CN113235672A - Sensor installation method for pile foundation detection - Google Patents
Sensor installation method for pile foundation detection Download PDFInfo
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- CN113235672A CN113235672A CN202110495517.2A CN202110495517A CN113235672A CN 113235672 A CN113235672 A CN 113235672A CN 202110495517 A CN202110495517 A CN 202110495517A CN 113235672 A CN113235672 A CN 113235672A
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
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- E02D33/00—Testing foundations or foundation structures
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Abstract
The invention discloses a sensor installation method for pile foundation detection, which comprises the steps of determining a first drilling position on a test pile according to the pile diameter of the test pile under the condition that the pile sinking of the test pile reaches a preset elevation value; determining a second drilling position on the test pile according to a preset hole center distance; drilling a first mounting hole and a second mounting hole on the test pile according to the first drilling position and the second drilling position; and a strain force sensor and an acceleration sensor are respectively arranged on the first mounting hole and the second mounting hole through threaded fasteners. According to the embodiment of the invention, the strain force sensor and the acceleration sensor are installed by drilling and adopting a threaded fastener, the fixing mode is firm and reliable, the signal stability is ensured, the complete wave curve can be obtained, the steel pipe pile is not required to be installed, the sensor damage caused by larger hammering energy is avoided, the drilling position is determined according to the pile diameter of the test pile, and the drilling position can be rapidly determined and the detection requirement can be met.
Description
Technical Field
The invention relates to the technical field of constructional engineering, in particular to a sensor installation method for pile foundation detection.
Background
The offshore wind generating set adopts a large-scale steel pipe pile as a pile foundation, and the large-diameter steel pipe pile of the offshore wind generating set needs early-stage geological survey data, load and corresponding design specifications to design the pile diameter, the pile length, the mud penetration depth and the like of the supporting platform. After the steel pipe pile is driven to a preset depth according to the design specification, the bearing capacity of the pile is considered to meet the design requirement, various static load tests can not be adopted as the same as the pile foundation on land, and high strain detection is carried out on the bearing capacity and the integrity of the pile body of the pile foundation.
In high strain detection, the installation of a force sensor and an acceleration sensor is a key link for detection. The existing installation modes mainly comprise two modes, wherein one mode is that glue is adopted for adhesion, and the other mode is that prefabricated weldment is applied for installation. The former has simple installation mode and lower cost, but the detection effect of the sensor is poor, and particularly when the hammering energy is large or the glue is not firmly bonded, the sensor falls off along with the vibration of the steel pipe pile, so that a complete curve cannot be obtained; the latter has short installation time and high speed, but has high cost and needs electric welding matching, and when the steel pipe pile vibrates violently due to large hammering energy, the expansion screw used for fixing the sensor on the prefabricated weldment is firmer, so that the sensor is easy to damage, and a complete test curve cannot be obtained.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a sensor installation method for pile foundation detection, which is convenient to install and can ensure the effect of sensor signal acquisition.
In a first aspect, a sensor installation method for pile foundation detection according to an embodiment of the invention includes:
determining a first drilling position on a test pile according to the pile diameter of the test pile under the condition that the pile sinking of the test pile reaches a preset elevation value;
determining a second drilling position on the test pile according to a preset hole center distance;
drilling corresponding first mounting holes and second mounting holes on the test pile according to the first drilling positions and the second drilling positions;
and respectively installing a strain force sensor and an acceleration sensor on the first installation hole and the second installation hole through threaded fasteners.
The sensor installation method for pile foundation detection provided by the embodiment of the invention at least has the following beneficial effects: according to the embodiment of the invention, the strain force sensor and the acceleration sensor are installed by drilling and adopting a threaded fastener, the fixing mode is firm and reliable, the signal stability is ensured, the complete wave curve can be obtained, the steel pipe pile is not required to be installed, the sensor damage caused by larger hammering energy is avoided, the drilling position is determined according to the pile diameter of the test pile, and the drilling position can be rapidly determined and the detection requirement can be met.
According to some embodiments of the invention, the predetermined elevation value is 1-1.5 meters.
According to some embodiments of the invention, the predetermined elevation value is 1-1.2 meters.
According to some embodiments of the invention, determining a first drilling location on the test pile according to a pile diameter of the test pile comprises:
the distance between the first drilling position and the pile top of the test pile is 1.0-2.0 times of the pile diameter.
According to some embodiments of the invention, the predetermined hole center-to-center distance is 50-75 mm.
According to some embodiments of the invention, the predetermined hole center-to-center distance is 55-65 mm.
According to some embodiments of the invention, the number of the first drilling locations and the second drilling locations is plural, and the plural first drilling locations and the plural second drilling locations are circumferentially and evenly distributed on the outer wall of the test pile.
According to some embodiments of the invention, the number of the first drilling locations and the second drilling locations is 2 each, and 2 of the first drilling locations and the second drilling locations are symmetrically distributed on the outer wall of the test pile.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a flow chart illustrating steps of a method for installing a sensor for pile foundation detection according to an embodiment of the present invention;
FIG. 2 is a side view of a sensor mounting location according to an embodiment of the present invention;
FIG. 3 is a top view of a sensor mounting location according to an embodiment of the present invention;
FIG. 4 is a histogram of a borehole in accordance with an embodiment of the present invention;
FIGS. 5a, 5b, 5c and 5d are analysis graphs of the results of the embodiment of the present invention under the condition of 1.0-2.0 times of pile diameter;
FIG. 6a, FIG. 6b, FIG. 6c and FIG. 6d are graphs showing the results of the high strain detection initial fitting analysis according to the embodiment of the present invention;
fig. 7a, 7b, 7c and 7d are graphs of the results of the high strain detection initial fitting analysis according to the embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and larger, smaller, larger, etc. are understood as excluding the number, and larger, smaller, inner, etc. are understood as including the number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.
Referring to fig. 1, the present embodiment discloses a sensor installation method for pile foundation detection, including:
s100, determining a first drilling position on the test pile according to the pile diameter of the test pile under the condition that the pile sinking of the test pile reaches a preset elevation value.
Compared with the pile foundation on the land, the embodiment is mainly applied to the detection of the bearing capacity and the integrity of the pile body of the pile foundation on the sea, wherein the sensors used in the detection comprise a strain sensor 101 and an acceleration sensor 102, and the installation position of the sensors plays a key role in high-strain detection. In this embodiment, the preset elevation value is 1-1.5 m, and the penetration at this time is 2-6 mm, so as to satisfy the technical requirement of bearing capacity detection. In practical applications, in order to ensure that the technical requirements are met, the preset elevation value is usually set to be 1-1.2 meters, for example, 1 meter, 1.1 meters or 1.2 meters. Referring to fig. 2, determining a first drilling position on the test pile according to the pile diameter of the test pile specifically includes: the distance L1 between the first drilling position and the pile top of the test pile is 1.0-2.0 times of the pile diameter D, and for convenience of calculation, the first drilling position is usually determined in a step length of 0.1 times of the pile diameter, for example, the first drilling position is determined at a position 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times or 1.6 times of the pile diameter from the pile top of the test pile. It should be noted that two fixing holes are provided on the strain sensor 101, and therefore two holes need to be drilled at the first drilling position, and the distance between the two holes is adapted to the distance between the two fixing holes of the strain sensor 101.
And S200, determining a second drilling position on the test pile according to the preset hole center distance.
In the embodiment, the predetermined hole center distance L2 is 50 to 75 mm, and in practical applications, the predetermined hole center distance is usually 55 to 65 mm, such as 59 mm, 60 mm or 61 mm. Note that, in the present embodiment, the hole center distance means a distance in the horizontal direction between the first drilling position and the second drilling position.
And S300, drilling corresponding first mounting holes and second mounting holes on the test pile according to the first drilling positions and the second drilling positions.
In this embodiment, the quantity of first drilling position and second drilling position can be one or more, and when the quantity of first drilling position and second drilling position is a plurality ofly, the equal circumference equipartition in a plurality of first drilling position and second drilling position is on the outer wall of experimental stake, for example, please refer to fig. 2 and fig. 3, the quantity of first drilling position and second drilling position is 2, 2 first drilling positions and second drilling position equal symmetric distribution are on the outer wall of experimental stake, can reduce the eccentric influence of hammering energy conduction, be favorable to obtaining the effect of ensureing signal acquisition.
And S400, mounting the strain force sensor 101 and the acceleration sensor 102 on the first mounting hole and the second mounting hole respectively through threaded fasteners.
According to the embodiment of the invention, the strain force sensor 101 and the acceleration sensor 102 are installed by drilling and adopting a threaded fastener, the fixing mode is firm and reliable, the signal stability is ensured, the complete wave curve can be obtained, the steel pipe pile is not required to be installed, the sensor damage caused by large hammering energy can be avoided, the drilling position can be determined according to the pile diameter of the test pile, the drilling position can be determined quickly, and the detection requirement can be met.
In order to further understand the technical solution of the present invention, the following detailed description is made on the technical solution of the present invention with a specific example.
In a certain offshore wind power plant project, a wind turbine foundation is of a non-rock-socketed single-pile steel pipe pile structure, the height of the pile top is plus 12.0 m, the pile bottom is minus 56.8-67 m, the pile length is 67.5-78 m, the pile diameter is 6.0-6.8 m (variable diameter), the wall thickness of the steel pipe pile is 55-78 mm, the weight of the single pile is 756.89-944.77 tons, the high-strain detection condition of a pile sinking construction 21# steel pipe pile is taken as an example, and the bearing capacity and the integrity of the pile body of the steel pipe pile are tested.
According to the exploration result, the lithology of the stratum in the exploration depth range is the fourth system of accumulation (mainly comprising silty clay, cohesive soil, sandy soil with different grain diameters, sand gravel and the like), the Jinxian county-Wuxing mountain group, the thin river group limestone, silty mudstone and glutenite. The thickness of the site covering layer is greatly changed, and the fluctuation of the basement rock surface is large. The thickness of the field covering layer gradually increases from north to south. From the distribution of the field bedrock, the lithology of the north bedrock of the field is mainly conglomerate and silty mudstone, and the lithology of the middle bedrock and the south bedrock is mainly limestone and sanded limestone. Considering factors such as times, causes, lithology, sedimentary phase change combination, engineering characteristic difference and the like, the engineering geological large layers are comprehensively divided into 10 engineering geological large layers from top to bottom, and the specific characteristics of each geotechnical layer are shown in figure 4 from top to bottom.
Through geological survey data analysis earlier stage, this sea area geological conditions is complicated, and place cover layer thickness changes greatly, and the basement rock face fluctuation is great, has darker silty clay layer, and the diameter of steel pipe pile is big in addition, and it is darker to go into the mud part, needs great hammering energy when executing to beat, easily causes the destruction to the integrality of pile body, consequently, needs to test the bearing capacity and the pile body integrality of steel pipe pile.
In order to obtain a complete detection signal, the sensor is installed by adopting a method of tapping a nut in the embodiment, and the method comprises the following steps:
determining a second drilling position on one side of the first drilling position, wherein the hole center distance between the first drilling position and the second drilling position is 60 mm, and it should be noted that, in consideration of the eccentric influence, the number of the first drilling positions is 2, the 2 first drilling positions are symmetrically distributed on the outer wall of the test pile, and correspondingly, the number of the second drilling positions is also 2 and is arranged on one side of the corresponding first drilling positions;
drilling a first mounting hole and a second mounting hole on the test pile by using a 5.2 mm drill bit according to the first drilling position and the second drilling position, wherein the drilling depth is 20 mm, and the screw tap of M6 is used for tapping to the bottom so as to mount the screw of M6;
the strain sensor 101 is mounted on the first mounting hole and the acceleration sensor 102 is mounted on the second mounting hole through an M6 screw. The surface of the pile wall provided with the sensor is intact, no defect exists around the pile wall, the cross section of the pile wall is suddenly changed, and the sensor needs to be tightly attached to the pile wall.
It should be noted that, for different types of pile foundations, the installation requirements of the sensor are different, for example, for a steel pipe pile, the sensor is installed in a drilling and threading manner; for the H-shaped steel pile, a sensor is installed in a mode of punching and fixing by using bolts and nuts; for the concrete pile, an expansion bolt is adopted to install a sensor; for a cast-in-situ bored pile or a spiral bored pile, 4 strain force sensors 101 need to be installed on the pile body in consideration of the influence of the bidirectional bending.
After the sensor is installed, the IHCS-1800 hydraulic hammer is used as hammering equipment to start hammering, signal acquisition is carried out through the strain sensor 101 and the acceleration sensor 102, and the acquired signals are transmitted to a computer to be analyzed in real time, so that data such as static resistance, hammering force, pile body damage degree and the like are obtained. Fig. 5a, 5b, 5c, and 5d are fitting graphs (using the high strain method fitting program CAPWAP of PDI), which are obtained by processing signals from the strain sensor 101 and the acceleration sensor 102 by a high strain method. In FIG. 5a, the solid line represents the measured Force wave (Force Msd) curve and the dashed line represents the fitted Force wave (Force Cpt) curve; in FIG. 5b, the solid line represents the measured Force wave (Force Msd) curve and the dashed line represents the measured Velocity (Velocity Msd) curve; FIG. 5c is a static load test analysis chart of the Pile foundation, wherein the solid line represents data of the Top of the Pile foundation (Pile Top) and the dotted line represents data of the Bottom of the Pile foundation (Bottom); FIG. 5d is a plot of Shaft Resistance Distribution (Shaft Resistance Distribution) and pile force Distribution at extreme bearing capacity (Ru).
In the embodiment, strain force sensors 101 and acceleration sensors 102 are arranged on a test pile in a bilateral symmetry mode, force waves F (t) and acceleration waves a (t) acting on the test pile in each hammering process are measured under the condition that enough hammering energy is provided to enable certain relative displacement to be generated between pile soils, wherein velocity waves V (t) can be obtained after the acceleration waves a (t) are subjected to integral operation, and after signals are collected by the strain force sensors 101 and the acceleration sensors 102, the signals are transmitted to an analysis system for data processing, and a processing result is displayed.
The actual measurement curve fitting method is to determine the mechanical model and the parameter values of the pile and the soil through inversion by numerical calculation of a fluctuation problem. The process is as follows: and (3) assuming the pile and soil mechanics models of each pile unit and model parameters thereof, using the actually measured speed curve as an input boundary condition, solving a wave equation by numerical values, and calculating a force curve of the pile top in a reverse mode. If the calculated curve is not matched with the actually measured curve, the assumed model or the parameters thereof are unreasonable, and the model and the parameters are pertinently adjusted and calculated until the matching degree of the calculated curve and the actually measured curve is good and is not easy to further improve.
The system checks the quality of the pile body, when the amplitude of the velocity wave is suddenly increased and the force wave is suddenly decreased at a certain moment, the sensor receives a tension echo, and the position generated by the tension echo, namely the position of the pile body defect which reduces the impedance, can be calculated according to the moment of the tension echo. Impedance value Z of damaged section for pile body damage degree2Impedance value Z of normal section1The ratio beta is called pile section integrity coefficient, and the integrity of the pile body is judged by a high-strain dynamic detection method and is shown in table 1.
TABLE 1
| Integrity class | Beta value | Integrity class | Beta value |
| Class I | β＝1.0 | Class III | 0.6≤β＜0.8 |
| Class II | 0.8≤β＜1.0 | Class IV | β＜0.6 |
The ultimate bearing capacity of the 21# steel pipe pile high strain dynamic detection initial driving fitting method is 81765kN, the side friction resistance is 61775kN and the end resistance is 19991kN, the ultimate bearing capacity of the high strain dynamic detection secondary driving fitting method is 103371kN, the side friction resistance is 71387kN and the end resistance is 31985kN, the integrity type is I, and the specific parameters are detailed in a table 2.
TABLE 2
At present, the bearing capacity detection of the offshore large-diameter steel pipe pile is limited by offshore conditions, high strain detection is required, the analysis chart of the initial driving result of the high strain detection refers to fig. 6a, 6b, 6c and 6d, and the analysis chart of the secondary driving result of the high strain detection refers to fig. 7a, 7b, 7c and 7 d. Through the analysis of the field detection condition, the penetration degree during primary striking detection is controlled to be less than or equal to 6mm, the striking energy and the falling distance can be properly adjusted according to ground investigation data in the striking process, the phenomenon that the weak surface of a pile body is damaged due to overlarge striking energy is avoided, the hydraulic hammer rebounds, the striking energy is conducted to generate eccentricity, and the first hammer signals with larger striking energy are selected during analysis and calculation. The penetration degree is less than or equal to 4mm during repeated driving, and the large displacement of the steel pipe pile is avoided by controlling the hammering energy, so that the designed elevation of the pile top of the steel pipe pile and the depth of a mud entering part are not influenced.
The strain sensor 101 and the acceleration sensor are arranged on two sides of the pile body by a tapping nut method, the drilling position is vertically right above a scale mark and is 1.0-2.0 times of the pile diameter away from the pile top, and the sensors are symmetrically distributed on two sides of the pile body when being installed. The transmission signal is stable, and a complete wave curve is obtained.
The interval period of high strain detection initial driving and repeated driving is different, the resistance value is different, the initial driving time of high strain detection of the marine large-diameter steel pipe pile is generally tracked and detected in the pile sinking process, the stratum around the pile body is compacted during initial driving, the gap of the stratum around the steel pipe pile is compact, and the water pressure in the gap is increased. After a period of time, the stratum is solidified around the pile body again, and the bearing capacity of the steel pipe pile is improved through the combined action of the stratum around the pile and the pile during the repeated driving. The intermittent time from pile forming to repeated beating test is not too short, the intermittent period is more than or equal to 14 days, the offshore operation period and the equipment operation difficulty are considered, the appropriate intermittent period is selected, the detection precision is improved, and an accurate detection result is obtained.
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.
Claims (8)
1. A sensor installation method for pile foundation detection is characterized by comprising the following steps:
determining a first drilling position on a test pile according to the pile diameter of the test pile under the condition that the pile sinking of the test pile reaches a preset elevation value;
determining a second drilling position on the test pile according to a preset hole center distance;
drilling corresponding first mounting holes and second mounting holes on the test pile according to the first drilling positions and the second drilling positions;
and a strain force sensor (101) and an acceleration sensor (102) are respectively arranged on the first mounting hole and the second mounting hole through threaded fasteners.
2. The method for installing the sensor for detecting the pile foundation according to claim 1, wherein the preset elevation value is 1-1.5 m.
3. The method for installing the sensor for detecting the pile foundation according to claim 2, wherein the preset elevation value is 1-1.2 m.
4. The sensor installation method for pile foundation detection of claim 1, wherein determining a first drilling position on the test pile according to a pile diameter of the test pile comprises:
the distance between the first drilling position and the pile top of the test pile is 1.0-2.0 times of the pile diameter.
5. The method for installing the sensor for pile foundation detection according to claim 1, wherein the preset hole center distance is 50-75 mm.
6. The method for installing the sensor for detecting the pile foundation according to claim 5, wherein the preset hole center distance is 55-65 mm.
7. The method of any one of claims 1 to 6, wherein the number of the first and second drilling locations is plural, and the plural first and second drilling locations are circumferentially and uniformly distributed on the outer wall of the test pile.
8. The method of claim 7, wherein the number of the first and second drilling locations is 2, and the 2 first and second drilling locations are symmetrically distributed on the outer wall of the test pile.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115538506A (en) * | 2022-11-14 | 2022-12-30 | 北京中咨华安交通科技发展有限公司 | Method and device for detecting quality of pile body of bridge squeezed branch pile |
| CN115682998A (en) * | 2022-11-04 | 2023-02-03 | 广东科诺勘测工程有限公司 | Method and device for calculating pile length of tubular pile |
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| CN201177585Y (en) * | 2008-04-11 | 2009-01-07 | 国网北京电力建设研究院 | Pile foundation high strain detection device |
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- 2021-05-07 CN CN202110495517.2A patent/CN113235672A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201177585Y (en) * | 2008-04-11 | 2009-01-07 | 国网北京电力建设研究院 | Pile foundation high strain detection device |
Non-Patent Citations (1)
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| 刘春等: "《岩土工程测试与监测技术》", 30 June 2018 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115682998A (en) * | 2022-11-04 | 2023-02-03 | 广东科诺勘测工程有限公司 | Method and device for calculating pile length of tubular pile |
| CN115538506A (en) * | 2022-11-14 | 2022-12-30 | 北京中咨华安交通科技发展有限公司 | Method and device for detecting quality of pile body of bridge squeezed branch pile |
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