Roadbed construction method of expressway

Abstract

The invention relates to the technical field of expressway construction, and particularly discloses an expressway roadbed construction method, which comprises the following steps: S1, paving a filling material on a base construction surface, enabling the height of a paved sand layer to be more than 40cm, and roughly leveling the sand layer; s2, water is sprayed to the sand layer subjected to rough leveling, it is ensured that the water content of the surface of the sand layer is 8%-12% after water spraying, and the sand layer is leveled; s3, standing for 1-2 hours to enable the water content of the whole sand layer to be close to 4.5%; s4, a claw roller is adopted for rolling; and S5, the sand layer is leveled again, and then the sand layer is rolled through a rubber wheel roller. The number of paving layers in the roadbed layered filling process is reduced by increasing the original paving thickness of 40 cm to 40 cm or above, so that the construction effect is improved, and the compaction degree problem under the paving thickness of 40 cm or above is solved.

Description

Technical Field

[0001] The invention relates to the technical field of highway construction, and in particular to a highway roadbed construction method. Background Art

[0002] Roadbed: Roadbed is the foundation of track or road surface, formed by excavation or filling. Its main function is to provide necessary conditions for track or road surface laying and train or vehicle operation, and to bear the static and dynamic loads of track and locomotive vehicles or road surface and traffic loads, and at the same time transmit and diffuse these loads deep into the foundation. In civil engineering, roadbed occupies an important position in terms of construction quantity, land area and investment.

[0003] Classification of roadbed: There are two basic forms of roadbed according to the terrain conditions: embankment and cutting. Embankment is the roadbed formed by filling, while cutting is the roadbed formed by excavation. In addition, roadbed can also be classified according to dry and wet types, including dry, medium wet, wet and overly wet.

[0004] In the highway structure, the roadbed refers to the foundation part of the road. It plays a very important role in road construction. It can increase the stability of the road surface, improve the bearing capacity of the road, and prevent the road surface from settling and deforming. When the backfill roadbed is filled with sand, due to various factors, a large settlement will occur after the construction is completed, which is more serious after operation. Various roadbed diseases will appear, which will bring great difficulties to line maintenance and even affect driving safety.

[0005] In the current highway roadbed construction, if the filling height is too high, layered filling is required to ensure the roadbed quality. On this basis, in order to ensure the compaction requirements of the roadbed, the construction often takes time and the loose laying thickness is often 40cm. If the loose laying thickness is greater than 40cm, there will be a problem of insufficient compaction. Although the loose laying thickness of 40cm can ensure the compaction, it requires too many loose laying layers and the efficiency is not high.

[0006] The existing sand backfill embankment rolling technology has the following shortcomings: 1. The initial compaction is carried out by a bulldozer, which causes great wear and tear on the bulldozer.

[0007] 2. When using a vibratory roller, the number of times of rolling is generally 8-10 times, and the rolling time is too long. For each process of roadbed filling, the rolling time accounts for too large a proportion, which is not conducive to progress control.

[0008] 3. When using a vibratory roller, the loose paving thickness is generally limited to 40cm. When it reaches 50cm, the number of rolling times is generally 10-12 times, and the density pass rate cannot be guaranteed in one time.

[0009] 4. During the rolling process of the vibratory roller, the sand will be pushed away, destroying the overall integrity of the sand, which is not conducive to improving the compaction degree. Summary of the invention

[0010] The purpose of the present invention is to provide a highway roadbed construction method, which reduces the number of paving layers in the roadbed layered filling process by increasing the original 40cm paving thickness to more than 40cm, thereby increasing the construction effect and solving the compaction problem under 50cm paving thickness.

[0011] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for constructing a highway subgrade comprises the following steps: Step S1: Spreading filling materials on the base construction surface, the height of the spread sand layer is more than 40 cm, and rough leveling of the sand layer is performed; Step S2: Sprinkle water on the roughly leveled sand layer, ensure that the water content of the surface of the sand layer is 8% to 12% after sprinkling water, and level the sand layer; Step S3: let it stand for 1-2 hours until the water content of the entire sand layer is close to 4.5%; Step S4: rolling with a sheep horn roller; Step S5: leveling the sand layer again, and then rolling the sand layer with a rubber-wheel roller.

[0012] Preferably, the height of the sand layer is 50 cm.

[0013] Preferably, in step S1, rough leveling is performed using a bulldozer, and the requirements for rough leveling are that the center of the sand layer is low, the roadside of the sand layer is high, and the slope of the cross slope is less than 2%.

[0014] Preferably, in step S2, the surface moisture content of the sand layer is 10%.

[0015] Preferably, in step S4, the number of rolling passes of the sheep horn roller is three, the overlapping width of the rolling tracks is not less than 1 / 3, and the rolling speed of the sheep horn roller is 2-4 km / h.

[0016] Preferably, in step S5, the rubber-wheel roller performs three rolling passes.

[0017] Furthermore, the method further comprises step S4.1: detecting the surface of the sand layer, and if the surface of the sand layer is dry, watering the surface of the sand layer by spraying water with a watering truck, and waiting for 15 minutes with a rubber-wheel roller, and then proceeding to step S5.

[0018] Preferably, in step S4 and step S5, the requirements for rolling by the ram-horn roller and the rubber-wheel roller are: when rolling, the straight segments are rolled from both sides to the middle, and the curved segments are rolled from the inside to the outside, in a longitudinal forward and backward manner.

[0019] Preferably, the ram-horn roller is a 20t ram-horn roller, and the rubber-wheel roller is a 14t rubber-wheel roller.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The thickness of the sand layer after paving and rough leveling is 40 cm or more. The paved sand layer is rolled with a ram horn roller and a rubber wheel roller. By increasing the thickness of the sand layer, the number of layers required to be paved during the roadbed filling process is reduced. Reducing the number of paving layers can improve the overall construction efficiency. However, the compaction degree of the paving thickness above 40 cm is insufficient under conventional construction. The rolling method of the ram horn roller and the rubber wheel roller adopted in the present invention can ensure the compaction degree.

[0021] 2. After rough leveling, sprinkle water on the sand layer to ensure that the water content of the surface of the sand layer is 8% to 12%. When it exceeds 12%, a spring phenomenon will occur. When it is lower than 8%, it cannot penetrate into the bottom layer of sand, causing the sand to be loose and unable to be compacted. Then, after standing for 1-2 hours, the water content of the entire layer of sand can be close to the optimal water content of 4.5%. After reaching the optimal water content, the subsequent rolling effect is the best.

[0022] 3. The mechanical combination mode of the ram horn roller and the rubber wheel roller reduces the original rolling times from 8-10 times to 6 times, with the ram horn roller rolling 3 times and the rubber wheel roller rolling 3 times. The rolling time is greatly reduced and the construction progress is accelerated. It also avoids the extrusion and displacement of sand materials caused by the vibrating roller during the construction process, and the density of sand backfill is significantly improved, ensuring the first-time pass rate of the test and avoiding secondary rolling.

[0023] 4. Control the rolling speed of the Yangjiao roller at 2-4km / h. During construction, the rolling speed is one of the important factors that determine the area productivity of the roller. The faster the rolling speed, the higher the operating efficiency. However, under the same number of times, the faster the speed, the lower the compaction degree. When rolling 3 times, if the rolling speed is 2-4km / h, the compaction degree can reach 95%, and if the rolling speed is 5km / h, the compaction degree can reach 91%. Choosing rolling 3 times and a rolling speed of 2-4km / h can ensure both the rolling speed and the compaction degree. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below so as to provide a further understanding of the concept of the present invention, the technical problems solved, the technical features constituting the technical solutions and the technical effects brought about.

[0025] A method for constructing a highway subgrade comprises the following steps: Step S1: Spreading the filling material on the base construction surface, and roughly leveling the sand layer after paving, wherein the height of the roughly leveled sand layer is more than 40 cm; Step S2: Sprinkle water on the roughly leveled sand layer, ensure that the water content of the surface of the sand layer is 8% to 12% after sprinkling water, and level the sand layer; Step S3: let it stand for 1-2 hours until the water content of the entire sand layer is close to 4.5%; Step S4: rolling with a sheep horn roller; Step S5: leveling the sand layer again, and then rolling the sand layer with a rubber-wheel roller.

[0026] Preferably, the height of the sand layer is 50 cm.

[0027] Preferably, in step S1, rough leveling is performed using a bulldozer, and the requirements for rough leveling are that the center of the sand layer is low, the roadside of the sand layer is high, and the slope of the cross slope is less than 2%.

[0028] Preferably, in step S2, the water content on the surface of the sand layer is 10%.

[0029] Preferably, in step S4, the number of rolling passes of the sheep horn roller is three, the overlapping width of the rolling tracks is not less than 1 / 3, and the rolling speed of the sheep horn roller is 2-4 km / h.

[0030] Preferably, in step S5, the rubber-wheel roller performs three rolling passes.

[0031] Furthermore, the method further comprises step S4.1: detecting the surface of the sand layer, and if the surface of the sand layer is dry, watering the surface of the sand layer by spraying water with a watering truck, and waiting for 15 minutes with a rubber-wheel roller, and then proceeding to step S5.

[0032] Preferably, in step S4 and step S5, the requirements for rolling by the ram-horn roller and the rubber-wheel roller are: when rolling, the straight segments are rolled from both sides to the middle, and the curved segments are rolled from the inside to the outside, in a longitudinal forward and backward manner.

[0033] Preferably, the ram-horn roller is a 20t ram-horn roller, and the rubber-wheel roller is a 14t rubber-wheel roller.

[0034] Backfilling the roadbed is a key construction step in road construction, involving the excavation and backfilling of earth and stone. Due to the different geological and topographical conditions around the world, the selection of materials, construction equipment, and the construction sequence of construction equipment for embankment backfilling should be adapted to local conditions. According to the technical specifications of local roadbed construction, the local materials that may be used for embankment filling are studied and tested. While meeting the quality standards, the appropriate earth and stone materials are selected for embankment filling construction in combination with economy, construction convenience, and environmental protection.

[0035] Sand: refers to fine stone particles, usually granules with a particle size of 0.074 to 2 mm that are formed by weathering of rocks, washing with rainwater or rolling from rocks. There are many types of sand, including river sand, sea sand, metal sand, etc. It is widely used in construction, concrete, cementitious materials, road construction materials, etc. The present invention investigates and tests the materials that can be used for embankment filling in the Belgrade area of ​​Serbia. The river sand of the Danube River was selected as the material for embankment filling, and based on the experimental parameters of the river sand, the equipment type selection and construction sequence for embankment filling construction were studied, which greatly accelerated the construction progress of the project embankment filling. The experimental parameters of the river sand of the Danube River are shown in the following table: Particle size content (0.06mm--2.0mm) Optimum moisture content (%) Maximum density (g / cm³) Natural moisture content (%) ＞95% 18 1.6 8 The embankment filling materials of highway projects must meet the quality specifications for the optimum moisture content of less than 25%, liquid limit less than 65%, plastic limit less than 30%, and organic matter content less than 6%. According to experiments, the liquid limit of soil used in the borrow field is 65%~68%. If it does not meet the filling requirements, the cost of using lime-mixed soil is high and the construction progress is slow. According to experiments, the Danube River sand meets the above parameters and can be used for embankment filling construction.

[0036] At present, the existing technology mainly uses vibratory rollers for rolling of sand backfill roadbed. The bulldozer is used for rough leveling and fine leveling with the grader. The bulldozer is used as the initial compaction equipment for the sand-filled roadbed. During the initial compaction, the general earthwork compaction process is followed, and the wheel rolling is carried out from the edge of the roadbed to the inside. The overlapping width of the wheel tracks during rolling is not less than 1 / 2 of the wheel width. The wheel tracks cover one working surface for one time, and the rolling is repeated twice. After that, a vibratory roller of more than 20 tons is used for rolling. The number of rolling times is 6-8 times. The overlapping width of the wheel tracks during rolling should not be less than 1 / 3. The wheel tracks cover one working surface for one time. When rolling, it is slow at first and then fast, with high frequency and low vibration. The rolling speed does not exceed 4km / h. When rolling, the straight section is from both sides to the middle, and the curved section is from the inside to the outside, and the longitudinal advance and retreat is carried out. The longitudinal overlap of the front and rear adjacent sections is more than 2m to ensure that there is no leakage, no dead angle, and the rolling is uniform. The final compaction is performed by static compaction with a vibratory roller for 1-2 times. A small rammer is used to add pressure to the areas on the edge of the roadbed that the roller cannot reach.

[0037] The present invention uses a dump truck to evenly unload materials on the prepared base construction surface, that is, to spread the filling materials. During the construction, a bulldozer is used to spread and rough-level the road with the center of the road low, the road side high, and the cross slope controlled at about 2%. The shape of the sand layer after paving is a "pot bottom shape". The thickness of the sand layer after paving and rough-leveling is based on 50cm as the standard. Then the sand layer is sprinkled with water in an appropriate amount. After sprinkling, ensure that the water content of the surface of the sand layer is 8% to 12%. When it exceeds 12%, a spring phenomenon will occur. When it is lower than 8%, it cannot penetrate into the bottom sand, causing the sand to be loose and unable to be compacted. The spring phenomenon refers to the fact that when the roadbed soil is rolled, the compressed part sinks, the surrounding area bounces up, and shakes up and down like a spring. The roadbed soil forms a soft plastic state, the volume is not compressed, and the compaction degree does not meet the specified requirements. After the watering is completed, the sand layer is leveled with a grader. After the grader is finished, the permeability of the sand is used to stand for 1-2 hours. At this time, the moisture content of the entire layer of sand is close to the optimal moisture content of 4.5%, and then it is rolled. The rolling process is to first use a sheep horn roller to vibrate and roll it with strong vibration, and roll it three times for one round trip. After the rolling is completed, the sand surface is uneven, and it is leveled by the grader, and then it is rolled three times with a rubber wheel roller. The rolling speed of the Yangjiao roller is controlled at 2-4km / h. During construction, the rolling speed is one of the important factors that determine the area productivity of the roller. The faster the rolling speed, the higher the operating efficiency. However, under the same number of times, the faster the speed, the smaller the compaction degree. When rolling 3 times, if the rolling speed is 2-4km / h, the compaction degree can reach 95%. If the rolling speed is 5km / h, the compaction degree can reach 91%. In order to achieve the same compaction degree, the higher the rolling speed, the more rolling times are required. After test comparison, based on qualified quality, the maximum economical rolling speed is 2-4km / h.

[0038] When rolling, the straight section is rolled from both sides to the middle, and the curved section is rolled from the inside to the outside, in a longitudinal forward and backward manner. The front and rear adjacent sections overlap longitudinally by more than 2m to ensure no leakage, no dead angle, and uniform rolling.

[0039] Through backfilling with a thickness of 50 cm per layer, quantitative watering, and rolling with a 20t horn roller for 3 times and a 14t rubber wheel roller for 3 times; the compaction degree of each layer met the test requirements at one time, with a 100% pass rate at one time, which effectively guaranteed the construction progress and saved construction costs.

[0040] The terms “connection” and “fixation” mentioned in the description of the present invention may refer to fixed connection, processing and forming, welding or mechanical connection. The specific meanings of the above terms in the present invention shall be understood according to the specific circumstances.

[0041] In the description of the present invention, the terms "center", "upper", "lower", "horizontal", "inside", "outside", etc., which indicate the orientation or position relationship, are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying a specific orientation that the device or element referred to must have, and therefore cannot be understood as a limitation on the present invention.

[0042] 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 the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing a highway subgrade, characterized in that: The following steps are involved: Step S1: Spreading filling materials on the base construction surface, the height of the spread sand layer is more than 40 cm, and rough leveling of the sand layer is performed; Step S2: Sprinkle water on the roughly leveled sand layer, ensure that the water content of the surface of the sand layer is 8% to 12% after sprinkling water, and level the sand layer; Step S3: let it stand for 1-2 hours until the water content of the entire sand layer is close to 4.5%; Step S4: rolling with a sheep horn roller; Step S5: leveling the sand layer again, and then rolling the sand layer with a rubber-wheel roller.

2. A highway roadbed construction method according to claim 1, characterized in that: The height of the sand layer is 50 cm.

3. A highway roadbed construction method according to claim 1, characterized in that: In step S1, rough leveling is performed by a bulldozer, and the requirements for rough leveling are that the center of the sand layer is low, the roadside of the sand layer is high, and the slope of the cross slope is less than 2%.

4. A highway roadbed construction method according to claim 1, characterized in that: In step S2, the surface moisture content of the sand layer is 10%.

5. The method for constructing a highway subgrade according to claim 1, characterized in that: In the step S4, the number of rolling passes of the sheep horn roller is three, the overlapping width of the rolling track is not less than 1 / 3, and the rolling speed of the sheep horn roller is 2-4 km / h.

6. A highway roadbed construction method according to claim 1, characterized in that: In step S5, the rubber-wheeled roller performs three rolling passes.

7. A highway roadbed construction method according to claim 1, characterized in that: The method further includes step S4.1: detecting the surface of the sand layer, and if the surface of the sand layer is dry, watering the surface of the sand layer by spraying water with a watering truck, and waiting for 15 minutes with a rubber-wheel roller, and then continuing to step S5.

8. A highway roadbed construction method according to claim 1, characterized in that: In step S4 and step S5, the requirements for rolling by the ram-horn roller and the rubber-wheel roller are: when rolling, the straight segments are rolled from both sides to the middle, and the curved segments are rolled from the inside to the outside, in a longitudinal forward and backward manner.

9. A highway roadbed construction method according to claim 1, characterized in that: The ram-horn roller is a 20t ram-horn roller, and the rubber-wheel roller is a 14t rubber-wheel roller.