CN114279812B - Test device for simulating pile sinking of precast pile hammering - Google Patents
Test device for simulating pile sinking of precast pile hammering Download PDFInfo
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- CN114279812B CN114279812B CN202111497287.XA CN202111497287A CN114279812B CN 114279812 B CN114279812 B CN 114279812B CN 202111497287 A CN202111497287 A CN 202111497287A CN 114279812 B CN114279812 B CN 114279812B
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- 238000012360 testing method Methods 0.000 title claims abstract description 17
- 239000002689 soil Substances 0.000 claims abstract description 69
- 239000011435 rock Substances 0.000 claims abstract description 17
- 238000010276 construction Methods 0.000 claims abstract description 9
- 239000000523 sample Substances 0.000 claims description 36
- 229910052602 gypsum Inorganic materials 0.000 claims description 15
- 239000010440 gypsum Substances 0.000 claims description 15
- 230000000149 penetrating effect Effects 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 14
- 230000035515 penetration Effects 0.000 claims description 13
- 239000012528 membrane Substances 0.000 claims description 12
- 238000005070 sampling Methods 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 claims description 6
- 230000001133 acceleration Effects 0.000 claims description 3
- 238000004140 cleaning Methods 0.000 claims description 3
- 238000011161 development Methods 0.000 claims description 3
- 238000005553 drilling Methods 0.000 claims description 3
- 239000011521 glass Substances 0.000 claims description 3
- 239000002985 plastic film Substances 0.000 claims description 3
- 229920006255 plastic film Polymers 0.000 claims description 3
- 238000012545 processing Methods 0.000 claims description 3
- 238000013461 design Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000452 restraining effect Effects 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 206010008190 Cerebrovascular accident Diseases 0.000 description 1
- 208000006011 Stroke Diseases 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
Landscapes
- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
Abstract
The invention belongs to the technical field of foundation engineering, and relates to a test device for simulating a precast pile hammering pile sinking, wherein an undisturbed soil constraint device comprises undisturbed soil, a top cover, a first split half film, a second split half film, a pipe clamp, a rigid base, a vertical rod and a nut; the device has the advantages of simple structure and convenient operation, can ensure accurate test results, can observe the influence of piling on surrounding rock and soil bodies, and provides references for actual construction.
Description
Technical field:
The invention belongs to the technical field of foundation engineering, and relates to a test device for simulating a precast pile to hammer and sink a pile, which can simulate the piling process in a soil layer, especially weathered rock, accurately record the hammering number and penetration depth in the piling process, accurately calculate the piling energy, and observe the influence on the deformation of a rock-soil body around the pile in the precast pile construction process.
The background technology is as follows:
Hammering pile sinking is a method of driving precast piles to a predetermined depth or bearing layer by using the impact energy of a pile hammer to overcome the soil resistance around the pile, and is widely used because of convenient lifting in place and high piling efficiency. At present, after pile sinking is hammered on site, if the disturbance degree of the hammered pile to the soil body of a bearing layer is required to be observed, the influence of a hammering method on the bearing performance of a pile foundation is researched, and a common method is that the pile is required to be taken out, then a pile periphery or a pile end rock-soil core sample is drilled, the damage condition of the soil body around the pile can be observed, and the possibility of secondary disturbance damage to a rock/soil core sample in the pile taking and coring processes cannot be excluded.
In addition, the pile body is driven into the stratum by the hammering pile sinking in a continuous hammering mode, the hammering construction has the characteristics of long duration, high speed and high energy, the relation between hammering energy, hammering number and penetration depth cannot be accurately obtained, the static sounding test can approximately simulate the static pile sinking, but the perpendicularity in the penetrating process is difficult to ensure, and the damage condition of rock and soil bodies around the pile cannot be observed. Therefore, it is urgently required to design a test device and a method for simulating pile driving by hammering precast piles.
The invention comprises the following steps:
The invention aims to overcome the defects in the prior art, and designs the test device for simulating the hammering pile sinking of the precast pile, which not only can ensure the verticality of the precast pile in the process of simulating hammering pile sinking, but also can observe the damage condition of soil around the pile after pile sinking in real time.
In order to achieve the above purpose, the test device for simulating the hammering pile sinking of the precast pile comprises an undisturbed soil constraint device and a hammering device, wherein the undisturbed soil constraint device comprises undisturbed soil, a top cover, a first split half membrane, a second split half membrane, a pipe clamp, a rigid base, a vertical rod and a nut, the hammering device is formed by sequentially connecting a handle, a guide rod, a penetrating hammer, a hammer pad and a probe with scales from top to bottom, the first split half membrane and the second split half membrane are fixed through the pipe clamp, the undisturbed soil is placed in a cavity enclosed by the first split half membrane and the second split half membrane and is placed on the rigid base, the vertical rod is arranged on the rigid base, the top end of the vertical rod is provided with threads, the top cover is arranged on the top of the undisturbed soil, and the top cover passes through the vertical rod and is fixed through the nut.
Furthermore, the rigid base is a cylinder, and four upright posts are distributed in a cross shape on the rigid base.
Further, the thickness of the top cover is 10cm, a round hole with the diameter 1mm larger than that of the probe with the graduation is arranged in the center and used as a guide hole, and the probe with the graduation is inserted into the guide hole when in use; grooves corresponding to the upright posts in position and size are formed in the periphery of the top cover.
Further, the diameter ratio of the graduated probe to the undisturbed soil is 1: 50-1:80.
The concrete process for simulating the pile sinking test of the precast pile hammering comprises the following steps:
(1) Drilling holes and sampling at a construction site to obtain a sampling rock core, and wrapping the sampling rock core by a plastic film to prevent water loss;
(2) Processing the on-site sampling rock core by using a soil cutter to obtain undisturbed soil, so that the upper and lower ends of the undisturbed soil 1 are horizontal and have no cracks and dents;
(3) Wrapping undisturbed soil by using a first split film and a second split film, binding firmly by using a pipe clamp, and then placing on a rigid base to simulate the boundary condition of a precast pile during hammering construction;
(4) Covering the top cover on the first split film and the second split film, inserting the vertical rod into the groove of the top cover, screwing the nut, and connecting the rigid base and the top cover into a whole to prevent relative dislocation;
(5) Inserting a graduated probe into the guide hole of the top cover and keeping the graduated probe vertical, lifting the penetrating hammer to enable the penetrating hammer to fall freely along the guide rod, hammering the hammer pad repeatedly along with the penetrating hammer, and feeding the graduated probe into undisturbed soil;
(6) Recording the weight of the penetrating hammer, the height of each hammer, the height of the falling hammer and the descending depth of the probe with the scale, calculating hammering energy according to E= mgh, recording the penetration, namely the sinking depth of each ten hammers with the scale probe, and determining the penetration according to the number of hammers and the penetration depth so as to judge the property and the bearing capacity index of the rock and soil layer, wherein m is the weight of the penetrating hammer, g is the gravitational acceleration, 10m/s 2 is taken, h is the penetrating hammer, and the falling distance is 400mm;
(7) And (3) taking the sinking depth of the graduated probe as hammering completion after 8-9 cm, slowly pulling out the graduated probe, then adding water into calcium sulfate, mixing to prepare gypsum, injecting the gypsum along the hole wall, after the gypsum is solidified for 4-5 min, cutting undisturbed soil along the gap between the first split film and the second split film, cleaning the gypsum and soil scraps of surrounding rock-soil bodies by using a hairbrush, and observing pile sinking influence (crack development condition of the surrounding rock-soil bodies of the gypsum) by using an electronic magnifying glass.
Compared with the prior art, the diameter of the undisturbed soil is far larger than that of the probe with the scale, and the influence on the periphery of the undisturbed soil can be ignored in the process of penetration; secondly, the thickness of the top cover ensures that the probe with the scales penetrates into undisturbed soil along the vertical direction with enough rigidity and strength, and the rigid base and the top cover are integrated, so that relative dislocation cannot occur, and the test error is reduced; the device has the advantages of simple structure and convenient operation, can ensure accurate test results, can observe the influence of piling on surrounding rock and soil bodies, and provides references for actual construction.
Description of the drawings:
fig. 1 is a structural view of undisturbed soil according to the present invention.
Fig. 2 is a structural view of the undisturbed soil restraining device according to the present invention.
FIG. 3 is a cross-sectional view of the undisturbed soil restraining device of the present invention taken in section 1-1.
Fig. 4 is a structural view of the hammering device according to the present invention.
Fig. 5 is a structural diagram of the first split film 3 and the second split film 4 according to the present invention.
Fig. 6 is a top view of the top cover of the present invention.
Fig. 7 is a top view of a rigid chassis according to the present invention.
FIG. 8 is a graph showing the comparative example of the presence or absence of gypsum after cutting the undisturbed soil according to the example of the invention.
Fig. 9 is a graph of data relating to the effect of moisture content on simulated driving hammer impact according to an embodiment of the present invention.
Fig. 10 is a diagram showing the impact of hammering on pile tip soil disturbance according to an embodiment of the present invention.
The specific embodiment is as follows:
The invention is further illustrated by the following examples in conjunction with the accompanying drawings.
Example 1:
The experimental device for simulating the precast pile hammering pile sinking comprises an undisturbed soil constraint device and a hammering device, wherein the undisturbed soil constraint device comprises undisturbed soil 1, a top cover 2, a first split half film 3, a second split half film 4, a pipe clamp 5, a rigid base 6, a vertical rod 7 and a nut 8, the hammering device is formed by sequentially connecting a handle 9, a guide rod 10, a through hammer 11, a hammer pad 12 and a graduated probe 13 from top to bottom, the first split half film 3 and the second split half film 4 are fixed through the pipe clamp 5, undisturbed soil 1 is placed in a cavity enclosed by the first split half film 3 and the second split half film 4 and is placed on the rigid base 6, the top end of the vertical rod 7 is provided with threads, the top cover 2 is placed on the top of the undisturbed soil, the top cover 2 passes through the vertical rod 7 and is fixed through the nut 8, the rigid base 6 is a cylinder, and four vertical rods 7 are distributed in a cross shape on the rigid base 6; the thickness of the top cover 2 is 10cm, a round hole which is 1mm larger than the diameter of the probe 13 with the graduation is arranged in the center and is used as a guide hole, and the probe 13 with the graduation is inserted into the guide hole when in use; grooves corresponding to the upright posts in position and size are formed in the periphery of the top cover 2; the diameter of the graduated probe 13 was 10mm and the diameter of the undisturbed soil 1 was 89mm.
Example 2:
In this embodiment, in order to study the characteristics of mudstone and the influence of hammering pile sinking on the bearing capacity of the pile foundation with the bearing layer of mudstone, the device described in embodiment 1 is adopted to study the mudstone, and the concrete process is as follows:
the first step: drilling and coring (core diameter is 89 mm) by using a 108 drill bit at a construction site to obtain a sampling core, and wrapping the sampling core by using a plastic film to prevent water loss;
and a second step of: processing the on-site sampling rock core by using a soil cutter to obtain undisturbed soil 1, so that the upper end and the lower end of the undisturbed soil 1 are horizontal, and no cracks and dents exist;
And a third step of: wrapping undisturbed soil 1 by using a first split film 3 and a second split film 4, binding firmly by using a pipe clamp 5 (with slight elasticity), and then placing on a rigid base 6;
Fourth step: covering the top cover 2 on the left split film 3 and the right split film 4, inserting the vertical rod 7 into the groove of the top cover, screwing the nut 8, and connecting the base 6 and the top cover 2 into a whole;
Fifth step: the graduated probe 13 is inserted into the guide hole of the top cover 2, kept vertical, the through hammer 11 is lifted to enable the through hammer 11 to fall freely along the guide rod 10, and the graduated probe 13 is sent into the rock mass along with repeated hammering of the hammer pad 12 by the through hammer 11.
Sixth step: recording the weight of the through hammer 11, calculating hammering energy according to E= mgh according to the height of each hammer, the falling weight height and the descending depth of the graduated probe 13, and recording the penetration, namely the sinking depth of each 10 hammers with the graduated probe 13, wherein m is the weight of the through hammer 11, g is the weight acceleration of 10m/s 2, h is the through hammer 11, and the falling distance height is 400mm;
Seventh step: taking the sinking depth of the graduated probe 13 as 8-9 cm, then taking hammering out, slowly pulling out the graduated probe 13, then adding water into calcium sulfate, mixing to obtain gypsum, injecting the gypsum along the hole wall, after the gypsum is solidified for 4-5 min, cutting the undisturbed soil 1 along the gap between the first split film 3 and the second split film 4, cleaning the gypsum and the soil scraps of the surrounding rock-soil body by using a hairbrush, and observing the pile sinking influence (the crack development condition of the surrounding rock-soil body of the gypsum) by using an electronic magnifying glass, as shown in fig. 8;
Eighth step: the analysis of test results shows that the penetration of the pile and the water content of the sampling rock core are in positive correlation, along with the increase of the penetration depth, the friction resistance of the pile side is gradually exerted, the penetration is gradually reduced, the pile is in line with the actual situation of the site, in addition, the observation result of an electronic magnifier shows that the rock-soil body at the pile end has obvious transverse inclined cracks (other strong/apoplexy rocks are not cracked or are not obvious), the pile foundation bearing capacity is insufficient in the region where the pile foundation bearing layer is mudstone, the reason of the phenomenon is possibly related to the disturbance of the rock-soil body around the pile after the pile is driven by hammering through the test analysis, and the concrete result is shown in fig. 9 and 10.
Claims (2)
1. The test device is characterized by comprising an undisturbed soil constraint device and a hammering device, wherein the undisturbed soil constraint device comprises undisturbed soil, a top cover, a first split half membrane, a second split half membrane, a pipe clamp, a rigid base, a vertical rod and a nut, the hammering device is formed by sequentially connecting a handle, a guide rod, a penetrating hammer, a hammer pad and a probe with scales from top to bottom, the first split half membrane and the second split half membrane are fixed through the pipe clamp, the undisturbed soil is placed in a cavity surrounded by the first split half membrane and the second split half membrane and is placed on the rigid base, the vertical rod is arranged on the rigid base, the top end of the vertical rod is provided with threads, the top cover is arranged at the top of the undisturbed soil, and the top cover penetrates through the vertical rod and is fixed through the nut; the rigid base is a cylinder, and four upright posts are distributed in a cross shape on the rigid base; the thickness of the top cover is 10cm, a round hole with the diameter 1mm larger than that of the probe with the graduation is arranged in the center and used as a guide hole, and the probe with the graduation is inserted into the guide hole when in use; grooves corresponding to the upright posts in position and size are formed in the periphery of the top cover; the concrete process for simulating the precast pile hammering pile sinking test by adopting the device comprises the following steps:
(1) Drilling holes and sampling at a construction site to obtain a sampling rock core, and wrapping the sampling rock core by a plastic film to prevent water loss;
(2) Processing the on-site sampling rock core by using a soil cutter to obtain undisturbed soil, so that the upper and lower ends of the undisturbed soil 1 are horizontal and have no cracks and dents;
(3) Wrapping undisturbed soil by using a first split film and a second split film, binding firmly by using a pipe clamp, and then placing on a rigid base to simulate the boundary condition of a precast pile during hammering construction;
(4) Covering the top cover on the first split film and the second split film, inserting the vertical rod into the groove of the top cover, screwing the nut, and connecting the rigid base and the top cover into a whole to prevent relative dislocation;
(5) Inserting a graduated probe into the guide hole of the top cover and keeping the graduated probe vertical, lifting the penetrating hammer to enable the penetrating hammer to fall freely along the guide rod, hammering the hammer pad repeatedly along with the penetrating hammer, and feeding the graduated probe into undisturbed soil;
(6) Recording the weight of the penetrating hammer, the height of each hammer, the height of the falling hammer and the descending depth of the probe with the scale, calculating hammering energy according to E= mgh, recording the penetration, namely the sinking depth of each ten hammers with the scale probe, and determining the penetration according to the number of hammers and the penetration depth so as to judge the property and the bearing capacity index of the rock and soil layer, wherein m is the weight of the penetrating hammer, g is the gravitational acceleration, 10m/s 2 is taken, h is the penetrating hammer, and the falling distance is 400mm;
(7) Taking the sinking depth of the graduated probe as the hammering completion after 8-9 cm, slowly pulling out the graduated probe, then mixing calcium sulfate with water to prepare gypsum, injecting the gypsum along the hole wall, after 4-5 min of gypsum is solidified, cutting undisturbed soil along the slit of the first split film and the second split film, cleaning the gypsum and soil scraps of surrounding rock-soil mass by using a hairbrush, and observing the crack development condition of the surrounding rock-soil mass by using an electronic magnifying glass.
2. The test device for simulating pile driving by hammering a precast pile according to claim 1, wherein the diameter ratio of the graduated probe to undisturbed soil is 1: 50-1:80.
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- 2021-12-09 CN CN202111497287.XA patent/CN114279812B/en active Active
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|---|---|---|---|---|
| CN106592655A (en) * | 2016-12-30 | 2017-04-26 | 太原理工大学 | Tubular pile sinking simulation test device and method under gradient confining pressure |
| CN106836317A (en) * | 2017-02-24 | 2017-06-13 | 同济大学 | A kind of pile sinking model test apparatus for considering soil plug effect and its application |
| CN107100210A (en) * | 2017-05-04 | 2017-08-29 | 武汉工程大学 | The pile-soil interaction mechanical behavior test system of controllable ambient stress |
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