CN111848087A - Substitute sample for natural gas hydrate mining experiment and preparation method thereof - Google Patents
Substitute sample for natural gas hydrate mining experiment and preparation method thereof Download PDFInfo
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- CN111848087A CN111848087A CN202010740745.7A CN202010740745A CN111848087A CN 111848087 A CN111848087 A CN 111848087A CN 202010740745 A CN202010740745 A CN 202010740745A CN 111848087 A CN111848087 A CN 111848087A
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- gypsum
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- river sand
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/14—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
- C04B2111/00991—Uses not provided for elsewhere in C04B2111/00 for testing
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- Ceramic Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
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- Organic Chemistry (AREA)
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Abstract
The invention discloses a substitute sample for natural gas hydrate mining experiments and a preparation method thereof. The substitute sample for the natural gas hydrate mining experiment is prepared from the following components in percentage by mass: 50-70% of river sand; 10-20% of lime; 20-30% of gypsum. The substitute sample was prepared as follows: weighing river sand, lime and gypsum according to the proportion; uniformly mixing river sand, lime and gypsum, slowly adding water, and continuously and uniformly stirring to obtain a mixture; and (4) tamping the mixture, and then curing to obtain the concrete. The mechanical properties of the substitute sample for the natural gas hydrate mining experiment are as follows: the compression strength reaches 0.9-4.15 MPa, the tensile strength reaches 0.16-0.35 MPa, the main stress difference reaches 3-10.2 MPa, the elastic modulus reaches 0.1-1.35 GPa, the Poisson ratio is 0.1-0.21, the internal friction angle is 10-40 degrees, and the cohesive force is 0.5-2.05 MPa. The substitute sample prepared by the method has the mechanical property of the non-diagenetic hydrate and can be used as a substitute for a hydrate crushing experiment.
Description
Technical Field
The invention relates to a substitute sample for natural gas hydrate mining experiments and a preparation method thereof, belonging to the technical field of similar materials.
Background
Natural gas hydrates, also known as "combustible ice", are distributed mainly in polar and deep water land slope areas, with about 95% stored in deep water areas. The total amount of fine particle fracture type and dispersion type natural gas hydrates stored in deep water shallow layers is large, but the natural gas hydrates have the characteristics of shallow burying depth, non-diagenesis, poor cementation and the like, so the development difficulty is large and the risk is high. Aiming at the problem, the Zhou defends academicians firstly provides a solid fluidization green mining technology for the natural gas hydrate in the shallow layer of the sea bottom, which is different from methods such as pressure reduction, heat injection and the like, and the mining in the solid fluidization mining method belongs to the mechanical crushing of the non-diagenetic hydrate under the condition of not actively breaking the balance of the temperature and the pressure field of the hydrate. In order to research the breaking mechanism of the natural gas hydrate, the non-diagenetic hydrate deposit needs to be used as an experimental object for research, but the non-diagenetic hydrate deposit has high artificial synthesis cost, low yield, high safety risk and high possibility of decomposition at normal temperature and normal pressure, and cannot be used as an ideal experimental material for indoor mechanical breaking research.
The similar material model method is an important means for mining engineering research, the general mineral mining environment is rock mass, and the mining environment of seabed non-diagenetic hydrate is seabed. In order to simulate submerged jet conditions of seabed jet flow breakage, an experimental substitute sample is required to keep relatively stable mechanical properties in water, and research on similar materials of seabed non-diagenetic hydrates is blank at present.
Disclosure of Invention
The invention aims to provide a substitute sample for a hydrate mining experiment and a preparation method thereof, and aims to solve the problems of high artificial synthesis cost and the like of the existing non-diagenetic hydrate deposit.
The substitute sample for the natural gas hydrate mining experiment provided by the invention is prepared from the following components in percentage by mass:
50-70% of river sand;
10-20% of lime;
20-30% of gypsum.
The composition of the substitute sample for natural gas hydrate mining experiments can be any one of the following 1) to 3):
1) 60% of river sand; 12-16% of lime; 24-28% of gypsum;
2) 60% of river sand; 12% of lime; 28% of gypsum;
3) 60% of river sand; 16% of lime; and 24% of gypsum.
In the above substitute sample, the particle size of the river sand may be 0.04mm to 0.1mm, and the substitute sample may have a change in mechanical properties by controlling the ratio of the aggregate to the cementitious material and the contents of the cementitious material lime and gypsum and by using the difference in strength between the lime and gypsum after cementing.
In the above-mentioned substitute sample, the lime and the gypsum are used as a cementing material, and the lime gives off a large amount of heat in the setting process, so that air expands to generate a gap inside the substitute sample, thereby simulating a loose porous structure of the non-diagenetic hydrate.
The invention also provides a preparation method of the substitute sample, which comprises the following steps:
weighing the river sand, the lime and the gypsum according to the proportion; uniformly mixing the river sand, the lime and the gypsum, slowly adding water, and continuously and uniformly stirring to obtain a mixture; and tamping the mixture, and then maintaining to obtain the concrete.
In the above-mentioned production method, the stirring is carried out in a stirrer.
In the above preparation method, the tamping is carried out in a square container mold.
In the preparation method, the loading of the square container die after tamping is controlled to be 110-115% of the volume of the square container die.
In the above preparation method, the curing step is performed under a natural drying condition at room temperature; the curing time is 15-20 days;
the room temperature is 20-25 ℃.
Before sampling, standing for 30 minutes at room temperature, and demolding for use.
The mechanical properties of the substitute sample for natural gas hydrate mining experiments prepared by the invention are as follows: the compression strength reaches 0.9-4.15 MPa, the tensile strength reaches 0.16-0.35 MPa, the main stress difference reaches 3-10.2 MPa, the elastic modulus reaches 0.1-1.35 GPa, the Poisson ratio is 0.1-0.21, the internal friction angle is 10-40 degrees, and the cohesive force is 0.5-2.05 MPa.
The invention has the following advantages:
(1) the preparation method is simple, the raw materials are easy to obtain, and the cost is low;
(2) the substitute sample prepared by the method has the mechanical property of the non-diagenetic hydrate and can be used as a substitute for a hydrate crushing experiment.
Drawings
FIG. 1 is a graph showing the effect of aggregate content on uniaxial compressive strength.
Figure 2 is a graph of the effect of gypsum content in the cement on uniaxial compressive strength.
FIG. 3 is a graph showing the effect of aggregate content on elastic modulus.
Figure 4 is a graph of the effect of gypsum content in the cement on elastic modulus.
FIG. 5 is a graph showing the effect of aggregate content on cohesion and internal friction angle.
Figure 6 is a graph of the effect of gypsum content in the cement on cohesion and internal friction angle.
Detailed Description
The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
The parameters in the following examples were determined as follows:
and carrying out axial loading on the sample by using a uniaxial compression experiment until the sample fails, wherein the stress corresponding to the highest point of the obtained stress-strain curve is the uniaxial compressive strength of the rock.
Calculating the average elastic modulus of the material according to the stress-strain curve of the uniaxial compression experiment, wherein the average elastic modulus is calculated by adopting the following formula:
Eav＝(σb-σa)/(lb-la)
in the formula, σa-stress at the start of a straight line segment on the stress versus longitudinal strain curve;
σb-stress at the end of a straight line segment on a stress versus longitudinal strain curve;
lbstress of σbLongitudinal strain value of time;
lastress of σaLongitudinal strain value of time;
adopting a Brazilian splitting experiment to obtain the tensile strength, placing the material in a prototype to be loaded until the material is damaged, and calculating the tensile strength of the similar material according to the following experimental result:
σt＝2P/πDh
in the formula sigmat-tensile strength of rock in Mpa;
p is the test piece breaking load in N;
d, the diameter of the test piece in mm;
h is the thickness of the test piece in mm;
the Poisson ratio is measured by using a material compression tester with a dial indicator, namely, the radial strain of an elastic section in the compression process is recorded by using the dial indicator and substituted into the following formula for calculation:
μav＝(db-da)/(lb-la)
in the formuladbStress of σbTransverse strain values of time;
dastress of σaTransverse strain values of time;
lbstress of σbLongitudinal strain value of time;
lastress of σaLongitudinal strain value of time;
and recording the compression process according to the reading of the dial indicator on the pressure ring through a triaxial shear experiment, and then obtaining a stress-strain curve according to a corresponding pressure ring algorithm. And drawing the Mohr circle according to a Mohr circle drawing method to obtain the numerical values of the cohesive force and the internal friction angle.
The samples were prepared as follows:
taking fine river sand (the grain diameter is 0.04 mm-0.1 mm, the grain diameter is basically consistent with that of cemented sand grains of rock strata obtained by trial mining and drilling in south China sea of 5 months in 2017), gypsum (24%) and lime (16%) by using a metering container as standby raw materials.
Adding the fine river sand, the lime and the gypsum into a stirrer in sequence, uniformly mixing, slowly adding water into the uniformly mixed raw materials, and uniformly stirring by using the stirrer, wherein the whole feeding process is controlled within 5 minutes.
And (3) stopping adding water after the raw materials are mixed into slurry, continuously operating the stirrer, stirring for 5 minutes to uniformly mix the raw materials, and stopping operating the stirrer.
After the stirring work is finished, the mixture is taken out and filled in a square container mold for tamping, and the tamping amount is controlled to be 110-115% of the volume of the container.
The charged square container mold was left to stand at room temperature of about 20 ℃ and naturally dried, and maintained for 15 days while paying attention to the degree of drying of the sample.
And (3) standing for 30 minutes at room temperature before sampling, and demolding for use in a crushing experiment.
Experiments were conducted with the aggregate (fine river sand) mass fraction and the gypsum mass fraction in the cement set as single variables, and multiple sets of samples were set with the sand content, gypsum content, and lime content, as shown in table 1.
TABLE 1 experimental groups
1. Carrying out uniaxial compression experiment analysis aggregate content and the influence of gypsum content in the cementing material on uniaxial compressive strength, and taking the stress value of the highest point of the stress-strain curve as the uniaxial compressive strength:
1) the content of the aggregate is taken as a single variable, and the proportion of gypsum to quicklime in the cement is ensured to be 6: 4, controlling the aggregate content to be 60%, 65%, 70%, 75% and 80%. According to the experimental requirements of a uniaxial compression experiment in engineering rock mass experimental method standard, the compression rates are respectively set to be 1mm/min, 0.5mm/min and 0.2mm/min, and the experimental results are shown in figure 1.
2) The aggregate content was 60% and 70%, respectively, the gypsum content in the cement was used as a single variable, the compression rate was set to 0.5mm/min, and the experimental results are shown in fig. 2.
As can be seen from fig. 1 and 2, the compressive strength of the material gradually decreases with the increase of the sand content, and increases with the increase of the gypsum content in the cement, and when the ratio of gypsum to lime is 6: 4, the uniaxial compressive strength of the composite material is good in matching with the seabed non-diagenetic hydrate;
2. the axial stress-strain curve was analyzed from the data obtained from the uniaxial compression test, and the average modulus of elasticity of each group of materials was calculated, and the results are shown in fig. 3 and 4.
As can be seen from fig. 3 and 4, the elastic modulus decreases with increasing sand content, and at the three compression rates, no significant difference was seen in the elastic modulus of similar materials, which had better stability. As the content of gypsum increases, the elastic modulus tends to increase;
3. based on the uniaxial compression experiment, two materials with the uniaxial compressive strength of 2.6Mpa and 4.67Mpa are preferably selected according to the uniaxial compressive strength to carry out the Brazilian splitting experiment, and the breaking load and the tensile strength of the materials are obtained.
According to the experimental result, the diameter of the test piece is 50mm, the thickness of the test piece is 30mm, the breaking load of the first material test piece is 660N, and the breaking load of the second material test piece is 1931N. Through calculation, the tensile strength of the material I is 0.28MPa, and the tensile strength of the material II is 0.82 MPa. The tensile strength similarity constant of the two similar materials is 1, and both the tensile strength similarity constant and the tensile strength similarity constant accord with the similarity equation of a similar principle.
4. The poisson's ratio measurements were made on both materials using a material compression tester with a dial gauge.
According to the calculation of the experimental result, the Poisson ratio of the material I is 0.17, and the Poisson ratio of the material II is 0.21. The poisson ratio similarity constant of two similar materials is 1, and both the poisson ratio similarity constants conform to the similarity equation of the similar principle.
5. Based on the conclusions obtained from the uniaxial compression experiment and the Brazilian splitting experiment, the material with a certain adaptability to non-diagenetic hydrate is selected for the triaxial shear experiment, the cohesive force and the internal friction angle of the material are calculated, and the experimental group is shown in the table 2.
TABLE 2 three-axis experimental group
1) In an experiment with the aggregate content as a single variable, the proportion of gypsum to quicklime in the cement is kept to be 6: 4, controlling the aggregate content to be 60%, 65%, 70%, 75% and 80%. The experiment is carried out according to the related requirements of GBT-50266-1999 engineering rock mass experiment method standard, Mohr circles are calculated and drawn to obtain the corresponding values of cohesive force and internal friction angle, and the experiment result is shown in figure 5.
2) The aggregate content is 60%, the gypsum content in the cementing material is taken as a single variable, the proportions of the gypsum in the cementing material are selected to be 0.4, 0.5, 0.6 and 0.8 respectively, a triaxial shearing experiment is carried out, Mohr circles are calculated and drawn, and corresponding cohesive force and internal friction angle numerical values are obtained, and the experimental result is shown in figure 6.
As can be seen from fig. 5 and 6, the cohesive force of the similar material decreases and the internal friction angle increases as the aggregate content increases, and the cohesive force of the material increases and the internal friction angle increases as the gypsum content increases.
Through uniaxial compression experiments, triaxial shearing experiments and Brazilian splitting experiments, parameters such as uniaxial compressive strength, elastic modulus, Poisson's ratio, tensile strength, cohesive force, internal friction angle and the like are compared, so that the compressive strength, the elastic modulus and the cohesive force all tend to be reduced and the internal friction angle tends to be increased along with the increase of the content of the aggregate; with the increase of the content of gypsum in the cement, the compressive strength, the elastic modulus, the cohesive force and the internal friction angle all show an increasing trend. According to a similar principle, two similar materials which can respectively represent the average strength mechanical property and the peak strength mechanical property of the seabed non-diagenetic hydrate are determined, and the formula comprises 60 percent of aggregate, 60 percent of gypsum in the cementing material (accounting for 24 percent of the total mass of the formula) and 40 percent of lime (accounting for 16 percent of the total mass of the formula) (formula 1); 60% of aggregate, 70% of gypsum in the cement (expressed as 28% of the total mass of the formulation) and 30% of lime (expressed as 12% of the total mass of the formulation) (formulation 2).
The mechanical properties of the samples prepared from formulation 1 were as follows:
compressive strength (MPa): 2.6; tensile strength (MPa): 0.28; primary stress difference (MPa): 5.5; elastic modulus (GPa): 0.57; poisson ratio: 0.17; internal friction angle (°): 33; cohesion (MPa): 0.6.
the mechanical properties of the samples prepared from formulation 2 were as follows:
compressive strength (MPa): 4.67; tensile strength (MPa): 0.82; primary stress difference (MPa): 6.6; elastic modulus (GPa): 1.038; poisson ratio: 0.21; internal friction angle (°): 38; cohesion (MPa): 1.07.
Claims (8)
1. a substitute sample for a natural gas hydrate mining experiment is prepared from the following components in percentage by mass:
50-70% of river sand;
10-20% of lime;
20-30% of gypsum.
2. The surrogate sample of claim 1, wherein: the substitute sample for the natural gas hydrate mining experiment comprises any one of the following components 1) to 3):
1) 60% of river sand; 12-16% of lime; 24-28% of gypsum;
2) 60% of river sand; 12% of lime; 28% of gypsum;
3) 60% of river sand; 16% of lime; and 24% of gypsum.
3. The surrogate sample according to claim 1 or 2, wherein: the grain diameter of the river sand is 0.04 mm-0.1 mm.
4. A method of preparing a surrogate sample according to any of claims 1-3, comprising the steps of:
weighing the river sand, the lime and the gypsum according to the proportion; uniformly mixing the river sand, the lime and the gypsum, slowly adding water, and continuously and uniformly stirring to obtain a mixture; and tamping the mixture, and then maintaining to obtain the concrete.
5. The method of claim 4, wherein: stirring in a stirrer.
6. The production method according to claim 4 or 5, characterized in that: tamping is carried out in a square container mould.
7. The method of claim 6, wherein: the filling amount of the square container die after the tamping is controlled to be 110-115% of the volume of the square container die.
8. The production method according to any one of claims 4 to 7, characterized in that: the maintenance step is carried out at room temperature under natural drying conditions; the curing time is 15-20 days.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112341137A (en) * | 2020-11-05 | 2021-02-09 | 兰州理工大学 | Processing method of water-resistant magnesium oxychloride cement concrete |
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Non-Patent Citations (1)
| Title |
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| 张亦驰: ""海底非成岩天然气水合物机械绞吸式刀齿破碎性能研究"", 《中国优秀硕士学位论文全文数据库 基础科学辑》 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112341137A (en) * | 2020-11-05 | 2021-02-09 | 兰州理工大学 | Processing method of water-resistant magnesium oxychloride cement concrete |
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Application publication date: 20201030 |