and the main reinforcement of the reinforcement cage is welded with the stirrup additionally welded on the upper surface of the load box.
5. The operation method of the self-balancing static load test of the building foundation pile according to claim 1, wherein in the method for arranging the displacement pipeline and the oil pipe, the displacement pipeline comprises a displacement rod and a displacement protection pipe, the outer diameter of the displacement rod is more than or equal to 16mm, the wall thickness of the displacement rod is more than or equal to 1.5mm, the outer diameter of the displacement protection pipe is more than or equal to 32mm, the wall thickness of the displacement protection pipe is more than or equal to 2.0mm, the displacement protection pipe is connected to the ground along a reinforcement cage according to the designed length of the hole depth, the construction foundation pile is connected through screw threads, a raw material belt is wound when.
6. The operation method for the self-balancing static load test of the building foundation pile according to claim 1, wherein in the method for arranging the displacement pipeline and the oil pipe, the oil pipe is coiled at the load box in advance, and is continuously unfolded when the reinforcement cage is put down and is bound to the ground along a guide rib; the oil pipe is a high-pressure hose, is connected with the oil pipe after the load box and the reinforcement cage are welded for at least half an hour, is provided with protective guide reinforcements, and is hidden under the protective guide reinforcements to be led to the reinforcement cage.
7. The operation method for the self-balancing static load test of the building foundation pile as claimed in claim 1, wherein in the step of lowering the welded reinforcement cage and pouring concrete of the pile body, two lifting hooks are used for lifting, a main hook is connected with the upper part of the reinforcement cage, an auxiliary hook is connected with the middle lower part of the reinforcement cage, and the main hook and the auxiliary hook simultaneously lift and horizontally lift the reinforcement cage; receive the main messenger of colluding the upper portion of steel reinforcement cage is hoisted gradually, puts simultaneously vice colluding makes the lower part of steel reinforcement cage descends gradually, until the steel reinforcement cage is vertical state, removes vice colluding, through the main colluding with vertical the steel reinforcement cage is transferred downtheholely, carries out the ligature to displacement pipeline and oil pipe at the in-process of transferring.
8. The operation method for the self-balancing static load test of the building foundation pile according to claim 1, wherein the pile head pipeline protection is performed in a rest period from the completion of the steel reinforcement cage lowering to the start of the field detection, and a warning mark is arranged on the pile head to protect the displacement pipeline and the oil pipe.
9. The operation method for the self-balancing static load test of the building foundation pile as claimed in claim 1, wherein in the installation stage, pre-installation protection and post-installation protection are required for various pipelines involved in the test and detected; the scheme of protection before installation is that the engineering piles around the test pile are constructed preferentially by adopting a U-shaped route by taking the test pile as a center, and the engineering pile construction at the opening of the U-shaped route is finally completed; the protection scheme after installation is as follows: the test pile adopts a full reinforcement cage, and the main reinforcement and the reinforcing hoop reinforcement of the reinforcement cage at the hollow part are consistent with the reinforcement of the reinforcement cage at the upper end of the effective pile length.
10. The building foundation pile self-balancing static test operation method according to claim 1, wherein the step of grouting the broken surface of the load box is as follows: after the test is finished, the displacement rod and the detection line are taken out, and cement paste with the strength not lower than that of the pile body is injected into the position where the concrete at the load box is pulled open by a grouting pump through the displacement protective pipe; grouting is alternately carried out on the pipe by the pipe or a plurality of pipes, and the grouting pressure and the grouting amount are controlled according to double requirements.
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