CN114960597A - Method for testing strain-internal force of pile body of PHC pipe pile - Google Patents

Abstract

The invention discloses a method for testing strain-internal force of a PHC pipe pile body, which comprises the following steps: s1: binding a reinforcement cage body arranged in the pile body of the PHC tubular pile, fixedly arranging an occupying wooden mold on the reinforcement cage body, pouring concrete, and removing the occupying wooden mold after high-temperature and high-pressure steam curing to obtain the PHC tubular pile with the installation groove on the outer surface of the pile body; s2: a strain sensor is arranged in the mounting groove; filling a waterproof and moistureproof soft adhesive layer in the mounting groove; s3: and (3) sinking the PHC tubular pile construction with the strain sensor into the stratum, loading and measuring the strain data of the strain sensor, and calculating the internal force of the PHC tubular pile body test section according to the strain data. When the PHC pipe pile provided with the strain sensor by the occupying wood pattern occupying method is used for carrying out strain-internal force test, the strain sensor is convenient to install, the measurement result is accurate, the error is small, the precision is high, the test cost is low, and the operation is convenient.

Description

A test method for the strain-internal force of PHC pipe piles

technical field

The invention belongs to the field of civil engineering, in particular to a method for testing the strain-internal force of a PHC pipe pile body.

Background technique

For the pre-tensioned high-temperature steam curing process prestressed high-strength concrete (PHC) pipe pile concrete strain-internal force test process, there are mainly three existing methods in the past, namely the pile body through-length grooving method and the middle hole core filling method. method and pre-buried I-beam method, the above three methods all need to install a strain sensor on the test section of the pile body to measure the pile body strain. The internal force of the test section of the pile body is obtained.

The full-length grooving method of the pile body is to position the groove along the length of the pile body, and arrange the strain sensor and data line in the long-length groove. Most of them use fiber optic sensors, and then Waterproof glue is poured, and the corresponding strain test is carried out after the pile construction sinks into the stratum. The main defects of this method are as follows: 1. The long groove of the pile body causes great damage to the pile body. Although epoxy mortar is used to supplement the pile in the later stage, its influence on the pile body has not been studied; 2. The long groove is poured with waterproof glue. The area is large, and the waterproof glue and strain sensor are easily damaged by hard objects such as stones in the stratum, which reduces the survival rate of the strain sensor. , the pile length is limited.

The middle hole core filling method is to close the welded iron plate at the end of the PHC pipe pile to be tested and then to construct the pile. In the middle hole of the cross-sectional position of the PHC pipe pile to be tested, the strain gauge is fixed on a steel cage or measuring pipe. And put it into the middle hole of the PHC pipe pile, and then fill the core with concrete in the middle hole of the PHC pipe pile. The main defects of this method are as follows: 1. The concrete core is filled at the test section, which greatly changes the stiffness of the pipe pile at the test position; 2. The sensor cannot be directly arranged in the concrete of the pile body, but can only be arranged in the core-filled concrete , the measured data is the strain of the core-filled concrete, not the strain of the test target PHC pipe pile body, and the difference between the two is not clear.

The pre-embedded I-beam method is to embed I-beam on the outside of the pile where the cross-section position needs to be tested during the filling stage of PHC pipe pile production. After centrifugal forming and high-temperature steam curing, the sensor is attached to the surface of the I-beam; for strain For the wire treatment of the sheet, it is necessary to drill a wire hole along the radial direction of the pipe pile under the I-beam, straight through the inner hole of the PHC pipe pile, and the strain gauge wire passes through the inner wall of the PHC pipe pile and is led out from the top of the pile. The main defects of this method are as follows: 1. The elastic modulus of the I-beam is not consistent with that of concrete. The I-beam will definitely affect the elastic modulus of the test section of the pipe pile. The strain gauge directly measures the embedded I-beam. 2. The strain gauge is pasted on the surface of the I-beam, and it is difficult to ensure that the strain gauge is not damaged during the pile driving construction process, and it is not easy to carry out waterproof treatment.

It can be seen from the above that although the above three methods can calculate the internal force of the pile body according to the measured strain data and the empirical value of the elastic modulus of the reinforced concrete material using the existing theory, the above three methods have the following common problems: 1. Strain sensor 2. The test shows that the prestressed steel bar will gradually load with the axial pressure of the pipe pile to produce stress relaxation, and the pile body of the prestressed concrete pipe pile The strain-internal force relationship is not a linear relationship, that is, the elastic modulus of the pile body reinforced concrete is not a fixed value. The strain data is measured according to the above method, and then the internal force of the pile body is calculated by the empirical value of the elastic modulus of the reinforced concrete of the pile body, which obviously affects the measurement and calculation accuracy, and the error is difficult to estimate. Based on this, the present invention provides a new method for PHC pipe pile section strain-internal force test.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology, and to provide a test method for PHC pipe pile body strain-internal force with small measurement error, high accuracy and easy operation. In order to solve the above-mentioned technical problems, the technical scheme proposed by the present invention is:

A test method for the strain-internal force of a PHC pipe pile body, comprising the following steps:

S1: Bind the steel cage body set in the PHC pipe pile body, and fix the space-occupying wooden form on the steel cage body, then pour concrete, and after curing with high temperature and high pressure steam, remove the space-occupying wooden formwork to obtain the outer surface of the pile body. PHC pipe piles with mounting grooves;

S2: install a strain sensor in the installation groove, and the data line of the strain sensor is introduced through the central channel of the PHC pipe pile; then fill the installation groove with a waterproof and moisture-proof soft glue layer;

S3: sink the PHC pipe pile with the strain sensor installed into the stratum, load and measure the strain data of the strain sensor, and calculate the internal force of the test section of the PHC pipe pile body according to the strain data.

In the present invention, the test section refers to the cross section where the corresponding strain sensor is located, that is, the internal force obtained from the strain data of a strain sensor refers to the internal force at the cross section where the strain sensor is located. The above internal force generally refers to the axial force of the section. Measuring the internal force of the pipe pile at different positions is to determine the axial force distribution of the pile body and the vertical bearing capacity provided to the pipe pile by different soil layers, to provide a basis for the engineering design of using the pipe pile as the building foundation, or to verify the vertical direction of the pipe pile in the engineering design. The rationality of the value of bearing capacity parameters.

In the above test method, preferably, the PHC pipe pile is a commonly used 500AB-125 type PHC pipe pile, the outer diameter of the pile is 500mm, the wall thickness is 125mm, the concrete strength grade of the pile body is C80, and the test sections are evenly distributed in 4 groups. Strain sensor: The strain data of the strain sensor is measured by the on-site static load test, and then the internal force of the PHC pipe pile section is calculated according to the strain data through the strain-internal force function relationship of the test section. The specific process is as follows:

When each group of the strain sensors is a strain gauge (resistance strain gauge), measure the strain data of the strain gauge, and take the average value to obtain the strain data x ₁ , and calculate the internal force y ₁ of the test section of the PHC pipe pile according to the following formula, The formula is as follows:

y ₁ =72.69303+6.62273x ₁ -0.00122x ₁ ² ;

When each group of the strain sensors is a Hyun-type strain gauge, measure the strain data of the Hyun-type strain gauge, and take the average value to obtain the strain data x ₂ , and calculate the internal force y ₂ of the test section of the PHC pipe pile body according to the following formula. The formula is as follows :

y ₂ =98.12869+7.27296x ₂ -0.00273x ₂ ² ;

When each group of the strain sensors is a strain gauge and a Hyun-type strain gauge, the internal force y ₁ and the internal force y ₂ are calculated respectively, and the average of the two is obtained to obtain the internal force y ₃ of the test section of the PHC pipe pile.

In the above test method, we require a test section to be fixed with 4 installation grooves, which is also the number commonly used to ensure accuracy in this test; the number of installation grooves in the same section has a certain impact on the test accuracy, adding or reducing one installation groove. The influence on the calculation results is not more than 1.07%. If the number of installation slots is changed, the calculation results can be corrected for errors. In the above test method, the length of the installation groove used is 22.5cm, the width is 3.7cm, and the depth is the same as the thickness of the steel protective layer. The size of this installation groove can meet the installation needs of most mainstream strain sensors.

Generally, the more strain sensors are used to test the stress, the higher the accuracy of the calculation result obtained by calculating the internal force after averaging the multiple strain data. A more preferred solution of the present invention is to install a strain gauge and a strain gauge in each installation slot. type strain gage, the final measurement result has higher accuracy and smaller error.

In the above test method, preferably, the strain data of the strain sensor is loaded and measured, and according to the strain data, the internal force of the test section of the PHC pipe pile body does not need to be based on the empirical value of the elastic modulus of the reinforced concrete material of the pile body. That is, the internal force calculation does not use the traditional empirical constant value and linear function of the elastic modulus of the pile body reinforced concrete material, but uses the accurate nonlinear relationship function of the measured section of the pipe pile obtained by our research.

In the above test method, preferably, the placeholder wooden mold comprises a first block, and the first block is provided with a second cylinder and a pair of third cylinders (the spacing distance is determined according to the specification of the strain sensor), The second and third cylinders are fixed (preferably vertically fixed) on the same surface of the first block.

In the above test method, preferably, the thickness of the first block (thickness along the radial direction of the pile body) is not greater than the thickness of the sidewall concrete protection layer of the PHC pipe pile, and the thickness of the first block is the same as the thickness of the first block. The sum of the lengths of the second column is not less than the wall thickness of the PHC pipe pile. When the PHC pipe pile is prefabricated, the outer surface of the first block is on the same plane as the outer surface of the PHC pipe pile wall. The size of the first block can be adjusted according to the size of the strain sensor to be installed, and the sum of the thickness of the first block and the length of the second cylinder (referring to the radial length of the pile body) can be controlled, so that the second cylinder can obtain the same value as the PHC. The central channel of the pipe pile is connected with a through hole to install the data cable.

In the above test method, preferably, the sum of the thickness of the first block and the length of the third cylinder is less than the wall thickness of the PHC pipe pile. Controlling the sum of the thickness of the first block and the length of the third cylinder allows the third cylinder to obtain a blind hole that does not communicate with the central channel of the PHC pipe pile for mounting the strain sensor.

In the above-mentioned test method, preferably, the space-occupying wooden form can preferably be a hard wooden form. The first block is preferably a cuboid block for forming the mounting slot, the second cylinder can be cylindrical for forming through holes, and the third cylinder can also be cylindrical for forming blind holes, but the The length is shorter than the second cylinder. Each mounting slot can attach strain gauges on the bottom concrete, install strain gauges on blind holes, and more preferably install both strain gauges and strain gauges.

In the above test method, preferably, a plurality of space-occupying wooden molds are uniformly fixed at the same cross section of the reinforcement cage body, the first block is arranged on the outer surface of the reinforcement cage body, and the second block is arranged on the outer surface of the reinforcement cage body. The column body and the third column body face the center of the reinforcement cage body. When prefabricating PHC pipe piles, the steel cage body can be bound first, and then the space-occupying wooden formwork can be fixedly installed on the steel-reinforced cage body, concrete is poured, and after high-temperature steam curing, the space-occupying wooden formwork can be removed to form the strain sensor installation slot and blind spot. holes and data cable holes. Setting up multiple placeholder molds can form multiple strain sensor installation positions at the same cross section of the PHC pipe pile, so as to facilitate multi-point measurement and obtain accurate measurement results.

In the above test method, preferably, the surface of the PHC pipe pile wall is provided with an installation groove obtained from the first block, and the bottom of the installation groove is provided with a center obtained from the second column and connected to the center of the PHC pipe pile. A through hole communicated with a channel, and a blind hole obtained from the third cylinder is also provided at the bottom of the installation groove. The above-mentioned installation groove and blind hole are used for installing the strain sensor, and the above-mentioned through hole is used for the data line of the strain sensor to pass through the central channel into the PHC pipe pile. By installing the strain sensor in the above way, there is no need to perform cutting and grooving processing on the PHC pipe pile, and there is no need to pre-embed I-beams, steel plates, etc. The strain of the reinforced concrete pile body of the pipe pile is obtained.

In the above test method, preferably, the strain sensor includes a strain gauge and a Hyun-type strain gauge, the strain gauge is attached to the bottom of the installation groove, and the Hyun-style strain gauge is installed on the blind hole through the blind hole. At the bottom of the installation groove, the data line of the strain sensor is introduced into the central channel in the PHC pipe pile through the reserved through hole, and then led from the hollow part of the pipe pile to the outside of the pile top. The resistance strain gauge can only be pasted on the concrete surface at the bottom of the installation groove, or the Hyun-type strain gauge can be installed only on the reserved blind hole in the concrete at the bottom of the installation groove. It is more preferable to use both at the same time. average value.

In the above test method, preferably, the installation groove is provided with a waterproof and moisture-proof soft adhesive layer for protecting the strain sensor. After the strain sensor of each measuring point is installed, after the data cable is put on, it is confirmed that it can work normally after testing, and then the waterproof and moisture-proof soft glue layer can be set to play a waterproof and moisture-proof effect, such as pouring 703 waterproof soft glue for waterproof and moisture-proof. deal with. This method has been verified by the waterproof test, and the waterproof and moisture-proof effect is reliable.

In the above-mentioned test method, preferably, the notch of the installation groove is provided with a protective iron sheet for covering the notch, and the end of the protective iron sheet close to the bottom of the PHC pipe pile (one end of the pile bottom in the pile driving direction) is fixed by fixing. The parts are fixedly connected with the PHC pipe pile wall, and other parts of the protective iron sheet are not fixedly connected with the PHC pipe pile wall. In order to prevent the coarse-grained soil blocks and other debris from scratching the waterproof and moisture-proof soft rubber layer during the construction of the field test pile, a protective iron sheet can be installed on the outside after waterproof treatment. Only the lower end of the protective iron sheet is fixed, and the upper end and the side are not fixed, so as to prevent the protective iron sheet from locally restraining the test section of the pile and further ensure the measurement accuracy.

For the strain-internal force test method of the PHC pipe pile section, the existing test methods all need to be converted according to the strain data measured by the strain sensor, according to the elastic modulus of the pile body, through the empirical relationship between the pipe pile strain and the internal force. internal force. However, the existing test methods and the installation process of the strain sensor all have an impact on the section stiffness of the pile body and affect the strain test accuracy. The pile body strain-internal force relationship of the pipe pile is not a linear relationship, that is, the elastic modulus of the pile body reinforced concrete is not a fixed value. According to the strain data measured by the existing method, the internal force of the pile body is calculated by the empirical value of the elastic modulus of the reinforced concrete of the pile body, and the error is difficult to estimate. All these factors make the calculation of pile body stress have a large error.

The testing method of the present invention, when measuring the cross-section strain of the PHC pipe pile, compared with the method of grooving through the pile body, has less damage to the concrete of the pile body and less work for subsequent filling; The effect of hole filling on the pile stiffness and the internal force-strain relationship can directly measure the strain of the pile concrete; compared with the pre-buried I-beam method, the influence of the I-beam on the pile stiffness and the internal force-strain relationship is avoided. Strain sensors are easy to install, easy to protect, have a high survival rate, and can use either strain gages or concrete strain gages. The whole has many advantages, such as strong operability, high survival rate of strain sensor, and accurate measurement results. On the whole, the testing method of the present invention is convenient for the installation of the strain sensor. When the strain sensor is used to measure the strain of the PHC pipe pile, the test section of the tested pile body is less damaged, the shape of the installation groove is regular, and the glue filling area is small. , There is no need to fill the concrete core in the central channel of the PHC pipe, and there is no need to pre-embed I-beam and other external steel to affect the stiffness of the test section of the pile body. The waterproof and moisture-proof treatment is reliable, and the strain sensor has a high survival rate. The calculation of reinforced concrete strain and internal force does not need to use the empirical value of the elastic modulus of the pile body reinforced concrete material, the measurement and calculation results are more accurate, and the test cost is low. In addition, the PHC pipe pile of the present invention is not limited by the length of the pile, and can be applied to the inspected piles with pile-connecting construction, and has strong operability during prefabrication, and is not limited by the temperature and pressure of steam curing.

In the present invention, the PHC pipe pile with the strain sensor is installed by the space-occupying wooden formwork method, and the indoor test research is carried out, and based on the indoor test data, the true and accurate strain-internal force relationship curve of the test section of the PHC pipe pile is given. And the fitting function provides an accurate basis for the strain-internal force conversion of the tested pile test section, thereby minimizing the strain test and internal force calculation errors.

Compared with the prior art, the advantages of the present invention are:

1. The present invention adopts the wood mold occupying method to install the PHC pipe pile of the strain sensor for strain-internal force test, which is convenient for the installation of the strain sensor. When the strain sensor is used to measure the strain of the PHC pipe pile, the tested pile The body test section has little damage, the installation groove has a regular shape, and the glue repair area is small. It is not necessary to fill the concrete core in the central channel of the PHC pipe pile, and there is no need to pre-embed I-beam and other external steel to affect the stiffness of the test section of the pile body. Waterproof and moisture-proof treatment Reliable, the strain sensor has a high survival rate, can directly measure the reinforced concrete strain of the pipe pile body, the measurement result is accurate, the error is small, the precision is high, the test cost is low, and the operation is convenient.

2. In the test method of the present invention, the PHC pipe pile is not limited by the length of the pile, and can be applied to the inspected piles with pile-connecting construction. It has strong operability during prefabrication and is not limited by the temperature and pressure of steam curing.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are For some embodiments of the present invention, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a placeholder wooden mold in an embodiment.

FIG. 2 is a schematic diagram of the connection structure between the reinforcement cage body of the PHC pipe pile and the space-occupying wooden formwork in the embodiment.

FIG. 3 is a schematic view of the structure of the PHC pipe pile in the embodiment.

4 is a schematic structural diagram (partial cutaway view) when the waterproof and moisture-proof soft glue layer and the protective iron sheet are not shown at the installation groove of the PHC pipe pile in the embodiment.

5 is a schematic structural diagram showing a waterproof and moisture-proof soft rubber layer and a protective iron sheet at the installation groove of the PHC pipe pile in the embodiment.

illustration:

1. The first block; 2. The second cylinder; 3. The third cylinder; 4. PHC pipe pile; 5. Reinforcing cage body; 6. Installation slot; 7. Through hole; 8. Blind hole; 9. Strain sensor; 10. Data cable; 11. Waterproof and moisture-proof soft rubber layer; 12. Protective iron sheet.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and in detail below with reference to the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

Unless otherwise defined, all technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention.

Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or can be prepared by existing methods.

Example:

The test method for the strain-internal force of the PHC pipe pile body of the present embodiment includes the following steps:

S1: Bind the reinforcement cage body 5 arranged in the pile body of the PHC pipe pile 4, and fix the space-occupying wooden form on the reinforcement cage body 5, then pour concrete, and remove the space-occupying wooden form after curing to obtain the outer surface of the pile body. Install the PHC pipe pile 4 in the slot 6;

S2: Install the strain sensor 9 in the installation groove 6, and the data line 10 of the strain sensor 9 is introduced into the central channel of the PHC pipe pile 4 through the through hole 7; Waterproof soft glue);

S3: sink the PHC pipe pile 4 with the strain sensor 9 installed into the ground, load and measure the strain data of the strain sensor 9, and calculate the internal force of the test section of the PHC pipe pile 4 according to the strain data.

In this embodiment, the strain data of the strain sensor 9 is loaded and measured, and according to the strain data, the internal force of the test section of the PHC pipe pile 4 pile body does not need to be based on the empirical constant value of the elastic modulus of the reinforced concrete material of the pile body.

In this embodiment, the PHC pipe pile 4 is a 500AB-125 type PHC pipe pile, the outer diameter of the pile is 500mm, the wall thickness is 125mm, the concrete strength grade of the pile body is C80, and the test sections are evenly distributed with 4 sets of strain sensors 9; measure the strain Based on the strain data of sensor 9, the internal force of PHC pipe pile 4 is calculated according to the strain data. The specific process is as follows:

When each group of strain sensors 9 adopts strain gauges, measure the strain data of the strain gauges, and take the average value to obtain the strain data x ₁ , and calculate the internal force y ₁ of the test section of the PHC pipe pile 4 according to the following formula. The formula is as follows:

y ₁ =72.69303+6.62273x ₁ -0.00122x ₁ ² ;

When each group of strain sensors 9 uses a Hyun-type strain gauge, the strain data of the Hyun-type strain gauge is measured, and the average value is obtained to obtain the strain data x ₂ , and the internal force y ₂ of the test section of the PHC pipe pile 4 is calculated according to the following formula. The formula is as follows :

y ₂ =98.12869+7.27296x ₂ -0.00273x ₂ ² ;

When each group of strain sensors 9 uses strain gauges and Hyun-type strain gauges at the same time, the internal force y ₁ and the internal force y ₂ are calculated respectively, and the two are averaged to obtain the internal force y ₃ of the test section of the PHC pipe pile 4 .

As shown in FIG. 1 , in this embodiment, the placeholder wooden mold includes a first block 1 , and the first block 1 is provided with a second cylinder 2 and a pair of third cylinders 3 (distributed one above the other and the other is spaced apart). Determined by the specifications of the Hyun-type strain gauge), the second cylinder 2 and the third cylinder 3 are arranged on the same surface of the first block 1 .

In this embodiment, the thickness of the first block 1 is not greater than the thickness of the sidewall concrete protective layer of the PHC pipe pile 4 , and the sum of the thickness of the first block 1 and the length of the second column 2 is not less than the thickness of the PHC pipe pile 4 . wall thickness. The sum of the thickness of the first block 1 and the length of the third cylinder 3 is less than the wall thickness of the PHC pipe pile 4 .

In this embodiment, specifically, a hardwood form can be used to design the space-occupying wooden form for the installation of the concrete strain sensor 9 of the pile body. The surface of the wooden form needs to be flat and smooth. It is 3.7cm, the thickness is 4.5cm, the second cylinder 2 and the third cylinder 3 are cylinders, the diameters of the cylinders can be 1.5cm and 0.7cm respectively, and the length of the third cylinder 3 can be 3cm. The placeholder mold is fixed and pre-embedded in the concrete pipe wall. After curing, the placeholder wooden mold is removed to form the installation groove 6 of the strain sensor 9. Each test section can evenly arrange 4 strain measuring points in the circumferential direction. The size of the occupied wooden form has a small influence on the above strain-internal force calculation formula (the size of the first block 1 can meet the installation needs of most strain sensors, such as adjusting the size of the wooden form has a slight influence on the calculation result, The influence of the dimensions of the second cylinder 2 and the third cylinder 3 is negligible), preferably, the above dimensions have a good matching relationship with the aforementioned calculation formula, the test error is small, and the precision is high.

As shown in FIG. 2 , in this embodiment, a plurality of space-occupying wooden molds (4 in this embodiment) are evenly fixed at the same cross section of the reinforcement cage body 5 ; the first block 1 is arranged on the reinforcement cage body 5 , the second cylinder 2 and the third cylinder 3 face the center of the reinforcement cage body 5 .

As shown in Figures 3 and 4, in this embodiment, the surface of the PHC pipe pile 4 is provided with an installation groove 6 obtained from the first block 1, and the bottom of the installation groove 6 is provided with a second cylinder 2 and is connected with The central passage of the PHC pipe pile 4 communicates with the through hole 7 , and the bottom of the installation groove 6 is also provided with a blind hole 8 obtained from the third cylinder 3 .

As shown in FIG. 5 , in this embodiment, the strain sensor 9 includes a strain gauge and a Hyun-type strain gauge. The strain gauge is attached to the bottom of the installation groove 6 , and the Hyun-type strain gauge is installed at the bottom of the installation groove 6 through the blind hole 8 . The data line 10 of the sensor 9 is sent to the central channel of the PHC pipe pile 4 through the through hole 7 .

As shown in FIG. 5 , in this embodiment, the notch of the installation groove 6 is provided with a protective iron sheet 12 for covering the notch, and one end of the protective iron sheet 12 close to the bottom of the PHC pipe pile 4 passes through the fixing member and the pile wall of the PHC pipe pile 4 Fixed connection, other parts of the protection iron sheet 12 are not fixedly connected with the PHC pipe pile 4 pile wall.

In order to better understand the test method of the above strain-internal force, this embodiment is introduced as follows with a specific application example (the in-situ test of the bearing capacity of the round gravel and its overlying fine-grained soil layer PHC pipe pile):

Test site: Changde Liuye Lake·Golden Xiaodao Engineering Site;

The name of the soil layer of the site from top to bottom: silty clay, silt, fine sand, round gravel, the average thickness of the fine-grained soil layer above the round gravel is 12 meters;

Number of test piles: 7;

Design of the length of the test pile: The method of one pile and one drilling is used to conduct on-site investigation, and the length of the test pile is designed according to the drilling investigation data, and the depth of the pile end entering the round gravel bearing layer meets the requirements of the specification;

The position of the pile body sensor layout section: the interface between the fine-grained soil and the coarse-grained soil layer (round gravel layer), four installation grooves 6 are arranged in the circumferential direction of the pile section (see the size of the spacer wooden mold), resistance strain gauges and Xuan type The strain gages were used in combination; the results shown in Table 1 below were obtained.

Table 1: Summary table of test data analysis results of each test pile before and after grouting reinforcement

Claims (10)

1. a test method for PHC pipe pile body strain-internal force, is characterized in that, comprises the following steps: S1: Bind the steel cage body (5) set in the PHC pipe pile (4), and fix the space-occupying wooden form on the steel cage body (5), then pour concrete, and remove the space-occupying wooden form after curing to obtain PHC pipe piles (4) with installation grooves (6) on the outer surface of the pile body; S2: A strain sensor (9) is installed in the installation groove (6), and the data line (10) of the strain sensor (9) is introduced through the central channel of the PHC pipe pile (4); (6) The middle is filled with a waterproof and moisture-proof soft adhesive layer (11); S3: sink the PHC pipe pile (4) equipped with the strain sensor (9) into the ground, load and measure the strain data of the strain sensor (9), and calculate the pile body of the PHC pipe pile (4) according to the strain data Test the internal force of the section. 2. testing method according to claim 1, is characterized in that, described PHC pipe pile (4) is 500AB-125 type PHC pipe pile, and its pile outer diameter is 500mm, wall thickness is 125mm, pile body concrete strength grade It is C80, and the test section is evenly distributed with 4 sets of strain sensors (9); the strain data of the strain sensor (9) is measured, and the internal force of the PHC pipe pile (4) is calculated according to the strain data. The specific process is as follows: When each group of the strain sensors (9) is a strain gauge, the strain data of each strain gauge is measured, and the average value is obtained to obtain the strain data x ₁ , and the test section of the pile body of the PHC pipe pile (4) is calculated according to the following formula The internal force y ₁ of , the formula is as follows: y ₁ =72.69303+6.62273x ₁ -0.00122x ₁ ² ; When each group of the strain sensors (9) is a Hyun-type strain gauge, the strain data of the Hyun-type strain gauge is measured, and the average value is obtained to obtain the strain data x ₂ , and the PHC pipe pile (4) pile body test is calculated according to the following formula The internal force y ₂ of the section, the formula is as follows: y ₂ =98.12869+7.27296x ₂ -0.00273x ₂ ² ; When each group of the strain sensors (9) is a strain gauge and a Hyun-type strain gauge, the internal force y ₁ and the internal force y ₂ are calculated respectively, and the average of the two is obtained to obtain the internal force y of the test section of the PHC pipe pile (4). ₃ . 3. The test method according to claim 2, wherein the strain data of the strain sensor (9) is loaded and measured, and according to the strain data, it is not necessary to calculate the internal force of the test section of the PHC pipe pile (4) pile body According to the empirical value of the elastic modulus of the pile body reinforced concrete material. 4. The test method according to any one of claims 1-3, characterized in that, the placeholder wooden mold comprises a first block body (1), and the first block body (1) is provided with a first block body (1). Two cylinders (2) and a pair of third cylinders (3), the second cylinders (2) and the third cylinders (3) are arranged on the same surface of the first block (1). 5. The test method according to claim 4, characterized in that, the thickness of the first block (1) is not greater than the thickness of the sidewall concrete protective layer of the PHC pipe pile (4), and the first block (1) The sum of the thickness and the length of the second cylinder (2) is not less than the wall thickness of the PHC pipe pile (4). 6. The test method according to claim 4, characterized in that the sum of the thickness of the first block (1) and the length of the third cylinder (3) is less than the length of the PHC pipe pile (4). wall thickness. 7. The test method according to claim 4, characterized in that, a plurality of space-occupying wooden molds are uniformly fixed at the same cross-section of the reinforcement cage body (5); the first block (1) is provided with On the outer surface of the reinforcement cage body (5), the second cylinder (2) and the third cylinder (3) face the center of the reinforcement cage body (5). 8. The test method according to claim 4, characterized in that, the surface of the pile wall of the PHC pipe pile (4) is provided with an installation groove (6) obtained from the first block (1), and the installation groove ( 6) The bottom is provided with a through hole (7) obtained from the second column (2) and communicated with the central passage of the PHC pipe pile (4), and the bottom of the installation groove (6) is also provided with a third column. Blind hole (8) obtained from body (3). 9 . The testing method according to claim 8 , wherein the strain sensor ( 9 ) comprises a strain gauge and a Hyun-type strain gauge, the strain gauge is attached to the bottom of the installation groove ( 6 ), and the The Hyun-type strain gauge is installed at the bottom of the installation groove (6) through the blind hole (8); the data line (10) of the strain sensor (9) is sent to the PHC through the through hole (7) in the central channel of the pipe pile (4). 10. The test method according to claim 4, characterized in that, a protective iron sheet (12) for covering the notch is provided at the notch of the installation groove (6), and the protective iron sheet (12) is close to the One end of the bottom of the PHC pipe pile (4) is fixedly connected to the pile wall of the PHC pipe pile (4) through a fixing piece, and other parts of the protective iron sheet (12) are not fixedly connected to the pile wall of the PHC pipe pile (4) .

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