CN210194703U - Low strain integrality detection device of two survey points in hole of foundation pile - Google Patents
Low strain integrality detection device of two survey points in hole of foundation pile Download PDFInfo
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- CN210194703U CN210194703U CN201920690083.XU CN201920690083U CN210194703U CN 210194703 U CN210194703 U CN 210194703U CN 201920690083 U CN201920690083 U CN 201920690083U CN 210194703 U CN210194703 U CN 210194703U
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Abstract
The utility model discloses a two measurement point low strain integrality detection device in hole of foundation pile, including acceleration sensor, pre-buried pipe, pulse hammer, the lead wire and the data acquisition processing apparatus of taking fixing device. The sensor adopted by the device consists of an acceleration sensor and a fixing device, and after the acceleration sensor reaches a designated position, the fixing device is used for fixing the position of the acceleration sensor in the pipe. When the concrete pile is poured, the pipe fitting needs to be pre-buried in the steel reinforcement cage so as to hoist the sensor. When detection is carried out, the two sensors are respectively hoisted to the preset pipe to a specified depth, the pile top is knocked by the pulse hammer, and analysis is carried out according to the results of the two measuring points, so that the aims of measuring the wave velocity of concrete, detecting the pile length and quantitatively analyzing the defects of the pile body are fulfilled. The utility model discloses the advantage of traditional foundation pile low strain detection method and sound wave transmission method has characteristics such as quick, economy, harmless.
Description
Technical Field
The utility model belongs to the test equipment field, concretely relates to two survey points low integrality detection device that meets an emergency in hole of foundation pile.
Background
The quality detection of the pile foundation, which is the most important basic form, has been concerned by the engineering industry. In the domestic pile foundation dynamic detection, a low-strain reflection wave detection method and a sound wave transmission method are common and representative.
According to the traditional low-strain detection method, a sensor is placed on the pile top, when the pile length is detected, on one hand, the pile bottom is too deep, so that the sensor cannot receive reflected waves at the pile bottom, and on the other hand, the concrete wave speed adopted in calculation is usually set according to experience, so that large errors exist, and the calculation result is greatly different from the actual situation.
The sound wave transmission method is characterized in that a transmitting end and a receiving end are placed in the pre-buried sound measuring pipe, and the integrity of the pile body is detected by actually measuring the sound time, the wave speed and the like of sound waves transmitted in concrete. This method has the following disadvantages: firstly, when the outer side of the sound measuring tube has defects and even the main ribs are exposed, the method cannot detect the defects. Secondly, when the acoustic pipe is locally wrapped with mud, isolated with concrete, etc., the failure of the local measuring point can be caused.
The utility model discloses combined the advantage of traditional low strain detection method and sound wave transmission method, on the basis of low strain detection method, utilize the pre-buried pipe to arrange the sensor in the pile body inside, confirm the sensor according to the length of transferring of sensor lead wire and place the degree of depth, reach the purpose of the concrete elasticity longitudinal wave speed of more accurate detection foundation pile that awaits measuring, pile length or pile body integrality through the position that changes two sensors and distance.
Disclosure of Invention
An object of the utility model is to solve the problem that exists among the prior art to a two survey points low strain integrality detection device and method in the hole of foundation pile have been proposed. The utility model discloses on the basis of traditional low strain detection method, utilize the embedded pipe to arrange the sensor in the pile body inside, confirm the sensor according to the length of transferring of sensor lead wire and place the degree of depth, reach the purpose of the concrete elasticity longitudinal wave speed of more accurate detection foundation pile that awaits measuring, pile length or pile body integrality through the position that changes two sensors and distance.
The utility model adopts the following technical proposal:
a double-measuring-point low-strain integrity detection device in a hole of a foundation pile comprises a first acceleration sensor, a second acceleration sensor, a pre-buried pipe, a pulse hammer, a lead and a data acquisition and processing device; the pulse hammer is used for knocking the pile top of the concrete cast-in-place pile; at least one embedded pipe is vertically embedded in a reinforcement cage of the concrete cast-in-place pile; the first acceleration sensor and the second acceleration sensor are both hung in the embedded pipe and keep a distance; the two sensors are respectively provided with a fixing device for temporarily fixing the sensors on the pipe wall of the embedded pipe; the first acceleration sensor and the second acceleration sensor are connected with an external data acquisition and processing device through leads.
Preferably, the fixing device is an air bag fixing device, the air bag fixing device is a closed air bag with an inflation inlet, the air bag is wrapped outside the sensor in a surrounding mode, the inflation inlet of the air bag is connected with one end of an inflation tube in a closed mode, and the other end of the inflation tube is connected to the outside of the foundation pile.
Furthermore, the inner diameter of the embedded pipe needs to be larger than the maximum outer diameter of the sensor but smaller than the sum of the maximum outer diameters of the sensor and the air bag fixing device in an air leakage state.
Preferably, the fixing device is a spring fixing device, and the spring fixing device on each sensor comprises a guide pipe and a plurality of springs; a plurality of springs are fixed around the peripheral side surface of the sensor, and the inner diameter of the conduit is larger than that of the sensor; when the sensor is positioned in the conduit, the free end of the spring in the circumferential direction of the sensor is supported on the inner wall of the conduit in a compressed state to temporarily fix the sensor; a hard lead pipe is wrapped on a lead of each sensor, one end of each lead pipe is fixed on the sensor, and the other end of each lead pipe penetrates through the embedded pipe and extends out of the pile top of the concrete cast-in-place pile; the tail end of the spring and the inner wall of the catheter can slide under the thrust action of the lead tube; the length of the spring is such that: after the sensor slides out of the guide pipe, the spring can prop on the inner wall of the embedded pipe to temporarily fix the sensor.
Furthermore, the lead pipe is a steel pipe or a hard plastic pipe, and is a straight hollow round pipe.
Preferably, the embedded pipes are distributed at different positions of the cross section of the concrete cast-in-place pile.
Preferably, the lead is provided with a scale.
Preferably, the data acquisition and processing device is a dynamic measurement instrument.
Preferably, the inflation pipe is connected with an inflation device arranged outside the foundation pile, and an air stop valve is arranged on the inflation pipe.
The utility model discloses in, follow-up for the convenience of description, the defect that reduces for other positions cross-sectional area appears for a certain position in the pile body in the definition necking down defect. The cross-sectional area of the top of the necking defect is suddenly reduced from top to bottom when viewed from the top to the bottom of the foundation pile, and therefore the position is called a necking position; similarly, the cross-sectional area of the bottom portion of the neck defect is abruptly enlarged from top to bottom, and thus this position is called a neck-in.
Compared with the prior art, the utility model has the advantages of it is following:
1. the utility model discloses combined the low advantage of meeting an emergency detection method and sound wave transmission method of traditional foundation pile, on the basis of low detection method that meets an emergency, utilize the buried pipe to arrange the sensor in the pile body inside, confirm the sensor depth of placement according to the length of transferring of sensor lead wire, reach the purpose of the concrete elasticity longitudinal wave speed of more accurate detection foundation pile that awaits measuring, pile length or pile body integrality through the position that changes two sensors and distance. The utility model has the characteristics of it is quick, economical, harmless etc.
2. The utility model discloses compare in traditional low strain detection method, can detect pile body concrete wave speed more accurately, and change the pile bottom reflected wave of receiving the long pile.
3. The utility model discloses compare in the sound wave transmission method, can detect the defect that the buried pipe (sounding pipe) outside appears, and be difficult for receiving local defect's influence.
Drawings
FIG. 1 is a schematic view of a dual-gauge low-strain integrity test apparatus in a bore of a foundation pile;
FIG. 2 is a schematic view of an airbag securement device; wherein a) is before the airbag is inflated; b) inflating the air bag;
FIG. 3 is a schematic view of a spring retainer device; wherein a) is before the catheter is pulled out; b) after the catheter is pulled out;
FIG. 4 is a schematic diagram of the device of the present invention for detecting the wave velocity and pile length of concrete;
fig. 5 is a schematic diagram of the quantitative detection of pile body defects by using the device of the utility model.
The system comprises a first acceleration sensor 1, a second acceleration sensor 2, a pre-buried pipe 3, a concrete cast-in-place pile 4, a pulse hammer 5, a sensor lead 6, a data acquisition and processing device 7, an air bag 8, an inflation pipe 9, a spring 10, a guide pipe 11 and a lead pipe 12.
Detailed Description
The present invention will be further explained with reference to the accompanying drawings.
As shown in fig. 1, for the utility model discloses a low strain integrality detection device of two measurement points in hole of foundation pile in an embodiment, the device includes first acceleration sensor 1, second acceleration sensor 2, buried pipe 3 in advance, impulse hammer 5, lead wire 6 and data acquisition processing apparatus 7. The detection device is suitable for quality detection of common concrete piles. On the basis of a traditional low-strain detection method, the detection device utilizes the embedded pipe to place two acceleration sensors in a pile body, and the placement depth of the sensors is determined according to the placement length of sensor leads. The pulse hammer 5 is utilized to knock the pile top, the sensors with different heights respectively receive the vibration condition of the pile body and transmit the vibration condition to the data acquisition and processing device 7 on the ground through the lead 6, and the data acquisition and processing device is used for analyzing the result and achieving the purpose of more accurately detecting the concrete elastic longitudinal wave speed, the pile length or the integrity of the pile body of the foundation pile to be detected by changing the positions and the distances of the two sensors. The specific implementation structure of the detection device is described in detail below.
The device is provided with a pulse hammer 5 which is a vibration exciter generating transient exciting force and is used for knocking the pile top of the concrete cast-in-place pile 4. The pulse hammer 5 can be a commercial product and generally comprises a hammer body, a handle, an exchangeable hammer head and a counterweight. In the pulse hammer 5, a force sensor can be arranged between the hammer body and the hammer head to measure the hammering force, and the hammer head can be replaced according to the measurement requirement to change the excitation frequency range.
The embedded pipes 3 embedded in the cast-in-place concrete piles 4 are one or more, and the embedded pipes 3 are vertically embedded in reinforcement cages of foundation piles before concrete is poured and are poured together with the reinforcement cages. And after the concrete pouring is finished, the embedded pipes 3 are solidified in the foundation piles. Theoretically, one embedded pipe 3 can complete the basic detection function, but in consideration of the detection accuracy, a plurality of embedded pipes 3 can be arranged on the periphery of the reinforcement cage before the foundation pile is poured so as to perform multipoint measurement and reduce the measurement error.
The first acceleration sensor 1 and the second acceleration sensor 2 are both hung in the embedded pipe 3 through a lead 6, and a certain distance needs to be kept between the two sensors. The first acceleration sensor 1 and the second acceleration sensor 2 are both connected with an external data acquisition and processing device 7 through leads 6. The lead 6 is used for transmitting data of the first acceleration sensor 1 and the second acceleration sensor 2 to the data acquisition and processing device 7, and is used for hoisting the sensors into the embedded pipe 3 as a lifting rope. Therefore, a length scale can be drawn on the lead 6 to confirm the pick-and-place depth of the sensor in the pipe. The two sensors can be hung by using different leads 6, or the same strand of leads 6 can be used, but the data transmission needs to be kept independent. The data acquisition and processing device 7 can be various dynamic measuring instruments, preferably instruments with oscillography function and capable of realizing frequency spectrum conversion and signal integration.
Since the embedded pipe 3 usually contains water, the first acceleration sensor 1 and the second acceleration sensor 2 in the hole required by the device are generally acceleration sensors which can work under water. Moreover, the positions of the first acceleration sensor 1 and the second acceleration sensor 2 in the embedded pipe 3 should be adjustable, but the first acceleration sensor 1 and the second acceleration sensor 2 need to be conducted with the embedded pipe 3 for sensing wave signals, that is, when the sensors move to the specified positions in the embedded pipe 3, the sensors need to be fixed with the pipe wall, so that the purpose of measuring the vibration condition of the pile body is achieved. Therefore, a fixing device for temporarily fixing the sensor on the pipe wall of the embedded pipe 3 is arranged on each of the first acceleration sensor 1 and the second acceleration sensor 2. The utility model discloses in, provide two kinds of different fixing device, be gasbag fixing device and spring fixing device respectively, introduce one by one below.
As shown in fig. 2, the fixation device shown in the drawings is an airbag fixation device. The air bag fixing device is a closed air bag 8 with an inflation inlet, the air bag 8 is wrapped around the outside of a sensor (any one of the first acceleration sensor 1 and the second acceleration sensor 2, marked as 1/2 in the figure) to be fixed, the inflation inlet of the air bag is connected with an inflation device arranged outside the foundation pile through an inflation tube 9, and the inflation tube 9 is preferably provided with an air stop valve. The air bag 8 can be inflated and deflated through the inflation tube 9, and the air stop valve on the tube can adopt air stop devices such as an air stop clamp and an air stop valve, and the inflation and deflation of the air bag are directly controlled by adjusting the switch of the air stop valve, so that the operation is convenient. During the detection, the air bag 8 is first kept deflated, as shown in a in fig. 2; when the position below the sensor 1/2 reaches a designated position, the air bag 8 is inflated by an inflator or manually, and the air bag 8 expands and presses the inner wall of the embedded pipe 3, as shown by b in fig. 2. The sensor 1/2 can be fixed to the tube wall by closing the gas tube 9 with a gas check valve or other means to prevent gas leakage. When the sensor 1/2 is used or needs to be changed, the air bag 8 is deflated by exhausting air through the inflation tube 9, so that the sensor 1/2 can move. Therefore, the inner diameter of the embedded pipe 3 needs to be larger than the maximum outer diameter of the sensor 1/2, but smaller than the sum of the maximum outer diameters of the sensor and the airbag fixing device in the deflation state, so that the first acceleration sensor 1 and the second acceleration sensor 2 can freely move up and down in the deflation state. Because the device needs to be immersed in water for working, the space between the inflation tube 9 and the inflation port of the air bag 8 needs to be completely sealed, so that the air tightness is ensured, and the water is prevented from entering the air bag or being incapable of inflating.
For the air bag fixing device, whether the position of the sensor is fixed or not can be conveniently controlled through the inflation tube 9, so that the air bag fixing device is suitable for the detection process needing to temporarily adjust and fix the position of the sensor for multiple times. But because gasbag 8 appears slowly disappointing easily when using for a long time, causes the sensor to fix unstably, consequently the utility model provides a spring fixing device that another kind is applicable to long-term fixed more.
As shown in fig. 3, the illustrated securing device is a spring securing device. The spring fixing device can be arranged on each of the two sensors. The spring fixing means on each sensor comprises a conduit 11 and a number of springs 10. A plurality of springs 10 are fixed around the circumferential side surface of the sensor (referred to as any one of the first acceleration sensor 1 and the second acceleration sensor 2, and indicated by 1/2 in the drawing), and the number of the springs 10 can be adjusted as necessary so as to be able to fix the sensor 1/2 inside the pipe. The springs 10 are spaced as evenly as possible around the side wall of the sensor 1/2 to improve the stability of the sensor 1/2. In this spring fixing device, since the elastic force of the spring itself cannot be directly regulated by an external device, it is necessary to fix it at a target position by means of the fitting of the guide tube 11. To ensure that the sensor 1/2 is able to move freely up and down in the conduit 11, the conduit 11 should have a larger inner diameter than the sensor conduit 11. In use, the sensor 1/2 is first placed inside the conduit 11 and when the sensor is inside the conduit 11, the free end of the spring 10 around the sensor bears in compression against the inner wall of the conduit 11, temporarily fixing the sensor. However, the free end of the spring 10, i.e. the end in contact with the inner wall of the conduit 11, is not completely fixed to the inner wall of the conduit 11, but rather is supported by the spring force and is thus fixed by friction. The end of the spring 10 should be slidable against the inner wall of the guide tube 11 under the action of an external pushing force. Such external pushing force is provided by a rigid lead tube 12 wrapped around the outside of the lead 6 of each sensor 1/2, the lead tube 12 may be a steel tube or a rigid plastic tube, and in order to maintain the reliability of the lead 6 scale in terms of the depth of the sensor 1/2, the lead tube 12 is preferably a straight hollow circular tube. The inner wall of the feed-through tube 12 is preferably smooth to facilitate the sensor 1/2 being pushed out. One end of the lead pipe 12 is fixed on the sensor 1/2, and the other end axially penetrates through the guide pipe 11 and the embedded pipe 3 and extends out of the pile top of the cast-in-place concrete pile 4 for operation of a detector. Under the protection of the guide pipe 11, the spring 10 outside the sensor 1/2 does not contact with the inner wall of the embedded pipe 3, the embedded pipe can be extended downwards to a target position according to detection requirements, the lead pipe 12 can be fixed after the embedded pipe is in place, then the guide pipe 11 is pulled upwards, the sensor 1/2 slides out of the guide pipe 11, and the free end of the spring 10 is propped against the inner wall of the embedded pipe 3 to temporarily fix the sensor. Thus, the length of the spring 10 should satisfy: after the sensor 1/2 slides out of the guide tube 11, the spring 10 can prop against the inner wall of the embedded tube 3, and the elastic force is enough to keep the sensor 1/2 from sliding down. Since the spring 10 supports the sensor by means of mechanical elasticity, the sensor can be stably kept at a corresponding height for a long time, and the method is suitable for the situation that the sensor is not deeply arranged or needs to be monitored for a long time.
The double-measuring-point low-strain integrity detection device in the hole of the foundation pile can be used for detecting the concrete wave speed or the pile length of the foundation pile and also can be used for quantitatively analyzing the defect condition of the pile body.
Specifically, as shown in fig. 4, when the concrete wave velocity or the pile length of the foundation pile is detected, the distance between the first acceleration sensor 1 and the second acceleration sensor 2 is set to a certain value L0After the pulse hammer 5 strikes the pile top, the time difference delta t of the vibration response received by the two sensors is analyzed through the data acquisition and processor 70The curve shown in fig. 4 is a speed response curve received by the two sensors, so that the concrete wave velocity can be accurately obtained
According to the depth z of the second acceleration sensor 2 and the time difference delta t between the incident wave and the reflected wave received by the sensor1The total length of the pile can be obtained as
Taking an ideal necking pile as an example, the method is realized by adjusting the first acceleration sensor 1 and the second acceleration sensor 1 as shown in FIG. 5The placement depth and the distance of the speed sensors 2 change the relative positions of the first acceleration sensor 1 and the second acceleration sensor 2 and the defect. When the first acceleration sensor 1 is located above the defect and the second acceleration sensor 2 is located at the defect, it can be seen after knocking the pile top that the first acceleration sensor 1 can receive the characteristic reflected waves at the neck-down and neck-up, while the second acceleration sensor 2 only receives the characteristic reflected waves at the neck-up. According to the characteristics, the positions of the defects can be accurately analyzed by combining detection results of different positions. Further, according to the one-dimensional fluctuation theory, the following can be obtained: depth of start of necking, i.e. distance of highest position of top of necking defect from pile top
The depth at which the necking section ends, i.e. the distance of the lowest position of the bottom of the necking defect from the pile top
The degree of necking can be represented by the formula (a)
Or formula (b)
Determination (Z in the formula)1Is the section impedance of the normal pile body section, Z1＝ρ·S1·c，S1The area of the section of the normal pile body section; z2For the cross-sectional impedance, Z, of the section of the neck defect2＝ρ·S2·c，S2Is the equivalent area of the section of the necking section; ρ is the pile body material density). It is to be noted that the first formula (a) applies to the case where the first acceleration sensor 1 is located above the defect, regardless of the position of the second acceleration sensor 2; however, the second formula (b) is only applicable to the case where the first acceleration sensor 1 is above the defect, the second acceleration sensor 2 is at the defect, and the other cases are not applicable. Therefore, when the first acceleration sensor 1 is above the defect and the second acceleration sensor 2 is at the defect, the calculation results of the two formulas are processedThey can be verified against each other in theory. Therefore, when the defect and the sensor are positioned at different positions, the two sensors receive reflected waves with different characteristics, and the defect condition of the pile body can be quantitatively analyzed according to a similar method.
Therefore, the utility model discloses utilize pulse hammer 5 to strike the pile bolck, gather the received vibration response of two sensors, can reach the detection purpose according to sensor position and vibration response and analysis result. And according to the detection requirement, the positions and the intervals of the two sensors can be further adjusted and changed, the detection process is repeated, and a more accurate detection result is obtained. The different detection indexes can be measured alternatively or in combination. It should be noted that when a certain detection index needs to be monitored for a long time and the position of the sensor does not need to be moved frequently, a spring fixing device can be considered; however, it is preferable to use an airbag fixing device if the sensor position needs to be constantly moved.
Following the utility model provides a two survey point low strain integrality detection methods in hole of foundation pile based on above-mentioned detection device, this method can be used for detecting the concrete wave speed, the pile length and the pile body integrality of foundation pile simultaneously, and its concrete step is as follows:
1) the first acceleration sensor 1 and the second acceleration sensor 2 are suspended in the embedded pipe 3 by a lead wire 6 and fixed to the inner pipe wall of the embedded pipe 3 by fixing means, respectively. Moreover, in order to be able to locate the defect later, it is necessary to keep the position of the first acceleration sensor 1 at a defect-free height above the concrete cast-in-place pile 4, and in general, the probability of the defect occurring in the upper layer of the pile body close to the ground surface is small, so the first measurement may be considered to place the first acceleration sensor 1 in a shallow layer. After the two sensors are fixed, the distance L between the first acceleration sensor 1 and the second acceleration sensor 2 is recorded through scales on the lead 60The depth of the second acceleration sensor 2 located below from the pile top is z.
2) The pile top of the concrete cast-in-place pile 4 is knocked by the pulse hammer, and response data of the first acceleration sensor 1 and the second acceleration sensor 2 are acquired through the data acquisition and processing device 7.
3) Calculating the vibration response time difference (namely the response time difference of the incident waves) deltat of the first acceleration sensor 1 and the second acceleration sensor 2 to the knocking at this time0Obtaining the wave velocity of the concrete in the concrete filling pile 4
4) Calculating the time difference delta t between the incident wave and the reflected wave at the bottom of the pile received by the second acceleration sensor 2 after the knocking1To obtain the total length of the pile
5) Judging the integrity of the pile body according to the reflected wave characteristics of the first acceleration sensor 1 and the second acceleration sensor 2 collected by knocking:
if the first acceleration sensor 1 and the second acceleration sensor 2 only receive the reflected waves at the bottom of the pile, it is judged that no defect exists in the current foundation pile, and the pile body is complete.
If the first acceleration sensor 1 or the second acceleration sensor 2 receives the characteristic reflected wave of the defect of the pile body besides the reflected wave at the pile bottom, the defect existing in the current foundation pile is judged, and the pile body is incomplete. In this case, there may be a plurality of cases of the defect, and the type of the defect can be determined from the waveform of the reflected wave. In general, a necking defect has a large negative effect on the bearing capacity of the pile body, while a necking defect has a positive effect on the bearing capacity of the pile, so that the necking defect can be regarded as a defect, but the necking defect is subjected to the following further position determination and defect degree detection so as to take a countermeasure later.
6) For the concrete cast-in-place pile 4 with the necking defect, the position of the necking defect is further judged according to the reflected wave characteristics of the first acceleration sensor 1 and the second acceleration sensor 2:
a. if the second acceleration sensor 2 only receives the characteristic reflected wave at the neck-expanding part but not the characteristic reflected wave at the neck-contracting part, judging that the current position of the second acceleration sensor 2 is the position of the defect;
b. if the second acceleration sensor 2 can receive the characteristic reflected waves at the neck-down part and the neck-expanding part, judging that the position of the defect is positioned below the second acceleration sensor 2;
c. if the second acceleration sensor 2 does not receive the characteristic reflected wave at the neck and the characteristic reflected wave at the neck spread, it is determined that the defect is located above the second acceleration sensor 2.
7) According to the judgment result of the step 6), if the position of the second acceleration sensor 2 is the position of the necking defect, the position of the defect can be determined according to the current scale shown by the lead 6. However, if the second acceleration sensor 2 is not located at the position of the neck defect, i.e., in the latter two cases b and c, the second acceleration sensor 2 needs to be moved toward the position of the neck defect by adjusting the fixing device, and the specific moving distance can be roughly estimated from the signals of the incident wave and the reflected wave detected in the previous time. And then repeating the steps 2) to 6) again until the condition a is met, and determining the position of the necking defect.
8) When the position of the neck-in defect is determined, the degree of neck-in can be quantitatively determined according to the above equations (a) and (b). However, since it is necessary to satisfy both of the equations (a) and (b) in the case where the first acceleration sensor 1 is located above the position of the neck defect and the second acceleration sensor 2 is located at the position of the neck defect, it is necessary to calculate by substituting the wave response data obtained in this case into the equations. In general, if the length of the defect segment is not large and the distance between the two sensors is long enough, the wave response data can be obtained in the previous steps and can be directly used for calculation. However, if the distance between the two sensors is smaller than the height of the neck, it may happen that both sensors are located in the neck defect section, and the previous data cannot be directly used for calculation, and it is necessary to keep the second acceleration sensor 2 stationary, then move the first acceleration sensor 1 upward until it is located above the defect, then perform tapping and detection again, and record the wave response data through the data acquisition and processing device 7. The following describes a method for quantitatively analyzing the defect degree (including the starting point of the defect and the necking degree) by acquiring wave response data (denoted as D) of two sensors after the pile top is knocked by the obtained impulse hammer under the condition that the first acceleration sensor 1 is located above the position of the necking defect and the second acceleration sensor 2 is located at the position of the necking defect:
when the wave response data D is obtained through recording, the height difference between the corresponding first acceleration sensor 1 and the pile top is z1The height difference between the second acceleration sensor 2 and the pile top is z2。
And then calculating the height difference between the top position of the necking defect and the pile top as h1：
In the formula: Δ t2The time difference between the incident wave received by the first acceleration sensor 1 in the wave response data and the characteristic reflected wave at the neck is obtained;
calculating the height difference between the bottom position of the necking defect and the pile top to be h2：
In the formula: Δ t3The time difference between the incident wave received by the second acceleration sensor 2 in the wave response data and the characteristic reflected wave at the neck-expanding part is obtained;
from h1And h2The length of the defect can be determined.
Respectively calculating the equivalent cross-sectional area S of the position of the necking defect according to the formulas (a) and (b)2：
In the formula: a. the1Is the amplitude of the incident wave received by the first acceleration sensor 1 in the wave response data; a. the2The amplitude of the characteristic reflected wave at the neck received by the first acceleration sensor 1 in the wave response data is obtained; a. the3Is the amplitude of the incident wave received by the second acceleration sensor 2 in the wave response data; s1The cross section area of the normal pile body section without defects in the concrete cast-in-place pile 4 is obtained.
S obtained by the above two formulas2Can be mutually verified, if the error between the two is not large, one of the two or the average can be taken as the equivalent cross-sectional area S2If the error between the two values is large, the measurement needs to be carried out in the multiple embedded pipes 3 again so as to improve the measurement accuracy. It should be noted that the equivalent cross-sectional area S measured by the method2Only to approximate the extent of the defect, and since defects are not generally ideal neck shapes, the estimated value is not completely accurate, but substantially reflects the degree of neck.
In addition, when the wave velocity and the pile length of the concrete are measured, comparison can be carried out based on results obtained by multiple measurements, or an average value can be obtained, so that errors are reduced as much as possible. When the stake that awaits measuring is longer, the reflection at the bottom of the stake can not be surveyed to the traditional low strain detection method, through the utility model discloses a place as deep as possible in the stake can be put down to two sensors to the method, then strikes the pile bolck again and carry out corresponding detection.
The above-mentioned embodiments are merely a preferred embodiment of the present invention, but it is not intended to limit the present invention. Various changes and modifications can be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, all the technical schemes obtained by adopting the mode of equivalent replacement or equivalent transformation fall within the protection scope of the utility model.
Claims (9)
1. The utility model provides a two survey point low strain integrality detection device in hole of foundation pile which characterized in that: the device comprises a first acceleration sensor (1), a second acceleration sensor (2), a pre-buried pipe (3), a pulse hammer (5), a lead (6) and a data acquisition and processing device (7); the pulse hammer (5) is used for knocking the pile top of the concrete cast-in-place pile (4); at least one embedded pipe (3) is vertically embedded in a reinforcement cage of the concrete cast-in-place pile (4); the first acceleration sensor (1) and the second acceleration sensor (2) are both hung in the embedded pipe (3) and keep a distance; the two sensors are respectively provided with a fixing device for temporarily fixing the sensors on the pipe wall of the embedded pipe (3); the first acceleration sensor (1) and the second acceleration sensor (2) are connected with an external data acquisition and processing device (7) through leads (6).
2. The dual-gauge low-strain integrity test device in a hole in a foundation pile of claim 1, wherein: the fixing device is an air bag fixing device, the air bag fixing device is an airtight air bag (8) with an inflation inlet, the air bag (8) is wrapped outside the sensor in a surrounding mode, the inflation inlet of the air bag is connected with one end of an inflation tube (9) in an airtight mode, and the other end of the inflation tube (9) is connected to the outside of the foundation pile.
3. The dual-gauge low-strain integrity test device in a hole in a foundation pile of claim 2, wherein: the inner diameter of the embedded pipe (3) needs to be larger than the maximum outer diameter of the sensor, but is smaller than the sum of the maximum outer diameters of the sensor and the air bag fixing device in an air leakage state.
4. The dual-gauge low-strain integrity test device in a hole in a foundation pile of claim 1, wherein: the fixing device is a spring fixing device, and the spring fixing device on each sensor comprises a guide pipe (11) and a plurality of springs (10); a plurality of springs (10) are fixed around the peripheral side surface of the sensor, and the inner diameter of the conduit (11) is larger than that of the sensor; when the sensor is positioned in the guide pipe (11), the free end of the spring (10) in the circumferential direction of the sensor is supported on the inner wall of the guide pipe (11) in a compressed state to temporarily fix the sensor; a lead wire (6) of each sensor is wrapped with a hard lead wire tube (12), one end of each lead wire tube (12) is fixed on the sensor, and the other end of each lead wire tube passes through the pre-buried tube (3) and extends out of the pile top of the concrete cast-in-place pile (4); the tail end of the spring (10) and the inner wall of the guide pipe (11) can slide under the thrust action of the lead pipe (12); the length of the spring (10) is such that: after the sensor slides out of the guide pipe (11), the spring (10) can prop against the inner wall of the embedded pipe (3) to temporarily fix the sensor.
5. The dual-gauge low-strain integrity test device in a hole in a foundation pile of claim 1, wherein: the embedded pipes (3) are distributed at different positions of the cross section of the concrete cast-in-place pile (4).
6. The dual-gauge low-strain integrity test device in a hole in a foundation pile of claim 1, wherein: the lead (6) is provided with scales.
7. The dual-gauge low-strain integrity test device in a hole in a foundation pile of claim 1, wherein: the data acquisition and processing device (7) is a dynamic measurement instrument.
8. The dual-gauge low-strain integrity test device in a hole in a foundation pile of claim 4, wherein: the lead pipe (12) is a steel pipe or a hard plastic pipe and is a straight hollow round pipe.
9. The dual-gauge low-strain integrity test device in a hole in a foundation pile of claim 2, wherein: the inflation tube (9) is connected with an inflation device arranged outside the foundation pile, and an air stop valve is arranged on the inflation tube (9).
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| CN201920690083.XU CN210194703U (en) | 2019-05-15 | 2019-05-15 | Low strain integrality detection device of two survey points in hole of foundation pile |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110173005A (en) * | 2019-05-15 | 2019-08-27 | 浙江大学 | The Kong Zhongshuan measuring point low strain integrity test device and method of foundation pile |
| KR20230051011A (en) * | 2021-10-08 | 2023-04-17 | 주식회사 삼우에이엔씨 | Test system for tube well and method having the same |
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2019
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110173005A (en) * | 2019-05-15 | 2019-08-27 | 浙江大学 | The Kong Zhongshuan measuring point low strain integrity test device and method of foundation pile |
| KR20230051011A (en) * | 2021-10-08 | 2023-04-17 | 주식회사 삼우에이엔씨 | Test system for tube well and method having the same |
| KR102594336B1 (en) * | 2021-10-08 | 2023-10-27 | 주식회사 삼우에이엔씨 | Test system for tube well and method having the same |
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