Construction method of high-fill green lime micro-expansive soil fill roadbed

Abstract

The invention discloses a construction method for a high-fill green lime micro-expansive soil fill roadbed. The method comprises the steps of material pretreatment, accurate mixing, layered filling and pre-expansion treatment, dynamic combined compaction and closed maintenance. The proportion of the lime micro-expansive soil is optimized, so that the lime micro-expansive soil has a controllable micro-expansive characteristic and can still slowly expand after being compacted, settlement caused by self weight and traffic load is actively compensated, and the problem of uneven settlement is effectively reduced; the construction technology of layered filling and dynamic combined compaction is adopted, the compaction effect is enhanced, and the bearing capacity of the roadbed is improved; the expansion amount of the roadbed is monitored in real time by arranging the optical fiber displacement sensor in the roadbed, accurate control over the construction process is achieved, the potential settlement risk can be warned in advance, and the maintenance cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of geotechnical engineering and road construction technology, and in particular to a high-fill green lime micro-expansive soil fill roadbed construction method, which is particularly suitable for major projects such as highways, railways, and airport runways that have strict requirements on settlement control. Background Art

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

[0003] 1. Traditional lime soil is usually mixed with ordinary lime and plain soil (lime content is 8%~10%), with an expansion rate of only 0.1%~0.3%, which cannot offset the self-weight settlement of high fill.

[0004] 2. The construction technology is rough, the layered filling thickness is too large (usually ≥50cm), and the rolling technology is single (only static pressure or only vibration compaction), resulting in insufficient compaction (<90%);

[0005] 3. Poor water stability: Conventional methods do not strictly control the moisture content, and it is easy to soften or crack when the moisture content fluctuates by more than ±3%;

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

[0007] 5. Long maintenance cycle: Natural curing requires 7 to 14 days, and the construction period is unpredictable. With the continuous improvement of my country's infrastructure level, infrastructure demand, and the expansion of infrastructure scope, some infrastructure projects have roadbeds located within rice paddies, with fill heights of 8 meters, representing high-fill roadbeds. During the construction of high-fill roadbeds, insufficient soil compaction and poor long-term stability lead to uneven roadbed settlement, damaging the pavement structure, causing serious damage, and endangering road stability.

[0008] Therefore, in response to the above problems, a construction process for high fill roadbed has been developed to solve the problems of uneven settlement, insufficient compaction and poor long-term stability caused by insufficient soil expansibility in traditional high fill roadbed construction. This is a difficult problem that technical personnel in this field continue to solve. Summary of the Invention

[0009] To overcome the deficiencies of the above-mentioned prior art, the present invention provides a high-fill green lime micro-expansive soil fill roadbed construction method. By optimizing the mix ratio and construction process of the lime micro-expansive soil, the present invention solves the problems of uneven settlement, insufficient compaction, and poor long-term stability caused by insufficient soil expansibility in traditional high-fill roadbed construction. At the same time, an optical fiber displacement sensor is installed in the roadbed to monitor the expansion of the roadbed in real time.

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

[0011] A high-fill green lime micro-expansive soil fill roadbed construction method, the method is as follows: S1, pre-treating materials to prepare slaked lime, sieving it, and adding it into a mixer together with a micro-expansive agent and micro-expansive soil;

[0012] S2, precise mixing

[0013] Start the mixer for dry mixing;

[0014] Pre-add water to the mixer to 90% of the optimal moisture content and continue mixing. After mixing, add water to the optimal moisture content ±1.5%;

[0015] S3. Layered filling and pre-expansion treatment

[0016] Each layer is laid with a loose thickness of 25cm and then compacted to 20cm in layers. After compaction, the layer is left to stand and the dosage of the next layer of micro-expansion agent is adjusted according to the surface micro-cracks. S4. Dynamic combined compaction is carried out in sequence of initial compaction, re-compaction and final compaction according to the principle of light first, heavy second, stable first, vibrating second, slow first, fast second. S5. Closed curing

[0017] Cover with composite geotextile, spray water mist 3 times a day, and the maintenance period is 5 to 7 days.

[0018] Furthermore, in step S1, the slaked lime is obtained by adding quicklime and water to the mixture and simmering it for 24 hours, and then passing it through a 5mm sieve, and the amount of slaked lime is 4-6% by weight of the micro-expansive soil; the micro-expansive agent is a sulphoaluminate expansive agent, and the amount of the micro-expansive soil is 0.3-0.5% by weight; the liquid limit of the micro-expansive soil is ≤40%, the plasticity index is 10-20, and the maximum particle size is ≤2cm.

[0019] Furthermore, the specific method of step S2 is: starting the mixer and dry mixing at a speed of 30 r / min for 2 minutes;

[0020] Pre-add water to the mixer to reach 90% of the optimum moisture content, then continue stirring at a speed of 40 r / min for 3 minutes, and the mixing uniformity must be ≥95%. After stirring, add water to the optimum moisture content ±1.5%.

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

[0022] Furthermore, the specific method of step S4 is: S4-1, the initial compaction adopts a 26T double steel wheel roller, static compaction 1 to 2 times at a compaction speed of 1.5 to 2.5 km / h; when the roadbed has no superelevation, compaction is carried out from the outer shoulder to the center of the road; when there is superelevation, compaction is carried out from low to high; S4-2, the re-compaction adopts a 26T vibratory roller, compaction 3 to 4 times at a compaction speed of 2.5 to 3.5 km / h, and leveling is carried out with a grader; S4-3, the final compaction is carried out after leveling, using a 26T double steel wheel roller, compaction 2 to 3 times at a compaction speed of 3.0 to 4.0 km / h.

[0023] Furthermore, the specification of the composite geotextile in step S5 is 400g / m². When the ambient temperature is ≥15°C, the curing time is 5 days, and it also includes real-time measurement and acceptance of the expansion amount. The specific method is as follows: Fiber optic displacement sensors are buried in the roadbed according to the arrangement of one group every 50 mm, and the actual settlement of the roadbed is compared with the estimated model. The expansion rate is monitored, and when the expansion rate exceeds 1.2%, emergency water replenishment or dosage adjustment is carried out; During acceptance, each layer of the layered roadbed is tested by the sand injection method, and the compaction degree is ≥94% to be qualified; After the final compaction is completed, the roadbed is immersed in water for 4 days, and the CBR value is ≥8% to be qualified.

[0024] Furthermore, the method also includes surface clearing and slope greening protection, as follows: S0. Surface clearing: clearing the roadbed area, removing the existing surface road surface and soil containing turf, domestic garbage, tree roots, humus, and cultivated soil; S6. Slope greening protection: covering the roadbed slope with 300mm thick planting soil, and spraying grass to protect the slope.

[0025] Furthermore, during rolling in steps S4-1 to S4-3, adjacent rolling strips overlap by 1 / 3 to 1 / 2 of the rolling strip width, and one rolling is completed when the entire width of the road surface is rolled.

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

[0027] 1. By optimizing the proportion of lime micro-expansive soil, it has controllable micro-expansion characteristics. After compaction, it can still expand slowly, actively compensating for settlement caused by its own weight and traffic load, and effectively reducing the problem of uneven settlement;

[0028] 2. Adopt the construction technology of layered filling and dynamic combined compaction to enhance the compaction effect and improve the bearing capacity of the roadbed;

[0029] 3. By installing fiber optic displacement sensors in the roadbed to monitor the expansion of the roadbed in real time, precise control of the construction process can be achieved, which can provide early warning of potential settlement risks and reduce maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a construction flow chart of the present invention;

[0031] Figure 2 It is a construction schematic diagram of the present invention. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions of various embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0033] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections, or mutual communication; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0034] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

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

[0036] Example 1

[0037] like Figure 1 、 2 As shown, this embodiment is a high fill green lime slightly expansive soil fill roadbed construction method, the method is as follows:

[0038] S0. Surface Clearing: Clear the roadbed area, removing the existing surface pavement and soil containing turf, domestic waste, tree roots, humus, and cultivated soil. S1. Material Pretreatment: Prepare slaked lime, screen it, and add it to a mixer along with a micro-expansive agent and micro-expansive soil. The slaked lime is obtained by simmering quicklime with water for 24 hours, then passing it through a 5mm sieve. The slaked lime content is 4-6% of the micro-expansive soil weight. The micro-expansive agent is a sulphoaluminate-based expansive agent, and its content is 0.3-0.5% of the micro-expansive soil weight. The micro-expansive soil has a liquid limit of ≤40%, a plasticity index of 10-20, and a maximum particle size of ≤2cm.

[0039] S2, precise mixing

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

[0041] Pre-add water to the mixer to reach 90% of the optimum moisture content, then continue stirring at a speed of 40 r / min for 3 minutes, and the mixing uniformity must be ≥95%. After stirring, add water to the optimum moisture content ±1.5%.

[0042] S3. Layered filling and pre-expansion treatment

[0043] Each layer is laid with a loose thickness of 25cm, with an error of ±2cm. After compaction, the filling is carried out in layers of 20cm. After compaction, it is left to stand for 1-2 hours. If the surface micro-cracks are greater than 1.5%, the dosage of the micro-expansion agent in the next layer is adjusted. S4. Dynamic combined compaction is carried out in the principle of light first, heavy second, stable first, vibrating second, and slow first, fast second, with initial compaction, repeated compaction, and final compaction.

[0044] S4-1. Initial compaction: Use a 26T double-steel-wheel roller for static compaction at a speed of 1.5-2.5 km / h for 1-2 passes. If the roadbed has no superelevation, compact from the outer shoulder to the center of the road. If there is superelevation, compact from the lower part to the higher part. S4-2. Secondary compaction: Use a 26T vibratory roller for 3-4 passes at a speed of 2.5-3.5 km / h, and use a motor grader for leveling. S4-3. Final compaction: After leveling, use a 26T double-steel-wheel roller for 2-3 passes at a speed of 3.0-4.0 km / h.

[0045] During rolling in steps S4-1 to S4-3, adjacent rolling strips overlap by 1 / 3 to 1 / 2 of the rolling strip width. When the full width of the road surface is rolled, it is considered one pass. S5. Closed maintenance

[0046] Cover with composite geotextile with specification of 400g / m², spray water mist 3 times a day, and the curing period is 5 to 7 days; when the ambient temperature is ≥15℃, the curing time is 5 days;

[0047] This also includes real-time expansion measurement and acceptance testing. The specific method is as follows: Fiber optic displacement sensors are buried in the roadbed, with one sensor per 50 mm. The actual settlement of the roadbed is compared with the estimated model to monitor the expansion rate. When the expansion rate exceeds 1.2%, emergency water replenishment or dosage adjustment is implemented. During acceptance, each layer of the layered roadbed is tested using the sand injection method, and a compaction degree of ≥94% is considered acceptable. After final compaction, the roadbed is immersed in water for four days, and a CBR value of ≥8% is considered acceptable. S6. Slope Greening Protection: The roadbed slopes are covered with 300mm thick planting soil and sprayed with grass for slope protection.

[0048] Construction and testing were carried out according to the above ratio and process. The quality data were compared with those of traditional methods as follows:

[0049]

[0050] As can be seen from the above table, the optimization of the mix ratio and construction process provided by this embodiment has significantly improved the performance and quality of the roadbed.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A high fill green lime slightly expansive soil fill roadbed construction method, characterized in that, The method is as follows: S1. Pre-treat the materials to prepare slaked lime, sieve it and add it into the mixer together with the micro-expansion agent and micro-expansion soil; S2, precise mixing Start the mixer for dry mixing; Pre-add water to the mixer to 90% of the optimal moisture content and continue mixing. After mixing, add water to the optimal moisture content ±1.5%; S3. Layered filling and pre-expansion treatment Each layer is laid with a loose thickness of 25cm and then compacted to 20cm in layers. After compaction, the layer is left to stand and the dosage of the next layer of micro-expansion agent is adjusted according to the surface micro-cracks. S4. Dynamic combined compaction is carried out in sequence of initial compaction, re-compaction and final compaction according to the principle of light first, heavy second, stable first, vibrating second, slow first, fast second. S5. Closed curing Cover with composite geotextile, spray water mist 3 times a day, and the maintenance period is 5 to 7 days.

2. A high fill green lime micro-expansive soil fill roadbed construction method according to claim 1, characterized in that, In step S1, the slaked lime is prepared by adding quicklime and water to the mixture, simmering the mixture for 24 hours, and passing the mixture through a 5 mm sieve. The slaked lime is added in an amount of 4 to 6% by weight of the micro-expansive soil. The micro-expansive agent is a sulphoaluminate expansive agent, and the amount thereof is 0.3 to 0.5% by weight of the micro-expansive soil. The liquid limit of the micro-expansive soil is ≤40%, the plasticity index is 10 to 20, and the maximum particle size is ≤2 cm.

3. A high fill green lime micro-expansive soil fill roadbed construction method according to claim 1, characterized in that, The specific method of step S2 is: starting the mixer and dry mixing at a speed of 30 r / min for 2 minutes; Pre-add water to the mixer to reach 90% of the optimum moisture content, then continue stirring at a speed of 40 r / min for 3 minutes, and the mixing uniformity must be ≥95%. After stirring, add water to the optimum moisture content ±1.5%.

4. A high fill green lime micro-expansive soil fill roadbed construction method according to claim 1, characterized in that, The error of the loose laying thickness of 25 cm in step S3 is ±2 cm; the static time is 1 to 2 hours, and if the surface microcracks are greater than 1.5%, the dosage of the next layer of micro-expansion agent is adjusted.

5. A high fill green lime micro-expansive soil fill roadbed construction method according to claim 1, characterized in that, The specific method of step S4 is: S4-1, the initial compaction adopts a 26T double steel wheel roller, static compaction 1 to 2 times at a compaction speed of 1.5 to 2.5 km / h; when the roadbed has no superelevation, compaction is carried out from the outer shoulder to the center of the road; when there is superelevation, compaction is carried out from low to high; S4-2, the re-compacting adopts a 26T vibratory roller, compaction 3 to 4 times at a compaction speed of 2.5 to 3.5 km / h, and leveling is carried out with a grader; S4-3, the final compaction is carried out after leveling, using a 26T double steel wheel roller, compaction 2 to 3 times at a compaction speed of 3.0 to 4.0 km / h.

6. A high fill green lime slightly expansive soil fill roadbed construction method according to claim 1, characterized in that: The specification of the composite geotextile in step S5 is 400g / m². When the ambient temperature is ≥15°C, the curing time is 5 days, and it also includes real-time measurement and acceptance of the expansion amount. The specific method is as follows: Arrange one group every 50mm, bury the optical fiber displacement sensor in the roadbed, compare the actual settlement of the roadbed with the estimated model, monitor the expansion rate, and when the expansion rate exceeds 1.2%, perform emergency water replenishment or adjust the dosage; During acceptance, each layer of the layered roadbed is tested by sand injection method, and the compaction degree is ≥94% to be qualified; After the final compaction is completed, the roadbed is immersed in water for 4 days, and the CBR value is ≥8% to be qualified.

7. A high fill green lime slightly expansive soil fill roadbed construction method according to claim 1, characterized in that: The method also includes surface clearing and slope greening protection, as follows: S0. Surface clearing: clear the roadbed area, remove the existing surface road surface and soil containing turf, domestic garbage, tree roots, humus, and cultivated soil; S6. Slope greening protection: cover the roadbed slope with 300mm thick planting soil, and spray plant grass to protect the slope.

8. A high fill green lime slightly expansive soil fill roadbed construction method according to claim 5, characterized in that: During rolling in steps S4-1 to S4-3, adjacent rolling strips overlap by 1 / 3 to 1 / 2 of the rolling strip width, and one pass of rolling is completed when the entire width of the road surface is rolled.

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