CN113123185A - Toughness inflation dirt road bed structure based on nanometer silica and carbon fiber - Google Patents
Toughness inflation dirt road bed structure based on nanometer silica and carbon fiber Download PDFInfo
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- CN113123185A CN113123185A CN202110409608.XA CN202110409608A CN113123185A CN 113123185 A CN113123185 A CN 113123185A CN 202110409608 A CN202110409608 A CN 202110409608A CN 113123185 A CN113123185 A CN 113123185A
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- edge covering
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 100
- 239000004917 carbon fiber Substances 0.000 title claims abstract description 46
- 229920000049 Carbon (fiber) Polymers 0.000 title claims abstract description 34
- 239000000377 silicon dioxide Substances 0.000 title claims description 32
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims description 23
- 239000002689 soil Substances 0.000 claims abstract description 220
- 239000003607 modifier Substances 0.000 claims abstract description 34
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 34
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims abstract description 33
- 235000011941 Tilia x europaea Nutrition 0.000 claims abstract description 33
- 239000004571 lime Substances 0.000 claims abstract description 33
- 239000005543 nano-size silicon particle Substances 0.000 claims abstract description 31
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 31
- 230000002209 hydrophobic effect Effects 0.000 claims abstract description 28
- 239000000463 material Substances 0.000 claims abstract description 16
- -1 polyethylene carbon Polymers 0.000 claims description 12
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 11
- 229910052791 calcium Inorganic materials 0.000 claims description 11
- 239000011575 calcium Substances 0.000 claims description 11
- 238000005056 compaction Methods 0.000 claims description 10
- 238000012258 culturing Methods 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 5
- 230000008961 swelling Effects 0.000 claims description 5
- 238000007605 air drying Methods 0.000 claims description 3
- 239000004033 plastic Substances 0.000 claims description 3
- 229920003023 plastic Polymers 0.000 claims description 3
- 238000007873 sieving Methods 0.000 claims description 3
- 238000005507 spraying Methods 0.000 claims description 3
- 230000007480 spreading Effects 0.000 claims description 3
- 230000001502 supplementing effect Effects 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 16
- 230000035699 permeability Effects 0.000 abstract description 12
- 238000010276 construction Methods 0.000 abstract description 7
- 239000010410 layer Substances 0.000 description 47
- 230000000694 effects Effects 0.000 description 7
- 239000004927 clay Substances 0.000 description 5
- 230000006378 damage Effects 0.000 description 4
- 230000006872 improvement Effects 0.000 description 3
- 230000007774 longterm Effects 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical class O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000010881 fly ash Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000007385 chemical modification Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000009545 invasion Effects 0.000 description 1
- 230000003020 moisturizing effect Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
Images
Classifications
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C3/00—Foundations for pavings
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—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
- C04B28/10—Lime cements or magnesium oxide cements
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K17/00—Soil-conditioning materials or soil-stabilising materials
- C09K17/02—Soil-conditioning materials or soil-stabilising materials containing inorganic compounds only
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C3/00—Foundations for pavings
- E01C3/04—Foundations produced by soil stabilisation
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/20—Securing of slopes or inclines
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
- C04B2111/00732—Uses not provided for elsewhere in C04B2111/00 for soil stabilisation
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K2103/00—Civil engineering use
Abstract
The invention provides a tough expansive soil roadbed structure based on nano silicon dioxide and carbon fibers, and belongs to the field of geotechnical engineering. The tough expansive soil roadbed structure comprises an expansive soil filling core, a roadbed top binding layer, a roadbed bottom binding layer and two roadbed slope binding layers, wherein the expansive soil filling core is arranged in a closed space surrounded by the four binding layers. The paving materials of the four edge covering layers are all modified expansive soil and are formed by uniformly mixing a modifier, water, carbon fibers and field expansive soil, and the modifier is prepared by mixing hydrophobic nano silicon dioxide and lime. The method for filling the expansive soil roadbed by adopting the modified expansive soil edge wrapping method has the characteristics of wide applicability, remarkably shortened construction period, high edge wrapping layer strength, low permeability, low expansibility and good durability.
Description
Technical Field
The invention relates to a toughness expansive soil roadbed structure based on nano silicon dioxide and carbon fiber, and belongs to the field of geotechnical engineering and geological engineering.
Background
In the natural state, the expansive soil is generally high in strength and low in compressibility and shows good engineering characteristics, but the expansive soil is deteriorated in properties when it meets water. According to the research of 'improvement technology and engineering application of expansive soil' issued by scientific publishing agency of 'J' (Wangbu, Zhang Fuhai. geotechnical, 2009 (5): 1380 and 1380), the expansive soil is widely distributed, so that the expansive soil can not be prevented from passing through the expansive soil region in engineering. Due to the swelling and shrinkage property and the change of the water content of the expansive soil, cracks usually appear on the pavement structure, and the cracks are reflected on the pavement. The continuous circulation of the process enables the cracks on the road to be larger and larger, so that the normal use of the road is influenced on one hand, and on the other hand, the cracks also provide a channel for water, so that the roadbed is softened, the structural damage of the road surface is accelerated, and the service life of the road surface is shortened. Therefore, two methods for solving the problem of expansive soil subgrade damage exist, namely inhibiting the expansibility of expansive soil or controlling the change of the water content of the expansive soil.
Common treatment methods of the expansive soil subgrade include a replacement method, a water content control method, a chemical modification method and the like. The filling and replacement method generally uses non-expansive clay or coarse-grained soil, has good improvement effect and simple construction, but when the filling and replacement depth is too deep, the source and transportation of the filling and replacement soil can greatly improve the construction cost. The water content control method usually selects a compacted clay covering layer as roadbed seepage prevention treatment, and because the compacted clay has a lower permeability coefficient, the invasion of water to an underlying soil body can be effectively isolated, but the method fails due to cracks on the clay surface under the condition of long-term service. The lime is a very excellent expansive soil chemical modifier, the price is low, the effect is obvious, and the lime modified soil has good waterproof and moisturizing effects due to the low permeability of the lime modified soil. However, lime modified soil also has some disadvantages. According to research of dry-wet cycle characteristic test research [ J ] of improved expansive soil in document 2, yang research, charpy, industrial building, 2012, 42 (01): 98-102+ 12), although expansive soil improved by lime-fly ash has excellent engineering characteristics, the swelling and shrinkage properties and the content of sticky particles of the improved soil increase with the increase of the dry-wet cycle times, and the content and strength of the sticky particles decrease with the increase of the dry-wet cycle times, because the dry-wet cycle damages cementitious substances generated by lime, the lime-fly ash improved soil as an edge covering layer can also crack to cause failure of the edge covering layer under the effect of long-term dry-wet cycle.
In summary, the existing method for improving the expansive soil roadbed has the following problems: the replacement method cannot solve the source and transportation cost of the replacement filling soil, and the construction cost is high; the compacted clay cover and lime modified soil have poor long-term performance and have a great loss in effect in wet areas where rainfall is frequent. Therefore, the method for improving the expansive soil roadbed by lime is further improved so as to increase the durability of the expansive soil roadbed and reduce the construction cost of the expansive soil roadbed.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provide a tough expansive soil roadbed structure based on calcium-based nano silicon dioxide and carbon fibers, and particularly, the site expansive soil is modified by a modifier prepared by mixing hydrophobic nano silicon dioxide and lime, the modified expansive soil is used as soil bodies of four surface layers in the roadbed structure, the carbon fibers are added layer by layer in the laying process and are compacted, the overall toughness and the pore filling property of the roadbed structure are enhanced, and the defects of poor durability and long construction period of lime modified soil are overcome.
The invention aims to realize the purpose, and provides a toughness expansive soil roadbed structure based on nano silicon dioxide and carbon fiber, which comprises an expansive soil filling core, a roadbed top edge covering layer, a roadbed bottom edge covering layer and two roadbed slope edge covering layers, wherein the two roadbed slope edge covering layers are used for connecting the roadbed top edge covering layer and the roadbed bottom edge covering layer;
the paving materials of the roadbed top binding layer, the roadbed bottom binding layer and the roadbed side slope binding layer are modified expansive soil and carbon fibers; recording the expansive soil which is obtained by digging from the field where the roadbed is located and meets the preset water content w as field expansive soil, wherein the modified expansive soil is formed by uniformly mixing a modifier, water and the field expansive soil, and the modified expansive soil comprises the following components in parts by weight in the sequence: 4.7% -6%, 15.9% -18.8% and 75.2% -79.4%; recording the weight composition of the modifier as modifier mixing amount A;
the modifier is a flexible calcium-based nano silicon dioxide modifier prepared by mixing hydrophobic nano silicon dioxide and lime, wherein the weight ratio B of the hydrophobic nano silicon dioxide to the lime and the doping amount A of the modifier are selected as follows:
the site expansive soil is weak expansive soil: b is 1: 8-1: 10, A is 6%;
the site expansive soil is medium expansive soil: b is 1: 6-1: 7, A is 6%;
the site expansive soil is strong expansive soil: b is 1: 4-1: 5, A is 8%;
the roadbed top binding layer, the roadbed bottom binding layer and the roadbed side slope binding layer are all paved from bottom to top in a layered mode, carbon fibers are uniformly spread on the surface of the modified expansive soil when the pavement is finished by 0.5m, manual compaction is carried out after the spreading is finished, and the degree of compaction is not lower than 92%; the weight ratio of the carbon fibers to the modified expansive soil is 0.5: 99.5-1: 99;
the paving material of the expansive soil core is site expansive soil or improved expansive soil, and particularly, when the site expansive soil is weak expansive soil or medium expansive soil, the paving material of the expansive soil core is the site expansive soil; when the expansive soil in the field is strong expansive soil, the paving material of the expansive soil core is improved expansive soil which is formed by uniformly mixing the expansive soil in the field and lime in a weight ratio of 97% to 3%;
the thickness of the top edge covering layer of the roadbed is 1.2-1.8 m, the thickness of the bottom edge covering layer of the roadbed is 0.3-0.5 m, and the thickness of the side slope edge covering layer of the roadbed along the vertical direction of the slope surface is 3-3.5 m.
Preferably, the weak expansive soil, the medium expansive soil and the strong expansive soil are defined as follows:
40％≤δefless than 60%, weak expansive soil;
60％≤δefless than 90%, medium swelling soil;
δefnot less than 90 percent, strong expansive soil;
wherein, deltaefThe free expansion rate of the expansive soil.
Preferably, the water content w of the site expansive soil is controlled to be 0.97-1.2wpIn the range of, wherein, wpThe plastic limit of the field expansive soil is controlled in a specific mode as follows: firstly, placing expansive soil dug from a field where a roadbed is located in a material mixing field near the field, flattening, air-drying, crushing and sieving by a sieve with the size of 5-10 mm; then detecting the preset water content w, and controlling the preset water content w to be 0.97-1.2w by supplementing water spraying or airingp。
Preferably, the carbon fiber is polyethylene carbon fiber, the polyethylene carbon fiber is strip-shaped, the length of the polyethylene carbon fiber is 5 cm-10 cm, the width of the polyethylene carbon fiber is 1 cm-2 cm, and the thickness of the polyethylene carbon fiber is 3 mm-6 mm.
Preferably, the particle size of the hydrophobic nano-silica is 1nm to 10 nm.
Preferably, the expansive soil filling core is paved from bottom to top in layers, compaction is carried out every 0.5m of pavement, and the degree of compaction is not lower than 92%.
Preferably, the flexible calcium-based nano silica modifier is prepared as follows:
immersing hydrophobic nano-silica in water, placing the nano-silica on an ultrasonic oscillator, fully shaking the nano-silica for 1 to 2 hours, and then placing the nano-silica in an oven at the temperature of between 80 and 150 ℃ for culturing, wherein the culturing time is between 0.5 and 1 hour;
mixing the cultured hydrophobic nano-silica with lime according to the weight ratio B to prepare the flexible calcium-based nano-silica modifier.
Because the invention adopts the tough expansive soil roadbed structure consisting of four binding layers and an expansive soil filling core, and the four binding layers are the modified expansive soil containing the flexible calcium-based nano silicon dioxide modifier and the carbon fiber, compared with the prior art, the invention has the following beneficial effects:
1. the invention enhances the overall tensile strength of the roadbed structure. The carbon fibers are added to enhance the integral tensile strength of the modified expansive soil body and well inhibit the generation of cracks.
2. The invention improves the durability of the path structure. The modified expansive soil has stronger water resistance due to the addition of the hydrophobic nano silicon dioxide, and the attenuation of the dry-wet circulating strength of the lime modified soil is effectively avoided.
3. The invention improves the early strength of the roadbed structure. The addition of the hydrophobic nano-silica greatly improves the lime reaction process, obviously improves the early strength in the roadbed structure, and enables the roadbed structure to meet the strength requirement in engineering more quickly, thereby reducing the construction period.
4. The roadbed structure of the invention is more compact. The size of the hydrophobic nano silicon dioxide is 1 nm-10 nm, and the filling effect of the hydrophobic nano silicon dioxide on micropores in a soil body enables the roadbed soil body structure to be more compact.
5. The invention has certain environmental protection. Due to the doping of the hydrophobic nano silicon dioxide, the doping amount of lime in the prior art is reduced, and the environmental pollution is effectively reduced.
6. The invention has wide application range and better ecological benefit. Tests prove that the modified expansive soil has good improvement effect on strong expansive soil, medium expansive soil and weak expansive soil.
Drawings
Fig. 1 is a cross-sectional view of a roadbed structure in the embodiment of the invention;
FIG. 2 is a plot of unconfined compressive strength of modified bentonite in accordance with an embodiment of the present invention;
FIG. 3 is a graph showing the permeability coefficient of modified expansive soil according to an embodiment of the present invention;
FIG. 4 is a free expansion ratio graph of modified expansive soil in an example of the present invention.
In the figure: 1-a roadbed top edge covering layer, 2-a roadbed bottom edge covering layer, 3-a roadbed slope edge covering layer and 4-an expansive soil filling core.
Detailed Description
The technical scheme of the invention will be clearly and completely described with reference to the accompanying drawings.
Example 1: fig. 1 is a cross-sectional view of the roadbed structure in the embodiment of the invention in fig. 1. As can be seen from fig. 1, the tough expansive soil roadbed structure based on the nano silicon dioxide and the carbon fiber is a trapezoidal structure and comprises an expansive soil filling core 4, a roadbed top edge covering layer 1, a roadbed bottom edge covering layer 2 and two roadbed side slope edge covering layers 3 which are used for connecting the roadbed top edge covering layer 1 and the roadbed bottom edge covering layer 2, wherein the expansive soil filling core 4 is arranged in a closed space surrounded by the roadbed top edge covering layer 1, the roadbed bottom edge covering layer 2 and the two roadbed side slope edge covering layers 3.
And the paving materials of the roadbed top edge covering layer 1, the roadbed bottom edge covering layer 2 and the roadbed side slope edge covering layer 3 are modified expansive soil and carbon fibers. Recording the expansive soil which is obtained by digging from the field where the roadbed is located and meets the preset water content w as field expansive soil, wherein the modified expansive soil is formed by uniformly mixing a modifier, water and the field expansive soil, and the modified expansive soil comprises the following components in parts by weight in the sequence: 4.7% -6%, 15.9% -18.8% and 75.2% -79.4%; the weight composition of the modifier is recorded as modifier addition A.
The modifier is a flexible calcium-based nano silicon dioxide modifier prepared by mixing hydrophobic nano silicon dioxide and lime, wherein the weight ratio B of the hydrophobic nano silicon dioxide to the lime and the doping amount A of the modifier are selected as follows:
the site expansive soil is weak expansive soil: b is 1: 8-1: 10, A is 6%;
the site expansive soil is medium expansive soil: b is 1: 6-1: 7, A is 6%;
the site expansive soil is strong expansive soil: b is 1: 4-1: 5, and A is 8%.
The roadbed top edge covering layer 1, the roadbed bottom edge covering layer 2 and the roadbed side slope edge covering layer 3 are all laid in a layered mode from bottom to top, carbon fibers are uniformly spread on the surface of the modified expansive soil when the laying is finished by 0.5m, manual compaction is carried out after the spreading is finished, and the compaction degree is not lower than 92%. The weight ratio of the carbon fibers to the modified expansive soil is 0.5: 99.5-1: 99.
The paving material of the expansive soil core 4 is site expansive soil or improved expansive soil, and particularly, when the site expansive soil is weak expansive soil or medium expansive soil, the paving material of the expansive soil core 4 is the site expansive soil; when the expansive soil on the site is strong expansive soil, the paving material of the expansive soil core 4 is improved expansive soil which is formed by uniformly mixing the site expansive soil and lime, and the weight ratio of the site expansive soil to the lime is 97%: 3 percent.
The thickness of the roadbed top binding layer 1 is 1.2-1.8 m, the thickness of the roadbed bottom binding layer 2 is 0.3-0.5 m, and the thickness of the roadbed side slope binding layer 3 in the slope surface vertical direction is 3-3.5 m.
In the present embodiment, the weak expansive soil, the medium expansive soil and the strong expansive soil are defined as follows:
40％≤δefless than 60%, weak expansive soil;
60％≤δefless than 90%, medium swelling soil;
δefnot less than 90 percent, strong expansive soil;
wherein, deltaefThe free expansion rate of the expansive soil.
In this embodiment, the water content w of the site expansive soil is controlled to be 0.97-1.2wpIn the range of, wherein, wpThe plastic limit of the field expansive soil is controlled in a specific mode as follows: firstly, placing expansive soil dug from a field where a roadbed is located in a material mixing field near the field, flattening, air-drying, crushing and sieving by a sieve with the size of 5-10 mm; then detecting the preset water content w, and controlling the preset water content w to be 0.97-1.2w by supplementing water spraying or airingp。
In this embodiment, the carbon fiber is a polyethylene carbon fiber, and the polyethylene carbon fiber is in a strip shape, has a length of 5cm to 10cm, a width of 1cm to 2cm, and a thickness of 3mm to 6 mm.
In this embodiment, the particle size of the hydrophobic nano-silica is 1nm to 10 nm.
In this embodiment, the expansive soil core 4 is layered from the bottom to the top, and compacted at a compaction degree of not less than 92% for every 0.5m of the layer.
In this embodiment, the flexible calcium-based nano silica modifier is prepared as follows:
immersing hydrophobic nano-silica in water, placing the nano-silica on an ultrasonic oscillator, fully shaking the nano-silica for 1 to 2 hours, and then placing the nano-silica in an oven at the temperature of between 80 and 150 ℃ for culturing, wherein the culturing time is between 0.5 and 1 hour;
mixing the cultured hydrophobic nano-silica with lime according to the weight ratio B to prepare the flexible calcium-based nano-silica modifier.
In the specific implementation process, the tough expansive soil roadbed structure based on the nano silicon dioxide and the carbon fibers is designed for different expansive soil foundations, and good effects are obtained. The data are detailed in the examples below.
Example 1: detecting to obtain the free expansion rate delta of the expansive soil in the fieldef55 percent of the modifier belongs to weak expansive soil, the weight ratio B of hydrophobic nano silicon dioxide to lime is 1: 10, and the doping amount A of the modifier is 6 percent. Based on the total weight of the modified expansive soil, the doping amount of the hydrophobic nano silicon dioxide is 0.54 percent, the doping amount of the lime is 5.46 percent, the doping amount of the carbon fiber is 0.5 percent, and the water content w is 22 percent.
Example 2: detecting to obtain the free expansion rate delta of the expansive soil in the fieldef67 percent of the modified bentonite belongs to medium expansive soil, the weight ratio B of hydrophobic nano silicon dioxide to lime is 1: 7, and the doping amount A of the modifier is 6 percent. Based on the total weight of the modified expansive soil, the doping amount of the hydrophobic nano silicon dioxide is 0.75 percent, the doping amount of the lime is 5.25 percent, the doping amount of the carbon fiber is 0.5 percent, and the water content w is 23.1 percent.
Example 3: detecting to obtain the free expansion rate delta of the expansive soil in the fieldef91 percent of the modifier, belongs to strong expansive soil, the weight ratio B of hydrophobic nano silicon dioxide to lime is 1: 7, and the doping amount A of the modifier is 8 percent.Based on the total weight of the modified expansive soil, the doping amount of the hydrophobic nano silicon dioxide is 1%, the doping amount of the lime is 7%, the doping amount of the carbon fiber is 1%, and the water content w is 24.7%.
In order to verify the performance of the roadbed structure, the unconfined compressive strength, the permeability coefficient and the free expansion rate delta of the modified expansive soil of the four edge-covered layers in the roadbed structure are subjected to unconfined compressive strength, permeability coefficient and free expansion rate deltaefThe test of (1). Fig. 2 is a plot of unconfined compressive strength of the modified expansive soil in the example of the present invention, fig. 3 is a plot of permeability coefficient of the modified expansive soil in the example of the present invention, and fig. 4 is a plot of free expansion ratio of the modified expansive soil in the example of the present invention. In the three figures, "weak expansive soil", "medium expansive soil" and "expansive soil" refer to the properties of site expansive soil in the modified expansive soil.
As can be seen from figure 2, the compressive strength of the modified expansive soil of the four edge-covered layers reaches more than 2MPa in any curing period, and the unconfined compressive strength of 14d reaches about 85% of the unconfined compressive strength of 28 d. This shows that the nano-silica accelerates the pozzolanic reaction of lime, so that the overall strength of the roadbed structure is at a higher level and also meets the roadbed strength standard.
As can be seen from FIG. 3, the permeability coefficient of the modified expansive soil corresponding to the weak expansive soil is 6.97E-10m/s, the permeability coefficient of the modified expansive soil corresponding to the medium expansive soil is 3.27E-10m/s, and the permeability coefficient of the modified expansive soil corresponding to the strong expansive soil is 4.73E-10 m/s. In addition, the permeability coefficient drops by an order of magnitude at any curing age. The reduction of the permeability coefficient of the edge covering layer can keep the water content of the internal expansive soil filling core stable, thereby avoiding the harm caused by the expansibility of the expansive soil.
As can be seen from fig. 4, the expansibility of the modified expansive soil corresponding to the weak expansive soil and the expansibility of the modified expansive soil corresponding to the medium expansive soil at each curing age is reduced to a risk-free degree, and the modified expansive soil corresponding to the strong expansive soil reaches the risk-free degree after being cured for 14 d.
Claims (7)
1. The tough expansive soil roadbed structure based on the nano silicon dioxide and the carbon fibers is characterized by comprising an expansive soil filling core (4), a roadbed top edge covering layer (1), a roadbed bottom edge covering layer (2) and two roadbed side slope edge covering layers (3) connecting the roadbed top edge covering layer (1) and the roadbed bottom edge covering layer (2), wherein the expansive soil filling core (4) is arranged in a closed space surrounded by the roadbed top edge covering layer (1), the roadbed bottom edge covering layer (2) and the two roadbed side slope edge covering layers (3);
the paving materials of the roadbed top edge covering layer (1), the roadbed bottom edge covering layer (2) and the roadbed slope edge covering layer (3) are modified expansive soil and carbon fibers; recording the expansive soil which is obtained by digging from the field where the roadbed is located and meets the preset water content w as field expansive soil, wherein the modified expansive soil is formed by uniformly mixing a modifier, water and the field expansive soil, and the modified expansive soil comprises the following components in parts by weight in the sequence: 4.7% -6%, 15.9% -18.8% and 75.2% -79.4%; recording the weight composition of the modifier as modifier mixing amount A;
the modifier is a flexible calcium-based nano silicon dioxide modifier prepared by mixing hydrophobic nano silicon dioxide and lime, wherein the weight ratio B of the hydrophobic nano silicon dioxide to the lime and the doping amount A of the modifier are selected as follows:
the site expansive soil is weak expansive soil: b is 1: 8-1: 10, A is 6%;
the site expansive soil is medium expansive soil: b is 1: 6-1: 7, A is 6%;
the site expansive soil is strong expansive soil: b is 1: 4-1: 5, A is 8%;
the roadbed top binding layer (1), the roadbed bottom binding layer (2) and the roadbed slope binding layer (3) are all laid in a layered mode from bottom to top, carbon fibers are uniformly spread on the surface of the modified expansive soil when the laying is finished by 0.5m, manual compaction is carried out after the spreading is finished, and the compaction degree is not lower than 92%; the weight ratio of the carbon fibers to the modified expansive soil is 0.5: 99.5-1: 99;
the paving material of the expansive soil filling core (4) is site expansive soil or improved expansive soil, and particularly, when the site expansive soil is weak expansive soil or medium expansive soil, the paving material of the expansive soil filling core (4) is the site expansive soil; when the expansive soil on the site is strong expansive soil, the paving material of the expansive soil filling core (4) is improved expansive soil which is formed by uniformly mixing the expansive soil on the site and lime in a weight ratio of 97 to 3 percent;
the thickness of the roadbed top edge covering layer (1) is 1.2-1.8 m, the thickness of the roadbed bottom edge covering layer (2) is 0.3-0.5 m, and the thickness of the roadbed side slope edge covering layer (3) in the slope surface vertical direction is 3-3.5 m.
2. The tough expansive soil roadbed structure based on the nano silica and the carbon fiber, as claimed in claim 1, wherein the weak expansive soil, the medium expansive soil and the strong expansive soil are defined as follows:
40％≤δefless than 60%, weak expansive soil;
60％≤δefless than 90%, medium swelling soil;
δefnot less than 90 percent, strong expansive soil;
wherein, deltaefThe free expansion rate of the expansive soil.
3. The tough expansive soil roadbed structure based on nano silicon dioxide and carbon fiber as claimed in claim 1, wherein the preset water content w is controlled to be 0.97-1.2wpIn the range of, wherein, wpThe plastic limit of the field expansive soil is controlled in a specific mode as follows: firstly, placing expansive soil dug from a field where a roadbed is located in a material mixing field near the field, flattening, air-drying, crushing and sieving by a sieve with the size of 5-10 mm; then detecting the preset water content w, and controlling the preset water content w to be 0.97-1.2w by supplementing water spraying or airingp。
4. The tough expansive soil roadbed structure based on nano silicon dioxide and carbon fibers, according to claim 1, wherein the carbon fibers are polyethylene carbon fibers, the polyethylene carbon fibers are in a strip shape, the length of the polyethylene carbon fibers is 5 cm-10 cm, the width of the polyethylene carbon fibers is 1 cm-2 cm, and the thickness of the polyethylene carbon fibers is 3 mm-6 mm.
5. The tough expansive soil roadbed structure based on nano-silica and carbon fiber as claimed in claim 1, wherein the particle size of the hydrophobic nano-silica is 1 nm-10 nm.
6. The tough expansive soil roadbed structure based on nano silica and carbon fiber as claimed in claim 1, wherein the expansive soil filling core (4) is layered from bottom to top, and is compacted by 0.5m per layer, and the degree of compaction is not less than 92%.
7. The tough expansive soil roadbed structure based on nano-silica and carbon fiber, according to claim 1, wherein the flexible calcium-based nano-silica modifier is prepared by the following steps:
immersing hydrophobic nano-silica in water, placing the nano-silica on an ultrasonic oscillator, fully shaking the nano-silica for 1 to 2 hours, and then placing the nano-silica in an oven at the temperature of between 80 and 150 ℃ for culturing, wherein the culturing time is between 0.5 and 1 hour;
mixing the cultured hydrophobic nano-silica with lime according to the weight ratio B to prepare the flexible calcium-based nano-silica modifier.
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