CN114935524A - Method for testing maximum compression ratio and maximum molding density of stone filling material - Google Patents

Method for testing maximum compression ratio and maximum molding density of stone filling material Download PDF

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CN114935524A
CN114935524A CN202210559438.8A CN202210559438A CN114935524A CN 114935524 A CN114935524 A CN 114935524A CN 202210559438 A CN202210559438 A CN 202210559438A CN 114935524 A CN114935524 A CN 114935524A
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maximum
filling material
sample
stone
test
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梁军林
彦志铭
杨洋
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Guangxi University
Guangxi Vocational and Technical College of Communications
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Guangxi University
Guangxi Vocational and Technical College of Communications
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
    • G01N9/02—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity by measuring weight of a known volume
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D1/00—Investigation of foundation soil in situ
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
    • G01N15/02—Investigating particle size or size distribution
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
    • G01N3/12—Pressure testing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/24—Earth materials
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
    • G01N9/02—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity by measuring weight of a known volume
    • G01N2009/022—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity by measuring weight of a known volume of solids
    • G01N2009/024—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity by measuring weight of a known volume of solids the volume being determined directly, e.g. by size of container
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0019—Compressive
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Abstract

The invention discloses a method for testing the maximum compression ratio and the maximum molding density of a stone filling material, which is characterized in that similar grading test design is carried out according to the similarity of the filling characteristic and the crushing characteristic of the stone filling material, the molding pressure is determined according to the contact stress of a road roller and the stone filling material, a load-displacement curve in the molding process is measured, initial pressure displacement and final pressure displacement are determined by using the load-displacement curve, the compression ratio and the molding density are calculated, and the maximum compression ratio, the maximum molding density and the crushing rate under different working conditions are determined by establishing the relationship among the compression ratio, the molding density, the crushing rate and the content of framework particles. The invention provides a forming means for researching the physical and mechanical properties of the rock-fill material and establishing the constitutive relation of the rock-fill material, has important application value for the experimental research of the rock-fill material and the compaction control of the rock-fill roadbed, and can obviously improve the level of the research of the rock-fill material and the quantitative compaction control of the rock-fill roadbed by applying the invention.

Description

Method for testing maximum compression ratio and maximum molding density of stone filling material
Technical Field
The invention belongs to the technical field of compaction control of a stone-filling roadbed, and particularly relates to a test method for maximum compression ratio and maximum molding density of a stone-filling material.
Background
The application of the rockfill subgrade in highway engineering is very common, and in the compaction control of the rockfill subgrade, the compaction degree of the rockfill subgrade can be measured only by determining the maximum compression deformation rate or the maximum forming density, and the void ratio of the rockfill subgrade after compaction forming is calculated. As the particle size of the rock-fill material is large, the rock-fill material is broken in the forming process, the maximum compression ratio and the maximum forming density of the rock-fill material are difficult to determine by an indoor test, and a compaction degree detection method corresponding to the indoor test is not available in field compaction control.
The existing design specifications and construction technical specifications of the highway subgrade both stipulate the control requirements of the compaction porosity of the stone-filled subgrade, the porosity calculation relates to the natural density and the bulk density of stone-filled particles, and no corresponding test detection method is given out according to the specifications; the method for testing the maximum dry density of coarse-grained soil and large-grained soil recommended by the highway geotechnical test regulations needs to adopt fully similar gradation, has great difference between the forming work and the on-site compaction work, cannot reflect the influence of the accumulation and the crushing of the particles of the stone-filling material on the forming density, and cannot directly measure the forming density of the stone-filling roadbed on site.
Therefore, at present, the compaction control of the stone-filled roadbed mainly adopts rolling pass control after the tonnage of a given road roller or compaction deformation difference control of one-to-two times of additional compaction after forming, so that the compaction degree and the porosity of the stone-filled roadbed cannot be determined, and the strength, the deformation and the stability of the stone-filled roadbed cannot be evaluated.
Disclosure of Invention
The invention aims to provide a test method for testing the maximum compression ratio and the maximum molding density of a stone-filled material so as to measure the strength, deformation and stability of a stone-filled roadbed.
In order to achieve the technical purpose of the invention, the invention is specifically realized by the following technical scheme:
a test method for maximum compression ratio and maximum molding density of stone-filling materials comprises the following steps:
s1 experiment material selection, determining the similar gradation of the filling material according to the proportion of skeleton particles and gap-filling particles in the filling material; the maximum grain size of the filling material is reduced to the maximum grain size of similar gradation, so that the maximum grain size requirement of an indoor forming test is met; determining the content range of coarse particles in the similar gradation according to the similarity of the content of the coarse particles in the similar gradation to the content of the framework particles in the stone filling material;
s2, determining parameter evolution, and determining the maximum forming pressure according to the standard tonnage of the road roller for constructing the rockfill roadbed and the final forming state of the rockfill roadbed; measuring a load-displacement curve in the molding process of the similar gradation sample, determining an initial pressure state and a final pressure state by using the load-displacement curve, and calculating a compression deformation rate and a molding density; carrying out a screening test on the formed stone filling material, and measuring the content of coarse particles;
and S3 drawing a measuring drawing, wherein the measuring drawing is drawn by measuring the compression deformation rate and the forming density of the similar graded filling stone material when 5 different coarse particle contents are measured, and the measuring drawing comprises a relation curve of the compression deformation rate, the forming density, the crushing rate and the coarse particle content, and the maximum compression deformation rate, the maximum forming density and the crushing rate are determined.
Further, the skeleton particles filled with the stone material in the S1 comprise stone blocks, and the grain diameter ratio of the skeleton particles to the gap-filling particles is 8: 10; wherein the maximum particle sizes of similar gradation include 40mm and 5mm, the particles exceeding 40mm are skeleton particles, and the particles smaller than 5mm are gap-filling particles; the method comprises the steps of determining the maximum compression ratio, the maximum molding density and the corresponding crushing rate by establishing the relationship among the compression deformation rate, the molding density, the crushing rate and the content of coarse particles by adopting the fact that the content of the coarse particles in the molded similar gradation is similar to the content of framework particles in the molded stone filling material.
Further, in the step S1, a compaction cylinder is used in the indoor forming test, the diameter of the compaction cylinder is 152mm, and the height of the compaction cylinder is 170 mm; the upper pressing plate and the lower backing plate are both circular solid steel plates with the diameter of 150mm and the height of 50 mm;
the control experiment of the similar gradation comprises the steps of filling the similar gradation into a test cylinder, wherein the height of a sample filled is 120mm, and the sample is flatly filled to the top surface of the test cylinder for a molding experiment; the depth of the upper pressure plate pressed into the sample is not more than 50mm during the molding test, and the standard molding pressure is 200 kN.
Further, the experimental material selection in S1 includes
1) The molding test is carried out by adopting a microcomputer control electro-hydraulic servo hydraulic universal testing machine, a load control mode is adopted in a loading mode, and a load-displacement mode is adopted in a recording mode; the upper pressing plate and the lower backing plate are vertically connected in series and superposed, a load-displacement curve is measured, and the deformation of the oil cylinder of the testing machine under different loads is determined;
2) and (3) uniformly pressing the upper pressing plate serving as a loading plate into the test cylinder, measuring a load-displacement curve in the pressing process, and stopping the test when the pressing load reaches the control load or the pressing depth reaches 45 mm.
3) And after compaction and forming, taking out the sample from the test cylinder, and measuring the coarse particle content and the crushing rate of the sample by adopting a screening test method.
Further, the step S2 determining the evolution of the parameter includes:
deducting the deformation of the oil cylinder under the initial forming load according to the inflection point of the initial segment of the load-displacement curve measured by a forming test, and determining the initial compression deformation; according to the displacement of which the load on a load-displacement curve is 200kN measured by a forming test, deducting the deformation of the oil cylinder under the forming load of 200kN and the real-pressure deformation, and determining the final compression deformation;
subtracting the initial compression deformation amount from the final compression deformation amount to obtain the compression deformation amount of the rock filling material sample; dividing the compression deformation of the rock filling material sample by the height of the initial pressure sample to determine the compression deformation rate of the rock filling material, wherein the compression deformation rate is expressed by percentage;
determining the height of the compacted sample according to the final compression deformation of the similar graded filling material sample, and calculating the volume of the sample; the compacted density was calculated from the sample mass and sample volume as the measured density of a similar graded fill stone sample.
Further, drawing the determination drawing in S3 includes:
1) drawing a compression deformation rate-coarse particle content curve by taking the coarse particle content of the molded sample as a horizontal coordinate and the compression deformation rate of the stone filling material sample as a vertical coordinate, and determining the maximum compression deformation rate of the stone filling material;
2) drawing a molding density-coarse particle content curve by taking the coarse particle content of the molded sample as an abscissa and the molding density of the stone-filling material sample as an ordinate, and determining the maximum molding density of the stone-filling material;
3) and drawing a curve of the breaking rate-coarse particle content of the stone filling material by taking the coarse particle content of the molded sample as an abscissa and the breaking rate as an ordinate, and determining the characteristic breaking rate of the stone filling material.
The invention has the beneficial effects that:
1. the similar grading design method of the invention grasps the key characteristics that the content of coarse particles is similar to the content of stones in the filling material; the test is carried out by adopting 5 similar grading samples with different coarse particle contents, the key influence of the stone filler particle crushing and the gap filling on the compaction process is grasped, the test can adapt to the stone filler forming test and compaction control requirements with large grading range and hardness degree difference, and the problem that the key grasping is not realized by full-grading similar is solved.
2. According to the maximum compression ratio test method, the measured maximum compression ratio is very close to the maximum compression ratio determined by a field compaction test, and the maximum compression ratio determined by an indoor test is configured according to similar grades and can be used as the basis for field compaction control; the compression ratio method is adopted to detect the compaction degree of the rock-filled roadbed, the field detection method is corresponding to the indoor test method, the detection speed is high, the precision is high, the result is stable, the compaction degree standard does not need to be changed, and the problems that the workload of the indoor test and the field detection is large, the precision is poor, the discreteness is large, and quantification cannot be achieved are solved.
3. According to the maximum molding density test method, the measured maximum molding density can be used as a reference for field density detection, the compression ratio method is adopted on the field to detect the compaction degree, the compaction density can be converted into the field compaction density, the porosity is calculated according to the natural density and the compaction density of the rock block, the rationality of the standard is verified, the field compaction conformity degree is evaluated, and the problem that the control on the compaction porosity of the rock-filled roadbed can not be detected for a long time is solved.
4. The test method for the maximum breaking rate of the stone filling material can be used for evaluating the hardness degree of the stone filling material and researching the influence of the breaking rate on the compaction characteristics and the physical and mechanical properties of the stone filling material, so that the compaction process of the stone filling roadbed is improved, and the effects of reinforcing compaction and dynamic compaction are evaluated.
5. The compaction forming method of the stone filling material provided by the invention can control the key grading characteristics, the particle crushing characteristics and the forming density of the stone filling material, obtain the design parameters such as the strength, the deformation and the like of the stone filling material in different compaction states, study the influence of compaction control on the bearing capacity, the deformation and the stability of a roadbed of the stone filling material and expand the application range of the stone filling material.
6. The inventor derives a compactness calculation formula based on the field compression ratio and the maximum compression ratio according to the mass conservation principle and the definition of the compactness, and detects the compactness of the rock-fill roadbed according to the maximum compression ratio and the field compression ratio. If the forming density at the maximum compression ratio can be measured, the strength and the deformation property of the stone filling material can be measured according to different forming densities, the design parameters of the stone filling material and the stone filling roadbed are determined, the porosity of the stone filling roadbed is detected by adopting a compression ratio method, and the strength, the deformation and the stability of the stone filling roadbed are evaluated.
7. The invention starts from the filling characteristic and the crushing characteristic in the forming process of the rock filling material, adopts the proportion similarity of skeleton particles and interstitial particles, simulates a rock filling material sample, determines the forming pressure of the rock filling material through contact mechanics analysis, establishes a relation curve of the compression ratio and the coarse particle content, the forming density and the coarse particle content, and the crushing ratio and the coarse particle content under the standard forming pressure, determines the maximum compression ratio, the maximum forming density and the characteristic crushing ratio, solves the difficulties of incompatibility, uncertainty and inaccuracy of indoor test and field test of rock filling material compaction control, and provides a standard method and technical support for forming control of the rock filling material, physical and mechanical property test research of the rock filling material, design parameter acquisition of a rock filling roadbed, field compaction control and the like.
Drawings
FIG. 1 is a schematic view of a molded test tube in an embodiment of the present invention.
FIG. 2 is a schematic diagram of deformation calibration loading of a testing machine oil cylinder and a forming device in the embodiment of the invention.
FIG. 3 is a load-displacement curve of a molding process in an embodiment of the present invention.
FIG. 4 is a graph showing the relationship between the molding density and the coarse particle content in the examples of the present invention.
FIG. 5 is a graph showing the relationship between compressibility and coarse particle content in the example of the present invention.
FIG. 6 is a graph showing the relationship between the crushing rate and the coarse particle content in the example of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to specific embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The reference numerals include: the device comprises an upper pressing plate 1, a test tube 2, a lower backing plate 3, a testing machine upper pressing plate 4, a forming upper pressing plate 5, a forming lower pressing plate 6 and a testing machine oil cylinder top plate 7.
Referring to fig. 1-6, the invention provides a method for testing the maximum compression ratio and the maximum molding density of a rock-fill material, which can quickly and accurately obtain the test results of the maximum compression ratio and the maximum molding density of the rock-fill material, and improve the scientificity and reliability level of compaction control. The overall flow of one implementation is as follows: preparing and calibrating instrument and equipment; preparing a similar gradation sample; measuring the maximum compression ratio; measuring the maximum molding density; measuring the breakage rate of the stone filling material; and (4) analyzing and reporting the test.
A test method for maximum compression ratio and maximum molding density of stone-filling materials comprises the following steps:
step one, adopting filling materials of the same parent rock, crushing the filling materials of similar gradation, and preparing the filling materials according to the similar content of coarse particles and the content of skeleton particles in the filling materials:
1) taking a sufficient amount of stone fillers, measuring the maximum particle size of the stone fillers, and determining the particle sizes of skeleton particles and interstitial particles according to the maximum particle size of the stone fillers, wherein the maximum particle size of the skeleton particles is the maximum particle size of the stone fillers, and the ratio of the maximum particle size of the skeleton particles to the maximum particle size of the interstitial particles is 8-10;
2) processing the stone filling material into similar stones passing through a 40mm round hole sieve, preparing similar-grade stone filling materials, wherein the maximum grain size of skeleton grains (coarse grains) of the similar-grade stone filling materials is 40mm, the maximum grain size of interstitial grains (fine grains) is 5mm, and separating the skeleton grains and the interstitial grains by using the 5mm round hole sieve for later use;
3) the proportion of skeleton particles and gap-filling particles in the similar grading is represented by coarse particle content, the coarse particle content is the percentage of coarse particles in all particles, and 5 similar grading filling materials with different coarse particle contents are prepared according to the coarse particle content interval of 10-20%.
4) Taking the similarly graded rock-filling materials to carry out a screening test, wherein the test adopts a standard geotechnical test sieve, the sizes of sieve pores (round holes) are 60, 40, 20, 10, 5, 2, 1, 0.5, 0.25 and 0.075mm, the actual grading of each similarly graded rock-filling material sample is determined, and the coarse particle content of the sample before forming is determined according to the percentage of particles with the size of more than 5mm in all rock-filling material particles.
Step two, preparing a testing machine and testing instrument equipment according to the following steps:
1) the forming tester adopts a microcomputer control electro-hydraulic servo hydraulic universal tester, the tonnage of the tester is (300-1000) kN, the tester has load control and displacement control functions, and the microcomputer has a load-displacement recording mode software function;
2) the test cylinder 2 adopts a standard heavy compaction cylinder, the diameter is 152mm, the height is 170mm, and the height of a loose sample is 120 mm; the diameter of the cushion block at the lower part of the test cylinder 2 and the upper pressing plate 1 is 150mm, the thickness is 50mm, and a steel solid cushion block and a steel solid pressing plate are adopted;
3) the testing machine comprises a testing machine upper pressing plate 4, a forming upper pressing plate 5, a forming lower pressing plate 6 and a testing machine oil cylinder top plate 7.
Step three, filling the similar graded rock filling material sample, and controlling the loose filling height of the sample:
1) taking air-dried filling materials, preparing 5 samples with different coarse particle contents, wherein each sample with 1 coarse particle content has the mass of about 6 kg;
2) taking similar grading filling materials with each coarse particle content to perform a screening test, and determining the grading and coarse particle content of the similar grading filling materials before forming;
3) filling the lower cushion block into the bottom of the test cylinder 2, then filling the uniformly mixed sample into the test cylinder 2 in three layers, filling the sample on the top surface of the test cylinder 2, and filling gaps of coarse particles with gap-filling particles;
4) measuring the mass of the sample in the test tube 2, wherein the mass of the sample in the test tube 2 is about 4.5kg, and the mass of the sample is based on the measured value;
5) the upper pressing plate 1 is arranged in the test tube 2, the upper pressing plate 1 is rotated to enable the upper pressing plate 1 to be in close contact with the top surface of the sample, the upper pressing plate 1 is prevented from being pressed on the edge of the test tube 2, and the depth or exposed height of the upper pressing plate 1 pressed into the sample is measured by a vernier caliper to be accurate to 0.1 mm.
Step four, measuring a load-displacement curve in the forming process:
1) setting the testing machine as load control or displacement control, wherein when the load control is adopted, the maximum control load is more than 200kN and is not more than 85% of the tonnage of the testing machine; when the displacement control is adopted, the maximum control displacement is not more than 45 mm; the recording mode of the testing machine adopts a load-displacement curve mode, and automatic recording is carried out;
2) the test tube 2 provided with the lower base plate 3, the sample and the upper pressing plate 1 is installed on a testing machine, the installation center position of the sample is aligned with the centers of the upper pressing plate and the lower pressing plate of the testing machine, the upper pressing plate 4 of the testing machine is contacted with the upper pressing plate 1 of the test tube 2, then the load and displacement values are automatically recorded, and a load-displacement curve is drawn.
3) The forming test is completed within 5-10 min, when the control load or control displacement value is reached, the testing machine should be automatically stopped, otherwise, the testing machine should be manually stopped, the data and the diagram are derived and transmitted to the terminal equipment such as a computer or a mobile phone.
Step five, measuring the breakage rate and the coarse particle content after forming:
1) pouring the molded sample into a tray, completely using the molded sample for a screening test, performing the screening test by using a standard geotechnical test sieve, and measuring the molded crushing rate and the coarse particle content;
2) and (3) calculating the breaking rate of the sample according to the screening test results before and after forming:
Figure BDA0003653216380000101
in the formula: b M -the percentage of breakage (%) of similarly graded fill stones;
i-numbering the standard geotechnical test sieves according to the sieve pores arranged from big to small;
P i0 -percent passing through sieve mesh No. i of similarly graded rock-fill material before forming (%)
P i The percent (%) of passing through the No. i sieve holes of the similarly graded filling material after molding is obtained;
3) according to the formed screening test result, determining the coarse grain content of the sample, wherein the coarse grain content of the sample is as follows:
C M ＝100-P 5 (2)
in the formula: c M -the coarse content (%) of similarly graded fill material;
P 5 -fine particle content (%) after formation through a 5mm mesh.
The following is a description:
firstly, preparing and calibrating instrument and equipment
The invention provides a method for testing the maximum compression ratio and the maximum molding density of a stone-filling material, which comprises the following steps of: preparing a forming test cylinder 2, a base plate and a pressing plate; and preparing and calibrating a forming tester.
1. The molding test tube 2, the backing plate and the press plate were prepared. The adopted forming test cylinder is a standard heavy compaction test cylinder 2, and the lower backing plate 3 and the upper pressing plate 1 are improved backing plates and pressing plates of the standard heavy compaction test cylinder 2, as shown in figure 1, the forming test cylinder has the following characteristics:
1) the steel plate used in the test tube 2 should have enough thickness, the tube wall thickness should be larger than 5mm, the inner diameter of the test tube 2 is 152mm, the height is 170mm, the test tube 2 is subjected to heat treatment, and no obvious deformation is generated under the action of molding pressure and lateral pressure;
2) the test tube 2 is provided with a lower cushion plate 3 and an upper pressing plate 1 respectively, the diameters of the lower cushion plate 3 and the upper pressing block are 150mm, the thickness of the lower cushion plate 3 and the upper pressing block is 50mmm, the lower cushion plate and the upper pressing block are made of solid steel plates, the end faces of the lower cushion plate and the upper pressing block are flat, and bending deformation does not occur in the forming process.
2. And preparing and calibrating a forming tester. The adopted forming tester is a microcomputer-controlled electro-hydraulic servo hydraulic universal tester and has the following characteristics:
1) the tonnage of the testing machine meets the requirement of maximum forming pressure, and (300-1000) kN is selected;
the testing machine has the load control and displacement control servo functions and realizes proportional loading; the microcomputer control system has a load-displacement control module and an automatic recording function, automatically acquires data and draws a load-displacement curve;
2) the deformation calibration of the oil cylinder and the loading device adopts a method of superposing the lower backing plate 3 and the upper pressing plate 1, as shown in figure 2, when the oil cylinder and the loading device are calibrated to deform, the maximum test load is more than 1.25 times of the standard forming load.
3. The determination of the standard forming pressure and the loading mode has the following characteristics:
1) the standard forming pressure of the filling material is determined by the contact stress of on-site compaction, the contact stress is estimated according to the Hertz contact theory of the steel cylinder and the road base, the diameter of the steel wheel of the vibratory roller is 1600mm, the wheel width is 2130mm, the linear static pressure is 57.8N/mm, the excitation force is 374kN, and the maximum linear pressure during excitation is 175.6N/mm. The steel wheel vibration pressure is real-time, and the forming pressure is as follows:
Figure BDA0003653216380000111
in the formula: q. q.s 0 -the forming compressive stress (MPa) of the rock-fill material;
p is the maximum line pressure (N/mm) of the vibratory roller during vibration excitation;
r-radius of steel wheel of vibratory roller (mm)
E-modulus of resilience (MPa) of the rock-fill material;
ν -Poisson's ratio of the fill material.
2) The dynamic elastic modulus of the hard rock filling material is 200-1200 MPa, the Poisson ratio is 0.30, and the forming pressure in static pressure is 40 kN; the maximum compaction pressure was 174kN when vibrocompaction reached the most dense state. In consideration of reinforcement compaction measures such as a vibratory roller, an impact roller or a dynamic compaction with larger exciting force in engineering, the maximum forming pressure of an indoor test is 200kN, the loading and load holding time is 5-10 min, the indoor forming work is basically the same as the on-site maximum compacting work, and the control standard of the forming pressure and the loading time can be used.
Preparation of second and similar gradation samples
The invention provides a method for testing the maximum compression ratio and the maximum molding density of a stone filling material, which comprises the following steps of: determining the particle sizes of the skeleton particles and the interstitial particles; determining the proportion of skeletal particles and interstitial particles; 5 similar grading samples with different coarse particle contents are prepared, and the filling characteristic and the crushing characteristic in the process of compacting the stone filling material are simulated.
1. The invention determines the particle size of skeleton particles and interstitial particles in the stone filler according to the compaction characteristics of the stone filler, and has the following characteristics:
1) the skeleton particles are particles which can mutually contact and play a skeleton role in the molding process of the stone filling material, and the maximum particle size of the skeleton particles is the maximum particle size of the stone filling material and can be directly measured and determined;
2) the gap-filling particles are particles filled in gaps of the skeleton particles, the ratio of the skeleton particles to the gap-filling particles is 8-10, and the maximum particle size of the gap-filling particles is determined according to the maximum particle size of the skeleton particles and the ratio of the skeleton particles to the gap-filling particles;
3) the maximum particle size of the similarly graded framework particles is 40mm (round hole sieve), and the maximum particle size of the interstitial particles is 5mm (round hole sieve).
2. The invention determines the proportion of skeleton particles and gap-filling particles according to the key grading characteristics in the forming process of the stone-filling material, and has the following characteristics:
1) the content of skeleton particles before the molding of the filling material is 30-85%, the skeleton particles after the molding are crushed, the content of the skeleton particles is reduced, the content of gap filling particles is increased, and the optimal content of the skeleton particles exists after the molding, so that the compression rate is maximized or the molding density is maximized;
2) before the similar grading stone filling material is formed, the content range of skeleton particles is larger than that before the site stone filling material is formed, and the content range of the skeleton particles after the forming is larger than that after the site stone filling material is formed.
3. The invention determines the maximum compression ratio and the maximum molding density of the rock-fill material, needs 5 similar samples with different skeleton particle contents to determine the maximum compression ratio and the maximum molding density, and has the following characteristics:
1) the framework particle content range of 5 samples in the similar gradation is larger than that of the filling material before forming, and the framework particle content interval of the 5 samples is 10-20%;
2) the particle composition of the similar grading sample is subjected to sieve analysis by adopting a complete set of geotechnical test standard sieves, and is used as a basis for calculating the particle breakage rate;
3) the content of skeleton particles before molding of similar gradation samples is determined by a screening test, each sample is about 6kg, and the similar gradation samples are uniformly mixed after the screening test and can be repeatedly used for a molding test.
Third, measurement of maximum compression set
The invention provides a method for testing the maximum compression ratio and the maximum molding density of a stone filling material, which comprises the following steps of: loading and installing the test cylinder 2; setting a loading mode; and (4) measuring a load-displacement curve.
1. The maximum compression deformation rate of the invention is measured, and the loading and installation of the test cylinder 2 have the following characteristics:
1) the test tube 2 is placed on a flat ground, and the lower base plate 3 is placed in the test tube 2 and falls into the bottom surface of the test tube 2; accurately weighing about 6kg of sample from one similar graded filling material sample, and filling the sample into the test cylinder 2 in three layers until the top surface of the test cylinder 2 is leveled; when charging, the skeleton particles are not higher than the top surface of the test cylinder 2, and the gaps on the surface of the skeleton particles are leveled by using gap filling particles, so that the thickness ratio of the rest test samples is basically the same as that before charging; accurately weighing the mass of the rest sample to obtain the accurate mass of the sample loaded in the test tube 2, wherein the accurate mass is 5 g;
2) moving the test tube 2 filled with the sample and the lower backing plate 3 to a forming tester; installing an upper pressing plate 1 on the top surface of a sample, rotating the upper pressing plate 1 to enable the periphery of the upper pressing plate to completely enter a test cylinder 2, enabling the bottom surface of the upper pressing plate to be in uniform contact with the surface of the sample, and measuring the exposed height of the upper pressing plate 1 or the depth of the upper pressing plate pressed into the test cylinder 2 by using a vernier caliper to be accurate to 0.1 mm; and (3) moving the test tube 2 to the center of the upper and lower pressure plates of the testing machine, wherein the center of the test tube 2 is aligned with the center of the upper and lower pressure plates of the testing machine.
2. The invention relates to a method for measuring the maximum compression deformation rate, which comprises the following steps of:
1) for hard rock filling materials, a loading mode is preferably a load control mode, and the maximum test load should not exceed 250 kN; for softer rock filling materials, when the forming pressure is lower, the loading mode can select a displacement control mode, and the maximum displacement should not exceed 45 mm;
2) the setting of the loading speed is comprehensively determined according to the control requirements of the maximum test load (maximum control displacement), the loading and the load holding time, and the loading is finished within the range of 5-10 min;
3) the recording mode adopts a load-displacement curve mode, the load recording precision is 10N, and the displacement recording precision is 0.01 mm.
3. The method for measuring the maximum compressibility of the invention adopts a load-displacement curve measuring method to automatically record the load and the displacement, and has the following characteristics:
1) after the test cylinder 2 is loaded, installed in place and the loading mode is set, a testing machine is started to carry out pressure forming, automatic loading is controlled by a microcomputer, the upper pressure plate 1 is observed to be uniformly pressed into the surface of a sample in the forming process, and the periphery of the upper pressure plate is not pressed on the edge of the test cylinder 2;
2) observing the change condition of a load-displacement curve output by a microcomputer, wherein the compression deformation amount is increased quickly when loading is started, the curve is gentle, and initial pressure is finished when an inflection point appears; after an inflection point appears, the load is increased quickly, particles are crushed and gaps are filled, when the stone filling material particles are crushed and crushed in a large amount, a load-displacement curve becomes gentle, the load begins to drop after the load is damaged, and the displacement is increased quickly;
3) when the test load reaches 200kN or the total deformation reaches 45mm, if the testing machine is not automatically stopped, the testing machine is immediately manually stopped to prevent the framework particles from being excessively crushed and the lateral pressure from being too large to extrude the test cylinder 2 to deform, or the upper pressure plate 1 presses the top surface of the test cylinder 2 to ensure that the test cylinder 2 is deformed under pressure.
4. The method comprises the steps of adopting 5 similar gradation samples with different framework particle contents, respectively measuring the compression ratio and the framework particle content after molding, drawing a relation curve of the compression ratio and the framework particle content, and determining the maximum compression ratio according to the curve.
Fourth, maximum molded Density measurement
The invention provides a method for testing the maximum compression ratio and the maximum molding density of a stone filling material, wherein the maximum molding density comprises the following steps: measuring the quality of the sample; measuring the volume of the sample; and calculating the apparent density and the molding density.
1. And (4) measuring the quality of the sample. The mass of the sample contained in the cartridge 2 is measured, and the mass of the sample contained in the cartridge 2 is accurately weighed by the method of item 1) in the third section of this specification.
2. The method comprises the following steps and methods for measuring the volume of a sample, wherein the volume of the sample comprises the initial volume of the sample and the volume of the sample after forming:
1) and measuring the initial volume of the sample. The diameter and the height of the test cylinder 2 and the thicknesses of the lower backing plate 3 and the upper pressing plate 1 are measured, and when the same set of test cylinder 2, the lower backing plate 3 and the upper pressing plate 1 are adopted, each set of no more than 5 test pieces is formed and is measured once, and the accuracy is 0.1 mm; after loading and mounting the upper platen 1, the exposed height or the depth of the sample pressed into the upper platen 1 is measured. The diameter of the sample is the inner diameter of the test cylinder 2, and the initial height of the sample is determined by subtracting the thickness of the lower backing plate 3 and the pressing depth of the upper pressure plate 1 from the height of the test cylinder 2.
2) And (4) measuring the volumes of the initial pressure sample and the final pressure sample. Measuring the volume of a sample after initial pressing; the volume of the sample after final pressing is measured, and the method has the following characteristics:
a. and (4) measuring the height of the sample after initial pressing from the inflection point of the load-displacement curve, and calculating the volume of the sample. Taking the initial point after the inflection point of the load-displacement curve as an initial pressure state, reading an initial pressure displacement value, and subtracting the deformation of the oil cylinder and the device corresponding to the inflection point load to obtain the compression deformation of the initial pressure; the height of the sample after initial pressing is equal to the initial height of the sample minus the compressive deformation amount of the initial pressing, and the accuracy is 0.1 mm. Calculating the volume of the sample after initial pressing according to the diameter of the sample and the height of the sample after initial pressing;
b. the height of the sample after final pressure was measured from the load-displacement curve, and the volume of the sample was calculated. The initial displacement value is a displacement starting point, a displacement value at the final pressure is read from a position, where the load value on a load displacement curve is 200kN, the displacement value at the starting point is subtracted, and then a deformation value of the oil cylinder and the loading device at 200kN is deducted; and calculating the volume of the sample after final pressing according to the diameter of the sample and the height of the sample after final pressing.
3. The initial pressing density and the molding density are measured and calculated, and the method has the following characteristics:
1) the initial pressure density is corresponding to the on-site loose paving density, and is determined by calculating the ratio of the mass of the sample to the volume of the sample after initial pressure, and the unit of the initial pressure density is kg/m 3 To the accuracy of 10kg/m 3 。
2) The molding density is the density of specific skeleton particle content, specific molding pressure and crushing rate, and is determined by calculating the ratio of the sample mass to the sample volume at final pressure, and the molding density unit is kg/m 3 To the accuracy of 10kg/m 3 。
Fifthly, determining the breakage rate of the stone filling material
The influence of the content of the skeleton particles and the particle breakage rate on the maximum compression ratio and the maximum molding density after molding. The determination of the content of skeleton particles and the particle breakage rate comprises the following steps: screening test of similar grading filling material before forming; screening test of the formed similar graded filling material; and calculating the content of skeleton particles and the breakage rate of the stone filling material.
1. And (3) performing a similar-gradation rock filling material screening test before forming, performing a test by adopting similar-gradation air-dried rock filling materials and a standard geotechnical test screen, and determining the passing percentage of the similar-gradation test sample in each standard test screen hole.
2. And (3) performing a screening test on the similarly graded filling material after molding, performing a test by adopting the filling material poured out of the test cylinder 2 after molding and the same standard geotechnical test sieve, and determining the passing percentage of the molded sample in each standard test sieve pore.
3. Calculating the content of the framework particles before forming according to the formula (2) according to the result of the similar grading screening test before forming; calculating the content of the molded framework particles according to the formula (2) according to the screening test result of the molded sample; and (3) calculating the crushing rate of the stone-filled sample according to the formula (1) according to the screening test results of the sample before and after forming.
Sixthly, analysis and report of test results
The analysis and reporting includes: the method comprises the following steps of similar grading analysis, maximum compression ratio analysis, maximum molding density analysis and rock filling material breakage rate analysis.
1. And (4) carrying out similar grading analysis. The similar gradation of the filling material is the gradation with similar compaction characteristics; the similar compaction characteristics comprise similar proportion of skeleton particles and interstitial particles and similar filling characteristics; the stone-filling material has similar breaking rate. The grading range of on-site rock fill material is very variable and multiple similar grades need to be employed to achieve similar compaction characteristics. Report the maximum particle size of the aggregate, the maximum particle size of the interstitial particles, and the range of the ratio of skeletal particles to interstitial particles.
2. And (5) analyzing the maximum compression ratio. The test method of the maximum compression ratio of the stone filling material adopts 5 similar-grade stone filling materials with different skeleton particle contents to carry out the test, wherein the maximum particle size of the similar-grade stone filling material is 40mm, and the maximum particle size of the gap filling particles is 5 mm; the deformation of the oil cylinder and the loading device can reach 0.5 mm-1. Omm, and the deformation is calibrated and deducted when measuring; the measured value of the final deformation is greatly influenced by the charging density and the initial deformation, and the initial deformation is deducted in the compression ratio test so that the compression ratio measurement has the same standard; the compression deformation of the sample is related to the forming pressure and the granule breakage, the standard forming pressure of the compaction test is specified, and the breakage rate of the formed filling material is measured. Reporting the content of skeleton particles before and after molding, the initial compression deformation, the compression deformation under the standard molding pressure, the compression ratio of a single sample, the relation between the compression ratio and the content of the skeleton particles after molding, the maximum compression ratio and the corresponding content of the skeleton particles.
3. Analysis of maximum formed density. The test method of the maximum molding density of the stone-filling material adopts 5 similar grading stone-filling materials with different framework particle contents to carry out the test, measures the compression deformation under the standard molding pressure by a load-displacement curve, and determines the maximum molding density according to the relationship between the molding density of a sample and the framework particle content. And reporting the sample mass, the initial pressing volume, the final pressing volume, the initial pressing density and the molding density of a single sample, the relationship between the molding density and the content of the molded framework particles, the maximum molding density and the corresponding content of the framework particles.
4. And (4) analyzing the breakage rate of the stone filling material. According to the method for testing the breakage rate of the stone-filling material, the breakage rate is represented by the passing rate curve before and after forming and the area change rate surrounded by logarithmic particle size coordinates, and the sizes of sieve pores before and after forming correspond to each other one by one. The results of the sieve tests (percent pass) before and after forming, the percent crush of the individual stone-fill samples, and the skeletal grain content of the individual stone-fill samples after forming are reported.
According to the test results, the following results are obtained:
1) by implementing the filling material similar grading of the invention, the filling characteristic similarity and the crushing characteristic similarity can be realized, thereby ensuring the compaction characteristic similarity, simplifying the requirement of full-grading similarity, saving the trouble of filling material grading test and covering the compaction characteristic of the filling material in a full range;
2) the maximum compression rate can be used as a reference for compaction control of the stone-filling material, the indoor test is used for determining the maximum compression rate, the test is far simpler than a field test, the test precision, the stability and the reproducibility are far higher than those of the field test, the compaction degree is determined by adopting the maximum compression rate standard, the indoor test method corresponds to a field detection method, the quantitative detection of the compaction degree of the stone-filling roadbed can be realized, and the compaction effect evaluation is performed by adopting the same standard;
3) the maximum forming density can be used as a density reference for compacting control of the stone-filling material, the degree of compaction is measured by a compression ratio method on site, the void ratio can be calculated according to the degree of compaction and the maximum forming density, and compared with the requirements of the existing design, construction and quality inspection evaluation standards, the scientificity and the quantification level of compacting control of the stone-filling roadbed are improved;
3) the test result of the breakage rate of the filling material can be used for evaluating the hardness degree of the filling material, improving the compaction process, and evaluating the influence of reinforcing compaction such as impact compaction, dynamic compaction and the like on the breakage rate and the compaction effect;
4) the invention also has the important effects that the compression rate, the forming density and the crushing rate of the rock filling material can be controlled by applying the forming method, the design parameters of the rock filling material are measured, the physical and mechanical properties of the rock filling material are researched, the constitutive relation of the rock filling material is established, the scientific research of the rock filling material and the rock filling roadbed is promoted, and the application level of the quantitative research of the rock filling material and the compaction control of the rock filling roadbed is obviously improved.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (6)

1. A test method for the maximum compression ratio and the maximum molding density of a stone-filling material is characterized by comprising the following steps:
s1, selecting materials through experiments, and determining the similar grading of the stone filling material according to the proportion of the skeleton particles and the interstitial particles in the stone filling material; the maximum grain size of the filling material is reduced to the maximum grain size of similar gradation, so that the maximum grain size requirement of an indoor forming test is met; determining the content range of coarse particles in the similar gradation according to the similarity of the content of the coarse particles in the similar gradation to the content of the framework particles in the stone filling material;
s2, determining parameter evolution, and determining the maximum forming pressure according to the standard tonnage of the road roller for constructing the rockfill roadbed and the final forming state of the rockfill roadbed; measuring a load-displacement curve in the molding process of the similar gradation sample, determining an initial pressure state and a final pressure state by using the load-displacement curve, and calculating a compression deformation rate and a molding density; carrying out a screening test on the formed stone filling material, and measuring the content of coarse particles;
and S3 drawing a measuring drawing, wherein the measuring drawing is drawn by measuring the compression deformation rate and the forming density of the similar graded filling stone material when 5 different coarse particle contents are measured, and the measuring drawing comprises a relation curve of the compression deformation rate, the forming density, the crushing rate and the coarse particle content, and the maximum compression deformation rate, the maximum forming density and the crushing rate are determined.
2. The method for testing the maximum compression ratio and the maximum molding density of the stone-filling material according to claim 1, wherein: the skeleton particles of the filling stones in the S1 comprise stones, and the grain diameter ratio of the skeleton particles to the gap-filling particles is 8: 10; wherein the maximum particle sizes of similar gradation include 40mm and 5mm, the particles exceeding 40mm are skeleton particles, and the particles smaller than 5mm are gap-filling particles; the method comprises the steps of determining the maximum compression ratio, the maximum molding density and the corresponding crushing rate by establishing the relationship among the compression deformation rate, the molding density, the crushing rate and the content of coarse particles by adopting the fact that the content of the coarse particles in the molded similar gradation is similar to the content of framework particles in the molded stone filling material.
3. The method for testing the maximum compression ratio and the maximum molding density of the stone-filling material according to claim 1, wherein:
in the step S1, a compaction cylinder is used in the indoor forming test, the diameter of the compaction cylinder is 152mm, and the height of the compaction cylinder is 170 mm; the upper pressing plate and the lower backing plate are both circular solid steel plates with the diameter of 150mm and the height of 50 mm;
the control experiment of the similar gradation comprises the steps of filling the similar gradation into a test cylinder, wherein the sample filling height is 120mm, and the similar gradation is flatly filled to the top surface of the test cylinder for a molding experiment; the depth of the upper pressure plate pressed into the sample is not more than 50mm during the forming test, and the standard forming pressure is 200 kN.
4. The method for testing the maximum compression ratio and the maximum molding density of the stone-filling material according to claim 1, wherein:
the experimental material selection in S1 comprises
1) The molding test is carried out by adopting a microcomputer control electro-hydraulic servo hydraulic universal testing machine, the loading mode adopts a load control mode, and the recording mode adopts a load-displacement mode; an upper pressing plate and a lower backing plate are vertically stacked in series, a load-displacement curve is measured, and deformation of the oil cylinder of the testing machine under different loads is determined;
2) and (3) uniformly pressing the upper pressing plate serving as a loading plate into the test cylinder, measuring a load-displacement curve in the pressing process, and stopping the test when the pressing load reaches the control load or the pressing depth reaches 45 mm.
3) And after compaction and forming, taking out the sample from the test cylinder, and measuring the coarse particle content and the crushing rate of the sample by adopting a screening test method.
5. The method for testing the maximum compression ratio and the maximum molding density of the stone-filling material according to claim 4, wherein: the step S2 of determining the evolution of the parameter includes:
deducting the deformation of the oil cylinder under the initial forming load according to the inflection point of the initial segment of the load-displacement curve measured by a forming test, and determining the initial compression deformation; according to the displacement of which the load on a load-displacement curve is 200kN measured by a forming test, deducting the deformation of the oil cylinder under the forming load of 200kN and the real-pressure deformation, and determining the final compression deformation;
subtracting the initial compression deformation amount from the final compression deformation amount to obtain the compression deformation amount of the rock filling material sample; dividing the compression deformation of the rock filling material sample by the height of the initial pressure sample to determine the compression deformation rate of the rock filling material, wherein the compression deformation rate is expressed by percentage;
determining the height of the compacted sample according to the final compression deformation of the similar graded filling material sample, and calculating the volume of the sample; the compacted density was calculated from the sample mass and sample volume as the measured density of a similar graded fill stone sample.
6. The method for testing the maximum compression ratio and the maximum molding density of the stone-filling material according to claim 5, wherein: drawing the determination drawing in the S3 comprises the following steps:
1) drawing a compression deformation rate-coarse particle content curve by taking the coarse particle content of the molded sample as an abscissa and the compression deformation rate of the stone filling sample as an ordinate, and determining the maximum compression deformation rate of the stone filling;
2) drawing a molding density-coarse particle content curve by taking the coarse particle content of the molded sample as a horizontal coordinate and the molding density of the stone filling material sample as a vertical coordinate, and determining the maximum molding density of the stone filling material;
3) and drawing a curve of the breaking rate-coarse particle content of the stone filling material by taking the coarse particle content of the molded sample as an abscissa and the breaking rate as an ordinate, and determining the characteristic breaking rate of the stone filling material.
CN202210559438.8A 2022-05-20 2022-05-20 Method for testing maximum compression ratio and maximum molding density of stone filling material Pending CN114935524A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117169049A (en) * 2023-09-21 2023-12-05 中国水利水电科学研究院 Method and device for testing relative density of field original grading blasting pile material

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117169049A (en) * 2023-09-21 2023-12-05 中国水利水电科学研究院 Method and device for testing relative density of field original grading blasting pile material

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Inventor after: Liang Junlin

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