CN113087455B - High liquid limit large pore structural soil and sample preparation method thereof - Google Patents
High liquid limit large pore structural soil and sample preparation method thereof Download PDFInfo
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- 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
- C04B28/02—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 hydraulic cements other than calcium sulfates
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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
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Abstract
The invention discloses high liquid limit large pore structural soil and a preparation method thereof. The invention provides a simple, feasible and effective scheme for manually preparing structural soil, which can solve the problem that the field soil sampling disturbs the soil sample structure, better control the uniformity of a sample and quickly prepare the structural soil with high liquid limit and large pores. According to the invention, the raw material soil is added with early strength cement to form a chemical cementing effect, diatomite and calcium bentonite are added to improve the liquid limit, and the macropores formed after urea particles with different mass percentages are added for hydration are added to simulate the natural high-liquid-limit macropore structural soil.
Description
Technical Field
The invention relates to a geotechnical engineering research method, in particular to artificial structural soil for simulating natural undisturbed soil bonding and high liquid limit and large pore characteristics and a sample preparation method thereof, belonging to the field of civil engineering.
Background
With the rapid development of economy and the rapid promotion of urbanization process in China, various domestic engineering construction projects are increasing day by day, such as: industrial and civil buildings, roads and bridges, underground engineering, water conservancy facilities, port engineering and the like. Particularly, in the east and south coastal areas with developed economy, the areas are widely distributed with soft clay stratums and are limited by geographical conditions and land resources, so that more engineering construction projects are carried out in the soft clay foundation environment. The natural soft clay generally has the characteristics of high water content, large porosity ratio, low strength, thixotropy, high compressibility, structural property and the like, the soil body is slow in drainage and consolidation and can be compressed by a large amount, so that the problems of poor foundation stability, post-construction settlement and the like are prominent, and under the action of external load, the soil body is inevitably damaged suddenly, so that great harm is caused to engineering construction.
Some scholars have tried to artificially prepare samples having the same properties as the natural soil. Researchers have prepared structural sand by placing cement in the sand. Also, researchers have passed through silty soil with Ca (OH)2Mixing, compacting, sampling, introducing carbon dioxide gas to simulate CaCO between soil particles3And (5) cementing. All of these methodsThe characteristics of the macroporosity of the structural earth cannot be taken into account very well. Researchers also prepare structural soil by adopting a mixture of clay, kaolin, cement and salt granules in a certain proportion, but the water solubility of the salt granules is low, so that the maintenance time of a sample in water is long, the solubility of urea is three to four times of that of the salt granules at the temperature of 30 ℃, and the solubility of urea is increased along with the increase of the temperature, so that the maintenance time of the sample can be shortened by using the urea under the same condition, and the sample preparation efficiency is improved. If the macroporous structural soil is prepared, a large amount of salt particles or urea needs to be added, and due to the low solubility of the salt particles, all the salt particles cannot be dissolved by water in a sample within a certain time, the prepared structural soil sample has poor uniformity, and the macroporous structural soil sample cannot be obtained.
In recent years, some students have conducted intensive research on indoor preparation of structural soil, and a small amount of cement and ice particles are doped into raw material soil in a low-temperature environment to form particle cementation and macropore characteristics so as to simulate the structural property of natural soft clay; in addition, the original loess material is adopted, and CaCO is passed between particles by artificial intervention3Formation of cementation and macroporosity features a structural loess sample was prepared. Malandrak used a high temperature firing method mixed with a small amount of kaolin to create cementation between the sample particles. However, the above method for preparing structural soil is harsh in conditions, and it is difficult to prepare structural soil samples indoors under ordinary test conditions. In the case of producing structural soil indoors, the conventional researchers only pay attention to indexes such as structural strength (cementation) and macroporosity (porosity ratio) of the produced sample. Meanwhile, in early research, the subject group provides a preparation scheme of macroporous structural soil, natural structural soil is simulated by adding macropores formed after urea particles with different mass percentages are hydrated, and macroporous structural soil which is consistent with pores of the natural structural soil is finally obtained, but the physical characteristic of simulating the liquid limit and the plastic limit of natural structural soft clay is not solved. Meanwhile, in recent years, no other scholars consider the physical and mechanical characteristics of the liquid limit and the plastic limit of the soil body, so that the simulation test and the analysis research of the natural soil with high liquid limit and large pores are still difficult. Bard is based on mass stickinessThe statistics of the soil compression test show that the compression index is in direct proportion to the liquid limit. If the difference between the liquid limits of the artificially prepared structural soil and the natural soft soil is too large, the high compressibility characteristic of the natural soft soil cannot be well simulated. For natural structural soft clay, particularly natural soil in sedimentary areas such as sea facies or lake facies, the water content is higher, the liquid limit is also larger, so that the essential physical characteristic of high liquid limit cannot be ignored, and the structural soil is not suitable for experimental research by applying a traditional indoor preparation method.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a simple, feasible and effective scheme for manually preparing high liquid limit structural soil, which can solve the problem of disturbance to a soil sample structure caused by field soil borrowing, better control the uniformity of a sample and quickly prepare the high liquid limit large pore structural soil, so that people can better perform experimental research on the structural characteristics of natural structural soft clay, particularly natural soil in sedimentary regions such as marine facies or lake facies.
According to the invention, the chemical cementing effect is formed by adding early strength cement into raw material soil, the liquid limit of a soil sample is improved by adding diatomite and calcium bentonite, and natural high-liquid-limit large-pore structural soil is simulated by adding large pores formed by hydrating urea particles with different mass percentages.
According to a first embodiment of the present invention, there is provided a high liquid limit large pore structural soil.
The structural soil with high liquid limit and large pores is prepared by taking base soil, kaolin, diatomite, calcium bentonite, cement and urea as raw materials, mixing and compacting all the raw materials, and finally performing water injection curing and constant-temperature curing.
Preferably, the content of each raw material component in the structural soil is as follows:
and (3) base soil: 28 to 50 parts by weight, preferably 30 to 45 parts by weight, more preferably 32 to 40 parts by weight.
Kaolin: 13 to 28 parts by weight, preferably 15 to 26 parts by weight, more preferably 18 to 24 parts by weight.
Diatomite: 18 to 32 parts by weight, preferably 20 to 30 parts by weight, more preferably 22 to 28 parts by weight.
Calcium bentonite: 2 to 10 parts by weight, preferably 3 to 9 parts by weight, more preferably 4 to 8 parts by weight.
Cement: 1 to 8 parts by weight, preferably 2 to 7 parts by weight, more preferably 3 to 6 parts by weight.
Urea: 4 to 16 parts by weight, preferably 6 to 14 parts by weight, more preferably 8 to 12 parts by weight.
Preferably, the structural soil has a liquid limit water content of 65 to 83%, preferably 70 to 80%, more preferably 73 to 78%.
Preferably, the plastic limit water content of the structural soil is 28 to 38%, preferably 29 to 35%, more preferably 30 to 33%.
Preferably, the foundation soil is muddy soil at the bottom of a lake.
Preferably, the cement is an early strength cement.
Preferably, the muddy soil on the bottom of the lake is dried muddy soil on the bottom of the lake. The early strength cement is 425R cement.
Preferably, the particle size of the foundation soil is 0.01 to 0.5mm, preferably 0.02 to 0.45mm, and more preferably 0.03 to 0.4 mm.
Preferably, the particle size of the kaolin is from 0.5 to 5 μm, preferably from 1 to 4 μm, more preferably from 1.5 to 3 μm.
Preferably, the diatomaceous earth has a particle size of 0.5 to 5 μm, preferably 1 to 4 μm, more preferably 1.5 to 3 μm.
Preferably, the particle size of the calcium bentonite is 0.5 to 5 μm, preferably 1 to 4 μm, and more preferably 1.5 to 3 μm.
Preferably, the cement has a particle size of 1 to 40 μm, preferably 3 to 35 μm, and more preferably 5 to 30 μm.
Preferably, the urea has a particle size of 0.05 to 2mm, preferably 0.08 to 1.8mm, more preferably 0.1 to 1.5 mm.
According to a second embodiment of the present invention, there is provided a method for preparing a sample of a high liquid limit large pore structural soil.
A method for preparing a sample of high liquid limit macroporous structural soil or a method for preparing a sample of high liquid limit macroporous structural soil according to the first embodiment, the method comprising the following steps:
1) component detection: and detecting the plastic limit water content, the liquid limit water content and the specific gravity of the base soil, the kaolin, the diatomite and the calcium bentonite respectively, and detecting the specific gravity of the cement.
2) Mixing: according to the condition of component detection, mixing the base soil, the kaolin, the diatomite, the calcium bentonite, the cement and the urea, and uniformly stirring to obtain a mixture.
3) Preparing a sample: and pouring the mixture into a sample preparation device, and compacting to obtain a sample.
4) And (5) maintenance: and putting the sample into a container, vacuumizing, injecting water for maintenance, and finally performing constant-temperature maintenance.
5) Removing the mold: and taking out the sample, and removing the mold to obtain the structural soil sample.
Preferably, the adding amount of each raw material component in the step 2) is as follows:
and (3) base soil: 28 to 50 parts by weight, preferably 30 to 45 parts by weight, more preferably 32 to 40 parts by weight.
Kaolin: 13 to 28 parts by weight, preferably 15 to 26 parts by weight, more preferably 18 to 24 parts by weight.
Diatomite: 18 to 32 parts by weight, preferably 20 to 30 parts by weight, more preferably 22 to 28 parts by weight.
Calcium bentonite: 2 to 10 parts by weight, preferably 3 to 9 parts by weight, more preferably 4 to 8 parts by weight.
Cement: 1 to 8 parts by weight, preferably 2 to 7 parts by weight, more preferably 3 to 6 parts by weight.
Urea: 4 to 16 parts by weight, preferably 6 to 14 parts by weight, more preferably 8 to 12 parts by weight.
Preferably, in step 1), the specific gravity of the selected base soil is 2.4 to 3, preferably 2.5 to 2.9, and more preferably 2.6 to 2.8. The plastic limit water content of the selected base soil is 20-30%, preferably 22-28%, and more preferably 24-26%. The liquid limit water content of the selected base soil is 37-49%, preferably 40-47%, and more preferably 42-45%.
Preferably, kaolin is used having a specific gravity of 2.3 to 3, preferably 2.4 to 2.9, more preferably 2.5 to 2.8. The plastic limit water content of the selected kaolin is 30-43%, preferably 33-40%, and more preferably 35-38%. The liquid limit water content of the selected kaolin is 63-75%, preferably 65-72%, and more preferably 67-70%.
Preferably, diatomaceous earth is used having a specific gravity of 2 to 2.9, preferably 2.1 to 2.7, more preferably 2.2 to 2.5. The water content of diatomite is 47-58%, preferably 48-55%, more preferably 50-53%. The liquid limit water content of the diatomite is 95-98%, preferably 95.5-97.5%, more preferably 96-97%.
Preferably, the specific gravity of the calcium bentonite is 1.9-2.5, preferably 2.0-2.4, and more preferably 2.4-2.3. The plastic limit water content of the selected calcium bentonite is 39-49%, preferably 41-47%, and more preferably 43-45%. The liquid limit water content of the calcium bentonite is 70-80%, preferably 72-78%, and more preferably 74-76%.
Preferably, the specific gravity of the selected cement is 2.6-3.6, preferably 2.8-3.4, and more preferably 3.0-3.2.
Preferably, urea is used having a specific gravity of 1.1 to 2.1, preferably 1.3 to 1.9, more preferably 1.5 to 1.7.
Preferably, step 3) is specifically: pouring the mixture into a sample preparation device for 2-8 times (preferably 3-5 times), compacting and shaving while controlling the dry density of the sample to 1.0-1.7g/cm3Preferably 1.1 to 1.9g/cm3More preferably 1.2 to 1.5g/cm3。
Preferably, the step 4) is specifically: the sample is put into a container and is firstly vacuumized for 0.5 to 5 hours (preferably 1 to 4 hours, and more preferably 1.5 to 3 hours). Then injecting water for curing for 8-72h (preferably 12-48h, more preferably 18-36 h). Finally, the sample is put into a constant temperature water bath and maintained for 2 to 12 days (preferably 3 to 10 days, more preferably 5 to 8 days) at the temperature of 20 to 50 ℃ (preferably 25 to 40 ℃, more preferably 30 to 35 ℃).
Preferably, the method is characterized in that: the porosity ratio of the structural soil sample obtained in step 5) is 1.1 to 2.1, preferably 1.3 to 2.0, more preferably 1.5 to 1.9. The specific gravity of the structural soil sample is 2.2 to 2.9, preferably 2.3 to 2.8, and more preferably 2.4 to 2.7.
In the prior art, researchers often only pay attention to indexes such as structural strength (cementation) and macropore characteristics (porosity ratio) of a prepared sample when preparing structural soil, and do not consider physical characteristics such as liquid limit and plastic limit of a soil body, and the physical characteristics directly influence high compressibility characteristics of the prepared structural soil. For natural structural soft clay, especially natural soil in sedimentary areas such as sea facies or lake facies, the water content is higher and the liquid limit is larger, so that the essential physical characteristic of high liquid limit cannot be ignored, and the structural soil is not suitable for experimental research by applying the traditional indoor preparation method. At the present stage, no relevant report discloses simulation sample preparation research and manual simulation sample preparation scheme for the high liquid limit structural soil, and no scholars can prepare the high liquid limit large pore structural soil.
According to the invention, urea is added into the prepared structural soil, urea particles can be completely dissolved in a short time due to the advantages of the dissolving speed and the solubility of the urea, pores formed after the urea is dissolved simulate the pores of natural structural soil, and the pore ratio of the structural soil is controlled by adding urea with different mass fractions. The structural soil prepared by the method can better control the uniformity of a sample, and urea with different mass fractions can be added to simulate the original structural soil with different natural pore ratios. The manual preparation of the structural soil can effectively avoid disturbance generated by field sampling and the like, and provides convenience for better research on mechanical properties of the structural soil.
According to the invention, aiming at the characteristics that natural soft clay generally has high water content, large pore ratio, low strength, thixotropy, high compressibility, structure and the like, the natural high liquid limit large pore structure soil is simulated by adding early strength cement into raw material soil to form chemical cementation, improving liquid limit by adding diatomite and calcium bentonite and adding large pores formed by hydrating urea particles with different mass percentages. In the invention, the calcium bentonite has water absorption and larger expansibility, if the adding amount is too low, the calcium bentonite cannot absorb enough water to enable the structural soil sample to obtain the characteristic of high liquid limit, and if the adding amount is too much, the volume change of the sample is influenced, so that the adding amount needs to be reasonably controlled, the whole structural soil sample added with the calcium bentonite can improve the liquid limit water content and the whole expansibility is not influenced, and the adding amount is generally 2-10 wt%, preferably 3-9 wt%, more preferably 4-8 wt%, for example 5 wt%. The diatomite has a very high liquid limit, and the liquid limit of the whole mixed soil sample can be adjusted and controlled by adding the diatomite into the whole structural soil sample, so that the liquid limit value of the whole artificially prepared structural soil sample is consistent with the characteristic of high liquid limit natural structural soil, meanwhile, the diatomite has a high non-plastic characteristic and can solve the problem of increased expansibility caused by calcium bentonite, but the excessive addition of the diatomite has a great influence on the whole viscosity of the structural soil sample, so that the excessive addition is not suitable, the general addition amount is 18-3 wt%, preferably 20-30 wt%, more preferably 22-28 wt%, and for example, the addition amount is 25 wt%.
In the present invention, the void ratio e ═ Vv/Vs。VvIs the pore volume; vsIs the volume of the mixture in step 2). Wherein Vsi＝msi/(γsi·ρw)；ρwIs the density of water, i.e. 1g/cm3；γsiThe specific gravity of the component i of the mixture; m issiQuality of component I of the mixture, Vs＝Vs1+Vs2+Vs3+···+Vsi(ii) a That is to say VsIs the sum of the volumes of the components in the mixture. V is Vs+Vv(ii) a V is the total volume, namely the volume of the sample preparation device; vv＝V-Vs. After hydration, urea with different mass percentages is dissolved, the volume of the mixture is reduced, the pore volume is increased, and then the large-pore-ratio structural soil with different pore ratios is formed.
In the invention, through triaxial tests of different liquid limit structural soils, it can be determined that the peak strength of the artificially prepared high liquid limit structural soil is reduced along with the increase of the liquid limit of the structural soil, the residual strength of the artificially prepared high liquid limit structural soil is also reduced along with the increase of the liquid limit of the structural soil, and the liquid limit has great influence on the mechanical properties of the structural soil.
In the invention, through a one-dimensional compression consolidation experiment, parameters such as specific gravity, porosity, liquid limit, plastic limit, plasticity index, yield strength, compression index, rebound index, compression coefficient, rebound coefficient and the like of the osaka bay natural soil and the artificially prepared high liquid limit large pore structural soil are compared, and the two parameters are found to be relatively close, thereby further proving the feasibility and the effectiveness of the artificially prepared high liquid limit large pore structural soil.
Compared with the prior art, the invention has the following beneficial technical effects:
1. according to the invention, through a simple, feasible and effective scheme for manually preparing the high liquid limit large pore structural soil, the problems of disturbance to a soil sample structure, difficulty in sampling and the like caused by field soil sampling can be solved, and a simple and controllable sample preparation method is provided for rock and soil tests and macroscopic research.
2. According to the invention, the natural high liquid limit large pore structural soil is simulated by adding early strength cement into raw material soil to form a chemical cementing effect, adding diatomite and calcium bentonite to improve the liquid limit, and adding large pores formed by hydrating urea particles with different mass percentages. Namely, three important indexes of the cementing strength, the large pore ratio and the high liquid limit are considered in the artificial preparation method, so that the characteristics of the prepared structural soil are closer to those of natural soil.
3. According to the method, the samples are prepared in batches and in layers, and then the required samples can be obtained more accurately after vacuum curing and constant-temperature curing, so that the samples obtained through manual preparation are closer to actual soil samples. Provides a simple and controllable sample preparation method for rock and soil tests and macroscopic research.
Drawings
FIG. 1 is a graph showing the relationship between the cone penetration depth and the water content of the mixed material according to the embodiments of the present invention.
FIG. 2 is a graph showing the relationship between the cone penetration depth and the water content of different raw material components.
Fig. 3 is a stress-strain relation graph of triaxial non-drainage compression tests of artificially prepared different liquid-limited structural soils with the porosity ratio e being 1.7.
Fig. 4 is a p-q relation graph of three-axis no-drainage compression tests of artificially prepared different liquid-limited structural soils with the porosity ratio e being 1.7.
FIG. 5 is a graph of the relationship between liquid limit, plastic limit and plasticity index and peak strength of artificially prepared high liquid limit macroporous structural soil of the invention.
FIG. 6 is a graph of liquid limit, plastic limit and the relationship between plasticity index and residual strength of artificially prepared high liquid limit large pore structural soil of the present invention.
Fig. 7 is a one-dimensional compression e-p plot of high liquid limit large pore structural soil and osaka bay natural soil prepared from the mix of example 5 of the present invention.
Figure 8 is a graph of the epsilon-q of the natural soil of osaka bay.
Figure 9 is a graph of p' -q of Osaka gulf native soil.
FIG. 10 is a plot of the ε -q of a high liquid limit macroporous structural soil prepared from the blend of example 5 of the present invention.
FIG. 11 is a p' -q graph of a high liquid limit macroporous structural soil prepared from the mixture of example 5 of the invention.
Detailed Description
The technical solution of the present invention is illustrated below, and the claimed scope of the present invention includes, but is not limited to, the following examples.
A sample preparation method of high liquid limit large pore structural soil comprises the following steps:
1) component detection: and detecting the plastic limit water content, the liquid limit water content and the specific gravity of the base soil, the kaolin, the diatomite and the calcium bentonite respectively, and detecting the specific gravity of the cement.
2) Mixing: according to the condition of component detection, mixing the base soil, the kaolin, the diatomite, the calcium bentonite, the cement and the urea, and uniformly stirring to obtain a mixture.
3) Preparing a sample: and pouring the mixture into a sample preparation device, and compacting to obtain a sample.
4) And (5) maintenance: and putting the sample into a container, vacuumizing, injecting water for maintenance, and finally performing constant-temperature maintenance.
5) Removing the mold: and taking out the sample, and removing the mold to obtain the structural soil sample.
Preferably, the adding amount of each raw material component in the step 2) is as follows:
and (3) base soil: 28 to 50 parts by weight, preferably 30 to 45 parts by weight, more preferably 32 to 40 parts by weight.
Kaolin: 13 to 28 parts by weight, preferably 15 to 26 parts by weight, more preferably 18 to 24 parts by weight.
Diatomite: 18 to 32 parts by weight, preferably 20 to 30 parts by weight, more preferably 22 to 28 parts by weight.
Calcium bentonite: 2 to 10 parts by weight, preferably 3 to 9 parts by weight, more preferably 4 to 8 parts by weight.
Cement: 1 to 8 parts by weight, preferably 2 to 7 parts by weight, more preferably 3 to 6 parts by weight.
Urea: 4 to 16 parts by weight, preferably 6 to 14 parts by weight, more preferably 8 to 12 parts by weight.
Preferably, the foundation soil is lake bottom silt soil (for example, the lake bottom silt soil is dried lake bottom silt soil).
Preferably, the cement is an early strength cement (e.g., 425R cement).
Preferably, in step 1), the specific gravity of the selected base soil is 2.4 to 3, preferably 2.5 to 2.9, and more preferably 2.6 to 2.8. The plastic limit water content of the selected base soil is 20-30%, preferably 22-28%, and more preferably 24-26%. The liquid limit water content of the selected base soil is 37-49%, preferably 40-47%, and more preferably 42-45%.
Preferably, kaolin is used having a specific gravity of 2.3 to 3, preferably 2.4 to 2.9, more preferably 2.5 to 2.8. The plastic limit water content of the selected kaolin is 30-43%, preferably 33-40%, and more preferably 35-38%. The liquid limit water content of the selected kaolin is 63-75%, preferably 65-72%, and more preferably 67-70%.
Preferably, diatomaceous earth is used having a specific gravity of 2 to 2.9, preferably 2.1 to 2.7, more preferably 2.2 to 2.5. The water content of diatomite is 47-58%, preferably 48-55%, more preferably 50-53%. The liquid limit water content of the diatomite is 95-98%, preferably 95.5-97.5%, more preferably 96-97%.
Preferably, the specific gravity of the calcium bentonite is 1.9-2.5, preferably 2.0-2.4, and more preferably 2.4-2.3. The plastic limit water content of the selected calcium bentonite is 39-49%, preferably 41-47%, and more preferably 43-45%. The liquid limit water content of the calcium bentonite is 70-80%, preferably 72-78%, and more preferably 74-76%.
Preferably, the specific gravity of the selected cement is 2.6-3.6, preferably 2.8-3.4, and more preferably 3.0-3.2.
Preferably, urea is used having a specific gravity of 1.1 to 2.1, preferably 1.3 to 1.9, more preferably 1.5 to 1.7.
Preparation examples
A sample preparation method of high liquid limit large pore structural soil comprises the following steps:
1: component detection:
1.1: specific gravity detection:
taking base soil (lake bottom silt soil), kaolin, diatomite, calcium bentonite and cement for later use. And then, carrying out air drying and drying on the base soil, grinding and sieving by a 0.5mm sieve to obtain the base soil for the test. The kaolin, the diatomite and the calcium bentonite are purchased experimental grade raw materials, and the particle size of the raw materials is larger than 4000 meshes (the particle size is about smaller than 2.7 um). Finally, specific gravity tests are respectively carried out on the raw material components according to JTGE40-2007 Highway geotechnical test regulations, and the test results are shown in Table 1.
TABLE 1 specific gravity test data for each of the raw material components used in the test
Three parallel tests are independently carried out on each raw material component by adopting a pycnometer, and the average value is taken as the specific gravity of the corresponding raw material component. The experimental data are shown in table 1 and were determined by calculation: the specific gravity of the base soil is 2.72; the specific gravity of the kaolin is 2.62; the specific gravity of the diatomite is 2.30; the specific gravity of the calcium bentonite is 2.15; the specific gravity of the cement was 3.13.
1.2: limit water content (liquid limit W) of soilLAnd plastic limit WP) And (3) detection:
according to JTGE40-2007 Highway soil engineering test regulations, liquid limit W is respectively carried out on earth materials (foundation soil, kaolin, diatomite and calcium bentonite) of raw materialsLPlastic limit WPAnd plasticity index IPThe measurement of (1). Taking the dried base soil, kaolin, diatomite and calcium bentonite for later use; grinding each dried soil material, sieving by a 0.5mm sieve, respectively containing each soil material independently by three material containing vessels, adding distilled water with different quantities, and respectively controlling the water content of each soil material in a liquid limit state, a plastic limit state and a liquid limit and plastic limit intermediate state. And then uniformly mixing the materials by using a soil adjusting knife, covering wet cloth, standing for 18 hours, finally measuring the limit water content of each soil material by using a liquid-plastic limit joint tester, measuring three groups of soil penetration depths of each limit water content, and taking an average value. The results of measuring the limit water content of each soil are shown in Table 2. The depth h of penetration of the cone and the water content w are plotted on a log-log double coordinate, see fig. 2.
TABLE 2 boundary water content test data of each soil material
The test adopts a 76g conical head, and the water content corresponding to the cone penetration depth of 17mm is taken as a liquid limit, and the water content corresponding to the cone penetration depth of 2mm is taken as a plastic limit. From fig. 2, it can be seen that: the liquid limit water content of the base soil is 43.5 percent; the plastic limit water content is 25.3%. Plasticity index Ip43.5-25.3-18.2; the liquid limit water content of the kaolin is 68.7 percent; the plastic limit water content is 36.9%. Plasticity index Ip68.7-36.9-31.8; the liquid limit water content of the diatomite is 96.5 percent; the plastic limit water content is 51.6%. Plasticity index Ip96.5-51.6-44.9; the liquid limit water content of the calcium bentonite is 74.6 percent; the plastic limit water content is 44.9%. Plasticity index Ip＝74.6-44.9＝29.7。
2: mixing:
2.1: mixing and proportioning the following raw materials:
taking the raw material components, and determining the mixture ratio combination for preparing the structural soil with certain bonding strength and high liquid limit large pore ratio according to the specific gravity of the base soil, the kaolin, the diatomite, the calcium bentonite, the cement and the urea; the detailed grouping ratio results of each mixture are shown in table 3.
TABLE 3 mixture ratio grouping test data
2.2: limit water content (liquid limit W) of mixtureLAnd plastic limit WP) And (3) detection:
according to JTG E40-2007 Highway soil test regulations, liquid limit W is respectively carried out on each group of mixed materialsLPlastic limit WPAnd plasticity index IPThe measurement of (1). And (3) taking each group of dried mixture for testing, sieving the dried mixture by a 0.5mm sieve, separately loading the soil material into three soil containing vessels, adding different amounts of distilled water, and respectively controlling the water content of the mixture to be in a liquid limit state, a plastic limit state and an intermediate state of the liquid limit state and the plastic limit state. Uniformly mixing by using a soil adjusting knife, covering wet cloth, standing for 18h, determining the limit water content of the mixture by using a liquid-plastic limit joint determinator, determining three groups of soil penetration depths of each water content, and taking an average value. The results of the boundary water content measurement of each blend are shown in Table 4. The depth h of penetration of the cone and the water content w are plotted under a log-log coordinate, and the result is shown in fig. 1.
TABLE 4 example limit moisture content test data for different mixes
The test adopts a 76g conical head, and the water content corresponding to the cone penetration depth of 17mm is taken as a liquid limit, and the water content corresponding to the cone penetration depth of 2mm is taken as a plastic limit. From fig. 1, it can be seen that: the liquid limit water content of the mixture of the group A-1 is 57.9%; the plastic limit water content is 27.6%. Plasticity index Ip57.9-27.6-30.3; the liquid limit water content of the mixture of the group A-2 is 66.6%; plastic limit water ratioThe content was 30.2%. Plasticity index Ip66.6-30.2-36.4; the liquid limit water content of the A-3 group mixture is 78.0%; the plastic limit water content is 32.4%. Plasticity index Ip78.0-32.4-45.6; the liquid limit water content of the A-4 group of mixture is 92.2%; the plastic limit water content is 41.6%. Plasticity index Ip92.2-41.6-50.6; the liquid limit water content of the mixture of the group E is 75.9 percent; the plastic limit water content is 31.7%. Plasticity index Ip＝75.9-31.7＝44.2。
3: preparing a sample: according to the grouping shown in Table 3, the mixtures of the examples are controlled according to a certain initial dry density, and the mixtures are poured into the mixture for 4 times (so as to obtain 4 layers) independently
The sample preparation device (2) is compacted (the compaction is needed once after one time of material addition), and finally the sample of each example is obtained.
4: and (5) maintenance:
the samples of the examples are respectively put into a saturation barrel to be vacuumized for 2 hours, and after water is injected for maintenance for one day, the samples of the examples are respectively put into a constant temperature water bath pot to be maintained in a flowing state for 6 days at 30 ℃.
5: removing the mold:
and curing the sample of each example for 7 days, taking out, and removing the three split molds to obtain the high liquid limit large pore structural soil sample prepared from the mixture of each example.
The three-axis non-drainage compression test was performed on all of the high liquid-limiting large pore structural soil samples prepared from the respective mixes of example 1(a-1), example 2(a-2), example 3(a-2), example 4(a-4) and example 5(E), and the results are shown in fig. 3 and 4. The preparation method of the structural soil is proved to be feasible from the aspect of macroscopic test.
FIG. 3 is a graph of stress-strain relationship of three-axis non-drainage compression tests of artificially prepared different liquid-limited structural soils with a porosity e of 1.7; fig. 4 is a p-q relationship graph of triaxial non-drainage compression tests of artificially prepared different liquid-limited structural soils with a porosity e of 1.7. As can be seen from the three-axis no-drainage compression test of fig. 3 and 4: the structural soil can generate a strain softening phenomenon in the loading process, the stress drop is relatively slow, and the structural soil cementation failure is a gradual process; the stress-strain relation curve shows that: the peak strength of the structural soil with low liquid limit is higher than that of the structural soil with high liquid limit; the structural soil with a low liquid limit has higher residual strength than the structural soil with a high liquid limit.
Fig. 5 is a liquid limit, plastic limit and a relation curve between plasticity index and peak strength of the artificially prepared high liquid limit and large pore structural soil, and it can be seen from fig. 5 that the peak strength of the structural soil is reduced along with the increase of the liquid limit of the structural soil.
Fig. 6 is a graph of relationship between liquid limit, plastic limit and plasticity index and residual strength of artificially prepared high liquid limit large pore structural soil, similar to the results in fig. 5, and can be also seen from fig. 6: the residual strength of the structural soil also decreases with increasing structural soil liquid limit. It can be seen that the liquid limit has a great influence on the mechanical properties of the structural soil.
Comparative test
The comparison test between the high liquid limit large pore structural soil sample prepared from the mixture of example 5(E) of the present invention and the natural soil of osaka bay (the natural soil of osaka bay is natural clay of osaka region of japan) shows that:
i: deformation feature alignment (one-dimensional CRL test):
the high liquid limit large pore structural soil sample prepared from the mixed material of the example 5(E) and the natural soil of Osaka bay are subjected to a one-dimensional compression comparison test, and the test results are shown in FIG. 7. As can be seen from fig. 7, the one-dimensional compression curve of the artificially prepared high liquid limit large pore structural soil is very close to the one-dimensional compression curve of the osaka bay natural soil, which indicates that the artificially prepared high liquid limit large pore structural soil can simulate the compression characteristics of the natural soil, i.e., the artificially prepared high liquid limit large pore structural soil of the present scheme is feasible.
ii: strength feature comparison (compression and tensile experiments):
the high liquid limit large pore structural soil sample prepared from the mixture of example 5(E) and the osaka bay natural soil were subjected to the triaxial compression and triaxial tensile tests, and the test results are shown in fig. 8 to 11. Fig. 8 and 9 are triaxial compression and tension curves of reference osaka bay natural soil; FIGS. 10 and 11 are triaxial compression and tension curves of a high liquid limit macroporous structural soil sample obtained from the compound prepared in example 5 (E). As can be seen from the comparison between fig. 8 and 10 and the comparison between fig. 9 and 11, the three-axis compression and tensile related properties of the high liquid limit large pore structural soil prepared by the present invention are similar to those of the natural soil in osaka bay, and the peak intensity simulation and the residual intensity simulation are relatively close to each other, which indicates that the present solution of the high liquid limit large pore structural soil prepared by the present invention is really feasible.
iii: liquid limit WLPlastic limit WPAnd plasticity index IPThe comparison of (1):
according to JTGE40-2007 Highway soil engineering test regulations, the high liquid limit large pore structural soil sample prepared from the mixture of example 5(E) and the Osakawan natural soil are subjected to liquid limit WLPlastic limit WPAnd plasticity index IPThe results are shown in Table 5; comparing the Osaka gulf natural soil with the liquid limit W of the high liquid limit large pore structural soil artificially prepared by the schemeLPlastic limit WPAnd plasticity index IP(ii) a Can obtain the liquid limit W of the artificially prepared high-liquid-limit large-pore structural soilLPlastic limit WPAnd plasticity index IPClose to the natural soil of the Osaka bay, the fact proves that the large-pore structural soil with high liquid limit can be artificially prepared.
Table 5 comparative data of boundary moisture content test of high liquid limit large pore structural soil of example 5 and osaka bay natural soil
| Category of soil | Liquid limit WL/(％) | Plastic limit Wp/(％) | Plasticity index Ip |
| Osaka bay natural soil | 69.2-75.1 | 24.5-27.3 | 41.9-50.6 |
| High liquid limit large pore structural soil | 75.9 | 31.7 | 44.3 |
iii: alignment of other basic parameters:
the data of the one-dimensional compression test of the high liquid limit large pore structural soil sample and the osaka bay natural soil obtained from the mix prepared in example 5(E) can be calculated as follows: the results of the correlation indexes of the artificially prepared high liquid limit structural soil in the scheme are shown in tables 6 and 7. The comparison can be carried out as follows: the parameter of the high liquid limit large pore structural soil sample prepared by the scheme is very small from the parameter of the Osaka gulf natural soil. Namely, the high liquid limit large pore structural soil prepared by the preparation method is really feasible, and the high liquid limit large pore structural soil prepared by the preparation method can effectively simulate the structural characteristics of the natural soil of Osaka Bay.
Table 6 comparative table (one) of parameters of high liquid limit large pore structural soil of example 5 and osaka bay natural soil
| Category of soil | Void ratio | Specific gravity of | pc′/kPa |
| Osaka bay natural soil | 1.67-1.92 | 2.67-2.70 | 94.1 |
| High liquid limit large pore structural soil | 1.70 | 2.55 | 86.9 |
Table 7 comparative table of parameters of high liquid limit large pore structural earth and osaka bay natural earth of example 5 (ii)
In summary, the mixed components and the mixture ratio in the embodiment 5(E) are optimally designed, and the natural high liquid limit large pore structural soil is simulated by adding early strength cement into the raw material soil to form chemical cementation, adding diatomite and calcium bentonite to improve the liquid limit, and adding large pores formed after urea particles with different mass percentages are added for hydration. However, the study of the prior scholars on the artificial preparation of the structural soil does not consider the characteristic of high liquid limit, and the scholars can not prepare the large-pore structural soil with high liquid limit. Through a one-dimensional compression consolidation experiment, compared with the natural soil of Osaka Bay and the artificially prepared high liquid limit large pore structural soil of the scheme, the specific gravity, the porosity, the liquid limit, the plastic limit, the plasticity index, the yield strength, the compression index, the rebound index, the compression coefficient, the rebound coefficient and other parameters of the natural soil are relatively close to each other, and therefore, the scheme of artificially preparing the high liquid limit large pore structural soil is really feasible. The cementing strength, the pore ratio and the liquid limit of the structural soil can be simultaneously controlled in the preparation process, the difficulties that the natural structural soil is easy to disturb and difficult to sample are overcome, and a simple and controllable sample preparation method is provided for rock-soil tests and macroscopic researches.
Claims (23)
1. A high liquid limit large pore structural soil is characterized in that: the structural soil is prepared by taking base soil, kaolin, diatomite, calcium bentonite, cement and urea as raw materials, then mixing and compacting all the raw materials, and finally performing water injection maintenance and constant-temperature maintenance; the content of each raw material component in the structural soil is as follows: and (3) base soil: 28-50 parts by weight; kaolin: 13-28 parts by weight; diatomite: 18-32 parts by weight; calcium bentonite: 2-10 parts by weight; cement: 1-8 parts by weight; urea: 4-16 parts by weight;
wherein: the foundation soil is muddy soil at the bottom of the lake; the cement is early strength cement.
2. The structural soil of claim 1, wherein: the content of each raw material component in the structural soil is as follows: and (3) base soil: 30-45 parts by weight; kaolin: 15-26 parts by weight; diatomite: 20-30 parts by weight; calcium bentonite: 3-9 parts by weight; cement: 2-7 parts by weight; urea: 6-14 parts by weight.
3. The structural soil of claim 1, wherein: the content of each raw material component in the structural soil is as follows: and (3) base soil: 32-40 parts by weight; kaolin: 18-24 parts by weight; diatomite: 22-28 parts by weight; calcium bentonite: 4-8 parts by weight; cement: 3-6 parts by weight; urea: 8-12 parts by weight.
4. The structural soil of claim 1, wherein: the liquid limit water content of the structural soil is 65-83%; the plastic limit water content of the structural soil is 28-38%.
5. The structural soil of claim 1, wherein: the liquid limit water content of the structural soil is 70-80%; the plastic limit water content of the structural soil is 29-35%.
6. The structural soil of claim 1, wherein: the liquid limit water content of the structural soil is 73-78%; the plastic limit water content of the structural soil is 30-33%.
7. The structural soil of claim 1, wherein: the lake bottom silt soil is dried lake bottom silt soil; the early strength cement is 425R cement.
8. The structural soil of any one of claims 1 to 7, wherein: the particle size of the foundation soil is 0.01-0.5 mm; the particle size of the kaolin is 0.5-5 μm; the particle size of the diatomite is 0.5-5 μm; the particle size of the calcium bentonite is 0.5-5 mu m; the particle size of the cement is 1-40 mu m; the particle size of the urea is 0.05-2 mm.
9. The structural soil of claim 8, wherein: the particle size of the foundation soil is 0.02-0.45 mm; the particle size of the kaolin is 1-4 μm; the particle size of the diatomite is 1-4 mu m; the particle size of the calcium bentonite is 1-4 mu m; the particle size of the cement is 3-35 mu m; the particle size of the urea is 0.08-1.8 mm.
10. The structural soil of claim 8, wherein: the particle size of the foundation soil is 0.03-0.4 mm; the particle size of the kaolin is 1.5-3 μm; the particle size of the diatomite is 1.5-3 mu m; the particle size of the calcium bentonite is 1.5-3 mu m; the particle size of the cement is 5-30 mu m; the particle size of the urea is 0.1-1.5 mm.
11. A method for preparing the high liquid limit large pore structural soil according to any one of claims 1 to 10, characterized in that: the method comprises the following steps:
1) component detection: detecting the plastic limit water content, the liquid limit water content and the specific gravity of the base soil, the kaolin, the diatomite and the calcium bentonite respectively, and detecting the specific gravity of the cement;
2) mixing: according to the condition of component detection, mixing the base soil, the kaolin, the diatomite, the calcium bentonite, the cement and the urea, and uniformly stirring to obtain a mixture;
3) preparing a sample: pouring the mixture into a sample preparation device, and compacting to obtain a sample;
4) and (5) maintenance: putting the sample into a container, vacuumizing, injecting water for maintenance, and finally performing constant-temperature maintenance;
5) removing the mold: and taking out the sample, and removing the mold to obtain the structural soil sample.
12. The method of claim 11, wherein: in the step 1), the specific gravity of the selected base soil is 2.4-3; selecting base soil with plastic limit water content of 20-30%; selecting base soil with liquid limit water content of 37-49%; selecting kaolin with the specific gravity of 2.3-3; selecting kaolin with plastic limit water content of 30-43%; selecting kaolin with liquid limit water content of 63-75%; selecting diatomite with specific gravity of 2-2.9; the plastic limit water content of the selected diatomite is 47-58%; selecting diatomite with liquid limit water content of 95-98%; the specific gravity of the selected calcium bentonite is 1.9-2.5; the plastic limit water content of the selected calcium bentonite is 39-49%; the liquid limit water content of the calcium bentonite is 70-80%; selecting cement with the specific gravity of 2.6-3.6; the specific gravity of the urea is 1.1-2.1.
13. The method of claim 11, wherein: in the step 1), the specific gravity of the selected base soil is 2.5-2.9; selecting base soil with plastic limit water content of 22-28%; selecting base soil with liquid limit water content of 40-47%; selecting kaolin with the specific gravity of 2.4-2.9; selecting kaolin with plastic limit water content of 33-40%; selecting kaolin with liquid limit water content of 65-72%; the specific gravity of the diatomite is 2.1-2.7; selecting diatomite with plastic limit water content of 48-55%; selecting diatomite with liquid limit water content of 95.5-97.5%; the specific gravity of the selected calcium bentonite is 2.0-2.4; selecting calcium bentonite with plastic limit water content of 41-47%; the liquid limit water content of the calcium bentonite is 72-78%; selecting cement with the specific gravity of 2.8-3.4; the specific gravity of the urea is 1.3-1.9.
14. The method of claim 11, wherein: in the step 1), the specific gravity of the selected base soil is 2.6-2.8; selecting base soil with plastic limit water content of 24-26%; selecting base soil with liquid limit water content of 42-45%; selecting kaolin with the specific gravity of 2.5-2.8; selecting kaolin with plastic limit water content of 35-38%; selecting kaolin with liquid limit water content of 67-70%; selecting diatomite with specific gravity of 2.2-2.5; selecting diatomite with plastic limit water content of 50-53%; selecting diatomite with liquid limit water content of 96-97%; the specific gravity of the selected calcium bentonite is 2.4-2.3; selecting calcium bentonite with plastic limit water content of 43-45%; the liquid limit water content of the calcium bentonite is 74-76%; selecting cement with the specific gravity of 3.0-3.2; the specific gravity of the urea is 1.5-1.7.
15. The method according to any one of claims 11-14, wherein: the step 3) is specifically as follows: pouring the mixture into a sample preparation device for 2-8 times, compacting by layers and scraping hair, and simultaneously controlling the dry density of the sample to be 1.0-1.7g/cm3。
16. The method according to any one of claims 11-14, wherein: the step 3) is specifically as follows: pouring the mixture into a sample preparation device for 3-5 times, compacting by layers and scraping hair, and simultaneously controlling the dry density of the sample to be 1.1-1.9g/cm3。
17. The method of claim 15, wherein: the step 3) is specifically as follows: the dry density of the sample is controlled to be 1.2-1.5g/cm3。
18. The method according to any one of claims 11-14, wherein: the step 4) is specifically as follows: putting the sample into a container, and vacuumizing for 0.5-5 h; then injecting water for maintenance for 8-72 h; finally, the sample is put into a constant temperature water bath kettle and is maintained for 2 to 12 days at the temperature of between 20 and 50 ℃.
19. The method according to any one of claims 11-14, wherein: the step 4) is specifically as follows: putting the sample into a container, and vacuumizing for 1-4 h; then injecting water for maintenance for 12-48 h; finally, the sample is put into a constant temperature water bath kettle and is maintained for 3 to 10 days at the temperature of between 25 and 40 ℃.
20. The method according to any one of claims 11-14, wherein: the step 4) is specifically as follows: putting the sample into a container, and vacuumizing for 1.5-3 h; then injecting water for maintenance for 18-36 h; finally, the sample is put into a constant temperature water bath kettle and is maintained for 5 to 8 days at the temperature of between 30 and 35 ℃.
21. The method according to any one of claims 11-14, wherein: the porosity ratio of the structural soil sample obtained in the step 5) is 1.1-2.1; the specific gravity of the structural soil sample is 2.2-2.9.
22. The method according to any one of claims 11-14, wherein: the porosity ratio of the structural soil sample obtained in the step 5) is 1.3-2.0; the specific gravity of the structural soil sample is 2.3-2.8.
23. The method according to any one of claims 11-14, wherein: the porosity ratio of the structural soil sample obtained in the step 5) is 1.5-1.9; the specific gravity of the structural soil sample is 2.4-2.7.
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