CN111767598A - Refined old pile recycling method - Google Patents
Refined old pile recycling method Download PDFInfo
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- CN111767598A CN111767598A CN202010564461.7A CN202010564461A CN111767598A CN 111767598 A CN111767598 A CN 111767598A CN 202010564461 A CN202010564461 A CN 202010564461A CN 111767598 A CN111767598 A CN 111767598A
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- 238000000034 method Methods 0.000 title claims abstract description 24
- 238000004064 recycling Methods 0.000 title claims abstract description 17
- 238000012360 testing method Methods 0.000 claims abstract description 30
- 238000004458 analytical method Methods 0.000 claims abstract description 24
- 238000013461 design Methods 0.000 claims abstract description 22
- 238000006073 displacement reaction Methods 0.000 claims abstract description 19
- 230000003068 static effect Effects 0.000 claims abstract description 18
- 230000001066 destructive effect Effects 0.000 claims abstract description 7
- 238000005070 sampling Methods 0.000 claims abstract description 4
- 238000004364 calculation method Methods 0.000 claims description 11
- 239000002689 soil Substances 0.000 claims description 11
- 229910000831 Steel Inorganic materials 0.000 claims description 6
- 239000010959 steel Substances 0.000 claims description 6
- 238000012937 correction Methods 0.000 claims description 3
- 238000010276 construction Methods 0.000 abstract description 6
- 238000004062 sedimentation Methods 0.000 abstract description 4
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- 238000006243 chemical reaction Methods 0.000 description 2
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- 238000011161 development Methods 0.000 description 2
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- 230000032683 aging Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 208000037265 diseases, disorders, signs and symptoms Diseases 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000009659 non-destructive testing Methods 0.000 description 1
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- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/13—Architectural design, e.g. computer-aided architectural design [CAAD] related to design of buildings, bridges, landscapes, production plants or roads
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Abstract
The invention discloses a refined old pile recycling method, and belongs to the technical field of pile foundation construction. The invention comprises the following steps: pile foundation sampling static load test; step two: establishing friction resistance-displacement parameters; step three: identifying the pile length, the pile body integrity and the bearing stratum depth of each utilized old pile in a nondestructive low-strain testing mode; step four: establishing a nonlinear boundary condition analysis model; step five: checking the bearing capacity; step six: and (6) optimizing and adjusting. The method obtains the actual nonlinear boundary condition of the old pile in the same period through the destructive test of the unused old pile, and analyzes the nonlinear boundary condition according to the actual rigidity through the analysis parameters obtained in the steps, thereby solving the problem of partial danger of the design of the newly-built pile foundation; the problem of low utilization rate of old piles in old pile recycling engineering is solved by considering the old piles which do not meet the bearing capacity according to the nonlinear sedimentation piles.
Description
Technical Field
The invention relates to the technical field of pile foundation construction, in particular to a refined old pile recycling method.
Background
The pile foundation is an old basic type, and the technology goes through the development process of thousands of years. However, with the rapid development of national economy in China, the traffic volume of highway traffic rises sharply, the bridge load becomes increasingly heavy, and due to the reasons of design, construction, aging and the like, the bridge diseases in operation are caused to occur continuously, the bearing capacity is reduced, the normal use of the bridge is seriously influenced, and the maintenance, reinforcement or reconstruction is urgently needed. The new and old pile foundation treatment measures of new and old buildings bring certain problems to engineering construction. But there is no clear regulation for the reuse of old piles in the current regulations. In the past project in China, the following main problems exist for the reuse of old piles: 1. in most of domestic old pile utilization, new and old piles are subjected to bearing capacity requirement analysis by adopting uniform parameters. However, in general, the upper effect of most structures of reconstruction projects is larger than that of the original structures, so that the calculated bearing capacity of most old piles does not meet the requirements of new reconstruction structures. Finally, most old piles in good conditions can only be processed in an unused mode, so that engineering waste is caused; 2. according to the standard, the bearing capacity of the old pile foundation which is stable for a long time has an improvement coefficient. However, for the friction pile, the displacement of the pile bottom is limited, and the pile bottom soil layer still does not generate complete compression deformation. The old pile which is stable for many years does not represent a pile bottom bearing layer and is compacted and stabilized for a long time, and the original design safety reserve is actually occupied by the method for improving the bearing capacity of the old pile. In a limit state, if the displacement of the old pile is increased nonlinearly, the new pile contributes to the load and even exceeds the bearing capacity of the old pile, so that potential safety hazards are caused; 3. when pile group calculation is carried out according to the standard when the old piles are reused, all the piles are considered according to the same displacement rigidity during pile foundation calculation, and simultaneously, the bearing platform is considered according to the rigid body. However, the displacement rigidity of the pile top of the old pile which is stable for many years is larger than that of the new pile, and the actual contribution of the old pile in the normal use stage is larger than that of a theoretical calculated value, so that the partial danger calculation and analysis condition is caused.
Disclosure of Invention
1. Technical problem to be solved by the invention
Aiming at the defects and shortcomings in the prior art, the invention provides a refined old pile recycling method, the invention obtains the actual nonlinear boundary condition of the old pile in the same period through the destructive test without using the old pile, and analyzes the nonlinear boundary condition according to the actual rigidity through the analysis parameters obtained in the steps, thereby solving the problem of partial danger of newly-built pile foundation design; the problem of low utilization rate of old piles in old pile recycling engineering is solved by considering the old piles which do not meet the bearing capacity according to the nonlinear sedimentation piles.
2. Technical scheme
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the invention discloses a refined old pile recycling method, which comprises the following steps:
the method comprises the following steps: pile foundation sampling static load test;
step two: establishing friction resistance-displacement parameters;
step three: identifying the pile length, the pile body integrity and the bearing stratum depth of each utilized old pile in a nondestructive low-strain testing mode;
step four: establishing a nonlinear boundary condition analysis model;
step five: checking the bearing capacity;
step six: and (6) optimizing and adjusting.
Further, the first step: and carrying out destructive static load test on the old structure removed pile without using a representative old pile, measuring the axial force of the pile body by using a steel bar strain gauge, and symmetrically arranging the steel bar strain gauge at the interface of the rock-soil layer of the pile body.
Further, the second step: and establishing various soil layer friction resistance-displacement curve parameters according to the static load axial force-depth result.
Further, the fourth step: and establishing an analysis model by adopting a nonlinear boundary condition according to the relevant data of the static load test and the small strain test, and obtaining the pile top counter force.
Further, the fifth step: and adjusting the mechanical property of the soil layer according to the geological survey report and the static load test result, calculating the bearing capacity and the corrected bearing capacity to investigate the actual pile body safety reserve, comparing the calculation result of the bearing capacity with the result of the previous step, enabling the grouped piles meeting the bearing capacity to meet the design and implementation requirements, and enabling the bearing capacity not to meet the verified change and correction link entering the next step.
Further, the sixth step: for the pile group foundation with the old pile bearing capacity not meeting the requirements, the occupation of safety reserves is not considered, the safety reserves are directly considered according to the nonlinear settlement pile, at the moment, the old pile is pressed and settled, the equivalent vertical displacement is increased, and the new pile support contribution is improved. And further examining the structural bearing capacity after self-balancing of the supporting force, wherein the old pile bearing capacity and the displacement rigidity do not consider the old pile foundation improvement coefficient. When the bearing capacity of the new pile does not meet the requirement, the structural design needs to be changed.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
the method obtains the actual nonlinear boundary condition of the same-period old pile through the destructive test of the unused old pile, obtains the integrity parameters of the old pile through the nondestructive test of all the old piles which are possibly utilized, and solves the problem that the design parameters and the analysis result deviate from the actual condition; through the analysis parameters obtained in the steps, nonlinear boundary condition analysis is carried out according to actual rigidity, and the problem of partial danger of newly-built pile foundation design is solved; the problem of low utilization rate of old piles in old pile recycling engineering is solved by considering the old piles which do not meet the bearing capacity according to the nonlinear sedimentation piles.
Drawings
FIG. 1 is a schematic diagram of the generalized friction-displacement curve parameters of the static load test of the present invention;
FIG. 2 is a graph of the small strain test and results of the present invention using old piles;
FIG. 3 is a graph showing the results of nonlinear parametric analysis according to the present invention;
FIG. 4 is a schematic diagram of the present invention that fails to meet the load bearing capacity requirement with 1 old pile;
FIG. 5 is a schematic diagram of the present invention showing a smaller calculated force with 2 new piles;
fig. 6 is a schematic diagram of the analysis result of the old pile-to-nonlinear settling pile of the present invention.
Detailed Description
The invention is further described with reference to the following figures and examples:
example 1
As can be seen from fig. 1 to 6, the method for recycling refined old piles in the present embodiment includes the following steps:
the method comprises the following steps: pile foundation sampling static load test;
step two: establishing friction resistance-displacement parameters;
step three: identifying the pile length, the pile body integrity and the bearing stratum depth of each utilized old pile in a nondestructive low-strain testing mode;
step four: establishing a nonlinear boundary condition analysis model;
step five: checking the bearing capacity;
step six: and (6) optimizing and adjusting.
The method comprises the following steps: and carrying out destructive static load test on the old structure removed pile without using a representative old pile, measuring the axial force of the pile body by using a steel bar strain gauge, and symmetrically arranging the steel bar strain gauge at the interface of the rock-soil layer of the pile body.
Step two: and establishing various soil layer friction resistance-displacement curve parameters according to the static load axial force-depth result.
Step four: and establishing an analysis model by adopting a nonlinear boundary condition according to the relevant data of the static load test and the small strain test, and obtaining the pile top counter force.
Step five: according to the geological survey report and the static load test result, the soil layer mechanical property is adjusted, the bearing capacity and the corrected bearing capacity are calculated to investigate the actual pile body safety reserve, the bearing capacity calculation result is compared with the result of the previous step, the group piles meeting the bearing capacity meet the design and implementation requirements, the bearing capacity does not meet the verification, and the change and correction link entering the next step is carried out
Step six: for the pile group foundation with the old pile bearing capacity not meeting the requirements, the occupation of safety reserves is not considered, the safety reserves are directly considered according to the nonlinear settlement pile, at the moment, the old pile is pressed and settled, the equivalent vertical displacement is increased, and the new pile support contribution is improved. And further examining the structural bearing capacity after self-balancing of the supporting force, wherein the old pile bearing capacity and the displacement rigidity do not consider the old pile foundation improvement coefficient. When the bearing capacity of the new pile does not meet the requirement, the structural design needs to be changed.
Example 2
wherein: 28-5 in figure 3, 31-1 and 31-3 in figures 4, 5 and 6 are newly built pile foundations, and the rest are used old piles.
Assuming that 31-X1 is an original planned used pile and 31-1 and 31-3 are newly-built pile foundations in a certain old pile utilization project, it is found through calculation and analysis that due to the non-uniformity of the support stiffness, the contribution difference of each pile is large, and optimization cannot be performed by assuming that the old pile is an elastic support and the settlement is increased, and the original design scheme needs to be changed and adjusted, as shown in fig. 4.
Increasing the pile group scale, changing the number of the old piles from 1 to two, finding that the reaction force still slightly exceeds the bearing capacity after increasing the A4 old piles, and performing an equivalent elastic support check calculation to obtain the actual bearing capacity design value of the new pile, finding that the reaction force still slightly exceeds the bearing capacity after increasing the A4 old piles, and obtaining the actual bearing capacity design value of the new pile, wherein the calculated value of the new pile stress 431t is smaller and the equivalent elastic support check calculation is performed, as shown in FIG. 5.
Considering the nonlinear settlement of the old pile, and simultaneously after the friction resistance around the old pile is reduced according to the friction resistance state, the maximum new pile top counter force is known to be 495t, new pile length checking calculation is carried out according to the counter force design value, and simultaneously, the bearing platform is designed according to an envelope method, so that the final design is completed.
The technical problem to be solved by the invention is as follows: the new pile and the old pile are subjected to bearing capacity requirement analysis by adopting unified parameters, so that the old pile with good conditions cannot be utilized, engineering waste is caused, the bearing capacity of the old pile is improved according to the specification, so that potential safety hazards exist in the limit state of the new pile, and the old pile is subjected to partial stress danger in the normal use stage if the actual compression rigidity analysis of the new pile and the old pile is not carried out.
The core idea of the invention is to use one or two unused old piles to carry out a strain test and a static load failure test, make a stress-strain map of the pile foundation and establish friction resistance-displacement parameters of each soil layer according to the stress-strain map; then, identifying the pile length, the integrity of the pile body and the depth of a bearing stratum of all utilized old piles in a nondestructive testing mode to determine other parameters of subsequent analysis; establishing an analysis model by adopting a nonlinear boundary condition to check the bearing capacity; and for the pile group foundation with the bearing capacity of the old pile not meeting the requirement, the occupation of the safety reserve is not considered, the construction design adjustment is directly carried out according to the nonlinear settlement pile, and the construction design adjustment is carried out when the bearing capacity of the new pile does not meet the checking calculation.
The method obtains the actual nonlinear boundary condition of the same-period old pile through the destructive test of the unused old pile, obtains the integrity parameters of the old pile through the nondestructive test of all the old piles which are possibly utilized, and solves the problem that the design parameters and the analysis result deviate from the actual condition; through the analysis parameters obtained in the steps, nonlinear boundary condition analysis is carried out according to actual rigidity, and the problem of partial danger of newly-built pile foundation design is solved; the problem of low utilization rate of old piles in old pile recycling engineering is solved by considering the old piles which do not meet the bearing capacity according to the nonlinear sedimentation piles.
The present invention and its embodiments have been described above schematically, without limitation, and what is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.
Claims (6)
1. A refined old pile recycling method is characterized by comprising the following steps: the method comprises the following steps:
the method comprises the following steps: pile foundation sampling static load test;
step two: establishing friction resistance-displacement parameters;
step three: identifying the pile length, the pile body integrity and the bearing stratum depth of each utilized old pile in a nondestructive low-strain testing mode;
step four: establishing a nonlinear boundary condition analysis model;
step five: checking the bearing capacity;
step six: and (6) optimizing and adjusting.
2. The method for recycling refined old piles according to claim 1, wherein: the first step is as follows: and carrying out destructive static load test on the old structure removed pile without using a representative old pile, measuring the axial force of the pile body by using a steel bar strain gauge, and symmetrically arranging the steel bar strain gauge at the interface of the rock-soil layer of the pile body.
3. The method for recycling refined old piles according to claim 1, wherein: the second step is that: and establishing various soil layer friction resistance-displacement curve parameters according to the static load axial force-depth result.
4. The method for recycling refined old piles according to claim 1, wherein: the fourth step is that: and establishing an analysis model by adopting a nonlinear boundary condition according to the relevant data of the static load test and the small strain test, and obtaining the pile top counter force.
5. The method for recycling refined old piles according to claim 1, wherein: the fifth step is as follows: and adjusting the mechanical property of the soil layer according to the geological survey report and the static load test result, calculating the bearing capacity and the corrected bearing capacity to investigate the actual pile body safety reserve, comparing the calculation result of the bearing capacity with the result of the previous step, enabling the grouped piles meeting the bearing capacity to meet the design and implementation requirements, and enabling the bearing capacity not to meet the verified change and correction link entering the next step.
6. The method for recycling refined old piles according to claim 1, wherein: the sixth step is as follows: for the pile group foundation with the old pile bearing capacity not meeting the requirements, the occupation of safety reserves is not considered, the safety reserves are directly considered according to the nonlinear settlement pile, at the moment, the old pile is pressed and settled, the equivalent vertical displacement is increased, and the new pile support contribution is improved. And further examining the structural bearing capacity after self-balancing of the supporting force, wherein the old pile bearing capacity and the displacement rigidity do not consider the old pile foundation improvement coefficient. When the bearing capacity of the new pile does not meet the requirement, the structural design needs to be changed.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010564461.7A CN111767598B (en) | 2020-06-19 | 2020-06-19 | Method for recycling refined old piles |
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| CN202010564461.7A CN111767598B (en) | 2020-06-19 | 2020-06-19 | Method for recycling refined old piles |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0960007A (en) * | 1995-08-24 | 1997-03-04 | Shimizu Corp | Foundation of new building using existing pile foundation |
| KR20080093692A (en) * | 2007-04-18 | 2008-10-22 | 주식회사 대우엔지니어링 | Behavior analyzing method of pile-bent structure |
| CN101487267A (en) * | 2009-01-14 | 2009-07-22 | 南京工业大学 | Support stiffness-adjustable pile-raft foundation and construction process |
| CN103266634A (en) * | 2013-01-09 | 2013-08-28 | 交通运输部公路科学研究所 | Determination method of bearing capacity of overlong bored pile |
| CN106546495A (en) * | 2016-11-09 | 2017-03-29 | 广西交通科学研究院 | The naked beam Static Load Test Method of Loading Control moment of flexure is determined based on strain |
| CN110952582A (en) * | 2019-11-22 | 2020-04-03 | 江苏省中成建设工程总公司 | Old and new combined pile-raft foundation structure considering old pile concrete aging and construction method |
-
2020
- 2020-06-19 CN CN202010564461.7A patent/CN111767598B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0960007A (en) * | 1995-08-24 | 1997-03-04 | Shimizu Corp | Foundation of new building using existing pile foundation |
| KR20080093692A (en) * | 2007-04-18 | 2008-10-22 | 주식회사 대우엔지니어링 | Behavior analyzing method of pile-bent structure |
| CN101487267A (en) * | 2009-01-14 | 2009-07-22 | 南京工业大学 | Support stiffness-adjustable pile-raft foundation and construction process |
| CN103266634A (en) * | 2013-01-09 | 2013-08-28 | 交通运输部公路科学研究所 | Determination method of bearing capacity of overlong bored pile |
| CN106546495A (en) * | 2016-11-09 | 2017-03-29 | 广西交通科学研究院 | The naked beam Static Load Test Method of Loading Control moment of flexure is determined based on strain |
| CN110952582A (en) * | 2019-11-22 | 2020-04-03 | 江苏省中成建设工程总公司 | Old and new combined pile-raft foundation structure considering old pile concrete aging and construction method |
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