High fill green lime micro-expansive soil fill roadbed construction method

Abstract

The application discloses a kind of high fill green lime micro-expansive soil fill roadbed construction methods, method includes material pretreatment, accurate mixing, layered filling and pre-expansion treatment, dynamic combination compaction and closed maintenance;The application is by optimizing the proportion of lime micro-expansive soil, so that it has controllable micro-expansion characteristics, can still slowly expand after compaction, actively compensate the settlement caused by dead weight and traffic load, effectively reduce the problem of uneven settlement;The construction technology of layered filling and dynamic combination compaction is used to enhance the compaction effect and improve the bearing capacity of roadbed;The expansion of roadbed is monitored in real time by setting optical fiber displacement sensor in roadbed, accurate control of construction process is realized, potential settlement risk can be warned in advance, and maintenance cost is reduced.

Description

Technical Field

[0001] This invention relates to the fields of geotechnical engineering and road construction technology, specifically to a construction method for high-fill green lime micro-expansion soil embankment roadbed, which is particularly suitable for major projects such as highways, railways, and airport runways where settlement control is strictly required. Background Technology

[0002] In traditional high embankment roadbed construction, the existing raw materials and processes have the following problems:

[0003] 1. Traditional lime-soil mixtures often use ordinary lime mixed with plain soil (lime content 8%~10%), with an expansion rate of only 0.1%~0.3%, which cannot offset the settlement of high fills due to their own weight.

[0004] 2. The construction process is rough, the layer filling thickness is too large (usually ≥50cm), and the compaction process is simple (only static pressure or only vibration compaction), resulting in insufficient compaction degree (<90%).

[0005] 3. Poor water stability: Conventional methods are not strict in controlling moisture content. When the moisture content fluctuates by more than ±3%, it is easy to soften or crack.

[0006] 4. Cost and environmental issues: High lime content (usually ≥8%) leads to large carbon emissions and poor economic efficiency;

[0007] 5. Long maintenance cycle: Natural curing requires 7-14 days, and the construction period is uncontrollable. With the continuous improvement of my country's infrastructure level and demand, as well as the expansion of infrastructure scope, some infrastructure projects have roadbeds located in paddy fields, with a fill height of 8 meters, constituting high embankment roadbeds. During the construction of high embankment roadbeds, insufficient soil compaction and poor long-term stability lead to uneven roadbed settlement, damaging the pavement structure, causing serious defects, and endangering road stability.

[0008] Therefore, developing a construction technology for high embankment subgrades to address the above problems, and to solve the problems of uneven settlement, insufficient compaction, and poor long-term stability caused by insufficient soil expansibility in traditional high embankment subgrade construction, is a problem that those skilled in the art need to continue to solve. Summary of the Invention

[0009] To overcome the shortcomings of the prior art, this invention provides a construction method for high-fill green lime micro-expansion soil embankment. By optimizing the mix proportion and construction process of lime micro-expansion soil, it solves the problems of uneven settlement, insufficient compaction and poor long-term stability caused by insufficient soil expansibility in traditional high-fill embankment construction. At the same time, fiber optic displacement sensors are installed in the embankment to monitor the expansion of the embankment in real time.

[0010] This invention is achieved through the following technical solutions:

[0011] A construction method for high-fill green lime micro-expansion soil embankment subgrade is as follows: S1. Material pretreatment to prepare quicklime, which is then sieved and added to the mixer along with micro-expansion agent and micro-expansion soil;

[0012] S2, Precision Mixing

[0013] Start the mixer to dry mix;

[0014] Add water to the mixer until it reaches 90% of the optimum moisture content, then continue mixing. After mixing, add water until the optimum moisture content is ±1.5%.

[0015] S3, Layered Filling and Pre-expansion Treatment

[0016] Each layer is laid with a loose thickness of 25cm, compacted to a thickness of 20cm, and then filled in layers. After compaction, the layers are allowed to stand, and the dosage of micro-expansion agent for the next layer is adjusted according to surface micro-cracks. S4. Dynamic combined compaction follows the principle of light to heavy, stable to vibratory, and slow to fast, proceeding with initial compaction, intermediate compaction, and final compaction in sequence. S5. Sealed curing.

[0017] Cover with composite geotextile, spray water mist 3 times a day, and maintain for 5 to 7 days.

[0018] Further, in step S1, hydrated lime is obtained by adding water to quicklime and letting it sit for 24 hours, and then passing it through a 5mm sieve. The amount of hydrated lime is 4-6% of the weight of the micro-expansion soil. The micro-expansion agent is a sulfoaluminate-based expansion agent, and the amount is 0.3-0.5% of the weight of the micro-expansion soil. The liquid limit of the micro-expansion soil is ≤40%, the plasticity index is 10-20, and the maximum particle size is ≤2cm.

[0019] Further, the specific method for step S2 is as follows: Start the mixer and dry mix at a speed of 30 r / min for 2 minutes;

[0020] Add water to the mixer to 90% of the optimum moisture content, then mix continuously at 40 r / min for 3 minutes, ensuring a mixing uniformity of ≥95%. After mixing, add water to bring the optimum moisture content to ±1.5%.

[0021] Furthermore, in step S3, the error of the loose layer thickness of 25cm is ±2cm; the standing time is 1-2h, and if the surface microcracks are >1.5%, the dosage of the next layer of micro-expansion agent is adjusted.

[0022] Further, the specific method for step S4 is as follows: S4-1. For the initial compaction, a 26T double-drum roller is used to perform static compaction for 1 to 2 passes at a compaction speed of 1.5 to 2.5 km / h. When there is no superelevation on the subgrade, compact from the outer shoulder towards the road center; when there is superelevation, compact from low to high. S4-2. For the re-compaction, a 26T vibratory roller is used to perform compaction for 3 to 4 passes at a compaction speed of 2.5 to 3.5 km / h, and a grader is used for leveling. S4-3. For the final compaction, after leveling, a 26T double-drum roller is used to perform compaction for 2 to 3 passes at a compaction speed of 3.0 to 4.0 km / h.

[0023] Further, in step S5, the specification of the composite geotextile is 400 g / m². When the ambient temperature ≥ 15°C, the curing time is 5 days, and it also includes real-time measurement of the swelling amount and acceptance. The specific method is as follows: Arrange 1 group every 50 mm, bury the fiber optic displacement sensor in the subgrade, compare the actual settlement of the subgrade with the prediction model, monitor the swelling rate, and when the swelling rate exceeds 1.2%, perform emergency water replenishment or admixture adjustment; during acceptance, conduct sand replacement method testing on each layer of the subgrade filled in layers, and a compaction degree ≥ 94% is qualified; after the final compaction, conduct immersion testing on the subgrade for 4 days, and a CBR value ≥ 8% is qualified.

[0024] Further, the method also includes surface cleaning and slope greening protection, which are as follows: S0. Surface cleaning. Conduct surface cleaning on the subgrade range, removing the existing surface pavement and soil containing sod, domestic waste, tree roots, humus, and cultivated soil. S6. Slope greening protection. Cover the subgrade slope with 300 thick planting soil and spray grass seeds for slope protection.

[0025] Further, during compaction in steps S4-1 to S4-3, the adjacent compaction zones all overlap by 1 / 3 to 1 / 2 of the compaction zone width. When the entire width of the road surface is compacted, it is considered one compaction pass.

[0026] Compared with the prior art, the technical advantages of the present invention are as follows:

[0027] 1. By optimizing the ratio of lime slightly expansive soil, it has controllable slightly expansive characteristics, can still expand slowly after compaction, and actively compensates for the settlement caused by self-weight and traffic loads, effectively reducing the problem of uneven settlement.

[0028] 2. Adopting the construction process of layered filling and dynamic combined compaction enhances the compaction effect and improves the bearing capacity of the subgrade.

[0029] 3. By setting fiber optic displacement sensors in the subgrade to monitor the swelling amount of the subgrade in real time, precise control of the construction process is achieved, potential settlement risks can be pre-warned, and maintenance costs can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flowchart illustrating the construction process of the present invention.

[0031] Figure 2 This is a construction diagram of the present invention. Detailed Implementation

[0032] The technical solutions of various embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0034] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0035] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0036] Example 1

[0037] like Figure 1 , 2 As shown in the figure, this embodiment is a construction method for a high-fill green lime micro-expansion soil embankment subgrade, and the method is as follows:

[0038] S0. Surface clearing: Clear the surface of the roadbed, removing the existing pavement and soil containing turf, household waste, tree roots, humus, and topsoil. S1. Material pretreatment: Prepare slaked lime, sieve it, and add it to the mixing plant along with a micro-expansion agent and micro-expansion soil. The slaked lime is obtained by adding water to quicklime and allowing it to sit for 24 hours, then sieving it through a 5mm sieve. The amount of slaked lime is 4-6% of the weight of the micro-expansion soil. The micro-expansion agent is a sulfoaluminate-based expansion agent, with a dosage of 0.3-0.5% of the weight of the micro-expansion soil. The liquid limit of the micro-expansion soil is ≤40%, the plasticity index is 10-20, and the maximum particle size is ≤2cm.

[0039] S2, Precision Mixing

[0040] Start the mixer and dry mix at 30 r / min for 2 minutes;

[0041] Add water to the mixer to 90% of the optimum moisture content, then mix continuously at 40 r / min for 3 minutes, ensuring a mixing uniformity of ≥95%. After mixing, add water to bring the optimum moisture content to ±1.5%.

[0042] S3, Layered Filling and Pre-expansion Treatment

[0043] Each layer is laid loosely with a thickness of 25cm, with an error of ±2cm. After compaction, it is filled in layers with a thickness of 20cm. After compaction, it is left to stand for 1-2 hours. If the surface micro-cracks are >1.5%, the amount of micro-expansion agent in the next layer is adjusted. S4. Dynamic combined compaction follows the principle of light to heavy, stable to vibratory, and slow to fast, proceeding in the order of initial compaction, intermediate compaction, and final compaction.

[0044] S4-1. Initial compaction: Use a 26T double-drum roller at a speed of 1.5–2.5 km / h for 1–2 passes of static compaction. When there is no superelevation, compact from the outer shoulder towards the center of the road. When there is superelevation, compact from the lower to the higher sections. S4-2. Secondary compaction: Use a 26T vibratory roller at a speed of 2.5–3.5 km / h for 3–4 passes, followed by leveling with a grader. S4-3. Final compaction: After leveling, use a 26T double-drum roller at a speed of 3.0–4.0 km / h for 2–3 passes of final compaction.

[0045] In steps S4-1 to S4-3, during compaction, adjacent compaction strips overlap by 1 / 3 to 1 / 2 of the compaction strip width. Compacting the entire width of the road surface constitutes one pass. S5, Closed Curing

[0046] Cover with a 400g / m² composite geotextile, spray water mist 3 times a day, and maintain for 5-7 days; when the ambient temperature is ≥15℃, the maintenance time is 5 days.

[0047] It also includes real-time measurement and acceptance of the swelling amount, and the specific methods are as follows: Arrange 1 group every 50 mm, embed the fiber displacement sensor in the subgrade, compare the actual settlement of the subgrade with the predicted model, monitor the swelling rate, and when the swelling rate exceeds 1.2%, carry out emergency water replenishment or dosage adjustment; During acceptance, use the sand replacement method to detect each layer of the subgrade filled in layers, and the compaction degree ≥ 94% is qualified; After the final compaction is completed, conduct immersion detection on the subgrade for 4 days, and the CBR value ≥ 8% is qualified. S6. Slope greening protection Cover the subgrade slope with 300 thick planting soil and spray grass seeds to protect the slope.

[0048] Construct and detect according to the above ratio and process. Compared with the traditional method, the quality data are as follows:

[0049]

[0050] As can be seen from the above table, the optimization of the ratio and construction process provided in this embodiment has significantly improved the performance quality of each item of the subgrade.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; And these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing a high embankment green lime micro-expansive soil embankment subgrade, characterized in that, The method is as follows: S1, material pretreatment; Preparation of slaked lime, after sieving, together with micro-expansion agent and micro-expansion soil, is added into a mixer; The slaked lime in step S1 is obtained by adding water to quicklime and aging for 24 hours, and is sieved through a 5mm sieve, and the amount of slaked lime is 4-6% of the weight of micro-expansion soil; the micro-expansion agent is a sulphoaluminate type expansion agent, and the amount is 0.3-0.5% of the weight of micro-expansion soil; the micro-expansion soil has a liquid limit of ≤40%, a plasticity index of 10-20, and a maximum particle size of ≤2cm; S2, accurate mixing; Start the mixer for dry mixing; After pre-adding water to the mixer to reach 90% of the optimum water content, continue mixing, and after mixing, add water to reach the optimum water content ±1.5%; The specific method of step S2 is: Start the mixer, dry mix at a speed of 30r / min for 2min; Pre-adding water to the mixer to reach 90% of the optimum water content, continue mixing at a speed of 40r / min for 3min, and the mixing uniformity is ≥95%, and after mixing, add water to reach the optimum water content ±1.5%; S3, layered filling and pre-expansion treatment; Each layer is filled in layers according to a loose thickness of 25cm, and after compaction, 20cm is performed in layers; and after compaction, stand still, and according to the surface micro-cracks, adjust the amount of micro-expansion agent in the next layer; The error of the loose thickness of 25cm in step S3 is ±2cm; the standing time is 1-2h, and if the surface micro-cracks are >1.5%, adjust the amount of micro-expansion agent in the next layer; S4, dynamic combined compaction; According to the principle of first light then heavy, first stable then vibration, and first slow then fast, sequentially perform primary compaction, secondary compaction, and final compaction; The specific method of step S4 is: S4-1, primary compaction; Use a 26T double steel roller compactor to statically compact 1-2 times at a rolling speed of 1.5-2.5km / h; When the subgrade has no super-high, roll from the outside shoulder to the center; when there is super-high, roll from low to high; S4-2, secondary compaction; Use a 26T vibrating compactor to roll 3-4 times at a rolling speed of 2.5-3.5km / h, and use a grader to level; S4-3, final compaction; After leveling, use a 26T double steel roller compactor to roll 2-3 times at a rolling speed of 3.0-4.0km / h; S5, closed curing; Cover with composite geotextile, spray water mist 3 times a day, and the curing period is 5-7 days; The specification of the composite geotextile in step S5 is 400g / m², when the environmental temperature is ≥15℃, the curing time is 5 days, and further includes real-time measurement of expansion amount and acceptance, the specific method is as follows: According to 1 group per 50mm, bury the optical fiber displacement sensor in the subgrade, compare the actual settlement of the subgrade with the estimated model, and monitor the expansion rate, when the expansion rate exceeds 1.2%, perform emergency water supplement or dosage adjustment; When accepting, detect each layer of the layered filling subgrade by the sand pouring method, and the compaction degree ≥94% is qualified; after the final compaction is completed, immerse the subgrade for 4 days for detection, and the CBR value ≥8% is qualified.

2. The high fill green lime micro-expansive soil fill subgrade construction method according to claim 1, characterized in that, The method further includes table cleaning and slope greening protection, specifically as follows: S1, table cleaning; Clean the surface of the subgrade, remove the surface existing pavement and soil containing grass, household garbage, tree roots, humus, and cultivated soil; S2, slope greening protection; S2, slope greening protection; 3. The high fill green lime micro-expansive soil fill subgrade construction method according to claim 1, characterized in that, In steps S4-1 to S4-3, adjacent rolling zones overlap 1 / 3 to 1 / 2 of the width of the rolling zone, and the full width of the road surface is rolled once.

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