CN102943493A

CN102943493A - Method for measuring internal force and deformation of precast pile

Info

Publication number: CN102943493A
Application number: CN2012105147380A
Authority: CN
Inventors: 邬俊杰; 陈锦剑; 王建华
Original assignee: Shanghai Jiao Tong University
Current assignee: Shanghai Jiao Tong University
Priority date: 2012-12-04
Filing date: 2012-12-04
Publication date: 2013-02-27
Anticipated expiration: 2032-12-04
Also published as: CN102943493B

Abstract

The invention proposes a method for measuring the internal force and deformation of prefabricated piles. After the piling process is completed, the sensor and the pile foundation vertical static load test equipment connected to the sensor are installed, and the load of a certain level is recorded before the next level of load is applied. The sensor reading below is the relative deformation between the observation point connected by the force cable and the reference point; the relative deformation is divided by the pile length of the section to obtain the relative strain of the observation section relative to the reference plane, and two adjacent observation points The strain difference between the two sections is obtained from the strain of the section relative to the reference plane, and the axial force of the pile body at the section of each anchor head is calculated according to the calibration result of the concrete elastic modulus of the pile body. A method for measuring the internal force and deformation of prefabricated piles in the present invention adopts the installation of sensors after the piling process is completed, avoiding damage to the sensors during the piling process, and has high measurement accuracy and can effectively control costs.

Description

Measure the method for preformed pile internal force and distortion

Technical field

The present invention relates to a kind of method of civil engineering pile foundation technical field of quality detection, be specifically related to a kind of method of measuring preformed pile internal force and distortion.

Background technology

Pile foundation is as a large amount of base forms that adopt of engineering construction at present, and is little except having sedimentation, the bearing capacity advantages of higher, and it also relates to the important component part of structural safety, and therefore the detection for pile foundation is vital.

Main method for the Internal forces test has reinforcing rib meter method and slip micrometer method at present.(1) reinforcing rib meter method: reinforcing rib meter is embedded on the pile body master muscle according to substructure, the ess-strain at the bottom of the detection a certain cross section of pile body and the post.This method of testing principle is simple, testing element is easy to install, but strain that can only measuring point, and the distortion between 2 can only be leaned on deduction, and because reinforcing rib meter is the average internal force of extrapolating stake according to the strain of any on the reinforcing bar, can there be no small error like this.Because the sensor such as reinforcing rib meter need to be embedded in the pile body, in the making of stake and piling process, cause damage easily, and affect test performance and the calibration coefficient of sensor, thereby can be lowered into motility rate and affect test result.In addition, because sensor can not be recycled after pre-buried, belong to medical disposable material, the cost of the test of increase.(2) slip micrometer method: with respect to the reinforcing rib meter method, slip micrometer method can be measured the strain under all each point axis directions loads at different levels on the whole pile body axis continuously, and can effectively revise and float zero.Measuring point is many although it has, and continuity is good, and precision advantages of higher, the shortcoming that its cost is high also are the factors that needs are considered.

Patent 200910056699.2 provides a kind of method, by vertical service sleeve or directly at the pile body longitudinal drilling, installs and measures system at pile body in sleeve pipe or boring, and this measuring system is comprised of anchor head, multiple position extensometer, extension bar and force pipe.According to the vertical deformation between adjacent two the anchor head positions with all of stake top vertical displacement observed result, a layering frictional resistance, stake end bearing power and the anchor head of each soil layer of reckoning stake side are buried the vertical displacement of section underground, thereby realize Internal forces and section vertical displacement measurement.

All there is at least one shortcoming in the above traditional method.For example, the former precision is not high enough, and because sensor is installed first, produces easily damage problem; Although latter's precision can reach requirement, high cost, economical not.

Summary of the invention

The problem that the object of the invention is to solve in the prior art low precision when measuring preformed pile internal force and distortion or high cost.

To achieve these goals, the present invention proposes a kind of method of measuring preformed pile internal force and distortion, it is characterized in that, may further comprise the steps: determine observation point anchorage head quantity and the position of burying section underground; Service sleeve on the pile body of described preformed pile is vertical; The benchmark anchorage head that has the hole is installed on stake top at described preformed pile; In the described position of burying section underground described observation point anchorage head is installed, and described observation point anchorage head and described sleeve pipe are fixedly linked, if run into the situation of pile extension, one anchoring temporarily point then is set in stake the last period, be used for fixedly passing the power transmission rope of pile extension section, the hole of passing through for described power transmission rope is set on the described anchoring temporarily point; The operation of driving piles if need pile extension, is then proceeded the pile extension operation; One sensor is provided, by the hole on the described benchmark anchorage head, is installed on the described power transmission rope, and described sensor is demarcated; The pile foundation vertical static loading experiment equipment that links to each other with described sensor is installed, is applied before the next stage load, record the sensor reading under certain grade of load, namely this power transmission rope connects the relative deformation of observation point place and benchmark place; This relative deformation is long divided by this section stake, obtain measuring frequency section with respect to the relative strain of datum, with the strain of adjacent two measuring frequency sections with respect to datum, obtain the strain value between these two sections, according to pile concrete modulus of elasticity calibration result, calculate the pile body axle power of each anchorage head section part.

Optionally, may further comprise the steps: the first step, determine that according to geotechnical investigation report, construction note, regional experience and the designing requirement in place, test pile place suitable observation point anchorage head quantity and its bury cross section place underground; Second step, casing axis should be parallel to the pile body longitudinal axis, and sleeve pipe should mate with the anchorage head of selecting; Burying sleeve pipe underground should be arranged symmetrically with along the cross-section center axis direction, the benchmark anchorage head of installing at place, stake top, in the middle of need perforate, convenient at last sensor is packed into, at determined section part the observation point anchorage head is installed, anchorage head and sleeve pipe is firmly fixing, if meet the situation that pile extension is arranged, then the anchoring temporarily point need to be set in stake the last period, convenient fixing need to be passed the power transmission rope of pile extension section, the anchoring temporarily point needs perforate, so that the power transmission rope can be passed through; The 3rd step began piling, according to normal construction process stake was squeezed into, if need pile extension, also carried out as requested pile extension; The 4th step after stake is squeezed into, by the hole of stake top benchmark anchorage head, installed to sensor on the power transmission rope, and sensor requires can free-hand perforate by the reference point anchorage head to pack in the sleeve pipe, and is stuck on the power transmission rope; The 5th step, conventional pile foundation vertical static loading experiment equipment is installed, record according to a conventional method load after on-test; The 6th step, stable at certain grade of load action bottom offset, apply before the next stage load, record the sensor reading under certain grade of load, namely this power transmission rope connects the relative deformation of observation point place and benchmark place, this relative deformation is long divided by this section stake, obtain measuring frequency section with respect to the relative strain of datum, with the strain of adjacent two measuring frequency sections with respect to datum, obtain the strain value between these two sections, according to pile concrete modulus of elasticity calibration result, calculate the pile body axle power of each anchorage head section part.

The useful technique effect that the present invention measures the method for preformed pile internal force and distortion is: the present invention measures the method for preformed pile internal force and distortion and takes sensor installation after finishing the piling operation, avoided sensor impaired in the piling process, and certainty of measurement is high, can effectively control cost.

Description of drawings

Fig. 1 is the apparatus structure schematic diagram of the present invention's method of measuring preformed pile internal force and distortion.

The specific embodiment

Below, 1 the present invention is described in further detail by reference to the accompanying drawings.Label among Fig. 1: 1-observation point anchorage head; The 2-sleeve pipe; 3-reference point anchorage head; The 4-sensor; 5-power transmission rope; The temporary fixed point of 6-power transmission rope; 7-pile extension head; The 8-data acquisition instrument.

Please refer to Fig. 1, Fig. 1 is the apparatus structure schematic diagram of the present invention's method of measuring preformed pile internal force and distortion, and the concrete steps of the inventive method are:

(1) determines that according to geotechnical investigation report, construction note, regional experience and the designing requirement in place, test pile place suitable observation point anchorage head quantity and its bury cross section place underground.Observation point anchorage head 1 generally can be embedded in two kinds of heterogeneity soil layers at the interface.

(2) when the system stake, bury sleeve pipe 2 underground.The sleeve pipe material will not limit, but requires casing axis should be parallel to the pile body longitudinal axis, and sleeve pipe 2 should mate with the observation point anchorage head 1 of selecting and reference point anchorage head 3; Burying sleeve pipe underground should be arranged symmetrically with along the cross-section center axis direction.At place, stake top reference for installation anchorage head 3, need perforate in the middle of the benchmark anchorage head 3, conveniently at last sensor 4 is packed into.At determined section part observation point anchorage head 1 is installed, with observation point anchorage head 1, reference point anchorage head 3 is firmly fixing with sleeve pipe 2.With power transmission rope 5 each observation point anchorage head 1 is connected with benchmark anchorage head 3 respectively, if meet the situation that pile extension is arranged, then anchoring temporarily point 6 need to be set in stake the last period, convenient fixing need to be passed the power transmission rope 5 of pile extension section.Anchoring temporarily point 6 needs perforate, so that the power transmission rope can be passed through

(3) begin piling, according to normal construction process stake is squeezed into, if need pile extension, also carry out as requested pile extension.

(4) after stake is squeezed into, by the hole of stake top benchmark anchorage head 3, sensor 4 is put into stake, and be installed on the power transmission rope 5.Transmitting wire by data links to each other with the data acquisition instrument 8 of outside.Install the demarcation of laggard line sensor, be that standard volume inputs to sensor undetermined 4, obtain simultaneously the output quantity of sensor 4, the sensor input and output amount that obtains is compared and treated, thereby obtain the calibration curve of both corresponding relations of a series of signs, obtain the measured result of sensor performance index.

(5) conventional pile foundation vertical static loading experiment equipment is installed, is recorded according to a conventional method load after on-test.

(6) stable at certain grade of load action bottom offset, apply before the next stage load, record the reading of the data acquisition instrument 8 under certain grade of load, i.e. the observation point place that connects of this power transmission rope and the relative deformation δ of benchmark place.This relative deformation δ divided by the long L of this section stake, then can be obtained measuring frequency section for the relative strain ε of datum.ε=δ/L。With the strain of adjacent two measuring frequency sections with respect to datum, then can obtain the strain value between these two sections.dε _i=ε _i+1-ε _i。ε _iBe that i observation point anchorage head place is with respect to the strain value of datum.According to pile concrete modulus of elasticity calibration result E=f (ε), pile body cross sectional area A then can calculate the pile body axle power N of each anchorage head section part _i=EA d ε _i

Although the present invention discloses as above with preferred embodiment, so it is not to limit the present invention.Have in the technical field of the present invention and usually know the knowledgeable, without departing from the spirit and scope of the present invention, when being used for a variety of modifications and variations.Therefore, protection scope of the present invention is as the criterion when looking claims person of defining.

Claims

1. A method for measuring prefabricated pile internal force and deformation, is characterized in that, comprises the following steps:

Determine the number of anchor heads at the observation point and the position of the buried section;

pre-embed casing in the longitudinal direction of the pile body of the prefabricated pile;

A benchmark anchor head with holes is installed on the pile top of the prefabricated pile;

The observation point anchor head is installed at the position of the buried section, and the observation point anchor head is fixedly connected with the casing. If a pile is encountered, a temporary anchor is set in the previous pile point, used to fix the catenary cable passing through the pile-connecting section, and the temporary anchor point is provided with a hole for the catenary cable to pass through;

Carry out the piling process, if the pile needs to be connected, then continue to carry out the pile connection process;

providing a sensor, mounted on the force cable through the hole on the reference anchor head, and calibrating the sensor;

Install the pile foundation vertical static load test equipment connected to the sensor, before applying the next level of load, record the sensor reading under a certain level of load, that is, the relative deformation between the observation point connected by the force cable and the reference point;

Divide the relative deformation by the pile length of this section to obtain the relative strain of the observed section relative to the datum plane, and use the strains of two adjacent observed sections relative to the datum plane to obtain the strain value between the two sections, according to the pile body The calibration result of the concrete elastic modulus is used to calculate the axial force of the pile body at the section of each anchor head.

2. pile body internal force and deformation measuring device according to claim 1, is characterized in that, comprises the following steps:

The first step is to determine the appropriate number of anchor heads at the observation point and the position of the buried section according to the geotechnical engineering investigation report, construction records, regional experience and design requirements of the site where the test pile is located;

In the second step, the axis of the casing should be parallel to the longitudinal axis of the pile, and the casing should match the selected anchor head; the embedded casing should be arranged symmetrically along the central axis of the cross section, and the reference anchor head installed at the top of the pile should be Open a hole to facilitate the final installation of the sensor, install the anchor head of the observation point at the determined section, and firmly fix the anchor head and the casing. If there is a pile connection, it is necessary to set up a temporary anchor in the previous section of the pile point, to facilitate the fixation of the transmission cable that needs to pass through the pile section, and the temporary anchor point needs to open a hole so that the transmission cable can pass through;

The third step is to start piling and drive the piles according to the normal construction process. If piles need to be connected, they should also be connected according to the requirements;

Step 4: After the pile is driven in, install the sensor on the force transmission cable through the hole of the reference anchor head on the top of the pile. superior;

The fifth step is to install conventional pile foundation vertical static load test equipment, and record the load according to the conventional method after the test starts;

The sixth step is that the displacement is stable under a certain level of load. Before applying the next level of load, record the sensor readings under a certain level of load, that is, the relative deformation between the observation point connected by the force cable and the reference point, and the relative deformation Divide by the pile length of this section to obtain the relative strain of the observed section relative to the datum level, and use the strains of two adjacent observed sections relative to the datum level to obtain the strain value between the two sections, according to the concrete elastic modulus of the pile body Calibrate the results and calculate the axial force of the pile body at the section of each anchor head.