CN-116607579-B - Pile foundation verticality detection method based on elastic deformation theory and static load test

CN116607579BCN 116607579 BCN116607579 BCN 116607579BCN-116607579-B

Abstract

The invention discloses a pile foundation verticality detection method based on elastic deformation theory and static load test, which comprises the steps of positioning and installing a distributed optical fiber sensor on the lowest section of reinforcement cage, vertically and upwards binding the distributed optical fiber sensor along a plurality of sections of reinforcement cage to form a test line, enabling the distributed optical fiber sensor to pass through a preformed hole on a loading device, placing a plurality of sections of connected reinforcement cage into a drill hole until reaching the design height of the reinforcement cage, fixing the test line on the top of a cast-in-place pile, pouring concrete, detecting the pile body concrete strength of the cast-in-place pile by adopting a rebound instrument, carrying out treatment leveling on the pile head of the cast-in-place pile after reaching a preset strength value, connecting an acquisition instrument with the test line, carrying out equipment debugging, carrying out standard vertical loading on the pile foundation of the cast-in-place pile, synchronously starting the acquisition instrument to acquire test line data, and obtaining the pile foundation verticality according to the acquired data. The device developed by the invention is simple, the cost is low, and the detection method is simple and easy to master.

Inventors

LIU JUN
LUO YANGYANG
GUO PAN
MA QINGWEN
WANG LEI
MA GUANGDONG
XU NING
CAI YINGCHUN
ZHOU HEKUAN

Assignees

郑州大学
河南省公路工程局集团有限公司
河南交投焦郑高速公路有限公司

Dates

Publication Date: 20260505
Application Date: 20230616

Claims (3)

1. A pile foundation verticality detection method based on elastic deformation theory and static load test is characterized by comprising the following steps: firstly, positioning and installing a distributed optical fiber sensor on the reinforcement cage of the lowest section, wherein the distributed optical fiber sensor is vertically and upwards bound along the reinforcement cage connected with a plurality of sections to form a measuring line; the distributed optical fiber sensors penetrate through the reserved holes on the loading device, a plurality of sections of connected reinforcement cages are lowered into the drilled holes until the design height of the reinforcement cages is reached, and the measuring lines are fixed on the top of the filling pile; pouring concrete, detecting the concrete strength of a pile body of the cast-in-place pile by adopting a rebound instrument, and performing treatment leveling on a pile head of the cast-in-place pile after reaching a preset strength value; connecting an acquisition instrument with the survey line, debugging equipment, carrying out standard vertical loading on the pile foundation of the cast-in-place pile after the debugging is completed, synchronously starting the acquisition instrument to acquire survey line data, and obtaining the perpendicularity of the pile foundation according to the acquired data; Positioning and installing the distributed optical fiber sensor relative to the center of the filling pile in a cross symmetry mode; In the process of enabling the distributed optical fiber sensor to pass through a preformed hole on a loading device, the optical fiber in the preformed hole is wound in a spiral mode, and the reserved telescopic length of the optical fiber is larger than 6cm; If the loading device adopts pile top loading, after the concrete strength of the pile body of the cast-in-place pile reaches 75% of the design strength, the pile head of the cast-in-place pile is broken; the test line data are strain data of the test line, the strain data of the test line are compared and analyzed to evaluate the perpendicularity of the pile foundation, the evaluation process comprises the steps of respectively obtaining strain amounts of two test lines, wherein the two test lines are two test lines positioned on the same line in the cross line layout, obtaining a perpendicularity expression corresponding to a pile foundation section based on a calculation formula of the strain amount, an elastic deformation theory and the pile foundation inclination, and obtaining the pile foundation perpendicularity according to a strain difference of any section on the two test lines and the perpendicularity expression; The specific analysis method comprises the following steps: The method comprises the steps that firstly, a first sensor measuring line (1), a second sensor measuring line (2), a third sensor measuring line (3) and a fourth sensor measuring line (4) are installed on the lowest section of reinforcement cage in a positioning mode relative to the center of a pile, the length of a distributed optical fiber sensor=pile length+500 cm is vertically and upwards bound along the reinforcement cage to form the measuring line, and the connecting line of the first sensor measuring line (1) and the third sensor measuring line (3) is perpendicular to the connecting line of the second sensor measuring line (2) and the fourth sensor measuring line (4) and is intersected at the center of the pile; Secondly, a reinforcement cage is lowered, and a distributed optical fiber sensor is bound, when a load box is adopted for loading, the distributed optical fiber sensor penetrates through a reserved hole reserved on the load box at the position of the load box, and optical fibers in the reserved hole adopt a spiral winding mode, wherein the elongation of the optical fibers is larger than 6cm; thirdly, after the reinforcement cage is completely lowered, fixing a first sensor measuring line (1) to a fourth sensor measuring line (4) on the pile top; Fourthly, pouring concrete, detecting the concrete strength of the pile body by adopting a rebound instrument, and after the concrete strength reaches 75% of the design strength, performing pile head breaking treatment and leveling, wherein when a load box is used for loading, no pile head breaking step is performed; Pile head treatment: 1) Firstly, the broken layer and weak concrete at the top of the pile should be chiseled off; 2) The top surface of the pile head should be flat, the central axis of pile head and pile body the central axes of the parts are coincident; 3) The main ribs of the pile head are all communicated below the pile top concrete protective layer, and all the main ribs are at the same height; 4) In the range of 1 time of pile diameter from the pile top, steel plates with the thickness of 3-5 m are used for wrapping or hooping is arranged in the range of 1.5 times of pile diameter from the pile top, the distance is not more than 100mm, 2-3 layers of reinforcing steel meshes are arranged on the pile top, and the distance is 60-100 mm; Fifthly, arranging a loading counterforce device on the pile top, wherein the loading device adopts a conventional anchor pile beam counterforce device, or a ballast platform counterforce device, or an anchor pile ballast combined counterforce device, and loading the bearing capacity of the counterforce device The formula is satisfied: ; Wherein, the Designing bearing capacity for pile foundations; Alpha is a correction coefficient, and when pile foundation bearing capacity test is carried out, alpha=2.6; When only pile body verticality is detected, α=1.3; Step six, connecting the test line to the acquisition instrument to debug the equipment, wherein the debugging process comprises the steps of 1, judging whether the sensor is intact, 2, resetting the acquisition instrument to zero, 3, pre-pressing the test pile before the test, wherein the pre-pressing load is 5% of the maximum loading amount, the pre-pressing time is 5min, and unloading to zero after the pre-pressing; The seventh step, vertical loading is carried out on the pile foundation, and a static load test is started, when the static load test of the pile foundation is carried out, loading working conditions are loaded according to relevant requirements, a synchronous starting acquisition instrument is carried out, and data of a test line are acquired; Eighth step, comparing and analyzing strain data of the first sensor measuring line (1) to the fourth sensor measuring line (4), and evaluating pile foundation verticality; according to the inclination of the pile body: K = ×100; ; the section of Li-pile hole i is the length from the section of the pile hole i to the hole opening, and the section of e1 i-pile hole i is the eccentric distance; when the strain epsilon 1, epsilon 2, epsilon 3 and epsilon 4 of any section of the first sensor measuring line (1), the second sensor measuring line (2), the third sensor measuring line (3) and the fourth sensor measuring line (4) meet the following formulas, the perpendicularity of the pile foundation meets the requirements; for the strain on any section i of the first sensor line (1) and the third sensor line (3), the strain is obtained - ; Wherein the connecting line of the measuring points 1i and 3i passes through the center of the pile; The perpendicularity of the pile foundation i section, Tanα= ; Tanα= ; Wherein D is the diameter of the pile foundation, Is the pile foundation inclination angle; the conversion is carried out so that, = ; ; Then the first time period of the first time period, = ; When the pile body gradient k is less than or equal to 1%, the strain difference on any section i of the first sensor measuring line (1) and the third sensor measuring line (3) is required to satisfy the following conditions: ≤ ; Similarly, the strain difference on any section i of the second sensor measuring line (2) and the fourth sensor measuring line (4) is as follows: ≤ ; When the formula is 、 When the two kinds of the components are satisfied at the same time, the gradient of the pile body meets the requirement.
2. The method for detecting perpendicularity of pile foundation based on elastic deformation theory and static load test according to claim 1, wherein, The length of the distributed optical fiber sensor is determined according to the pile length in a mode of taking the pile length, a fixed value and the length as the length of the distributed optical fiber sensor.
3. The method for detecting perpendicularity of pile foundation based on elastic deformation theory and static load test according to claim 1, wherein, If the loading device adopts pile top loading, a loading counterforce device is arranged on the pile top of the cast-in-place pile, any one of an anchor pile beam counterforce device, a ballast platform counterforce device and an anchor pile ballast combined counterforce device is adopted as the loading counterforce device, the bearing capacity of the loading counterforce device is determined according to the design bearing capacity of the pile foundation and a correction coefficient, and the correction coefficient is determined according to the detection position.

Description

Pile foundation verticality detection method based on elastic deformation theory and static load test Technical Field The invention belongs to the technical field of building industry, and particularly relates to a pile foundation verticality detection method based on elastic deformation theory and static load test. Background The bored pile foundation has the characteristics of high bearing capacity, wide application range and the like, and is widely applied to projects such as high-rise buildings, bridges and the like. Each construction procedure of the bored pile and each construction process adopted can directly influence the pile forming quality, and the bored pile has decisive effects on whether the bored pile finally meets the construction design requirement, whether the bored pile can meet the relevant quality acceptance criterion and the like. The perpendicularity of the bored pile after pile forming directly influences the stress state and the service life of the structure, so that the perpendicularity of the pile foundation is an important content of construction detection and is also an important index for evaluating construction quality in the pile foundation construction process. The related specifications make clear regulations on various parameters such as pore diameter, pore depth, pore inclination, sediment and the like of the pore, however, an effective detection method is not available for detecting the perpendicularity of the pile body after pile forming. Disclosure of Invention The invention aims to provide a pile foundation verticality detection method based on an elastic deformation theory and a static load test, so as to solve the problems in the prior art. In order to achieve the above purpose, the invention provides a pile foundation verticality detection method based on elastic deformation theory and static load test, comprising the following steps: firstly, positioning and installing a distributed optical fiber sensor on the reinforcement cage of the lowest section, wherein the distributed optical fiber sensor is vertically and upwards bound along the reinforcement cage connected with a plurality of sections to form a measuring line; the distributed optical fiber sensors penetrate through the reserved holes on the loading device, a plurality of sections of connected reinforcement cages are lowered into the drilled holes until the design height of the reinforcement cages is reached, and the measuring lines are fixed on the top of the filling pile; pouring concrete, detecting the concrete strength of a pile body of the cast-in-place pile by adopting a rebound instrument, and performing treatment leveling on a pile head of the cast-in-place pile after reaching a preset strength value; Connecting an acquisition instrument with the survey line, debugging equipment, carrying out standard vertical loading on the pile foundation of the cast-in-situ pile after the debugging is completed, synchronously starting the acquisition instrument to acquire survey line data, and obtaining the perpendicularity of the pile foundation according to the acquired data. Optionally, the distributed optical fiber sensors are positioned and installed in a cross symmetry mode relative to the center of the filling pile. Optionally, the length of the distributed optical fiber sensor is determined according to the pile length in a mode of taking the pile length, a fixed value and the length as the length of the distributed optical fiber sensor. Optionally, in the process of passing the distributed optical fiber sensor through the preformed hole on the loading device, the optical fiber in the preformed hole is wound in a spiral form, and the preformed telescopic length of the optical fiber is greater than 6cm. Optionally, if the loading device adopts pile top loading, after the concrete strength of the pile body of the cast-in-place pile reaches 75% of the design strength, the pile head of the cast-in-place pile needs to be broken. Optionally, if the loading device adopts pile top loading, a loading counterforce device is arranged on the pile top of the cast-in-place pile, any one of an anchor pile beam counterforce device, a ballast platform counterforce device and an anchor pile ballast combined counterforce device is adopted as the loading counterforce device, the bearing capacity of the loading counterforce device is determined according to the pile foundation design bearing capacity and a correction coefficient, and the correction coefficient is determined according to the detection position. Optionally, the test line data are strain data of the test line, the strain data of the test line are compared and analyzed to evaluate the perpendicularity of the pile foundation, the evaluation process comprises the steps of respectively obtaining strain amounts of two test lines, wherein the two test lines are two test lines positioned on the same line in a crisscross line layout, obtaining a perpendicularity expres