CN115637744A - Method for judging pile head damage in foundation pile static load test - Google Patents
Method for judging pile head damage in foundation pile static load test Download PDFInfo
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Abstract
The invention discloses a method for judging pile head damage in a foundation pile static load test, which is used for installing equipment required by the static load test; setting a total load application stage number; calculating a target load control value applied by each level of load, and applying the load through an oil pump; calculating the average value of pile displacement change and the average value of pile pressure change recorded each time in the time of applying the current-level load; calculating a judgment value k i And the oil pump loading rate according to the judgment value k i And the oil pump loading rate is used for carrying out oil pump power early warning and pile damage early warning. The invention can distinguish and early warn the oil pump power and pile damage, and can predict the load time in the later period.
Description
Technical Field
The invention belongs to the field of static load tests in foundation pile bearing capacity detection, and particularly relates to a method for judging pile head damage in a foundation pile static load test. The method is suitable for preventing and controlling engineering accidents caused by test platform collapse possibly caused by pile head damage in single-pile vertical compression resistance, single-pile vertical pulling resistance and single-pile horizontal static load tests.
Background
In foundation pile static test, higher vertical load (or horizontal load) and eccentric load are often born to static test pile head position, according to foundation pile detection standard requirement, no matter be bored concrete pile or precast pile, need handle the pile head, just can guarantee that experimental normal clear goes on. For the precast pile, the pile head is generally processed by adopting the modes of hoop head, concrete core filling and the like; the cast-in-place pile is generally processed in a pile head casting mode, a concrete pile cap is cast again on the basis of chiseling loose and broken layer concrete of an original pile body, and a test is carried out after the strength of the pile cap reaches.
Aiming at the treatment of the pile head, corresponding researchers in China apply for corresponding patents, such as a static load pile head protection device and a static load test system with the patent application number of CN 201720510080.4; the utility model mainly provides a static load pile head protection device and a static load test system, wherein the static load pile head protection device comprises a hoop part and a reinforcing structure; the hooping component is connected at the head, sleeved on the outer side wall of the pile head and hooped, and the device limits the axial deformation of the pile head through hooping the pile head, thereby preventing the pile head from bursting. And patent application No. CN200920172114.9 detachable bored concrete pile resistance to compression static load pile head protection device, this utility model relates to a detachable bored concrete pile resistance to compression static load pile head protection device, and protection device comprises two semicircle hoops, and the bolt is twisted two semicircle hoops and is fixed on the pile head outer circumference, protects the pile head in the static load test pile head and destroys.
Although the specification requires the treatment and protection of the pile head in the static load test, in the field detection process, the treatment of the pile head on the field often has the defects that the size of the hoop head is not proper, the pouring of the concrete pile cap is not strictly performed according to the specification requirement, and the pouring quality is not qualified, so that the condition of pile head damage still often occurs in the current static load test engineering detection; and the pile head of some test piles is processed, but the pile head is often damaged due to the conditions of uneven top surface of the pile head, eccentric installation of a jack, influence of underground water level and the like.
In the static load test, not only the load cannot be continuously applied after the pile head is damaged, but also the static load test cannot be carried out, and the contradiction between the construction and the detection party is caused under the condition that a quality accident is very easy to occur.
The static load test at the present stage is basically automatically carried out by using a static load tester instrument, so that the safety of field test personnel and equipment can be ensured to a greater extent, and the test efficiency can be increased; the accuracy of the field test data is guaranteed. The static load tester controls the application of pressure by limiting the rotation time of the oil pump at present. However, the oil pump rotation time has differences in oil pump oil output change and bearing capacity of a field test object, the time is set to be long, and even if pile head damage, pile damage or oil pump problems occur on the field, the oil pump can be controlled by an instrument to continuously apply load, so that accidents occur. If the loading time is short, the alarm condition is easy to set, and the field detection efficiency is influenced. Therefore, the judgment algorithm for pile head damage in the static load test and the matched early warning function are very necessary to be embedded into the static load acquisition instrument.
Disclosure of Invention
The invention aims to provide a method for judging pile head damage in a foundation pile static load test aiming at the technical problems in the prior art, which can be suitable for estimating and judging the time of a static load tester in applying a foundation pile static load test load, can be suitable for protecting the pile head damage in the static load test and the application of an oil pump loading control load, and further ensures the safety of a field test counter-force platform; the invention is embedded into a static load tester, so that the field test efficiency is improved while the safety of field tests and equipment is ensured.
The above object of the present invention is achieved by the following technical solutions:
a method for judging pile head damage in a foundation pile static load test comprises the following steps:
step 1, installing equipment required by a static load test according to the static load test requirement of a foundation pile;
step 2, controlling the front-end host to set the load Shi Jiazong stage number n according to the maximum test load value of the static load test;
step 3, controlling the front-end host to calculate a target load control value applied to each level of load in the process of calculating the maximum test load value from the initial load value;
step 4, the front-end control host issues a target load control value corresponding to the current-level load application to the oil pump driving device, so that the oil pump is controlled to rotate, and the load application is carried out through the oil pump;
step 5, calculating the loading rate V of the oil pump i ；
Wherein:
V i the loading rate of the oil pump of the ith level load is increased;
Q i applying the real-time load value of the ith level load in place;
Q i-1 for the real-time load value before the i-th level load is applied, when i =1, Q 0 Is an initial load value;
T i the time after the ith level load is applied in place;
T i-1 the time before the i-th level load is applied;
i is the serial number of load application stages; i is an element of {1 to n }
n is the total number of load application stages;
step 6, obtaining the loading rate V of the oil pump i Then, according to the oil pump loading rate V i And calculating the total load change quantity delta Q of the static load test of the next-stage load, and calculating the total load loading time T of the next-stage load i+1 ， T i+1 ＝ΔQ/V i ；
And 7, using a static load acquisition instrument to sequentially segment time within the time of applying the current-level load acquired by the front-end control host, recording pile displacement and pile pressure for multiple times, calculating the pile displacement change value and the pile pressure change value recorded in each time segment within the time of applying the current-level load, and calculating the average pile displacement change value deltas recorded in each time segment within the time of applying the current-level load j And pile pressure variation mean value Deltaq j (ii) a Wherein j is the serial number recorded by the current load level segment number, j belongs to { 1-m }, m is the total number of the current load level time segments,
at the beginning of the load application of the current level, calculating a judgment value k j ：
Wherein:
k j the ratio of the load to the displacement in the jth time period of the current load level is represented by kN/mm;
Δq j the value is the increment of the load in the j time period of the current load;
Δq j-1 the load is the increment value of the load in the j-1 time period of the current load;
Δs j testing the average increment value of the displacement table in the j time period of the current load;
Δs j-1 testing the average increment value of the displacement table in the j-1 time period of the current load;
j is the serial number of the current load level time segment number record, and a judgment value k is calculated j When j is greater than or equal to 2 and less than or equal to m;
step 8, in the load loading and load supplementing processes, if V appears i V equal to 0 or less than the i-1 th order load i-1 When the value is 1/3, giving prompt by early warning of the power of the oil pump, and stopping the static load test;
step 9, taking the next-level load application as the current-level load application, returning to the step 4 until all-level load application is completed, and if the value k is judged in the all-level load application process j And if the pile is continuously not more than 0 for 2 times, judging that the pile head of the test pile is damaged, or the pile body and the pile surrounding bearing layer are damaged, or the pile body steel bar is broken, carrying out pile damage early warning, and stopping the static load test.
The calculation method of the calculated load time period is calculated based on the following steps, if the maximum test load value is less than or equal to 2000kN, the value of m is 2, and the value of m is increased by 1 every time the maximum test load value is increased by 1000kN on the basis of 2000 kN.
In step 7 as described above, the pile displacement and pile pressure over the time of the current level of load application are recorded multiple times at the same time interval.
Compared with the prior art, the invention has the following beneficial effects:
1. the method can judge the vertical compression resistance of the single pile, the vertical pulling resistance of the single pile and the horizontal test of the single pile in the static load of the foundation pile, and has wide applicability.
2. When the static load test is carried out, the load-adding speed of the oil pump can be calculated to estimate the load time at the later stage, so that the automatic setting of the automatic judgment of the load time is realized, the situations of overlong and overlong longest load time can be avoided, the test efficiency of the field test is improved, and the safety of a field test platform, the oil pump and a jack is ensured to the greatest extent.
3. The invention is embedded in the control front-end host connected with the static load acquisition instrument, the pile head damage can be judged and responded in the fastest time, the problems of no hydraulic oil of an oil pump, oil leakage of an oil pipe, insufficient field counter force and the like can be distinguished from the pile head damage problem, the alarm content is refined, the misjudgment is reduced, and the field test efficiency is influenced.
4. The control front-end host connected with the static load acquisition instrument is embedded, and the calculation is realized by program judgment in the control front-end host, so that the normal operation of a static load test is not influenced under the condition that the control front-end host is embedded.
Detailed Description
The present invention will be described in further detail with reference to examples for the purpose of facilitating understanding and practice of the invention by those of ordinary skill in the art, and it is to be understood that the present invention has been described in the illustrative embodiments and is not to be construed as limited thereto.
Example 1:
a method for judging pile head damage in a foundation pile static load test comprises the following steps:
step 1, installing equipment required by a static load test according to the requirements of the static load test, inputting information required by the static load test, such as test load information, a jack calibration equation and an adopted oil pump, opening a static load acquisition instrument, and carrying out the static load test;
step 2, controlling the front-end host to set a load Shi Jiazong stage number n according to the maximum test load value of the static load test;
step 3, controlling the front-end host to calculate a target load control value applied by each level of load in the process from the initial load value to the maximum test load value;
step 4, the front-end control host issues a target load control value corresponding to the current-level load application to the oil pump driving device, so that the oil pump is controlled to rotate, and the load application is carried out through the oil pump;
step 5, calculating the loading rate V of the oil pump i ；
Wherein:
V i the loading rate of an oil pump of the ith level load is kN/S;
Q i applying the real-time load value of the ith level load in place;
Q i-1 for the real-time load value before the i-th level load is applied, when i =1, Q 0 Is an initial load value;
T i the time after the ith level load is applied in place;
T i-1 the time before the i-th level load is applied;
i is the serial number of load application stages; i is an element of {1 to n }
n is the total number of load application stages;
step 6, obtaining the loading rate V of the oil pump i Then, according to the oil pump loading rate V i And calculating the total load change quantity delta Q of the static load test of the next-stage load, and calculating the total load loading time T of the next-stage load i+1 ， T i+1 ＝ΔQ/V i ；
And 7, using a static load acquisition instrument to sequentially segment time within the time of applying the current-level load acquired by the front-end control host, recording pile displacement and pile pressure for multiple times, calculating the pile displacement change value and the pile pressure change value recorded in each time segment within the time of applying the current-level load, and calculating the average pile displacement change value deltas recorded in each time segment within the time of applying the current-level load j And pile pressure variation mean value Deltaq j (ii) a Wherein j is a sequence number recorded by the current load level segment number, j belongs to { 1-m }, and m is the total number of the current load level time segments;
at the beginning of the load application of the current level, calculating a judgment value k j ：
Wherein:
k j the unit of the ratio of the load to the displacement in the jth time period of the current load level is kN/mm;
Δq j the value is the increment of the load in the j time period of the current load;
Δq j-1 the load is the increment value of the load in the j-1 time period of the current load;
Δs j testing the average increment value of the displacement table in the j time period of the current load;
Δs j-1 testing the average increment value of the displacement table in the j-1 time period of the current load;
j is the serial number of the current load level time segment number record, and a judgment value k is calculated j When j is greater than or equal to 2 and less than or equal to m;
m total number of current load fraction segments; the value of m is 2 if the maximum test load value is less than or equal to 2000kN, and the value of m is increased by 1 every time the maximum test load value is increased by 2000kN on the basis of 2000 kN; and if the maximum test load is 10000kN, the value of m is 6.
T i To T i+1 M segments are divided, and the total time length of the m segments is T i+1 -T i The time length of the first m-1 time segments is (T) i+1 -T i ) The value of/m rounded down.
Step 8, in the load loading and load supplementing processes, if V appears i V equal to 0 or less than the i-1 th order load i-1 When the value is 1/3, giving prompt by early warning of the power of the oil pump, and stopping the static load test;
step 9, applying the next stage of loadAdding the load as the current level load application, returning to the step 4 until all level load application is finished, and judging the value k if the value k is judged in the all level load application process j And if the pile is continuously not more than 0 for 2 times, judging that the test pile has the conditions of pile head damage, pile body, pile peripheral bearing layer damage, pile body reinforcing steel bar breakage and the like, carrying out pile damage early warning, and stopping the static load test.
Example 2:
since 2020, after the determination method described in example 1 is embedded in a static load tester, early warning of pile head damage and insufficient power of an oil pump occurs in multiple tests, and the oil pump is protected while a reaction platform of a field static load test is protected.
Table 1 shows the real-time load value and pile displacement measurement table in this embodiment
As shown in the table above, after the load was loaded from 2160kN to 2430kN, a pressure drop occurred and no pilot was present on site.
At 12:24:04, automatically early warning by the front-end control host of the static load tester RSM-JC5 (A), stopping a static load test, simultaneously controlling the oil pump to automatically stop rotating, popping up the front-end control host of the static load tester RSM-JC5 (A) to prompt that a site test object is possibly damaged, and please check the site and then determine whether the test is continued.
And checking the treated pile head on site, and finding that the pile head is completely cracked. The oil pump is stopped to continuously pressurize in time, so that accidents on the test site are avoided.
The invention has the advantages that the early warning is carried out for many times since the early warning is embedded into the front-end control host of the static load tester, the property safety of field test equipment is ensured to the maximum extent while the field static load test accident is avoided, and the accident caused by the damage of the pile head is avoided.
It should be noted that the specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments, or alternatives may be employed, by those skilled in the art, without departing from the spirit or ambit of the invention as defined in the appended claims.
Claims (3)
1. A method for judging pile head damage in a foundation pile static load test is characterized by comprising the following steps:
step 1, installing equipment required by a static load test according to the static load test requirement of a foundation pile;
step 2, controlling the front-end host to set a load Shi Jiazong stage number n according to the maximum test load value of the static load test;
step 3, controlling the front-end host to calculate a target load control value applied by each level of load in the process from the initial load value to the maximum test load value;
step 4, the front-end control host issues a target load control value corresponding to the current-level load application to the oil pump driving device, so that the oil pump is controlled to rotate, and the load application is carried out through the oil pump;
step 5, calculating the loading rate V of the oil pump i ；
Wherein:
V i the loading rate of the oil pump of the ith level load is increased;
Q i applying the real-time load value of the ith level load in place;
Q i-1 for the real-time load value before the i-th level load is applied, when i =1, Q 0 Is an initial load value;
T i the time after the ith level load is applied in place;
T i-1 the time before the i-th level load is applied;
i is the serial number of load application stages; i is an element of {1 to n }
n is the total number of load application stages;
step 6, obtaining the loading rate V of the oil pump i Then, according to the oil pump loading rate V i And calculating the total load change quantity delta Q of the static load test of the next-stage load, and calculating the total load loading time T of the next-stage load i+1 ，T i+1 ＝ΔQ/V i ；
And 7, using a static load acquisition instrument to sequentially segment time within the time of applying the current-level load acquired by the front-end control host, recording pile displacement and pile pressure for multiple times, calculating the pile displacement change value and the pile pressure change value recorded in each time segment within the time of applying the current-level load, and calculating the average pile displacement change value deltas recorded in each time segment within the time of applying the current-level load j And pile pressure variation mean value Deltaq j (ii) a Wherein j is the serial number recorded by the current load level segment number, j belongs to { 1-m }, m is the total number of the current load level time segments,
at the beginning of the load application of the current level, calculating a judgment value k j ：
Wherein:
k j the ratio of the load to the displacement in the jth time period of the current load level is represented by kN/mm;
Δq j the value is the increment of the load in the j time period of the current load;
Δq j-1 the load is the increment value of the load in the j-1 time period of the current load;
Δs j testing the average increment value of the displacement table in the j time period of the current load;
Δs j-1 testing the average increment value of the displacement table in the j-1 time period of the current load;
j is the serial number of the current load level time segment number record, and a judgment value k is calculated j When j is greater than or equal to 2 and less than or equal to m;
step 8, in the load loading and load supplementing processes, if V appears i Value equal to 0 or less than the i-1 thV of the load order i-1 When the value is 1/3, giving prompt by early warning of the power of the oil pump, and stopping the static load test;
step 9, taking the next-level load application as the current-level load application, returning to the step 4 until all-level load application is completed, and if the value k is judged in the all-level load application process j And if the pile is continuously not more than 0 for 2 times, judging that the pile head of the test pile is damaged, or the pile body and the pile surrounding bearing layer are damaged, or the pile body steel bar is broken, carrying out pile damage early warning, and stopping the static load test.
2. The method for judging pile head damage in the foundation pile static load test according to claim 1, wherein the calculation of the calculated load time period is based on the following steps, wherein if the maximum test load value is less than or equal to 2000kN, m is 2, and the value of m is increased by 1 every time 1000kN is added on the basis of 2000 kN.
3. The method for judging pile head damage in the foundation pile static load test according to claim 1, wherein in step 7, pile displacement and pile pressure in the time of applying the current level load are recorded for a plurality of times at the same time interval.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117030487A (en) * | 2023-10-09 | 2023-11-10 | 武汉中岩科技股份有限公司 | Safety pre-warning method and device for ballast counter-force platform suitable for static load test |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117030487A (en) * | 2023-10-09 | 2023-11-10 | 武汉中岩科技股份有限公司 | Safety pre-warning method and device for ballast counter-force platform suitable for static load test |
| CN117030487B (en) * | 2023-10-09 | 2023-12-29 | 武汉中岩科技股份有限公司 | Safety pre-warning method and device for ballast counter-force platform suitable for static load test |
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