CN111827375A - Construction method for detecting foundation pile load based on self-balancing static load - Google Patents
Construction method for detecting foundation pile load based on self-balancing static load Download PDFInfo
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Abstract
The invention relates to the technical field of engineering detection tests, discloses a construction method for detecting foundation pile load based on self-balancing static load, and solves the problem of low test efficiency during foundation pile load tests. The construction method for detecting the load of the foundation pile based on the self-balancing static load comprises the following steps: (1) arranging a reinforcement cage; (2) putting down a reinforcement cage; (3) pouring concrete; (4) arranging a balance beam: one end of the balance beam is hinged with the first reference pile, the other end of the balance beam is welded with the second reference pile, and then a protective cover is built outside the test pile with the balance beam; (5) loading and unloading in a test; (6) observing displacement; (7) terminating the loading; (8) filling an annular load box: when the load detection test is finished, whether the test pile is damaged or not is judged, if the test pile is damaged, concrete is injected into the oil cylinder of the annular load box through the pre-buried pipe, and the pre-buried pipe is connected with the oil cylinder of the annular load box through the one-way valve to convert the test pile into the engineering pile.
Description
Technical Field
The invention relates to the technical field of engineering detection tests, in particular to a construction method for detecting foundation pile load based on self-balancing static load.
Background
With the continuous improvement of urban planning and the continuous maturity of urban rail transit construction technology, urban rail transit is widely applied. In the construction of urban rail transit, the traditional methods for foundation pile load tests include a pile loading method and an anchor pile method, the pile loading method and the anchor pile method are the same in principle, pressure is applied to the top of a test pile through a jack, and whether the bearing capacity of the test pile meets design requirements or not is judged by observing the counter force of the jack.
However, when the two experimental methods are used for carrying out the foundation pile load test, a heavy reaction frame needs to be constructed, hundreds of tons or thousands of tons of load materials are also needed, and particularly, when the foundation pile load test is carried out, the test pile can be used only once, so that the time required for carrying out the foundation pile load test is increased, and the test efficiency is not high.
Disclosure of Invention
The invention mainly aims to provide a construction method for detecting the load of a foundation pile based on self-balancing static load, which aims to realize quick and effective pressure test on the foundation pile and solve the problem of low test efficiency when the foundation pile load test is carried out.
The invention provides a construction method for detecting foundation pile load based on self-balancing static load, which is characterized by comprising the following steps of:
(1) arranging a reinforcement cage: welding an annular load box and a reinforcement cage, arranging a displacement rod, a sounding pipe, a grouting pipe and an oil pipe on the reinforcement cage, determining the position of a loading system, and then performing water injection detection on the sounding pipe;
(2) and (4) placing a reinforcement cage: hoisting the set reinforcement cage into the foundation pile well, and embedding the reinforcement strain gauge in the foundation pile well;
(3) pouring concrete: pouring concrete into a grouting pipe penetrating through the annular load box, pouring the concrete to the bottom of a foundation pile well through the grouting pipe, lifting the grouting pipe upwards while pouring the concrete, wherein the distance between the pipe orifice of the grouting pipe and the bottom of the foundation pile well is smaller than the distance between a lower cover of the annular load box and the bottom of the foundation pile well, when the height of the concrete at the upper part of the annular load box exceeds 2.5m, continuously lifting the grouting pipe upwards so that the distance between the pipe orifice of the grouting pipe and the bottom of the foundation pile well is larger than the distance between an upper cover of the annular load box and the bottom of the foundation pile well, continuously pouring the concrete so that the distance between the concrete and the bottom of the foundation pile well reaches a threshold value, and pulling out the grouting pipe to form a test pile;
(4) arranging a balance beam: hinging one end of a balance beam with a first reference pile, welding the other end of the balance beam with a second reference pile, arranging a displacement sensor on the balance beam, connecting the displacement sensor to the top of a displacement rod, and then building a protective cover outside a test pile on which the balance beam is installed;
(5) and (3) test loading and unloading: pressurizing or decompressing the oil cylinder of the annular load box by adopting a loading system through an oil pipe, and enabling the annular load box to move at a constant speed through pressure variation in the oil cylinder;
(6) and (3) displacement observation: acquiring displacement data of the test pile through a data acquisition system in the loading process and the unloading process of the test pile, and observing and recording the displacement data in the data acquisition system;
(7) and (4) terminating the loading: when the test pile is damaged, or when an observed value in a data acquisition system reaches a maximum estimated value, or when the accumulated moving distance of the annular load box exceeds the standard travel of the annular load box, or when the accumulated displacement of the displacement rod exceeds 40mm, or when a steep descending section for judging the ultimate load exists in a displacement curve corresponding to the annular load box in the data acquisition system, and the downward displacement settlement of the test pile exceeds 60mm, or when the current downward displacement of the displacement rod is more than 2 times of the downward displacement of the previous stage under the action of the level load of the test pile, and the current downward displacement of the displacement rod exceeds 24h and is not relatively stable yet, the loading is terminated;
(8) filling an annular load box: when the load detection test finishes, judge whether experimental stake is lossless, if experimental stake is lossless, then through the buried pipe to pour into the concrete into in the hydro-cylinder of annular load case, the buried pipe pass through the check valve with the hydro-cylinder of annular load case is connected, turns into the engineering stake with experimental stake.
Optionally, the welding annular load case specifically includes with the steel reinforcement cage:
utilize right-angle rib will go up the steel reinforcement cage welding on the excircle edge of the upper cover of annular load case, spot weld the loudspeaker muscle respectively on last steel reinforcement cage inner wall and on the interior circle edge of upper cover, then spot welding through strengthening rib fixed connection loudspeaker muscle is in go up the welding point on the steel reinforcement cage inner wall, confirm the annular load case for go up the gradient of steel reinforcement cage and be less than 5 thousandths, in order to weld annular load case with go up the mode welding of steel reinforcement cage annular load case and lower steel reinforcement cage.
Optionally, arranging the displacement rod, the sounding pipe, the grouting pipe and the oil pipe on the reinforcement cage specifically includes:
arranging a first protection pipe outside a displacement rod, clamping the first protection pipe on the displacement rod by using hydraulic tongs, fixing the displacement rod on an upper cover or a lower cover of the annular load box respectively, fixing the displacement rod on the inner wall of a reinforcement cage, and installing an acoustic pipe;
arranging a second protective pipe outside the sounding pipe, clamping the second protective pipe on the sounding pipe by using a hydraulic clamp, sequentially penetrating the sounding pipe through an upper cover and a lower cover of the annular load box, fixing the sounding pipe on the inner wall of the reinforcement cage, performing water injection detection on the sounding pipe, and installing a grouting pipe when the sounding pipe is not water-tight;
arranging a third protective pipe outside the grouting pipe, connecting the grouting pipe with the third protective pipe in a threaded manner, fixing the grouting pipe on the inner wall of the reinforcement cage, and installing an oil pipe;
and the annular load box is connected with the oil pipe, and the oil pipe is used for conveying or pumping oil into the annular load box.
Optionally, the number of the displacement rods is 4, wherein the tail ends of 2 displacement rods are connected to the upper surface of the upper cover of the annular load box, the tail ends of the other 2 displacement rods are connected to the upper surface of the lower cover of the annular load box, and the displacement rods are led out of the ground;
the number of the acoustic pipes is 3, the upper parts of the acoustic pipes are led out of the ground, and the lower parts of the acoustic pipes are flush with the bottom of the foundation pile well;
the number of the grouting pipes is 2, and the upper parts of the grouting pipes are led out of the ground;
the number of the oil pipes is 1, and the upper parts of the oil pipes are led out of the ground.
Optionally, the maximum pressurization value of the loading system is 60MPa, and the pressurization precision of the loading system is 0.4 MPa.
Optionally, hoisting the arranged reinforcement cage to the foundation pile well specifically includes:
and hoisting the set reinforcement cage in the foundation pile well by using a crane, determining the position of the annular load box, and protecting an oil pipe led out of the ground and a steel pipe end enclosure of the reinforcement cage by using a protection device.
Optionally, the protective cover is a windproof canopy frame, and the windproof canopy frame is arranged outside all the test devices led out of the ground.
Optionally, the loading system is configured to perform a step loading mode, the loading value of each test pile is 2 times of the maximum bearing value of the pile top, each step loading value is one fifteenth of the estimated limit bearing value of the test pile, and the test piles are unloaded in a step unloading mode, where the test piles are unloaded in 7 steps.
Optionally, the test pile diameter of the test pile is 1.5m or 1.6 m.
Optionally, the displacement observation specifically includes:
after the test piles are loaded in a grading manner through a loading system, respectively measuring and reading the measurement value of a displacement sensor once within the 5 th minute, the 15 th minute, the 30 th minute, the 45 th minute and the 60 th minute after each grade of load loading within the 1 st hour, measuring and reading the measurement value of the displacement sensor once within the 30 th minute after each grade of load loading, and when the measurement value of the displacement sensor is not more than 0.1mm within the 30 th minute, carrying out next grade of load loading and measuring and reading the measurement value of the displacement sensor;
after the test piles are unloaded in a grading manner through a loading system, observing the displacement resilience amount of the test piles after each grade of load is unloaded, wherein the observation method of the displacement resilience amount is the same as that during the grading loading of the test piles, after the displacement resilience amount of the test piles is stable, carrying out next grade of load unloading, after the load of the test piles is unloaded to 0, at least measuring and reading the measured value of the displacement sensor for 1.5 hours, measuring and reading the measured value of the displacement sensor once every 15 minutes within the initial 30 minutes within 1.5 hours of measuring and reading the displacement sensor, and measuring and reading the measured value of the displacement sensor once every 30 minutes after the initial 30 minutes.
According to the construction method for detecting the load of the foundation pile based on the self-balancing static load, the foundation pile load is detected by adopting the operation flow of arranging the reinforcement cage, lowering the reinforcement cage, pouring concrete, arranging the balance beam, carrying out test loading and unloading, observing displacement, terminating loading and filling the annular load box, and under the condition that the test pile is ensured to be intact and undamaged, the concrete is poured into the grouting pipe again to fill the gap in the annular load box, so that the test pile is converted into the engineering pile, the time for processing the test pile is saved, and the test efficiency of the foundation pile load test is improved.
Drawings
Fig. 1 is a schematic flow chart of a construction method for detecting a load of a foundation pile based on a self-balancing static load according to a first embodiment of the present invention;
FIG. 2 is a schematic diagram of a reinforcement cage arrangement according to an embodiment of the present invention;
FIG. 3 is a schematic view of a connection structure between an annular load box and a reinforcement cage according to an embodiment of the present invention;
reference numerals:
1. an annular load box; 2. a reinforcement cage; 3. a displacement rod; 4. a sound detection tube; 5. a grouting pipe; 6. an oil pipe; 7. loading the system; 8. a displacement sensor; 9. a balance beam; 10. a data acquisition system;
101. an upper cover; 102. a lower cover;
201. putting a reinforcement cage; 202. lowering a reinforcement cage; 203. a right-angle rib; 204. a horn rib; 205. and (5) reinforcing ribs.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. Unless otherwise specified, in the present invention, if there is an orientation or positional relationship indicated by terms of "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, rather than to indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore, the terms describing orientation or positional relationship in the present invention are for illustrative purposes only, and should not be construed as limiting the present patent, specific meanings of the above terms can be understood by those of ordinary skill in the art in light of the specific circumstances in conjunction with the accompanying drawings.
Unless expressly stated or limited otherwise, the terms "disposed," "connected," and "connected" are used broadly and encompass, for example, being fixedly connected, detachably connected, or integrally connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Other aspects, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which form a part of this specification, and which illustrate, by way of example, the principles of the invention. In the referenced drawings, the same or similar components in different drawings are denoted by the same reference numerals.
Referring to fig. 1, fig. 1 is a schematic flow chart of a first embodiment of a construction method for detecting a load of a foundation pile based on a self-balancing static load, the method including the following steps:
step one, arranging a reinforcement cage: welding an annular load box and a reinforcement cage, arranging a displacement rod, a sounding pipe, a grouting pipe and an oil pipe on the reinforcement cage, determining the position of a loading system, and then performing water injection detection on the sounding pipe;
referring to fig. 2, fig. 2 shows a layout structure of the reinforcement cage. Arranging the reinforcement cage is the process of fixing the annular load box 1, the displacement rod 3, the sounding pipe 4, the grouting pipe 5 and the oil pipe 6 on the reinforcement cage 2, and before arranging the reinforcement cage 2, the reinforcement cage 2 needs to be configured according to the length of the foundation pile and the lengths of the displacement rod 3, the sounding pipe 4, the grouting pipe 5 and the oil pipe 6 need to be configured according to the length of the reinforcement cage. In the experiment, the adopted test pile is that the pile body strength reaches the design requirement or the age reaches 28 days, the diameter of the test pile is 1.5m or 1.6m, the number of the displacement rods 3 is 4, the number of the sound measuring tubes 4 is 3, the number of the grouting tubes 5 is 2, the number of the oil tubes 6 is 1, an annular load box 1 (load box with anti-shearing function) capable of being used for loading is adopted, the annular load box 1 mainly comprises an upper cover, a piston, an oil cylinder and a lower cover, the outer diameters of the upper cover and the lower cover are slightly smaller than the outer diameter of the test pile, and the length of the upper cover and the lower cover which is smaller than the outer diameter of the test pile is 200 mm. The concrete method for arranging the reinforcement cage comprises the following steps:
(1) method for connecting annular load box and reinforcement cage
Referring to fig. 3, the connection structure between the annular load box and the reinforcement cage can be seen from fig. 3. Firstly, the annular load box 1 is placed on the flat ground, the upper reinforcement cage 201 is welded on the outer circle edge of the upper cover 101 of the annular load box through the right-angle rib 203, secondly, the horn rib 204 is respectively spot-welded on the inner wall of the upper reinforcement cage 201 and the inner circle edge of the upper cover, then, the reinforcing rib 205 is fixedly connected with the horn rib 204 and is spot-welded on the welding point on the inner wall of the upper reinforcement cage 201, the inclination of the annular load box 1 relative to the upper reinforcement cage is ensured to be less than 5 per thousand, finally, the annular load box 1 and the lower reinforcement cage 202 are welded in a mode of welding the annular load box 1 and the upper reinforcement cage 201, and the lower cover 102 of the annular load box 1 and the lower reinforcement cage 202 are welded together through the right-angle rib. When the annular load box 1 moves up and down due to a load, the annular load box 1 applies vertical pressure to the upper cage 201 and the lower cage 202, respectively.
(2) Displacement rod, sounding pipe, grouting pipe and oil pipe connecting method
Connecting method for all displacement rods
First pillar is sheathe in 4 displacement pole 3's outside at first, and utilize hydraulic tong to press from both sides first pillar tight on the displacement pole, then with 2 displacement pole 3 terminal fixed connection on annular load case 1's upper cover 101 upper surface, with 2 displacement pole 3 in addition pass through upper cover 101, and displacement pole 3 terminal fixed connection on annular load case 1's lower cover 102 upper surface, displacement pole 3 evenly distributed on annular load case 1's upper cover 101 and lower cover 102, and be 90 between displacement pole 3 and the annular load case 1 and arrange, tie up 4 displacement poles 3 on the inner wall of steel reinforcement cage 2 at last, in addition, ground is all drawn forth on 4 displacement pole 3's upper portion.
Method for connecting sound measuring tube
Firstly, the second protective pipe is sleeved on the outer portion of 3 acoustic pipes 4, the second protective pipe is clamped on the acoustic pipes 4 through hydraulic pliers, then the 3 acoustic pipes 4 sequentially penetrate through the upper cover 101 and the lower cover 102 of the annular load box and are fixed on the annular load box 1, the acoustic pipes 4 and the annular load box 1 are arranged at 90 degrees, finally the 3 acoustic pipes 4 are tied up on the inner wall of the steel reinforcement cage 2, in addition, the ground is led out from the upper portions of the 3 acoustic pipes 4, and the lower portions of the acoustic pipes 4 are flush with the bottom of the foundation pile well. After the fixing of the sounding pipe 4 is completed, a water injection test needs to be performed on the sounding pipe 4, and when the sounding pipe 4 does not leak water, the next step of operation is performed.
Connecting method of grouting pipe
Firstly, the third protective pipe is sleeved on the outer portions of 2 independent grouting pipes 5, the grouting pipes 5 are in threaded connection with the third protective pipe, then the 2 grouting pipes 5 sequentially penetrate through the inner circle of the upper cover 101 and the inner circle of the lower cover 102 and are fixed on the annular load box 1, the grouting pipes 5 and the annular load box 1 are arranged at 90 degrees, finally the grouting pipes 5 are tied up on the inner wall of the reinforcement cage 2, and in addition, the upper portion of the grouting pipes 5 is led out of the ground.
Oil pipe connecting method
One end of an oil pipe 6 is connected with an oil cylinder of the annular load box 1, the other end of the oil pipe 6 is led out of the ground and connected with a loading system 7, the oil pipe 6 is coiled on the annular load box 1, and when the lower portion of the steel reinforcement cage enters the foundation pile well, the oil pipe is straightened and led out of the ground.
(3) Setting method of loading system
The loading system 7 is connected with an oil pipe 6 led out of the ground, oil is filled into the oil pipe 6 through the loading system 7, the loading system 7 is a high-pressure oil pump, the maximum pressurization value is 60MPa, and the pressurization precision is 0.4 MPa.
Step two, placing the reinforcement cage: hoisting the set reinforcement cage into the foundation pile well, and embedding the reinforcement strain gauge in the foundation pile well;
and (3) utilizing a crane to place the lower part of the reinforcement cage arranged in the step one into the foundation pile well, determining the position of the annular load box in the reinforcement cage in the foundation pile well, and simultaneously determining the position of the steel bar strain gauge in the foundation pile well. Buried steel bar strainometer and surface-mounted steel bar strainometer are two kinds in the steel bar strainometer is taken, what adopt in this application is buried steel bar strainometer, and it is pre-buried inside the foundation pile well when putting the steel reinforcement cage down, exerts pressure through annular load case 1 to the concrete after pouring, detects the pressure variation that the concrete received. In addition, put the steel reinforcement cage that arranges down after, need make the safeguard procedures with the steel pipe head of oil pipe and steel reinforcement cage, if: the installation can dismantle baffle or encapsulation protective layer, prevents when concreting, and the concrete is poured into steel pipe or oil pipe.
Step three, concrete pouring: pouring concrete into a grouting pipe penetrating through the annular load box, pouring the concrete to the bottom of the foundation pile well through the grouting pipe, and lifting the grouting pipe upwards while pouring the concrete, wherein the distance between the pipe orifice of the grouting pipe and the bottom of the foundation pile well is smaller than the distance between a lower cover of the annular load box and the bottom of the foundation pile well, when the height of the concrete at the upper part of the annular load box exceeds 2.5m, the grouting pipe is continuously lifted upwards so that the distance between the pipe orifice of the grouting pipe and the bottom of the foundation pile well is larger than the distance between an upper cover of the annular load box and the bottom of the foundation pile well, and the concrete is continuously poured so that the distance between the concrete and the bottom of the foundation pile well reaches a threshold value, and the grouting pipe is pulled out to form a test pile;
concrete can be poured into the foundation pile well after the steel reinforcement cage is placed, a certain amount of concrete test blocks need to be manufactured before the concrete is poured, and the concrete strength and the elasticity modulus are tested before the test, so that the consistency of the concrete can reach the degree of fixing the steel reinforcement cage. When concrete is poured, pouring concrete into the grouting pipe, pouring the concrete to the bottom of the foundation pile well through the grouting pipe penetrating through the annular load box, and lifting the grouting pipe upwards, wherein the distance between the pipe orifice of the grouting pipe and the bottom of the foundation pile well is smaller than the distance between the lower cover of the annular load box and the bottom of the foundation pile well; with the continuous upturning of concrete, when the height of the concrete on the upper portion of the annular load box exceeds 2.5m, the grouting pipe continues to be lifted upwards, so that the distance between the pipe opening of the grouting pipe and the bottom of the foundation pile well is larger than the distance between the upper cover of the annular load box and the bottom of the foundation pile well, the distance between the concrete and the bottom of the foundation pile well is larger and larger until a threshold value is reached, the grouting pipe is pulled out, and a test pile is formed. In the concrete pouring process, the grouting pipes are lifted upwards by adopting a slow lifting mode, the concrete slump of the lower part of the annular load box is preferably larger than 200mm, the concrete is convenient to overturn at the annular load box, and the upper empty pile is lengthened to the position below the first concrete support bottom elevation by adopting plain concrete.
Step four, arranging a balance beam: one end of the balance beam is hinged with the first reference pile, the other end of the balance beam is welded with the second reference pile, a displacement sensor is arranged on the balance beam and connected to the top of the displacement rod, and then a protective cover is built outside the test pile with the balance beam;
after the concrete is poured, a balance beam 9 as shown in fig. 2 is arranged above the arranged reinforcement cage, wherein one end of the balance beam 9 is hinged with a first reference pile, and the other end is welded with a second reference pile, wherein the first reference pile and the second reference pile are two foundation columns for fixing and balancing the balance beam. In addition, the length of the balance beam is determined by the influence area of the test pile, generally, the length of the balance beam is not less than 6 times of the pile diameter of the test pile, and the test pile diameter of the test pile in the test is 1.5m and 1.6 m. After the balance beam is arranged, 6 displacement sensors 8 are magnetically connected to the balance beam as shown in fig. 2, wherein 2 displacement sensors 8 are used for measuring the upward displacement of the annular load box of the pile body, 2 displacement sensors 8 are used for measuring the downward displacement of the annular load box of the pile body, and 2 displacement sensors 8 are used for measuring the upward displacement of the pile top.
In addition, in order to reduce the influence of external factors during test of the test piles as much as possible, a protective cover is built outside the test piles, and the test instruments are completely covered in the protective cover, so that the test instruments are not influenced by the external environment. Wherein, the protective cover can be provided with a windproof tent frame.
It is further described that, during the period of the foundation pile carrying out the load test, two power supplies of 380V and 220V need to be ensured to supply power for the test uninterruptedly, and during the load test, no large vibration needs to be generated within 10 meters around the test pile, so as to ensure the accuracy of the measured data.
Step five, test loading and unloading: pressurizing or decompressing the oil cylinder of the annular load box by adopting a loading system through an oil pipe, and enabling the annular load box to move at a constant speed through pressure variation in the oil cylinder;
when the load capacity of the test pile is tested, one end of an oil pipe is connected with a loading system, the other end of the oil pipe is connected with an oil cylinder of an annular load box, the loading system is used for sucking or pressing oil into the oil cylinder of the annular load box through the oil pipe, the pressure in the oil cylinder is changed through the change of the oil quantity in the oil cylinder, the annular load box moves an upper cover and a lower cover under the pushing of an internal piston due to the change of the pressure in the oil cylinder, the pressure in concrete is changed due to the movement of the annular load box, the pressure received by a steel reinforcement cage is changed accordingly, and whether the load capacity born by the steel reinforcement cage is within a standard range is measured.
When the test piles are subjected to load detection, a low-speed load maintaining graded loading method is adopted, and the load capacity of each test pile is tested by uniformly and continuously loading and unloading loads to the test piles. And loading each test pile by 7 levels of loading capacity during loading, wherein the loading value of each test pile is 2 times of the maximum bearing value of the pile top, the loading value of each level is one fifteenth of the estimated limit bearing capacity of the test pile, and meanwhile, the test piles are unloaded by adopting the same graded unloading mode.
Step six, displacement observation: acquiring displacement data of the test pile through a data acquisition system in the loading process and the unloading process of the test pile, and observing and recording the displacement data in the data acquisition system;
during the loading and unloading process of the test pile, the data acquisition system 10 in fig. 2 is used to observe the test data, and the data acquisition mode is as follows:
(1) after the test piles are loaded in a grading manner through the loading system, respectively measuring and reading the measurement value of the displacement sensor once within 5 minutes, 15 minutes, 30 minutes, 45 minutes and 60 minutes within 1 hour after each grade of load loading, measuring and reading the measurement value of the displacement sensor once within 30 minutes after 1 hour after each grade of load loading, and when the measurement value of the displacement sensor is not more than 0.1mm within 30 minutes, carrying out next grade of load loading and measuring the measurement value of the displacement sensor;
(2) after the test piles are unloaded in a grading manner through the loading system, the displacement rebound amount of the test piles is observed after each grade of load is unloaded, the observation method of the displacement rebound amount is the same as that in the grading loading of the test piles, after the displacement rebound amount of the test piles is stable, the next grade of load is unloaded, when the load of the test piles is unloaded to 0, the measurement and reading can be stopped after the measurement and reading of the measurement value of the displacement sensor is carried out for at least 1.5 hours, the measurement value of the displacement sensor is measured and read every 15 minutes within the initial 30 minutes within 1.5 hours of the measurement and reading of the displacement sensor, and the measurement value of the displacement sensor is measured and read every 30 minutes after the initial 30 minutes.
After the self-balancing test of the test pile begins, the load generated by the annular load box is transmitted upwards and downwards along the axial direction of the test pile. Assuming that the structure of the test pile is intact (no damage, no segregation and fracture of concrete) after the test pile is loaded, the strain amount generated by the concrete under the action of each level of load is equal to the strain amount generated by the reinforcement cage, the stress-strain relationship obtained by each reinforcement cage under the action of each level of load can be measured by measuring the reinforcement strain gauge embedded in the foundation pile well in advance, the stress-strain relationship of the corresponding foundation pile section can be calculated according to the obtained measurement value, and the strain amount in the corresponding foundation pile section differential unit can also be calculated. Therefore, the transmission rule of the axial force, the axial force and the frictional resistance of the pile body of the section of each test pile under the action of each level of load along with the change of the load and the depth is obtained, and whether the test pile is qualified or not can be judged through the data obtained by the test and the calculation.
Step seven, terminating the loading: when the test pile is damaged, or when an observed value in a data acquisition system reaches a maximum estimated value, or when the accumulated moving distance of the annular load box exceeds the standard travel of the annular load box, or when the accumulated displacement of the displacement rod exceeds 40mm, or when a steep descending section for judging the ultimate load exists in a displacement curve corresponding to the annular load box in the data acquisition system, and the downward displacement settlement of the test pile exceeds 60mm, or when the current downward displacement of the displacement rod is more than 2 times of the downward displacement of the previous stage under the action of the level load, and the current downward displacement of the displacement rod exceeds 24h and is not relatively stable yet, the loading is terminated;
in the process of carrying out the load test, the conditions for terminating the test loading are as follows:
(1) the test pile is damaged due to overlarge pressure;
(2) the observed value in the data acquisition system reaches the maximum estimated value of the test pile;
(3) after applying pressure, the accumulated displacement of the annular load box exceeds the travel of the load box;
(4) after the pressure is applied, the accumulated displacement of the displacement rod exceeds 40 mm;
(5) in the display of a data acquisition system, a steep drop section for judging the ultimate load exists on the lower displacement curve of the annular load box, and the downward displacement settlement of the test pile exceeds 60 mm;
(6) when the test pile is under the action of grade load, the current downward displacement of the displacement rod is 2 times larger than the previous downward displacement under the action of previous grade load, and the current downward displacement of the displacement rod exceeds 24h and is not relatively stable yet.
When the 6 conditions appear in the experiment, the load on the test pile needs to be stopped in time.
If the adopted foundation pile is an engineering pile in the foundation pile load detection test, the condition for terminating the test loading is as follows:
(1) the engineering pile is damaged due to overlarge pressure;
(2) the observed value in the data acquisition system reaches the maximum estimated value of the engineering pile;
(3) after applying pressure, the accumulated displacement of the annular load box exceeds the travel of the load box;
(4) after the pressure is applied, the accumulated displacement of the displacement rod exceeds 20 mm;
(5) in the display of the data acquisition system, a steep drop section for judging the ultimate load exists on the lower displacement curve of the annular load box, and the downward displacement settlement of the engineering pile exceeds 40 mm;
(6) when the engineering pile is under the action of grade load, the current downward displacement of the displacement rod is 2 times larger than the previous downward displacement under the action of previous grade load, and the current downward displacement of the displacement rod exceeds 24h and is not relatively stable yet.
When the 6 conditions appear in the experiment, the load on the engineering pile needs to be stopped in time.
Step eight, filling an annular load box: when the load detection test is finished, whether the test pile is damaged or not is judged, if the test pile is damaged, concrete is injected into the oil cylinder of the annular load box through the pre-buried pipe, and the pre-buried pipe is connected with the oil cylinder of the annular load box through the one-way valve to convert the test pile into the engineering pile.
After the test is finished, whether the load of the test pile reaches the engineering standard or not and whether the test pile is intact or not is determined by analyzing the data information collected in the test, if the load of the test pile reaches the engineering standard or not and is intact, concrete is poured into the annular load box through the embedded pipe on the annular load box, and the gap in the annular load box is filled, so that the test pile can be used as the engineering pile, and the waste of resources is reduced.
The specific method for filling the annular load box comprises the following steps:
the method comprises the steps of pouring concrete into a pre-buried pipe arranged on an upper cover of an annular load box, pouring the concrete poured into the pre-buried pipe into an oil cylinder of the annular load box through a one-way valve, grouting through a liquid inlet pipe of the annular load box, closing the liquid inlet pipe after the grouting concentration of the concrete in a grout return pipe on the annular load box is consistent with the concentration of the initially poured concrete, stopping pouring the concrete into the pre-buried pipe after the pressure value in the annular load box is kept stable, and filling the gap between the oil cylinder and a piston of the annular load box with the concrete at the moment.
According to the construction method for detecting the load of the foundation pile based on the self-balancing static load, the foundation pile load is detected by adopting the operation flow of arranging the reinforcement cage, lowering the reinforcement cage, pouring concrete, arranging the balance beam, carrying out test loading and unloading, observing displacement, terminating loading and filling the annular load box, and under the condition that the test pile is ensured to be intact and undamaged, the concrete is poured into the grouting pipe again to fill the gap in the annular load box, so that the test pile is converted into the engineering pile, the time for processing the test pile is saved, and the test efficiency of the foundation pile load test is improved.
Further, based on the first embodiment of the construction method for detecting the load of the foundation pile based on the self-balancing static load, the second embodiment of the construction method for detecting the load of the foundation pile based on the self-balancing static load is provided.
The project main line design starting point mileage of a certain project A is BBB66+576, the terminal mileage is BBB66+288, and the project main line design starting point mileage is located in city C. The station length of the D station in the C city is 270m, the open cut section length is 444m, and the station and section demarcation mileage is BBB66+ 864. The diameter of the bearing pile of the D station is 1.5m, the pile length of the solid pile is 28-34 m, the length of the bearing pile entering the middle gasification rock stratum is 4.4-9.4 m, and the total number of the bearing pile is 40. The diameter of the bearing pile in the open cut section is 1.6m, the length of the solid pile is 20.7-33.7 m, the length of the bearing pile entering the medium-stroke gasified rock stratum is 3.1-13.2 m, and the total number of the bearing pile is 100. According to the design specification requirement, the engineering drilled pile is not less than three, and the single pile bearing capacity is determined by adopting a static load test. In order to ensure that the test process is safe, reliable, economical and reasonable, the static load test pile is tested by a self-balancing static load method, wherein 1 pile is respectively selected from the open cut interval from the D station, the D station to the E station and the auxiliary structure for testing, and the parameter statistical table of the test pile is as follows:
table 1 statistical table of pile parameters
Note that:
1. this time, the test pile is adopted for testing.
2. According to the regulation of the specification, the test pile providing basis for design is loaded to the limit load (namely, the breaking load), and the test scheme is considered to be about 2.2.
The quality control standard is as follows:
1. acceptance criteria, regulations
The construction method for detecting the load of the foundation pile is required to meet the technical specification for detecting the foundation pile of the building (JGJ 106-2014); technical Specifications for building pile foundations (JGJ 94-2008); building foundation design Specifications (DBJ 15-31-2003); building foundation pile self-balancing static load test technical regulation (JGJ/T403-2017); self-balanced static test technical protocol (DBJ 15-103) -; designing a hospital drawing and an engineering geological survey report.
2. Pre-test work arrangement
2.1 theoretical analysis and calculation
(1) Providing the design bearing capacity requirement of the foundation pile by a design unit;
(2) the testing unit analyzes the ultimate bearing capacity of the foundation pile according to the geological survey data, the steel reinforcement cage big sample drawing and the pile layout drawing;
(3) and (4) calculating by a test unit according to a self-balancing static load test method test pile theory to determine a balance point and a test load value.
2.2 identification and calibration of test elements of instruments and apparatus
(1) Calibration of loading system (electric oil pump, high pressure oil pipe, annular load box, etc.)
And the accuracy of test load is ensured after system calibration is carried out by a provincial metering department before loading.
(2) Calibration of test instruments
All electronic instruments (electronic watch, pressure gauge and long-distance displacement sensor) are debugged and calibrated in a laboratory by a provincial metering standard station.
2.3 on-site testing of test piles
(1) Processing the end sockets of the reinforcement cage of the test pile, opening the end sockets of the plurality of protective pipes, and performing an ultrasonic detection test;
(2) checking whether the load box works normally or not, and testing whether the instrument works normally or not;
(3) arranging a balance beam (reference beam) to finish the final debugging work of a test instrument and equipment;
(4) performing concrete test block strength and elastic modulus tests;
(5) test records are made for each test, the loading tonnage and the pile body displacement are checked, and measures for protecting the oil pipe, preventing impact and vibration of instruments and equipment and avoiding the influence of weather conditions are made in the whole test process;
(6) and (5) timely arranging and calculating related data to determine the destructive load of the test pile.
The quality assurance measures are as follows:
1. quality control work before reinforcing construction
(1) Before testing, organizing technicians can review the bidding documents and drawings, and practically understand and master the testing requirements and the testing technical standards;
(2) according to the requirements and characteristics of the test, an organization technician writes a specific test organization design, strictly compiles a test plan according to the content requirements of a quality system program, determines applicable implementation equipment and implements the equipment, emphasizes control means, monitoring equipment, auxiliary devices and resources (including manpower) in the test process to meet the specified requirements, and partially makes detailed test schemes for important procedures such as test pile construction, test and the like according to the technical requirements of the test so as to ensure that the quality of the test meets the requirements.
(3) Before testing, technical background work of all parts and procedures is needed, so that each tester can clearly master the technical specification requirements of the procedures to be tested, and the accuracy and the specification of the testing operation are ensured.
2. Quality control work of the whole testing process is well done
(1) And (4) matching human resources meeting the test requirements, and establishing a high-quality test team. The method specifically organizes the study of testers and performs necessary post training before testing to ensure the technical requirements of testing, operators need to hold effective post operation certificates, and technicians need to be familiar with the technical requirements of the project and know the characteristics and the field conditions of the project to ensure the normal operation of the testing;
(2) various devices meeting the test requirements are matched, and the devices can be subjected to field test after being overhauled, tested and qualified through inspection, so that the functions of the various devices in the test are ensured, and the requirements of the whole test are met;
(3) reinforcing test technology management;
(4) and recording the qualification of the detection equipment before all the test equipment enters the field.
The analysis of the test data is collated as follows:
1. description of engineering overview, test pile purpose and requirements, instrumentation, measurements and testing process;
2. drawing a Q-s curve of load and settlement, an s-lgt curve of settlement and time logarithm and an s-lgQ curve of settlement and load logarithm, and providing loading and unloading curves and an actually measured data table;
3. providing a recommended value of the vertical ultimate load bearing capacity of the test pile;
4. and providing a test pile engineering detection general report, and providing a conclusion and a suggestion.
The technical efficacy analysis was as follows:
the traditional foundation pile load testing method comprises a pile loading method and an anchor pile method, wherein an oil pressure jack is adopted in the pile loading method to apply load on a pile top, the counter force of the jack is balanced with the pile weight on a reaction 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. The equipment investment in the earlier stage of two technologies is many, no matter installation, inspection or maintenance in the operation process, the cost of manpower, material resources and financial resources is very high, and efficiency of software testing is not ideal moreover, and equipment can not used repeatedly.
By adopting the construction method for detecting the load of the foundation pile based on the self-balancing static load, the detection equipment can be used for testing in the environments of water, deep foundation pits, narrow site test piles and the like due to the fact that the equipment required for testing is simple; under the condition of ensuring that the load of the foundation pile is accurately detected, the test is not interfered by the field by arranging the protective cover, and the accuracy of test data is ensured; meanwhile, the annular load box is arranged, and the data acquisition system is used for acquiring the displacement of the displacement rod, so that the manpower, material resources and financial resources required by a foundation pile load test are reduced, and the test efficiency of the test is improved; concrete is poured into the annular load box after the test, and the test pile qualified in the test is used as the engineering pile, so that the waste of resources is reduced.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A construction method for detecting foundation pile load based on self-balancing static load is characterized by comprising the following steps:
(1) arranging a reinforcement cage: welding an annular load box and a reinforcement cage, arranging a displacement rod, a sounding pipe, a grouting pipe and an oil pipe on the reinforcement cage, determining the position of a loading system, and then performing water injection detection on the sounding pipe;
(2) and (4) placing a reinforcement cage: hoisting the set reinforcement cage into the foundation pile well, and embedding the reinforcement strain gauge in the foundation pile well;
(3) pouring concrete: pouring concrete into a grouting pipe penetrating through the annular load box, pouring the concrete to the bottom of a foundation pile well through the grouting pipe, lifting the grouting pipe upwards while pouring the concrete, wherein the distance between the pipe orifice of the grouting pipe and the bottom of the foundation pile well is smaller than the distance between a lower cover of the annular load box and the bottom of the foundation pile well, when the height of the concrete at the upper part of the annular load box exceeds 2.5m, continuously lifting the grouting pipe upwards so that the distance between the pipe orifice of the grouting pipe and the bottom of the foundation pile well is larger than the distance between an upper cover of the annular load box and the bottom of the foundation pile well, continuously pouring the concrete so that the distance between the concrete and the bottom of the foundation pile well reaches a threshold value, and pulling out the grouting pipe to form a test pile;
(4) arranging a balance beam: hinging one end of a balance beam with a first reference pile, welding the other end of the balance beam with a second reference pile, arranging a displacement sensor on the balance beam, connecting the displacement sensor to the top of a displacement rod, and then building a protective cover outside a test pile on which the balance beam is installed;
(5) and (3) test loading and unloading: pressurizing or decompressing the oil cylinder of the annular load box by adopting a loading system through an oil pipe, and enabling the annular load box to move at a constant speed through pressure variation in the oil cylinder;
(6) and (3) displacement observation: acquiring displacement data of the test pile through a data acquisition system in the loading process and the unloading process of the test pile, and observing and recording the displacement data in the data acquisition system;
(7) and (4) terminating the loading: when the test pile is damaged, or when an observed value in a data acquisition system reaches a maximum estimated value, or when the accumulated moving distance of the annular load box exceeds the standard travel of the annular load box, or when the accumulated displacement of the displacement rod exceeds 40mm, or when a steep descending section for judging the ultimate load exists in a displacement curve corresponding to the annular load box in the data acquisition system, and the downward displacement settlement of the test pile exceeds 60mm, or when the current downward displacement of the displacement rod is more than 2 times of the downward displacement of the previous stage under the action of the level load of the test pile, and the current downward displacement of the displacement rod exceeds 24h and is not relatively stable yet, the loading is terminated;
(8) filling an annular load box: when the load detection test finishes, judge whether experimental stake is lossless, if experimental stake is lossless, then through the buried pipe to pour into the concrete into in the hydro-cylinder of annular load case, the buried pipe pass through the check valve with the hydro-cylinder of annular load case is connected, turns into the engineering stake with experimental stake.
2. The construction method for detecting the load of the foundation pile based on the self-balancing static load as claimed in claim 1, wherein the welding of the annular load box and the reinforcement cage specifically comprises:
utilize right-angle rib will go up the steel reinforcement cage welding on the excircle edge of the upper cover of annular load case, spot weld the loudspeaker muscle respectively on last steel reinforcement cage inner wall and on the interior circle edge of upper cover, then spot welding through strengthening rib fixed connection loudspeaker muscle is in go up the welding point on the steel reinforcement cage inner wall, confirm the annular load case for go up the gradient of steel reinforcement cage and be less than 5 thousandths, in order to weld annular load case with go up the mode welding of steel reinforcement cage annular load case and lower steel reinforcement cage.
3. The construction method for detecting the load of the foundation pile based on the self-balancing static load as claimed in claim 2, wherein the arrangement of the displacement rod, the sounding pipe, the grouting pipe and the oil pipe on the reinforcement cage specifically comprises:
arranging a first protection pipe outside a displacement rod, clamping the first protection pipe on the displacement rod by using hydraulic tongs, fixing the displacement rod on an upper cover or a lower cover of the annular load box respectively, fixing the displacement rod on the inner wall of a reinforcement cage, and installing an acoustic pipe;
arranging a second protective pipe outside the sounding pipe, clamping the second protective pipe on the sounding pipe by using a hydraulic clamp, sequentially penetrating the sounding pipe through an upper cover and a lower cover of the annular load box, fixing the sounding pipe on the inner wall of the reinforcement cage, performing water injection detection on the sounding pipe, and installing a grouting pipe when the sounding pipe is not water-tight;
arranging a third protective pipe outside the grouting pipe, connecting the grouting pipe with the third protective pipe in a threaded manner, fixing the grouting pipe on the inner wall of the reinforcement cage, and installing an oil pipe;
and the annular load box is connected with the oil pipe, and the oil pipe is used for conveying or pumping oil into the annular load box.
4. The construction method for detecting the load of the foundation pile based on the self-balancing static load according to claim 3,
the number of the displacement rods is 4, wherein the tail ends of 2 displacement rods are connected to the upper surface of the upper cover of the annular load box, the tail ends of the other 2 displacement rods are connected to the upper surface of the lower cover of the annular load box, and the displacement rods are led out of the ground;
the number of the acoustic pipes is 3, the upper parts of the acoustic pipes are led out of the ground, and the lower parts of the acoustic pipes are flush with the bottom of the foundation pile well;
the number of the grouting pipes is 2, and the upper parts of the grouting pipes are led out of the ground;
the number of the oil pipes is 1, and the upper parts of the oil pipes are led out of the ground.
5. The construction method for detecting the load of the foundation pile based on the self-balancing static load according to claim 3,
the maximum pressurization value of the loading system is 60MPa, and the pressurization precision of the loading system is 0.4 MPa.
6. The construction method for detecting the load of the foundation pile based on the self-balancing static load as claimed in claim 1, wherein the hoisting of the arranged reinforcement cage into the foundation pile well specifically comprises:
and hoisting the set reinforcement cage in the foundation pile well by using a crane, determining the position of the annular load box, and protecting an oil pipe led out of the ground and a steel pipe end enclosure of the reinforcement cage by using a protection device.
7. The construction method for detecting the load of the foundation pile based on the self-balancing static load according to claim 1,
the protective cover is a windproof tent frame, and the windproof tent frame is arranged outside all the test devices led out of the ground.
8. The construction method for detecting the load of the foundation pile based on the self-balancing static load according to claim 1,
the loading system adopts a graded loading mode, the loading value of each test pile is 2 times of the maximum bearing value of the pile top, each grade of loading value is one-fifteenth of the estimated limit bearing value of the test pile, and the test pile is unloaded by adopting a graded unloading mode, wherein the test pile is unloaded by 7 grades in total.
9. The construction method for detecting the load of the foundation pile based on the self-balancing static load according to claim 8,
the test pile diameter of the test pile is 1.5m or 1.6 m.
10. The construction method for detecting the load of the foundation pile based on the self-balancing static load according to claim 1, wherein the displacement observation specifically comprises:
after the test piles are loaded in a grading manner through a loading system, respectively measuring and reading the measurement value of a displacement sensor once within the 5 th minute, the 15 th minute, the 30 th minute, the 45 th minute and the 60 th minute after each grade of load loading within the 1 st hour, measuring and reading the measurement value of the displacement sensor once within the 30 th minute after each grade of load loading, and when the measurement value of the displacement sensor is not more than 0.1mm within the 30 th minute, carrying out next grade of load loading and measuring and reading the measurement value of the displacement sensor;
after the test piles are unloaded in a grading manner through a loading system, observing the displacement resilience amount of the test piles after each grade of load is unloaded, wherein the observation method of the displacement resilience amount is the same as that during the grading loading of the test piles, after the displacement resilience amount of the test piles is stable, carrying out next grade of load unloading, after the load of the test piles is unloaded to 0, at least measuring and reading the measured value of the displacement sensor for 1.5 hours, measuring and reading the measured value of the displacement sensor once every 15 minutes within the initial 30 minutes within 1.5 hours of measuring and reading the displacement sensor, and measuring and reading the measured value of the displacement sensor once every 30 minutes after the initial 30 minutes.
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| CN113175006A (en) * | 2021-04-01 | 2021-07-27 | 华侨大学 | Novel pile foundation vertical load settlement curve prediction method |
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Application publication date: 20201027 |