CN114487348A - Similar material of loose granular stratum and preparation method thereof - Google Patents
Similar material of loose granular stratum and preparation method thereof Download PDFInfo
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- 239000000463 material Substances 0.000 title claims abstract description 192
- 238000002360 preparation method Methods 0.000 title abstract description 11
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 84
- 239000006004 Quartz sand Substances 0.000 claims abstract description 81
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 claims abstract description 57
- 238000012360 testing method Methods 0.000 claims description 83
- 239000002245 particle Substances 0.000 claims description 38
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 36
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- 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
Abstract
The invention discloses a similar material of a loose granular stratum and a preparation method thereof, wherein the similar material consists of 2-4-mesh quartz sand, 10-20-mesh quartz sand, 20-40-mesh quartz sand, 150-mesh barite powder and 600-mesh barite powder with different contents to form three types of loose granular stratum similar materials of a suspension compact type, a framework compact type and a framework gap type.
Description
Technical Field
The invention relates to the field of material model tests, in particular to a similar material of a loose granular stratum and a preparation method thereof.
Background
By using the model test, the natural prototype to be observed can be reduced, the observation process can be shortened, and certain factors in the isolated extraction process can be reduced, so that the causal relationship of the natural prototype can be easily compared, observed and discovered. In recent years, with the increase of the number of tunnels and foundation pits in loose granular formations such as boulders, sand pebbles and the like, the problems needing to be researched in the loose granular formations are more and more, and model tests aiming at the loose granular formations are also increasingly increased. The loose granular stratum is composed of boulders, pebbles, medium coarse sand and soil with different particle sizes, and has the special properties of large permeability coefficient, strong discrete type, difficult deformation, poor cementation, large gradation composition change and the like. In a traditional model test, gypsum, PbO powder, bentonite, clay, river sand, iron powder, vaseline, paraffin, water and other materials are generally adopted to manufacture a relatively homogeneous similar material which is used as a rock stratum or a soil stratum in the model test to carry out a related stress and deformation test type model test.
These materials are in the comparatively homogeneous lithologic stratum of simulation, clay and loess stratum, and the effect is all comparatively ideal, but in the model test of tunnel, foundation ditch and seepage precipitation in loose granule stratum, traditional similar material has very big defect, mainly shows: (1) the discrete type of graded particles in a loose particle body stratum cannot be simulated, so that the stratum has errors in the aspects of integral deformation and stress transfer; (2) the gradual destruction rule of the loose particle stratum in the non-support form or the weak support form after the excavation of the tunnel or the foundation pit cannot be simulated; (3) the permeability coefficient of the material in a seepage model test hardly meets the requirement of a similar ratio, and the material is easy to change physically or chemically after being soaked in water, so that the deviation of the test result is serious.
Therefore, when a loose granular stratum similar material is selected, stratum grading composition characteristics and structural performance characteristics of the loose granular stratum must be considered, simulation of characteristics such as discontinuity, discreteness, high permeability, weak cementation and the like on the stratum structure is realized, and a reliable test result can be obtained only when the conditions are met.
Disclosure of Invention
In order to overcome the defect that the stratum similar material is used for simulating the loose granular body stratum in the traditional model test, the invention provides a novel loose granular body stratum similar material, introduces preparation methods of the loose granular body stratum similar material in different tests, and has the characteristics of high similarity, simplicity in preparation, wide adjustment range, wide application range and reusability.
The invention is realized by the following technical scheme:
a similar material for a unconsolidated particulate body formation, including a macroparticle for use as a framework, a coarser fraction for use as a pack-filler, and a finer fraction for use as a pack-cement,
the large particle material is 2-4 meshes of quartz sand; the coarse grain group comprises 10-20 meshes of quartz sand and 20-40 meshes of quartz sand; the fine particle group included 150 mesh barite powder and 600 mesh barite powder.
Preferably, the similar materials comprise a suspension compact type stratum similar material, a framework gap type stratum similar material and a framework gap type stratum similar material.
Preferably, the suspension compact stratum similar material comprises, by mass, 5% -10% of 2-4 mesh quartz sand, 10% -20% of 10-20 mesh quartz sand, 15% -25% of 20-40 mesh quartz sand, 20% -30% of 150 mesh barite powder and 25% -35% of 600 mesh barite powder;
the framework gap type stratum similar material comprises, by mass, 30% -40% of 2-4-mesh quartz sand, 30% -40% of 10-20-mesh quartz sand, 5% -15% of 20-40-mesh quartz sand, 5% -15% of 150-mesh barite powder and 5% -15% of 600-mesh barite powder;
the similar material for the dense-framework stratum comprises, by mass, 20-30% of 2-4-mesh quartz sand, 20-30% of 10-20-mesh quartz sand, 0.5-5% of 20-40-mesh quartz sand, 20-30% of 150-mesh barite powder and 20-30% of 600-mesh barite powder.
A method of preparing a similar material for a unconsolidated particulate body formation, comprising the steps of:
step 1, determining similar material types according to the grading composition of a loose particle body stratum;
step 2, preparing a set amount of mixed dry material sample according to the proportion corresponding to the type of the similar material, and adjusting the water content of the mixed dry material sample to be the same as that of the unconsolidated granular stratum so as to obtain the mass percent of water in the similar material;
step 3, determining the geometric similarity ratio between the loose particle body stratum and the similar material determined in the step 1;
step 4, setting performance parameters of similar materials according to test types, comparing the performance parameter similarity ratio of the similar materials and the loose particle body stratum with the geometric similarity ratio, and adjusting the mass percentage of each material in a coarse particle group or a fine particle group in a similar material sample according to a comparison result to enable the performance of the similar materials to reach the performance parameters of the set similar materials, so as to obtain the mass percentages of each component in the similar materials;
and 5, preparing the similar material according to the total amount of the similar material required by the test and by combining the mass percentages of the components in the similar material obtained in the step 4 and the mass percentage of water.
Preferably, in step 1, the grading composition of the unconsolidated particulate body formation is determined based on the survey data of the unconsolidated particulate body formation.
Preferably, the determination method of the geometric similarity ratio in step 4 is as follows:
according to the average diameter of the giant grain groups in the loose granular body stratum and the average diameter of the giant grain materials in the similar materials, the grain size similarity ratio between the loose granular body stratum and the similar materials is calculated, and then the geometric similarity ratio between the loose granular body stratum and the similar materials is determined according to the grain size similarity ratio and economic indexes.
Preferably, when mechanical and deformation simulation tests are performed, the performance parameters are the elastic modulus E and the cohesive force c.
Preferably, the elastic modulus E and the cohesion force c are adjusted as follows:
the elastic modulus E is adjusted by the method that the total content of the coarse particle group is unchanged, and the mass contents of 10-20 meshes of quartz sand and 20-40 meshes of quartz sand in the coarse particle group are adjusted according to a preset increase and decrease percentage;
the cohesive force c is adjusted by keeping the total content of the fine particle group unchanged, and adjusting the mass content of 600-mesh barite powder and 150-mesh barite powder in the fine particle group according to a preset increase and decrease percentage;
preferably, when the model test of seepage and precipitation of the unconsolidated particle stratum is carried out, the performance parameter is the permeability coefficient k.
Preferably, the adjustment method of the permeability coefficient is as follows:
keeping the total content of the coarse grain group unchanged, and adjusting the mass content of 10-20 meshes of quartz sand and 20-40 meshes of quartz sand in the coarse grain group according to a preset increase and decrease percentage.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention provides a similar material of a loose particle body stratum, which is mainly characterized in that the difference between the properties of the loose particle body stratum and rock and soil media is large, the porosity is large, the deformation modulus is high, the internal friction angle is large, the cohesive force is small, the deformation of surrounding rock is mainly caused by the dislocation among particles, the particle grading satisfies the similarity principle, and is the key for realizing the simulation effect.
Furthermore, the similar materials are divided into three types according to the grading composition of the stratum, specific component content is given to each material, the composition of the similar materials is equivalent to that of a diameter-reduced loose particle stratum, the similar materials are naturally similar to the actual stratum on various dimensionless parameters (gravity, porosity and Poisson ratio), the similarity coefficient of the similar materials is 1, and the similar materials have the advantages of high similarity, simplicity in preparation, strong adjustability, low manufacturing and using cost, reusability and the like,
the invention also provides a preparation method of the similar material of the loose particle body stratum, different performance parameters are selected according to different tests, the performance parameter similarity ratio and the geometric similarity ratio of the similar material and the loose particle body stratum are compared, the relative content percentage of the materials in the coarse particle group or the fine particle group in a similar material sample is adjusted according to the comparison result, so that the similarity between the model and the prototype in the aspects of elastic modulus, cohesive force, internal friction angle, permeability coefficient and the like is realized, and after the final mix proportion of the basic sample is determined, batch mixing of the materials can be carried out and the test can be carried out. The similar material of the loose granular stratum has the advantages of high similarity, simplicity in preparation, strong adjustability, low manufacturing and using cost, reusability and the like, can be used for excavation failure tests of foundation pits and tunnels in the stratum, stress and deformation research tests of the stratum, precipitation and permeability tests, and realizes simulation of the characteristics of discontinuity, discreteness, high permeability, weak cementation and the like on the stratum structure. Furthermore, the similar material has good water stability, can well realize the adjustment of the water content, and can keep the stability in the seepage process in the seepage test.
Furthermore, the similar materials can be recycled in different tests through different material proportions, the cost is low, and a special mixing process and a mixing device are not needed in the mixing process. After the mixture ratio of various materials is determined in an indoor test, manual mixing or mixing by a small-sized stirrer can be carried out according to the mass ratio.
Drawings
Fig. 1 is a schematic flow chart of a method for preparing and adjusting a loose granular formation similar material in two types of common model tests (a mechanical and deformation model test and a seepage and precipitation model test) according to an embodiment of the present invention.
Fig. 2 is a diagram illustrating a variation of the crown sinking in the tunnel excavation process in the model test according to the first embodiment of the present invention.
Detailed Description
The present invention will now be described in further detail with reference to the attached drawings, which are illustrative, but not limiting, of the present invention.
A similar material of a loose granular body stratum is divided into a suspension compact type stratum similar material, a framework gap type stratum similar material and a framework compact type stratum similar material according to stratum grading components, and considering that the loose granular body stratum has large difference with rock and soil media, the loose granular body stratum is mainly characterized by large porosity, high deformation modulus, large internal friction angle and small cohesive force, so that the deformation of surrounding rocks is mainly caused by the dislocation among particles, and the grain grading meets the similarity principle and is the key for realizing simulation effect, therefore, quartz sand and barite powder with different meshes are adopted in the similar materials of each stratum as basic similar materials of the loose granular body stratum, including a large grain material used as a framework, a coarse grain group used as filling and gap filling and a fine grain group used as filling and cementing.
The large-particle material is 2-4 meshes of quartz sand; the coarse grain group comprises 10-20 meshes of quartz sand and 20-40 meshes of quartz sand; the fine particle group included 150 mesh barite powder and 600 mesh barite powder. The suspended compact stratum similar material comprises, by mass, 5% -10% of 2-4-mesh quartz sand, 10% -20% of 10-20-mesh quartz sand, 15% -25% of 20-40-mesh quartz sand, 20% -30% of 150-mesh barite powder and 25% -35% of 600-mesh barite powder.
Preferably, the suspension compact stratum similar material comprises, by mass, 10.7% of 2-4 mesh quartz sand, 14.8% of 10-20 mesh quartz sand, 20.8% of 20-40 mesh quartz sand, 25.3% of 150 mesh barite powder and 28.4% of 600 mesh barite powder.
The framework gap type stratum similar material comprises, by mass, 30% -40% of 2-4-mesh quartz sand, 30% -40% of 10-20-mesh quartz sand, 5% -15% of 20-40-mesh quartz sand, 5% -15% of 150-mesh barite powder and 5% -15% of 600-mesh barite powder.
Preferably, the skeleton void type stratum similar material comprises, by mass, 35.7% of 2-4 mesh quartz sand, 34.8% of 10-20 mesh quartz sand, 9.7% of 20-40 mesh quartz sand, 10.5% of 150 mesh barite powder and 9.3% of 600 mesh barite powder.
The similar material for the dense-framework stratum comprises, by mass, 20-30% of 2-4-mesh quartz sand, 20-30% of 10-20-mesh quartz sand, 0.5-5% of 20-40-mesh quartz sand, 20-30% of 150-mesh barite powder and 20-30% of 600-mesh barite powder.
Preferably, the similar material of the stratum with the compact skeleton comprises, by mass, 25.3% of 2-4-mesh quartz sand, 25.1% of 10-20-mesh quartz sand, 1.2% of 20-40-mesh quartz sand, 24.6% of 150-mesh barite powder and 23.8% of 600-mesh barite powder.
The weight distribution of the similar materials is 1.98-2.18 g/cm3Basically, the method can realize the consistency of the gravities of all loose granular formations and meet the gravity similarity constant Cγ11, in the presence of a catalyst. Secondly the permeability coefficient distribution of similar materials is 5.2X 10-5～2.1×10-4Basically, the simulation of the permeability of all loose granular formations can be realized, and the similarity constant C of the permeability coefficient is satisfiedk15 to 10.
Table 1 shows the mass percent contents of the respective materials in examples 1 to 9 of the present invention.
TABLE 1
The following detailed description of the method for preparing a similar material for the unconsolidated particulate body formation includes the following steps:
step 1, acquiring parameter information of the unconsolidated particle stratum according to the reconnaissance data of the unconsolidated particle stratum.
Specifically, before the test is carried out, the stratum survey data obtained on the engineering site is analyzed and analyzed to obtain the stratum composition, the water content, the elastic modulus, the cohesive force, the internal friction angle and the permeability coefficient information of the loose particle bodies, and the stratum composition, the water content, the elastic modulus, the cohesive force, the internal friction angle and the permeability coefficient information are used as basic information for preparing similar materials.
And 2, determining the type of the similar material according to the grading composition of the loose particle body stratum, preparing a mixed dry material sample with a set amount according to the corresponding proportion of the type of the similar material, and then adjusting the water content of the mixed dry material to be the same as that of the loose particle body stratum so as to determine the mass percentage of water in the similar material.
Specifically, the mass percentages of the quartz sand materials and the barite powders with different meshes in the similar materials are preliminarily determined according to the types of the similar materials, for example, the types of the similar materials are similar materials in a skeleton void type stratum, then, predetermined mass mixed dry material samples are prepared according to the mass percentages and geometric similarity ratios corresponding to the materials, in this embodiment, samples with a total amount of 5kg are prepared, in the preparation of the samples, the weights of the quartz sand materials with different meshes and the barite powders with different meshes are strictly weighed on a platform scale according to the weight content of the materials, and the weighed materials and the barite powders are put together and stirred uniformly, so that the uniformly mixed dry materials are obtained.
Then adding water with determined content into the dry material, and further stirring uniformly to form wet material. And uniformly adding the wet material into the test mold for 2-3 times, successively tamping the test mold, and slowly demolding the test block after the wet material is solidified. Obtaining the water content w of the sample through an indoor test, comparing the water content w with the water content of the loose granular body stratum, repeatedly adjusting the water adding amount in the dry material to ensure that the water content of the sample is the same as the water content of the loose granular body stratum, recording the total water adding amount, and calculating the mass percent m of water in the whole samplew/5。
The similar material itself is formed by a diameter reduction of the loose granular stratumThe class parameters (gravity, porosity, poisson's ratio) are similar to the natural characteristics of the actual stratum, and the similarity coefficient of 1 can be realized. According to the similarity ratio relationship, strain epsilon, Poisson ratio mu and internal friction angle can be obtained
And the similarity ratio of dimensionless parameters such as porosity p is equal to the similarity ratio of water content and is equal to 1, i.e.
And 3, determining the geometric similarity ratio between the loose granular body stratum and the similar material.
According to the particle grading distribution of the loose granular body stratum, the structural form of the loose granular body stratum is determined, and the average diameter (d) of the macro-granule group in the loose granular body stratum and the average diameter (d) of the macro-granule materials in the similar materials are usedm) The particle size similarity ratio between the loose granular body stratum and the similar material is calculated
Then, based on the ratio, comprehensively considering the feasibility and the economical efficiency of the test, determining the geometric similarity ratio between the unconsolidated particle body stratum and the similar material
The total amount of similar material required for the test is determined based on the geometric similarity ratio, in combination with the dimensions of the test chamber.
And 4, selecting different performance parameters according to different test types, and adjusting the relative content percentage of each component in the coarse grain group or the fine grain group in the similar material sample according to the performance requirement of the test to ensure that the performance of the similar material meets the performance requirement of the test.
The model test includes two categories, which are mechanics and deformation simulation test and stratum seepage and precipitation model test.
The elastic modulus E and the cohesive force c of similar materials need to be adjusted in mechanical and deformation simulation tests.
The permeability coefficient k of similar materials needs to be adjusted in model tests of formation seepage and precipitation.
The process of tuning the properties of similar materials in two simulation tests is described in detail below.
Firstly, adjusting the elastic modulus E and the cohesive force c of adjacent materials in a mechanical and deformation simulation test. In the model test of loose particle stratum foundation pit, tunnel mechanics and deformation, the similarity of main considerations includes the following:
the similar relationship between stress σ, volume weight γ, and geometry L is: cσ＝CγCL；
The similarity relationship between the stress σ, the strain ε, and the elastic modulus E satisfies: cσ＝CECε；
The similar relationship among the cohesive force c, the geometry L and the volume weight γ satisfies: cc＝CLCγ
Overall, the similar ratio of elastic modulus and cohesion between similar materials and the unconsolidated particulate body formation is equal to the geometric similar ratio obtained in step 3, namely CE＝Cc＝CL(the maximum allowable error is ± 0.1), other similarity ratio relationships can be determined, which are as follows:
initial values of the elastic modulus E and the cohesion c of the sample prepared from the similar material in step 2 are obtained.
Specifically, in a model test for loose particle body stratum mechanics and deformation, initial values of the elastic modulus E and the cohesive force c of a similar sample are obtained through an indoor direct shear test and a compression test, the obtained elastic modulus and the cohesive force are respectively compared with corresponding values of the loose particle body stratum to obtain corresponding similarity ratios, then the obtained similarity ratios are compared with the geometric similarity ratios obtained in the step 2, the comparison results are equal, the elastic modulus E and the cohesive force c of the similar material sample meet the requirements, and otherwise, the elastic modulus E and the cohesive force c do not meet the requirements.
When the elastic modulus E of the similar material sample does not meet the requirement, under the condition that the total content of the coarse particle group is kept unchanged, the mass content of 10-20-mesh quartz sand and 20-40-mesh quartz sand in the coarse particle group is adjusted according to the preset increase and decrease percentage, and the sample of the similar material is prepared again according to the step 2 until the elastic modulus E and the cohesive force c of the similar sample meet the requirement of the simulation test.
Specifically, when the elastic modulus E is too small, the mass content of the 20-40 mesh quartz sand is increased according to the increment of 1% by mass, the mass content of the 10-20 mesh quartz sand is reduced according to the decrement of 1% by mass, and the sample is prepared again according to the method in the step 2 every time the mass is adjusted until the requirement of the simulation test is met.
When the elastic modulus E is too large, the mass content of the 20-40 mesh quartz sand is reduced according to the decreasing amount of 1% by mass, and the mass content of the 10-20 mesh quartz sand is increased according to the increasing amount of 1% by mass.
When the cohesive force c of similar material samples does not meet the requirement, the method can be realized by adjusting the mass contents of 600-mesh barite powder and 150-mesh barite powder in the fine particle group under the condition of keeping the total content of the fine particle group unchanged.
Specifically, when the cohesive force c is too small, the mass content of 600-mesh barite powder is increased by 1% increment by mass, and the mass content of 150-mesh barite powder is reduced by 1% increment by mass;
when the cohesive force c is too large, the mass content of the 600-mesh barite powder is reduced by 1% of decrement by mass percentage, and the mass content of the 150-mesh barite powder is increased by 1% of increment by mass percentage.
When the performance of the similar materials meets the requirements, the similar materials required by the simulation test are prepared according to the mass percentage of each material and the total quantity of the requirements, and after the similar materials are prepared, boxing and arrangement of sensors are carried out according to the test requirements, so that the test is carried out, and the stratum destruction characteristics, the stratum displacement field, the change rule of the stress field and the stress characteristics of the structure are researched.
And secondly, adjusting the permeability coefficient of the similar material in the seepage and precipitation model test.
In conducting model tests of seepage and precipitation in unconsolidated particulate formations, the similarity relationships of major considerations include the following:
the similar relation between the flow velocity v and the seepage coefficient k is as follows: cv＝Ck；
The similar relationship among the seepage flow Q, the permeability coefficient k and the geometry L is: cQ＝CL 2Ck；
Similar relationships between water particle flow velocity v, permeability coefficient k and porosity p in the pores are:
Ck＝CvCp；
the similar relationship between time t, permeability coefficient k, geometry L and porosity p is: ctCk＝CLCμ。
In the test, as long as the similarity ratio of the permeability coefficients of the similar material and the unconsolidated particle body stratum is determined to be within the range of 5-10, other similarity ratio relations can be determined, and the concrete conditions are as follows:
and (3) acquiring an initial value of the permeability coefficient k of the sample prepared from the similar material in the step (2).
Specifically, in a model test of loose particle body stratum mechanics and deformation, an initial value of a permeability coefficient k of a similar sample is obtained through an indoor permeability test, the obtained permeability coefficient is compared with a corresponding value of the loose particle body stratum, a permeability coefficient similarity ratio is obtained, if the obtained similarity ratio is within the range of 5-10, the permeability of the similar material sample meets the requirement, and if not, the permeability of the similar material sample does not meet the requirement.
When the permeability coefficient of the similar material sample does not meet the requirement, under the condition that the total content of the coarse particle group is kept unchanged, the mass contents of 10-20-mesh quartz sand and 20-40-mesh quartz sand in the coarse particle group are adjusted according to the preset increasing and decreasing percentage, and the sample of the similar material is prepared again according to the step 2 until the permeability coefficient of the similar sample meets the requirement of the simulation test.
Specifically, when the permeability coefficient is too large, the mass content of the 20-40 mesh quartz sand is increased according to the increment of 1% by mass, the mass content of the 10-20 mesh quartz sand is reduced according to the decrement of 1% by mass, and the sample is prepared again according to the method in the step 2 every time the mass is adjusted until the requirement of the simulation test is met.
When the permeability coefficient is too small, the mass content of the 20-40 mesh quartz sand is reduced according to the decreasing amount of 1% by mass, and the mass content of the 10-20 mesh quartz sand is increased according to the increasing amount of 1% by mass.
After the content mass percentage of each part of the similar material is determined, the proportion of quartz sand, barite powder and water with different meshes can be carried out according to the actual total quantity required, after the material is prepared, boxing and arrangement of sensors are carried out according to the test requirement, the obtained similar material has good water stability, the adjustment of the water content can be well realized, the stability in the seepage process can be kept in the seepage test, the test is carried out by the method, and the structural water pressure distribution rule, the stratum seepage field change rule and the stratum water burst damage rule are researched.
The first embodiment is as follows:
a similar model test of tunnel non-support excavation is carried out aiming at a certain cobble stratum, 200kg of test materials are required to be prepared, and the preparation and adjustment processes of the similar materials are as follows:
step 1: according to the survey report of a certain boulder stratum, the grading composition of the stratum material belongs to a skeleton gap type, and the density is 2.01g/cm3The modulus of elasticity is 25MPa, the internal friction angle is 42.0 degrees, the cohesive force is 10.02kPa, the maximum particle size is 48cm, and the water content is 5.8 percent. According to the proportion of similar materials corresponding to the skeleton gap type, preliminarily determining the mass percentages of the materials in the similar materials as follows: 35.7% of 2-4 mesh quartz sand: 34.8% of 10-20 mesh quartz sand: 9.7% of 20-40 mesh quartz sand: 10.5% of barite powder of 150 mesh: 9.3 percent of 600-mesh barite powder.
Step 2: 5kg of samples are prepared according to the proportion, and the water content of similar samples is equal to that of the boulder stratum by repeatedly adjusting the water adding amount in the samples. The final determined amount of water added was 0.8kg, so the mass percentage of water required in the test was
And step 3: according to the similar ratio between the boulder stratum and the similar material boulder grain group
Simultaneously, the feasibility and the economy of the test are considered, and the geometric similarity ratio C of the test is finally determinedL60. The total amount of similar materials required for this test was determined to be 200kg, in combination with the dimensions of the test chamber.
And 4, step 4: initial values of cohesive force c and elastic modulus E of similar materials obtained by an indoor direct shear test and a compression test are 0.4MPa and 0.23kPa respectively. Therefore, the similar ratio of the elastic modulus between the boulder stratum and the similar material sample can be obtained as
Elastic modulus similarity ratio to geometric similarity ratio (C)L60) is-0.04, meeting the requirement.
The cohesive force similarity ratio is
Geometric similarity ratio (C)L60) is +0.27, which is not satisfactory.
The mass contents of the 600-mesh barite powder and the 150-mesh barite powder in the similar material proportioning scheme are adjusted to improve the cohesive force of the similar sample, and through repeated adjustment, the mass percentage of the 600-mesh barite powder is finally determined to be improved from the original 9.3 to 14.1, and the mass percentage of the 150-mesh barite powder is reduced from the original 10.5 to 5.7.
Therefore, the finally determined mass percentages of the materials in the similar materials are as follows: 35.7% of 2-4 mesh quartz sand, 34.8% of 10-20 mesh quartz sand, 9.7% of 20-40 mesh quartz sand, 5.7% of 150 mesh barite powder and 14.1% of 600 mesh barite powder.
And 5: according to the total amount of test requirements, 200kg of test materials are prepared, wherein the test materials comprise 32kg of water and 168kg of similar materials, and according to the determined content of the similar materials, the finally required mass of each material is respectively as follows: 59.976kg of 2-4-mesh quartz sand; 58.464kg of 10-20 mesh quartz sand; 16.296kg of 20-40 mesh quartz sand; 9.576kg of 150 mesh barite powder; 23.688kg of 600 mesh barite powder.
After the materials are prepared, boxing and arrangement of sensors are carried out according to test requirements, so that corresponding tests are carried out. Fig. 2 shows the change of the crown subsidence in the tunnel excavation process in the model test. It can be seen from the figure that the settlement of all the measuring points is increased all the time in the tunnel excavation process, the settlement of the arch part caused by excavation within the ranges of 15cm and 25cm respectively before and after the monitoring section accounts for more than 90% of the total settlement, the deformation of the surrounding rock of the arch part is smaller in the excavation stage of the cavern, and the deformation rule is similar to that of on-site monitoring.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (10)
1. A similar material for a unconsolidated particulate body formation, comprising a macro-grained material for use as a framework, a coarse-grained fraction for use as a pack-filler and a fine-grained fraction for use as a pack-cement,
the large particle material is 2-4 meshes of quartz sand; the coarse grain group comprises 10-20 meshes of quartz sand and 20-40 meshes of quartz sand; the fine particle group included 150 mesh barite powder and 600 mesh barite powder.
2. The unconsolidated particulate body formation simulant material of claim 3, wherein the simulant material comprises a suspension-compacted formation simulant material, a skeletal void formation simulant material, and a skeletal void formation simulant material.
3. A similar material of a unconsolidated particulate body formation according to claim 2,
the suspended compact stratum similar material comprises, by mass, 5% -10% of 2-4-mesh quartz sand, 10% -20% of 10-20-mesh quartz sand, 15% -25% of 20-40-mesh quartz sand, 20% -30% of 150-mesh barite powder and 25% -35% of 600-mesh barite powder;
the framework gap type stratum similar material comprises, by mass, 30% -40% of 2-4-mesh quartz sand, 30% -40% of 10-20-mesh quartz sand, 5% -15% of 20-40-mesh quartz sand, 5% -15% of 150-mesh barite powder and 5% -15% of 600-mesh barite powder;
the similar material for the dense-framework stratum comprises, by mass, 20-30% of 2-4-mesh quartz sand, 20-30% of 10-20-mesh quartz sand, 0.5-5% of 20-40-mesh quartz sand, 20-30% of 150-mesh barite powder and 20-30% of 600-mesh barite powder.
4. A method of producing a similar material for a unconsolidated particulate body formation, as claimed in any one of claims 1 to 3, comprising the steps of:
step 1, determining similar material types according to the grading composition of a loose particle body stratum;
step 2, preparing a set amount of mixed dry material sample according to the proportion corresponding to the type of the similar material, and adjusting the water content of the mixed dry material sample to be the same as that of the unconsolidated granular stratum so as to obtain the mass percent of water in the similar material;
step 3, determining the geometric similarity ratio between the loose particle body stratum and the similar material determined in the step 1;
step 4, setting performance parameters of similar materials according to test types, comparing the performance parameter similarity ratio of the similar materials and the loose particle body stratum with the geometric similarity ratio, and adjusting the mass percentage of each material in a coarse particle group or a fine particle group in a similar material sample according to a comparison result to enable the performance of the similar materials to reach the performance parameters of the set similar materials, so as to obtain the mass percentages of each component in the similar materials;
and 5, preparing the similar material according to the total amount of the similar material required by the test and by combining the mass percentages of the components in the similar material obtained in the step 4 and the mass percentage of water.
5. The method of claim 4, wherein the step 1 comprises determining the grading composition of the unconsolidated particulate body formation based on survey data of the unconsolidated particulate body formation.
6. The method for preparing a similar material for a unconsolidated particulate body formation of claim 4, wherein the geometric similarity ratio is determined in step 4 by the following method:
according to the average diameter of the giant grain groups in the loose granular body stratum and the average diameter of the giant grain materials in the similar materials, the grain size similarity ratio between the loose granular body stratum and the similar materials is calculated, and then the geometric similarity ratio between the loose granular body stratum and the similar materials is determined according to the grain size similarity ratio and economic indexes.
7. The method of claim 4, wherein the performance parameters are elastic modulus E and cohesion c when performing mechanical and deformation simulation tests.
8. The method for preparing a similar material for a unconsolidated particulate body formation of claim 7, wherein the elastic modulus E and cohesion c are adjusted as follows:
the elastic modulus E is adjusted by the method that the total content of the coarse particle group is unchanged, and the mass contents of 10-20 meshes of quartz sand and 20-40 meshes of quartz sand in the coarse particle group are adjusted according to a preset increase and decrease percentage;
the cohesive force c is adjusted by keeping the total content of the fine particle group unchanged and adjusting the mass content of 600-mesh barite powder and 150-mesh barite powder in the fine particle group according to a preset increase and decrease percentage.
9. The method of claim 4, wherein the property parameter is permeability coefficient k when the model test of seepage and precipitation of the unconsolidated particulate formation is performed.
10. The method of claim 9, wherein the permeability coefficient is adjusted by:
keeping the total content of the coarse grain group unchanged, and adjusting the mass content of 10-20 meshes of quartz sand and 20-40 meshes of quartz sand in the coarse grain group according to a preset increase and decrease percentage.
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| CN108118725A (en) * | 2017-12-04 | 2018-06-05 | 上海交通大学 | The experimental rig and method of base pit dewatering in equivalent material simulating artesian aquifer |
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| CN108118725A (en) * | 2017-12-04 | 2018-06-05 | 上海交通大学 | The experimental rig and method of base pit dewatering in equivalent material simulating artesian aquifer |
| CN108303298A (en) * | 2018-01-29 | 2018-07-20 | 招商局重庆交通科研设计院有限公司 | A kind of artificially preparation method of sand-pebble layer model test material |
| CN112067788A (en) * | 2020-09-01 | 2020-12-11 | 安徽建筑大学 | Model test device and method for drainage law of water-bearing stratum at bottom of thick surface soil and thin bedrock |
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