CN111622040A - Expansive soil composite roadbed structure type and construction method thereof - Google Patents
Expansive soil composite roadbed structure type and construction method thereof Download PDFInfo
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- CN111622040A CN111622040A CN202010468734.8A CN202010468734A CN111622040A CN 111622040 A CN111622040 A CN 111622040A CN 202010468734 A CN202010468734 A CN 202010468734A CN 111622040 A CN111622040 A CN 111622040A
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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
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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
- E01C3/04—Foundations produced by soil stabilisation
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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
- E01C3/06—Methods or arrangements for protecting foundations from destructive influences of moisture, frost or vibration
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A30/00—Adapting or protecting infrastructure or their operation
- Y02A30/60—Planning or developing urban green infrastructure
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Abstract
The invention discloses an expansive soil composite roadbed structure type and a construction method thereof. The expansive soil composite roadbed can form a closed water-resisting or water-blocking system, so that external water is prevented from infiltrating into an expansive soil core filling area, the humidity stability of the expansive soil core filling area is ensured, the long-term performance stability of the expansive soil roadbed is ensured, meanwhile, the roadbed structural form not only can utilize the expansive soil along the line as roadbed filling to the maximum extent, but also can make up the defects that the surrounding edge-covering soil source is unavailable and the environment is polluted by chemical improvement, and accords with the ecological environment protection concept.
Description
Technical Field
The invention relates to an expansive soil composite roadbed structure type and a construction method thereof, belonging to the field of highway roadbeds.
Background
The expansive soil is special soil rich in strongly hydrophilic clay minerals, is expanded when meeting water and contracted by dehydration, has poor engineering properties and is widely distributed in China. In the initial stage of construction of high-grade highways in China, chemical modification treatment is carried out on expansive soil by adding cement, lime, slag mixture and the like, so that the requirements on construction machinery and technology are high, the environmental protection performance is poor, and the engineering cost is greatly increased. In the middle and later stages of the last 90 th century, based on the basic principle of moisture preservation and seepage prevention, the roadbed structure forms of physical improvement methods such as non-expansive clay/gravel soil covering (including interbedded layers), geogrid/geogrid edge reinforcement, geotextile reinforcement and the like are adopted, and the roadbed structure forms are successfully applied to the major highways in Yunnan, high-speed roads in North and West provinces, roads in south and south friends, roads in Hunan and the like. However, some expansive soil areas lack edge-covering soil sources, and the construction cost is greatly increased by long-distance transportation. The reinforcement method mostly needs to adopt CMA solution to improve slope spraying with the depth of 1m, and the construction is complex. The geotextile is mostly laid on the full section, the obvious influence range on the atmospheric environment is not considered enough, and the engineering cost is increased.
Research results show that dry-wet circulation is a key factor influencing the performance of the expansive soil roadbed, and the influence depth of the dry-wet circulation of the expansive soil roadbed is only 2 m. The protection of the swelling soil subgrade slope is mostly implemented by grass planting protection and skeleton protection, but the grass planting protection has poor washout resistance, and the skeleton protection is easy to loosen, void and the like. The geocell is a novel high-strength three-dimensional geosynthetic material, and has the advantages of good durability, integrity and scouring resistance, excellent vertical face reinforcing effect and better greening effect. Therefore, the design of the expansive soil roadbed type needs to be comprehensively determined according to roadbed humidity influence factors and influence degrees thereof, roadbed peripheral filling materials, excellent protection measures and the like.
Disclosure of Invention
The invention aims to solve the problem of reasonable utilization of expansive soil as roadbed filling, considers the influence of atmospheric environment and the obvious influence depth, and provides a composite roadbed structure type of reinforced expansive soil and geocell ecological protection and a construction method thereof based on the basic principle of moisture preservation and seepage prevention.
The technical scheme of the invention is as follows:
the composite expanded soil roadbed structure includes bottom isolating layer, expanded soil filling area, edge reinforcing and seepage preventing area, earthwork lattice protecting area, embankment, roadbed and road surface structure layer.
Preferably, the bottom isolation layer is positioned above the foundation and is used for preventing moisture from migrating to the expansive soil core filling area due to the rising of underground water level or the action of capillary water; the expansive soil core filling area is positioned above the bottom isolation layer; the upper embankment is positioned above the expansive soil core filling area; the road bed is positioned above the upper embankment; the edge reinforcement and edge-covering seepage-proofing areas are positioned on side slopes on two sides of the roadbed; the geocell protection area is a fully paved geocell on the slope surface of the expansive soil subgrade.
Preferably, the expansive soil core filling area comprises a first geogrid, a first composite geotextile, a third geogrid, a third composite geotextile and expansive soil; the edge reinforcing and edge covering seepage-proofing area comprises a second geogrid and a second composite geotextile; wherein, the first geogrid and the first composite geotextile are fully paved above the bottom isolating layer in turn and are reversely wrapped; filling expansive soil above the first composite geotextile, laying a second geogrid and a second composite geotextile in turn on two sides of the roadbed after filling 1-2 m (4-8 layers) of expansive soil every time, and reversely wrapping until the expansive soil is filled to the design elevation of the expansive soil core filling area; and fully paving a third geogrid and a third composite geotextile at the designed elevation of the expansive soil core filling area.
Preferably, the bottom isolation layer is made of a material with high porosity and good water stability: gravel, mountain-opening stone slag and gravel soil, wherein the filling thickness is not less than 50 cm; the filling height of the expansive soil filling area is not more than 8m, and the slope rate is 1: 1.5-1: 1.75; the edge reinforcing and edge covering seepage-proofing area is formed by reversely wrapping two sides of the expansive soil filling area by adopting a second geogrid and a second composite geotextile and is used for preventing rainfall and side slope runoff from infiltrating the expansive soil filling area through the side slopes on the two sides; the width of the edge reinforced and edge covered seepage-proofing area is not less than 3.0m, and the width of the reverse covering is not less than 1.0 m; anchoring the geocell protection area by using hook-shaped riveting piles or U-shaped steel bars, fixing the spacing distance to be about 1m, and filling planting soil in the geocell space; the upper embankment can adopt common roadbed filling; the road bed is preferably made of hard and medium-hard coarse particles with good water stability: gravel and crushed stone, and materials with good gradation can also be adopted: crushed soil and gravel soil.
Preferably, the first geogrid, the second geogrid and the third geogrid are bidirectional plastic geogrids; the first geogrid is fully laid on the bottom isolating layer, the second geogrid is laid on the edge reinforced and anti-seepage area and the slope surface of the reverse-wrapped roadbed slope, and the third geogrid is fully laid on the top surface of the expansive soil core filling area; the first composite geotextile, the second composite geotextile and the third composite geotextile are composite geomembranes of two fabrics and one membrane; the first composite geotextile is laid on the first geogrid and is connected with the lowest part of the expansive soil core filling area; the second composite geotextile is laid on the second geogrid; the third composite geotextile is laid on the third geogrid and connected with the upper embankment; the expansive soil composite roadbed structure is suitable for weak expansive soil and medium expansive soil, but not suitable for strong expansive soil.
Preferably, the first geogrid, the second geogrid and the third geogrid are fixed on the lower filling layer by adopting U-shaped nails when being stretched and laid; the end part of the first geogrid is connected with the proper position of the second geogrid layer by a connecting rod, and the geogrid is tensioned and fixed; the end part of the lower layer second geogrid is connected with the proper position of the layer of second geogrid by a connecting rod, and the geogrid is tensioned and fixed; the proper position of the third geogrid is connected with the end part of the second geogrid of the lower layer reverse covering by a connecting rod, and the geogrid is tensioned and fixed; the first geogrid, the second geogrid, the third geogrid, the first composite geotextile, the second composite geotextile and the third composite geotextile are reversely wrapped and laid to correspond to the roadbed side slope in two days for temporary covering, and exposure and insolation are avoided.
Preferably, the maximum particle size of the filler within 30cm from the first geogrid, the first composite geotextile, the third geogrid and the third composite geotextile is not more than 10cm, and the filler is: gravel, mountain-opening stone slag, gravel soil and gravel soil; when a first layer of filler is paved on a geosynthetic material formed by the first geogrid, the first composite geotextile, the second geogrid, the second composite geotextile, the third geogrid and the third composite geotextile, the material should be fed in a backing mode, and the geosynthetic material cannot be directly rolled.
A construction method of an expansive soil composite roadbed structure type comprises the following steps:
step one, performing geotechnical test; the test contents comprise natural water content, liquid plastic limit, grain gradation, maximum dry density and optimal water content, CBR and CBR expansion amount, free expansion rate and standard moisture absorption water content;
evaluating the engineering property of the expansive soil, judging the grade of the expansive soil, and determining whether the expansive soil is available; if applicable, go to the next step; not applicable, discarded;
step three, measuring and paying off;
step four, processing the foundation according to the design requirement;
constructing a bottom isolation layer;
step six, laying the first geogrid and the first composite geotextile;
feeding and paving the first layer of expansive soil;
step eight, detecting the rolling moisture content; detecting the water content of the expansive soil, and performing rolling in the next step according with the requirement; if the requirement is not met, loosening and airing or watering and moistening are carried out;
step nine, rolling according to the construction process determined by the test road section, and detecting through a compaction standard; for the detection that the required compaction standard is not met, the reason is determined, and targeted measures are taken;
step ten, filling expansive soil and paving a second geogrid and a second composite geotextile;
step eleven, paving a third geogrid and a third composite geotextile;
step twelve, embankment construction is carried out, specifically: feeding the first layer of roadbed above the third composite geotextile by adopting a retreating feeding mode, paving and rolling;
step thirteen, road bed construction, rolling layer by layer to the road bed top surface elevation according to the relevant standard requirements;
fourteen, carrying out roadbed delivery and acceptance inspection;
and fifthly, constructing a pavement structure layer.
Preferably, in the geotechnical test in the first step, the CBR is used for testing CBRs of the expansive soil samples with different water contents, a relation curve of the CBR and the water content is drawn, and the applicable water content range of the expansive soil filling area is determined according to the requirement that the CBR of the expansive soil filling area is larger than or equal to 3%; and determining the compaction degree of the expansive soil filled area within the range of the water content by combining the compaction curve of the expansive soil according to the determined range of the applicable rolling water content.
Preferably, the step five to the step eleven are specifically: firstly, filling a layer of material with large porosity and good water stability, the thickness of which is not less than 50cm, on a treated foundation: gravel, mountain-opening stone slag and gravel soil are sequentially paved on the gravel, a first geogrid and a first composite geotextile are sequentially paved on the gravel, the mountain-opening stone slag and the gravel soil, and a reverse wrapping section with a certain length is reserved; the method comprises the following steps of feeding a first layer of expansive soil in a retreating feeding mode, unloading a proper amount of expansive soil into a grid according to the determined loose paving thickness, grid area and dump truck loading capacity of a test road section, paving and leveling by using a bulldozer, detecting according to the determined construction process of the test road section, and feeding, paving, rolling and detecting a second layer of expansive soil subgrade when the compaction standard is met; then sequentially carrying out feeding, paving, rolling and detection on the expansive soil at the third and fourth equal positions, building a slope according to a designed slope when the filling thickness of the expansive soil is 1-2 m, reversely wrapping and primarily tensioning the first geogrid and the first composite geotextile along the built slope, wherein the length of the reverse wrapping is not less than 1.0 m; sequentially laying a second geogrid and a second composite geotextile with the length not less than 3.0m on two sides of the embankment side slope, reserving a reverse wrapping section with a certain length, connecting the end part of the first geogrid with the proper position of the second geogrid on the layer by using a connecting rod, tensioning the geogrid and fixing; when the expansive soil with the thickness of 1-2 m is filled, constructing a slope according to a designed slope, reversely wrapping the second geogrid and the second composite geotextile reserved on the lower layer upwards along the constructed slope and primarily tensioning, wherein the length of the reversely wrapped is not less than 1.0 m; sequentially laying the layer of second geogrid and second composite geotextile with the length not less than 3.0m on two sides of the side slope of the embankment, reserving a reverse wrapping section with a certain length, connecting the end part of the lower layer of second geogrid with the proper position of the layer of second geogrid by using a connecting rod, tensioning the geogrid and fixing; and (3) filling the expansive soil to the top surface elevation of the expansive soil core filling area, fully paving a third geogrid and a third composite geotextile in sequence, connecting the end part of the second geogrid reversely wrapped at the lower layer at the proper position of the third geogrid by using a connecting rod, tensioning the geogrid and fixing the geogrid.
The invention has the beneficial effects that:
by adopting the technical scheme, the expanded soil composite roadbed structure, the geogrid, the composite geotextile and the isolation layer at the bottom of the geogrid and the composite geotextile inevitably cause water level rise or water migration to the expanded soil core filling area under the capillary water action. The geosynthetic reinforced and edge-covered seepage-proofing area can prevent rainfall and slope runoff from penetrating into the expansive soil filling area through the side slopes on two sides, and the stability of the expansive soil embankment body is improved. The geogrid and the composite geotechnical material which are fully paved on the top surface of the expansive soil core filling area can prevent the median zone from being waterproof and damaged and prevent the pavement cracks from seeping into the expansive soil core filling area, and can prevent the uneven settlement deformation of the expansive soil subgrade and improve the overall performance of the expansive soil subgrade. In conclusion, the expansive soil composite roadbed can form a closed water-resisting or water-blocking system, so that external water is prevented from infiltrating into the expansive soil core-filling area, the humidity stability of the expansive soil core-filling area is ensured, the long-term performance stability of the expansive soil roadbed is ensured, meanwhile, the roadbed structural form can not only furthest utilize expansive soil along the line as roadbed filling, but also make up the defects that no edge-covering soil source is available at the periphery and the environment is polluted by chemical improvement, and conforms to the ecological environment protection concept.
Drawings
Fig. 1 is a schematic structural view of an expansive soil composite roadbed according to an embodiment of the invention;
FIG. 2 is a schematic view of a geocell containment area provided by an embodiment of the present invention;
fig. 3 is a schematic view of a construction method of an expansive soil composite roadbed structure type according to an embodiment of the invention;
description of reference numerals:
the foundation comprises a foundation-1, a bottom isolation layer-2, an expansive soil filling area-3, an edge reinforcement and seepage-proofing area-4, a geocell protection area-5, an upper embankment-6, a roadbed-7, a pavement structure layer-8, a first geogrid-9, a first composite geotextile-10, a second geogrid-11, a second composite geotextile-12, a third artificial grid-13, a third composite geotextile-14, U-shaped nails-15 and connecting rods-16.
Detailed Description
The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and enable its practice, and the embodiments of the present invention are not limited thereto.
Fig. 1 shows an expansive soil composite roadbed structure type, which comprises a bottom isolation layer 2, an expansive soil core filling area 3, an edge reinforced and seepage-proofing area 4, a geocell protection area 5, an upper embankment 6, a roadbed 7 and a pavement structure layer 8.
The bottom isolation layer 2 is positioned above the foundation 1 and used for preventing water from migrating to the expansive soil filling area 3 caused by the rising of underground water level or capillary water action; the expansive soil filling area 3 is positioned above the bottom isolation layer 2; the upper embankment 6 is positioned above the expansive soil core filling area 3; the roadbed 7 is positioned above the upper embankment 6; the edge reinforced and edge covered seepage-proofing areas 4 are positioned on the side slopes on the two sides of the roadbed; the geocell protection area 5 is a fully-paved geocell on the slope surface of the expansive soil subgrade side slope.
The expansive soil filling area 3 comprises a first geogrid 9, a first composite geotextile 10, a third geogrid 13, a third composite geotextile 14 and expansive soil; the edge reinforcing and edge covering seepage-proofing area 4 comprises a second geogrid 11 and a second composite geotextile 12; wherein, the first geogrid 9 and the first composite geotextile 10 are sequentially fully paved above the bottom isolating layer 2 and are reversely wrapped; filling expansive soil above the first composite geotextile 10, and laying a second geogrid 11 and a second composite geotextile 12 on two sides of the roadbed in turn and reversely wrapping the geogrid and the second composite geotextile after filling 1-2 m4-8 layers of expansive soil until the expansive soil is filled to the design elevation of the expansive soil core filling area 3; and a third geogrid 13 and a third composite geotextile 14 are sequentially and fully paved at the designed elevation of the expansive soil core filling area 3.
The bottom isolation layer 2 is made of a material with large porosity and good water stability: gravel, mountain-opening stone slag and gravel soil, wherein the filling thickness is not less than 50 cm; the filling height of the expansive soil core filling area 3 is not more than 8m, and the slope rate is 1: 1.5-1: 1.75; the edge reinforcing and edge covering seepage-proofing area 4 is formed by reversely wrapping two sides of the expansive soil filling area 3 by adopting a second geogrid 11 and a second composite geotextile 12 and is used for preventing rainfall and side slope runoff from infiltrating the expansive soil filling area 3 through side slopes on two sides; the width of the edge reinforced and edge covered seepage-proofing area 4 is not less than 3.0m, and the width of the reverse covering is not less than 1.0 m; the geocell protection area 5 is anchored by hook-shaped riveting piles or U-shaped steel bars, the fixed interval is about 1m, and planting soil is filled in the geocell space; the upper embankment 6 can adopt common roadbed filling; the road bed 7 is preferably made of hard, medium-hard coarse particles with good water stability: gravel and crushed stone, and materials with good gradation can also be adopted: crushed soil and gravel soil.
The first geogrid 9, the second geogrid 11 and the third geogrid 13 are made of bidirectional plastic geogrids; the first geogrid 9 is fully paved on the bottom isolation layer 2, the second geogrid 11 is paved on the edge reinforced and anti-seepage area 4 and the reverse covered roadbed slope surface, and the third geogrid 13 is fully paved on the top surface of the expansive soil core filling area 3; the first composite geotextile 10, the second composite geotextile 12 and the third composite geotextile 14 are composite geomembranes with two fabrics and one membrane; the first composite geotextile 10 is laid on the first geogrid 9 and is connected with the lowest part of the expansive soil core filling area 3; a second composite geotextile 12 is laid on the second geogrid 11; the third composite geotextile 14 is laid on the third geogrid 13 and is connected with the upper embankment 6; the expansive soil composite roadbed structure is suitable for weak expansive soil and medium expansive soil, but not suitable for strong expansive soil.
When the first geogrid 9, the second geogrid 11 and the third geogrid 13 are stretched and laid, the first geogrid, the second geogrid and the third geogrid are fixed on the lower filling layer by adopting U-shaped nails 15; the end part of the first geogrid 9 is connected with the proper position of the layer of second geogrid 11 by a connecting rod 16, and the geogrid is tensioned and fixed; the end part of the lower layer second geogrid 11 is connected with the proper position of the layer of second geogrid 11 by a connecting rod 16, and the geogrid is tensioned and fixed; the proper position of the third geogrid 13 is connected with the end part of the second geogrid 11 of the lower layer reverse covering by a connecting rod 16, and the geogrid is tensioned and fixed; the first geogrid 9, the second geogrid 11 and the third geogrid 13 are covered with the first composite geotextile 10, the second composite geotextile 12 and the third composite geotextile 14 in a reverse wrapping mode within two days to temporarily cover the roadbed slope, and exposure and insolation are avoided.
The maximum grain diameter of the filler within 1430cm from the first geogrid 9, the first composite geotextile 10, the third geogrid 13 and the third composite geotextile is not more than 10cm, and the filler is: gravel, mountain-opening stone slag, gravel soil and gravel soil; when a first layer of filler is paved on the geosynthetic material formed by the first geogrid 9, the first composite geotextile 10, the second geogrid 11, the second composite geotextile 12, the third geogrid 13 and the third composite geotextile 14, the material should be fed in a reversing mode, and the geosynthetic material cannot be directly rolled.
Fig. 2 is a schematic view of a geocell protective area, wherein geocells of the geocell protective area are made of high-strength plastic and are laid from top to bottom along a slope, the geocells are fully unfolded during laying, are connected by special members and are anchored on the slope by hook-shaped riveting piles or U-shaped steel bars.
Fig. 3 shows a construction method of an expansive soil composite roadbed structure, which comprises the following steps:
step one, performing geotechnical test; the test contents comprise natural water content, liquid plastic limit, grain gradation, maximum dry density and optimal water content, CBR and CBR expansion amount, free expansion rate and standard moisture absorption water content;
evaluating the engineering property of the expansive soil, judging the grade of the expansive soil, and determining whether the expansive soil is available; if applicable, go to the next step; not applicable, discarded;
step three, measuring and paying off;
step four, processing the foundation 1 according to design requirements;
constructing a bottom isolation layer 2;
step six, laying the first geogrid 9 and the first composite geotextile 10;
feeding and paving the first layer of expansive soil;
step eight, detecting the rolling moisture content; detecting the water content of the expansive soil, and performing rolling in the next step according with the requirement; if the requirement is not met, loosening and airing or watering and moistening are carried out;
step nine, rolling according to the construction process determined by the test road section, and detecting through a compaction standard; for the detection that the required compaction standard is not met, the reason is determined, and targeted measures are taken;
step ten, filling expansive soil and paving a second geogrid 11 and a second composite geotextile 12;
step eleven, paving a third geogrid 13 and a third composite geotextile 14;
step twelve, constructing the upper embankment 6, specifically: feeding the first layer of roadbed above the third composite geotextile 14 by adopting a retreating feeding mode, paving and rolling;
step thirteen, constructing the road bed 7, and rolling layer by layer to the top surface elevation of the road bed 7 according to the relevant standard requirements;
fourteen, carrying out roadbed delivery and acceptance inspection;
and step fifteen, constructing the pavement structure layer 8.
In the geotechnical test in the first step, the CBR is required to test the CBR of the expansive soil samples with different water contents, a relation curve of the CBR and the water contents is drawn, and the applicable water content range of the expansive soil filling area 3 is determined according to the requirement that the CBR of the expansive soil filling area 3 is more than or equal to 3%; and determining the compaction degree of the expansive soil filled area 3 in the water content range according to the determined applicable rolling water content range and by combining the compaction curve of the expansive soil.
The fifth step to the eleventh step are specifically: firstly, filling a layer of material with large porosity and good water stability, the thickness of which is not less than 50cm, on a treated foundation 1: gravel, mountain-opening stone slag and gravel soil are sequentially paved on the gravel, a first geogrid 9 and a first composite geotextile 10 are sequentially paved on the gravel, the mountain-opening stone slag and the gravel soil, and a reverse wrapping section with a certain length is reserved; the method comprises the following steps of feeding a first layer of expansive soil in a retreating feeding mode, unloading a proper amount of expansive soil into a grid according to the determined loose paving thickness, grid area and dump truck loading capacity of a test road section, paving and leveling by using a bulldozer, detecting according to the determined construction process of the test road section, and feeding, paving, rolling and detecting a second layer of expansive soil subgrade when the compaction standard is met; then sequentially carrying out feeding, paving, rolling and detection on the expansive soil at the third and fourth equal positions, building a slope according to a designed slope when the filling thickness of the expansive soil is 1-2 m, and upwards turning and primarily tensioning the first geogrid 9 and the first composite geotextile 10 along the built slope, wherein the length of the turning is not less than 1.0 m; sequentially laying a second geogrid 11 and a second composite geotextile 12 with the length not less than 3.0m on two sides of the embankment side slope, reserving a reverse wrapping section with a certain length, connecting the end part of the first geogrid 9 with the proper position of the layer of the second geogrid 11 by using a connecting rod 16, tensioning the geogrid and fixing; when the expansive soil with the thickness of 1-2 m is filled, constructing a slope according to a designed slope, reversely wrapping the second geogrid 11 and the second composite geotextile 12 reserved on the lower layer upwards along the constructed slope and primarily tensioning, wherein the reversely wrapped length is not less than 1.0 m; sequentially laying the layer of second geogrid 11 and the second composite geotextile 12 with the length not less than 3.0m on two sides of the embankment side slope, reserving a reverse wrapping section with a certain length, connecting the end part of the lower layer of second geogrid 11 with the proper position of the layer of second geogrid 11 by using a connecting rod 16, tensioning the grids and fixing; and (3) filling the expansive soil to the top surface elevation of the expansive soil core filling area 3, fully paving a third geogrid 13 and a third composite geotextile 14 in sequence, connecting the end part of the second geogrid 11 reversely wrapped at the lower layer at the proper position of the third geogrid 13 by using a connecting rod 16, tensioning the geogrid and fixing the geogrid.
The above description is only a partial example of the present invention and is not intended to limit the present invention. All the modifications and improvements made to the above examples according to the technical essence of the present invention fall within the scope of the present invention.
Claims (10)
1. The utility model provides an inflation soil composite roadbed structural style, includes bottom isolation layer (2), inflation soil filler district (3), limit portion adds muscle and prevention of seepage district (4), geotechnological check room guard zone (5), goes up embankment (6), roadbed (7), road surface structural layer (8).
2. The expansive soil composite roadbed structure type according to claim 1, wherein the bottom isolation layer (2) is positioned above the foundation (1) for preventing the moisture migration to the expansive soil filled area (3) caused by the rising of the underground water level or the action of capillary water; the expansive soil core filling area (3) is positioned above the bottom isolation layer (2); the upper embankment (6) is positioned above the expansive soil core filling area (3); the roadbed (7) is positioned above the upper embankment (6); the edge reinforcing and edge covering seepage-proofing areas (4) are positioned on side slopes on two sides of the roadbed; the geocell protection area (5) is formed by fully paving the expansive soil subgrade slope surface.
3. The expanded soil composite subgrade structural style according to claim 1 or 2, characterized in that the expanded soil fill area (3) comprises a first geogrid (9) and a first composite geotextile (10), a third geogrid (13) and a third composite geotextile (14), expanded soil; the edge reinforcing and edge wrapping seepage-proofing area (4) comprises a second geogrid (11) and a second composite geotextile (12); wherein, the first geogrid (9) and the first composite geotextile (10) are sequentially fully paved above the bottom isolation layer (2) and reversely wrapped; filling expansive soil above the first composite geotextile (10), and laying a second geogrid (11) and a second composite geotextile (12) on two sides of the roadbed in turn and reversely wrapping the geogrid and the second composite geotextile after filling 1-2 m (4-8 layers) of expansive soil until the expansive soil is filled to the design elevation of the expansive soil filling area (3); and a third geogrid (13) and a third composite geotextile (14) are sequentially paved at the designed elevation of the expansive soil filling area (3).
4. The expansive soil composite subgrade structure according to the claim 1 or 2, characterized in that the bottom isolation layer (2) is a material with high porosity and good water stability: gravel, mountain-opening stone slag and gravel soil, wherein the filling thickness is not less than 50 cm; the filling height of the expansive soil filling area (3) is not more than 8m, and the slope rate is 1: 1.5-1: 1.75; the edge reinforcing and edge covering seepage-proofing area (4) is formed by reversely wrapping two sides of the expansive soil filling area (3) by adopting a second geogrid (11) and a second composite geotextile (12) and is used for preventing rainfall and side slope runoff from infiltrating into the expansive soil filling area (3) through side slopes on two sides; the width of the edge reinforcing and edge covering anti-seepage area (4) is not less than 3.0m, and the width of the reverse covering is not less than 1.0 m; the geocell protection area (5) is anchored by hook-shaped riveting piles or U-shaped steel bars, the fixed distance is about 1m, and planting soil is filled in the geocell space; the upper embankment (6) can adopt common roadbed filling; the road bed (7) is made of hard and medium-hard coarse particles with good water stability: gravel and crushed stone, and materials with good gradation can also be adopted: crushed soil and gravel soil.
5. The expansive soil composite roadbed structure type according to claim 3, wherein the first geogrid (9), the second geogrid (11) and the third geogrid (13) are bidirectional plastic geogrids; the first geogrid (9) is fully paved on the bottom isolation layer (2), the second geogrid (11) is paved on the edge reinforced and anti-seepage area (4) and the reverse-wrapped roadbed slope surface, and the third geogrid (13) is fully paved on the top surface of the expansive soil filling area (3); the first composite geotextile (10), the second composite geotextile (12) and the third composite geotextile (14) are composite geomembranes with two geotextiles and one membrane; the first composite geotextile (10) is laid on the first geogrid (9) and is connected with the lowest part of the expansive soil filling area (3); a second composite geotextile (12) is laid on the second geogrid (11); the third composite geotextile (14) is laid on the third geogrid (13) and is connected with the upper embankment (6); the expansive soil composite roadbed structure is suitable for weak expansive soil and medium expansive soil, but not suitable for strong expansive soil.
6. The expansive soil composite roadbed structure type according to claim 3, wherein the first geogrid (9), the second geogrid (11) and the third geogrid (13) are fixed on the lower filling layer by using U-shaped nails (15) when being stretched and laid; the end part of the first geogrid (9) is connected with the proper position of the second geogrid (11) by a connecting rod (16), and the geogrids are tensioned and fixed; the end part of the lower layer second geogrid (11) is connected with the proper position of the layer of second geogrid (11) by a connecting rod (16), and the geogrid is tensioned and fixed; the proper position of the third geogrid (13) is connected with the end part of the second geogrid (11) of the lower layer reverse wrapping by a connecting rod (16), and the geogrid is tensioned and fixed; the first geogrid (9), the second geogrid (11), the third geogrid (13), the first composite geotextile (10), the second composite geotextile (12) and the third composite geotextile (14) are reversely laid to temporarily cover the corresponding roadbed side slope within two days, and exposure and insolation are avoided.
7. An expansive soil composite subgrade structure according to claim 3, characterized in that the maximum particle size of the filler within 30cm from the first geogrid (9), the first composite geotextile (10), the third geogrid (13) and the third composite geotextile (14) is not more than 10cm, and the filler is: gravel, mountain-opening stone slag, gravel soil and gravel soil; when a first layer of filler is paved on the geosynthetic material formed by the first geogrid (9), the first composite geotextile (10), the second geogrid (11), the second composite geotextile (12), the third geogrid (13) and the third composite geotextile (14), the material should be fed in a reversing mode, and the geosynthetic material cannot be directly rolled.
8. A construction method of an expansive soil composite roadbed structure type comprises the following steps:
step one, performing geotechnical test; the test contents comprise natural water content, liquid plastic limit, grain gradation, maximum dry density and optimal water content, CBR and CBR expansion amount, free expansion rate and standard moisture absorption water content;
evaluating the engineering property of the expansive soil, judging the grade of the expansive soil, and determining whether the expansive soil is available; if applicable, go to the next step; not applicable, discarded;
step three, measuring and paying off;
step four, processing the foundation (1) according to design requirements;
constructing a bottom isolation layer (2);
step six, laying a first geogrid (9) and a first composite geotextile (10);
feeding and paving the first layer of expansive soil;
step eight, detecting the rolling moisture content; detecting the water content of the expansive soil, and performing rolling in the next step according with the requirement; if the requirement is not met, loosening and airing or watering and moistening are carried out;
step nine, rolling according to the construction process determined by the test road section, and detecting through a compaction standard; for the detection that the required compaction standard is not met, the reason is determined, and targeted measures are taken;
step ten, filling expansive soil and paving a second geogrid (11) and a second composite geotextile (12);
step eleven, paving a third geogrid (13) and a third composite geotextile (14);
step twelve, constructing an upper embankment (6), specifically: feeding the first layer of roadbed above the third composite geotextile (14) by adopting a retreating feeding mode, paving and rolling;
step thirteen, constructing the road bed (7), and rolling layer by layer to the top surface elevation of the road bed (7) according to the relevant specification requirements;
fourteen, carrying out roadbed delivery and acceptance inspection;
and fifteen, constructing a pavement structure layer (8).
9. The construction method of the expansive soil composite roadbed structure type according to claim 8, wherein in the soil test in the step one, CBR is used for testing CBR of expansive soil samples with different water contents, drawing a relation curve of the CBR and the water content, and determining the applicable water content range of the expansive soil filling area (3) according to the requirement that the CBR of the expansive soil filling area (3) is more than or equal to 3%; and determining the compaction degree of the expansive soil filled area (3) within the range of the water content by combining the compaction curve of the expansive soil according to the determined range of the applicable rolling water content.
10. The expansive soil composite roadbed structure type construction method according to claim 8, wherein the step five to the step eleven are specifically: firstly, filling a layer of material with large porosity and good water stability, the thickness of which is not less than 50cm, on a treated foundation (1): gravel, mountain-opening stone slag and gravel soil are sequentially paved on the gravel, a first geogrid (9) and a first composite geotextile (10) are sequentially paved on the gravel, the mountain-opening stone slag and the gravel soil, and a reverse wrapping section with a certain length is reserved; the method comprises the following steps of feeding a first layer of expansive soil in a retreating feeding mode, unloading a proper amount of expansive soil into a grid according to the determined loose paving thickness, grid area and dump truck loading capacity of a test road section, paving and leveling by using a bulldozer, detecting according to the determined construction process of the test road section, and feeding, paving, rolling and detecting a second layer of expansive soil subgrade when the compaction standard is met; then sequentially carrying out feeding, paving, rolling and detection on the expansive soil at the third and fourth equal positions, building a slope according to a designed slope when the filling thickness of the expansive soil is 1-2 m, reversely wrapping and primarily tensioning the first geogrid (9) and the first composite geotextile (10) along the built slope, wherein the reversely wrapped length is not less than 1.0 m; sequentially laying a second geogrid (11) with the length not less than 3.0m and a second composite geotextile (12) on two sides of the embankment side slope, reserving a reverse wrapping section with a certain length, connecting the end part of the first geogrid (9) with the proper position of the second geogrid (11) of the layer by using a connecting rod (16), tensioning the geogrids and fixing; when the expansive soil with the thickness of 1-2 m is filled, constructing a slope according to a designed slope, reversely wrapping the second geogrid (11) and the second composite geotextile (12) reserved on the lower layer upwards along the constructed slope and primarily tensioning, wherein the length of the reversely wrapped is not less than 1.0 m; sequentially laying the layer of second geogrid (11) and second composite geotextile (12) with the length not less than 3.0m on two sides of the embankment side slope, reserving a reverse wrapping section with a certain length, connecting the end part of the lower layer of second geogrid (11) with the proper position of the layer of second geogrid (11) by using a connecting rod (16), tensioning the grids and fixing; and (3) filling the expansive soil to the top surface elevation of the expansive soil filling area (3), fully paving a third geogrid (13) and a third composite geotextile (14) in sequence, connecting the end part of the second geogrid (11) which is reversely wrapped at the lower layer at the proper position of the third geogrid (13) by using a connecting rod (16), tensioning the geogrid and fixing the geogrid.
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