Construction method of expansive soil embankment

Abstract

The invention discloses a construction method of an expansive soil embankment, and belongs to the technical field of expansive soil roadbed construction. The method comprises the following steps: S1, expansive soil parameter determination: determining the filler consistency, the maximum dry density, the optimal water content, the expansive soil bearing ratio and the total expansion and shrinkage rate of the expansive soil through tests; s2, rolling the original ground: measuring, lofting and tedding the original ground, and then rolling the original ground; s3, filling two layers of expansive soil at the bottom of the embankment with lime soil, wherein the lime soil is covered with ash, soil is loaded, and leveling, tedding and rolling are conducted; s4, filling expansive soil, plain soil and lime soil in the middle of the embankment, wherein soil feeding, leveling, tedding and rolling are conducted; s5, filling the expansive soil on the top of the embankment with lime soil, wherein the lime soil is stuffed, the soil is loaded, leveled, tedded and ground; s6, inspection and acceptance: recording moisture content inspection, and inspecting and accepting actual measurement items. The method can realize on-site utilization of resources, is beneficial to energy conservation, environmental protection, emission reduction and efficiency improvement, guarantees the engineering quality, reduces the engineering cost, and improves the working efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of construction of expansive soil subgrades, and particularly to a construction method for an expansive soil embankment. Background Art

[0002] In recent years, with the rapid development of highways in China, a large number of high-grade highways face the use of expansive soil as a subgrade filling material during construction. In particular, the Jianghan Plain and the surrounding micro-hilly areas are all expansive soil areas. The filling of expansive soil subgrades directly affects the construction quality of the subgrade and even the pavement structure, and the problem of filling expansive soil subgrades has received attention and extensive concern. At present, the commonly used method for treating the original ground in China is lime admixture improvement. Briefly speaking, it is to carry out lime admixture treatment on medium-weak expansive soil that meets the requirements. This traditional original ground has the following problems: First, the amount of improvement materials is large, resulting in waste of resources; second, lime needs to be added during soil improvement, which is not environmentally friendly; third, it increases the cost and is not conducive to cost savings. Summary of the Invention

[0003] The purpose of the present invention is to provide a construction method for an expansive soil embankment, which can achieve local utilization of resources, is beneficial to energy conservation, environmental protection, emission reduction and efficiency improvement, while ensuring the project quality, reducing the project cost, improving the work efficiency, and accelerating the construction progress, so as to solve the problems raised in the above background art.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] A construction method for an expansive soil embankment includes the following steps:

[0006] S1: Determination of parameters of expansive soil: Determine the consistency, maximum dry density, optimum moisture content, swelling soil bearing ratio and total swelling and shrinkage rate of the expansive soil filler through tests;

[0007] S2: Compaction of the original ground: Measure, set out, sun-dry the original ground, and then carry out compaction;

[0008] S3: Laying two layers of lime soil of expansive soil at the bottom of the embankment: Lime soil moisture conditioning, soil spreading, leveling, sun-drying, compaction;

[0009] S4: Filling of the middle part of the embankment with expansive soil plain soil and lime soil: Soil spreading, leveling, sun-drying, compaction;

[0010] S5: Laying lime soil of expansive soil at the top of the embankment: Lime soil moisture conditioning, soil spreading, leveling, sun-drying, compaction;

[0011] S6: Inspection and acceptance: Inspection record of moisture content, inspection and acceptance of measured items.

[0012] Further, the specific method for determining the parameters of the expansive soil in S1 is as follows:

[0013] S101: Determine the consistency of expansive soil , the consistency of the expansive soil shall meet the requirement of 1.00 ≤ ≤ 1.30:

[0014]

[0015] In the formula: is the liquid limit (%) is the water content of the filler (%); is the plastic limit (%); [[ID=A]]

[0016] When the consistency of the expansive soil is less than 1.00, that is, when the water content is greater than the plastic limit, there is more weakly bound water in the expansive soil, and the expansive soil is in a plastic state, making it easy to produce the phenomenon of "rubbery soil" during compaction and difficult to compact; when the consistency of the filler is greater than 1.00, that is, when the natural water content is less than the plastic limit, the weakly bound water in the soil decreases and it is in a semi-solid state, then effective compaction can be carried out;

[0017] S102: Determine the California Bearing Ratio EBR of the expansive soil: When the expansive soil is used as the subgrade fill for the lower embankment, EBR shall not be less than 4.0%;

[0018] S103: Determine the optimum water content: When the natural water content of the expansive soil filler is greater than the optimum water content of the heavy compaction by dry method, the heavy compaction test method by wet method shall be used to determine the optimum water content and the maximum dry density of the filler; when the natural water content of the expansive soil filler is less than the optimum water content of the heavy compaction by dry method, the heavy compaction test method by dry method shall be used to determine the optimum water content and the maximum dry density;

[0019] S104: Determine the total swelling and shrinkage rate of the expansive soil filler: The total swelling and shrinkage rate of the expansive soil filler :

[0020]

[0021] In the formula: : swelling ratio under load (%); : shrinkage coefficient; : water content of the compacted filler (%); : lower limit value of the water content of the expansive soil subgrade (%).

[0022] Furthermore, the specific method of the original ground compaction in S2 is as follows:

[0023] S201: The measurement of the original ground of the road is carried out by the cross-section method. Generally, one cross-section is taken every 20m, and generally more than 5 points are taken for one cross-section. For areas with large undulations in the ground shape or wide road widths, the measurement points are correspondingly densified so that the measured data can sufficiently reflect the actual shape of the terrain and accumulate good original data for the future earthwork measurement work;

[0024] S202: Set out according to the cross-section designed on the drawing. Considering the positions of the road slope protection berm, the roadside ditch of the embankment, and the isolation fence, excavate a drainage ditch at the edge of the road red line range, with an excavation depth of about 80 cm (lower than the bottom of the blind ditch).

[0025] S203: According to the thickness requirement designed on the drawing, use a bulldozer to clear the surface of the roadbed within the range between the two drainage ditches on both sides.

[0026] S204: Compact the original ground within the cleared surface range and detect the compaction degree.

[0027] Furthermore, the specific method for filling two layers of expansive soil lime soil in S3 is as follows:

[0028] S301: Mark a 10m * 6m grid on the original ground with a lime line.

[0029] S302: Conduct lime-soil moistening treatment at the borrow pit to make the soil reach a sandy state.

[0030] S303: Detect the moisture content of the original ground soil before filling the lime soil. When the moisture content of the original ground soil is relatively high, air-dry the soil.

[0031] S304: Detect the moisture content of the soil. When the moisture content is 2% higher than the optimum moisture content, use a moldboard plow and a road mixer to break up the soil.

[0032] S305: Use a vibratory roller to compact the soil and detect the compaction degree.

[0033] S306: The construction process for filling the second layer of lime soil is the same as above.

[0034] Furthermore, the specific method for filling the middle part of the embankment with expansive soil, plain soil, and lime soil in S4 is as follows:

[0035] S401: Mark a 10m * 6m grid on the subgrade with a lime line.

[0036] S402: Load the soil in the order from the inside to the outside. First, fill the lime soil on the inside, then fill the plain soil in the middle, and finally fill the lime soil on the outside.

[0037] S403: Conduct lime-soil moistening treatment at the borrow pit to make the soil reach a sandy state.

[0038] S404: Detect the moisture content of the original ground soil before filling the lime soil and the plain soil. When the moisture content of the original ground soil is relatively high, air-dry the soil.

[0039] S405: Detect the moisture content of the soil. When the moisture content is 2% higher than the optimum moisture content, use a moldboard plow and a road mixer to break up the soil.

[0040] S406: Use a vibratory roller to compact the earthwork and detect the degree of compaction;

[0041] S407: The construction process for each subsequent layer of filling is the same as above until the corresponding elevation is reached.

[0042] Further, after the original ground compaction is completed, two layers of lime soil are filled to seal the water; then earthwork is filled above the two layers of lime soil, with the filling requirement being that the middle part is plain soil while the two sides are lime soil; to ensure the compaction of the lime soil, the minimum width of the lime soil on both sides of the middle filler is 2.5 meters, and the width of the lime soil gradually increases by 30 cm from bottom to top until the set elevation is reached or the entire cross-section is lime soil; after the middle filler reaches the corresponding elevation, lime soil is used to fill to the bottom of the roadbed.

[0043] Further, the maximum dry density and the optimum moisture content used for the compaction degree detection in S103 must be obtained through the wet method compaction test.

[0044] Further, the inspection and acceptance methods in S6 include: the compaction test of the earthwork, the expansion coefficient, the moisture content, the compaction degree, the longitudinal elevation, the midline deviation, the width, the flatness, and the cross slope of the slope conforming to the values specified in the design drawings and the specifications or the allowable deviations.

[0045] Compared with the prior art, the beneficial effects of the present invention are:

[0046] A construction method for an expansive soil embankment of the present invention utilizes the characteristics of lime soil and expansive soil, and adopts the "surrounding step filling method" to combine the filling of lime soil and plain soil. The expansive soil is surrounded by lime soil for filling, avoiding the swelling of the expansive soil caused by rainwater, and ensuring the strength of the roadbed; it can not only change the traditional construction method of expansive soil embankments, but also achieve resource conservation, meet the requirements of energy conservation, environmental protection, emission reduction and efficiency improvement, while ensuring the project quality, reducing the project cost, and improving the work efficiency. Brief Description of the Drawings

[0047] Figure 1 It is a flow chart of the embankment construction method of the present invention;

[0048] Figure 2 It is a cross-sectional view of the expansive soil embankment filling of the present invention. Detailed Embodiments

[0049] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0050] Please refer to Figure 1-2, an embodiment of the present invention provides a construction method for an expansive soil embankment, including the following steps:

[0051] Step 1: Determination of parameters of expansive soil

[0052] (1) Determination of the consistency of expansive soil , the consistency of the expansive soil should meet the requirement of 1.00 ≤ ≤ 1.30:

[0053]

[0054] In the formula: : Liquid limit (%) : Moisture content of the filler (%) : Plastic limit (%)

[0055] When the consistency of the expansive soil is less than 1.00, that is, when the moisture content is greater than the plastic limit, there is more weakly bound water in the expansive soil, and the expansive soil is in a plastic state, making it easy to produce the phenomenon of "rubbery soil" during compaction and difficult to compact; when the consistency of the filler is greater than 1.00, that is, the natural moisture content is less than the plastic limit, the weakly bound water in the soil decreases and it is in a semi-solid state, and then effective compaction can be carried out.

[0056] (2) Determination of the California Bearing Ratio EBR of the expansive soil: When the expansive soil is used as the filler for the lower embankment, the EBR should not be less than 4.0%.

[0057] (3) Determination of the optimum moisture content: When the natural moisture content of the expansive soil filler is greater than the optimum moisture content of the dry method heavy compaction, the wet method heavy compaction test method in the current "Code for Highway Geotechnical Tests" (JTG 3430) should be used to determine the optimum moisture content and the maximum dry density of the filler; when the natural moisture content of the expansive soil filler is less than the optimum moisture content of the dry method heavy compaction, the dry method heavy compaction test method should be used to determine the optimum moisture content and the maximum dry density.

[0058] (4) Determination of the total swelling and shrinkage rate of the expansive soil filler: The total swelling and shrinkage rate of the expansive soil filler :

[0059]

[0060] In the formula: : Swelling rate under load (%) : Shrinkage coefficient : Compaction moisture content of the filler (%) : Lower limit value of the moisture content of the expansive soil subgrade (%)

[0061] Step 2: Original ground compaction

[0062] (1) The measurement of the original road surface is carried out using the cross-section method. Each cross section is generally 20m long and more than 5 points are usually taken for each cross section. For areas with large fluctuations in the terrain or a wide road width, the measurement of points is increased accordingly so that the measured data can fully reflect the actual shape of the terrain and accumulate original data for future earthwork measurement work.

[0063] (2) Loft the cross section according to the design drawing. Considering the location of the road slope protection road, embankment ditch and isolation fence, dig the drainage ditch along the road red line with a depth of about 80cm (lower than the bottom of the blind ditch);

[0064] (3) According to the thickness requirements of the design drawings, use a bulldozer to clear the roadbed area between the drainage ditches on both sides;

[0065] (4) Roll the original ground within the clearing range and test the compaction degree.

[0066] Step 3: Fill two layers of expansive soil and ash

[0067] (1) Mark a 10m*6m grid on the original ground with lime lines;

[0068] (2) Carry out ash-soil sealing treatment at the borrow site to achieve the effect of sandification;

[0069] (3) Apply lime soil to test the moisture content of the original ground soil. If the moisture content of the original ground soil is high, dry the soil in the sun.

[0070] (4) Check the soil moisture content. When the moisture content is 2% higher than the optimum moisture content, use a plow in conjunction with a road mixer to break up the soil.

[0071] (5) Use a vibratory roller to compact the earthwork and test the compaction degree;

[0072] (6) The filling process of the second layer of ash soil is the same as above.

[0073] Step 4: Filling the middle part of the embankment with expansive soil and lime soil

[0074] (1) Mark a 10m*6m grid with lime lines on the underlying layer;

[0075] (2) Fill the soil from the inside to the outside, first filling the inner gray soil, then filling the middle plain soil, and finally filling the outer gray soil;

[0076] (3) Carry out ash-soil sealing treatment at the borrow site to achieve the effect of sandification;

[0077] (4) Add lime soil and plain soil to test the moisture content of the original ground soil. If the moisture content of the original ground soil is high, dry the soil in the sun;

[0078] (5) Detect the moisture content of the earthwork. When the moisture content is higher than the optimum moisture content by 2%, use a moldboard plow in combination with a road mixer to break up the earthwork.

[0079] (6) Use a vibratory roller to compact the earthwork and detect the degree of compaction.

[0080] (7) The construction process for each subsequent layer of filling is the same as above until the corresponding elevation is reached.

[0081] Step 5: Inspection and acceptance

[0082] The method includes: the compaction test of the earthwork, the expansion coefficient, the moisture content, the degree of compaction, the longitudinal elevation, the center line deviation, the width, the flatness, and the cross slope of the slope conform to the specified values or allowable deviations in the design drawings and specifications.

[0083] After the original ground is compacted, fill two layers of lime soil to seal the water; then fill the earthwork above the two layers of lime soil. The filling requirement is that the two sides are lime soil and the middle part is plain soil; to ensure the compaction of the lime soil, the minimum width of the lime soil on both sides of the middle filler is 2.5 meters, and the width of the lime soil gradually increases by 30 cm from bottom to top until the set elevation is reached or the whole section is lime soil; when the middle filler reaches the corresponding elevation, use lime soil to fill to the bottom of the roadbed.

[0084] In summary: The present invention utilizes the characteristics of lime soil and expansive soil, and adopts the "surrounding step filling method" to combine the filling of lime soil and plain soil. The expansive soil is surrounded by lime soil for filling, avoiding the swelling of the expansive soil due to rainwater, and ensuring the strength of the roadbed; it can not only change the traditional construction method of expansive soil embankment, but also achieve resource conservation, which is beneficial to energy conservation, environmental protection, emission reduction and efficiency improvement, while ensuring the project quality, achieving the goal of reducing project costs and improving work efficiency.

[0085] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. A construction method for an expansive soil embankment, characterized by: The following steps are involved: S1: Determination of expansive soil parameters: Determine the consistency, maximum dry density, optimum moisture content, expansive soil bearing ratio and total swelling and shrinkage ratio of the expansive soil filler through experiments; S2: Original ground rolling: measure, stake out, turn over and dry the original ground, and then roll it; S3: Fill the bottom of the embankment with two layers of expansive soil and ash soil: fill the ash soil with ash, top it with soil, level it, turn it over and dry it, and roll it; S4: Filling the middle part of the embankment with expansive soil and lime soil: filling, leveling, drying and rolling; S5: Filling the top of the embankment with expansive soil and ash: filling the ash and ash, adding soil, leveling, turning and drying, and rolling; S6: Inspection and acceptance: moisture content inspection records, inspection and acceptance of measured items.

2. The construction method of an expansive soil embankment according to claim 1, characterized in that: The specific method for determining the parameters of expansive soil in S1 is as follows: S101: Determining the consistency of expansive soils , the consistency of expansive soil should meet 1.00≤ Requirements for ≤1.30: Where: is the liquid limit (%); is the moisture content of the filler (%); is the plastic limit (%); When the consistency of expansive soil is less than 1.00, that is, the water content is greater than the plastic limit, there is more weakly bound water in the expansive soil, and the expansive soil is in a plastic state, which makes it easy to produce a "rubber soil" phenomenon during rolling and difficult to compact; when the consistency of the filler is greater than 1.00, that is, the natural water content is less than the plastic limit, the weakly bound water in the soil decreases, and the soil becomes semi-solid, which can be effectively compacted; S102: Determine the expansive soil bearing ratio (EBR): When expansive soil is used as lower embankment fill, the EBR should not be less than 4.0%; S103: Determine the optimum moisture content: When the natural moisture content of the expansive soil filler is greater than the optimum moisture content for dry heavy compaction, the wet heavy compaction test method should be used to determine the optimum moisture content and maximum dry density of the filler; when the natural moisture content of the expansive soil filler is less than the optimum moisture content for dry heavy compaction, the dry heavy compaction test method should be used to determine the optimum moisture content and maximum dry density; S104: Determine the total expansion and contraction rate of expansive soil filler: : Where: : Load expansion rate (%); : shrinkage coefficient; : Compacted moisture content of filler (%); : The lower limit of moisture content of expansive soil roadbed (%).

3. The construction method of an expansive soil embankment according to claim 2, characterized in that: The specific method of ground compaction in S2 is as follows: S201: The original road surface is measured using the cross-section method. Each cross section is generally 20 meters long, and more than 5 points are usually taken in each cross section. For areas with large fluctuations in terrain or wide road widths, more points are measured accordingly to ensure that the measured data can fully reflect the actual shape of the terrain and accumulate original data for future earthwork measurement work. S202: Loft the cross section according to the design drawings. Considering the location of the road slope protection road, embankment ditch and isolation fence, dig the drainage ditch along the road red line to a depth of about 80cm (lower than the bottom of the blind ditch). S203: According to the thickness requirements of the drawings, use a bulldozer to clear the roadbed area between the drainage ditches on both sides; S204: Roll the original ground within the clearing range and test the compaction degree.

4. The method for treating expansive soil embankment construction according to claim 3, wherein: The specific method of filling two layers of expansive soil and ash in S3 is as follows: S301: Mark a 10m*6m grid on the original ground with lime lines; S302: performing ash-soil sealing treatment at the borrow site to achieve a sandification effect; S303: Apply lime soil to detect the moisture content of the original ground soil. If the moisture content of the original ground soil is high, dry the soil; S304: Detect the soil moisture content. If the moisture content is 2% higher than the optimum moisture content, use a plow in conjunction with a road mixer to break up the soil. S305: Using a vibratory roller to compact the earthwork and testing the compaction degree; S306: The second layer of ash soil filling process is the same as above.

5. The construction method of an expansive soil embankment according to claim 4, characterized in that: The specific method of filling the middle part of S4 middle embankment with expansive soil and lime soil is as follows: S401: Mark a 10m*6m grid on the underlying layer with lime lines; S402: Fill the soil from the inside to the outside, first filling the inner lime soil, then filling the middle plain soil, and finally filling the outer lime soil; S403: Performing ash-soil sealing treatment at the borrow site to achieve a sandification effect; S404: Apply lime soil and plain soil to test the moisture content of the original ground soil. If the moisture content of the original ground soil is high, air the soil. S405: Detect the soil moisture content. When the moisture content is 2% higher than the optimum moisture content, use a plow in conjunction with a road mixer to break up the soil. S406: Using a vibratory roller to compact the earthwork and testing the compaction degree; S407: The construction process of each subsequent layer of filling is the same as above until the corresponding elevation is reached.

6. The method for constructing an expansive soil embankment according to claim 1, wherein: After the original ground is compacted, two layers of lime soil are filled to seal the water; then the earth is filled on top of the two layers of lime soil, and the filling requirement is that the middle part of the lime soil on both sides is plain soil; to ensure the compaction of the lime soil, the minimum width of the lime soil on both sides of the middle filling is 2.5 meters, and the width of the lime soil gradually increases by 30 cm from bottom to top until the set elevation is reached or the entire section is filled with lime soil; after the middle filling reaches the corresponding elevation, lime soil is used to fill to the bottom of the roadbed.

7. The construction method of an expansive soil embankment according to claim 1, characterized in that: The maximum dry density and optimum moisture content used in the compaction test of S103 must be obtained through a wet compaction test.

8. The method for constructing an expansive soil embankment according to claim 1, wherein: The inspection and acceptance methods in S6 include: compaction test of earthwork, expansion coefficient, moisture content, compaction degree, longitudinal elevation, centerline deviation, width, flatness, cross slope and side slope conforming to the design drawings and the specified values or allowable deviations in the specifications.

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