A granite residual soil roadbed structure and construction method thereof

Abstract

A granite residual soil roadbed structure and a construction method thereof, belonging to the field of environmental protection technology. It includes five parts: a bottom isolation layer, a granite residual soil filling area, a geocell protection area, a strength compensation layer and a pavement structure layer. The bottom of the granite residual soil filling area is a bottom isolation layer, and the two sides of the granite residual soil filling area are geocell protection areas respectively. The geocell protection area includes a left geocell slope protection area and a right geocell slope protection area. The top of the granite residual soil filling area is a strength compensation layer and a pavement structure layer. The subbase and base of the pavement structure layer are cement-stabilized gravel layers, and the subbase and base are full-width paved structures. There is a closed central dividing strip on the pavement structure layer. The present invention effectively prevents rainfall runoff from eroding the granite residual soil slope, prevents water from infiltrating the granite residual soil roadbed, ensures the humidity stability of the granite residual soil filling area, and ensures the long-term performance stability of the granite residual soil roadbed. The construction is more convenient and the cost is low.

Description

Technical Field

[0001] The invention relates to a granite residual soil roadbed structure and a construction method thereof, belonging to the technical field of environmental protection. Background Art

[0002] Granite residual soil is a special rock with complex engineering characteristics. It has high natural water content, high liquid limit, poor water stability, and is easy to soften and disintegrate when soaked in water, or even muddy. However, it has a high content of coarse-grained groups and is prone to slope erosion. It is widely distributed in Guangdong, Fujian, Hainan and other places in my country. Since its liquid limit is generally greater than 50%, it is mistakenly treated as high liquid limit soil, resulting in serious erosion and damage to the slopes of many granite residual soil roadbeds. In the early stage of high-grade highway construction in my country, it was mostly abandoned or completely modified, which had poor environmental protection and caused a significant increase in engineering costs. However, with the large-scale construction of highways in rainy granite residual soil areas, the research and engineering application of granite residual soil are increasing. Studies have shown that the CBR strength of granite residual soil is high, mostly above 10%, which fully meets the requirements of the current "Highway Roadbed Design Code" for roadbed filling, and is in good condition. However, granite residual soil as roadbed filling has the main problems of high natural water content, difficulty in drying, soft coarse-grained group rock, poor water stability, and easy slope erosion, making it unsuitable as roadbed filling. However, the current highway pavement structures in granite distribution areas such as Guangdong and Fujian mostly adopt closed central median asphalt concrete structures, which effectively avoids the adverse effects of central median and pavement seepage on the roadbed. As a new type of high-strength three-dimensional geosynthetics, geocells have good durability, integrity and erosion resistance, faster construction, excellent facade reinforcement effect, and better greening effect. Geocell protection can realize the simultaneous construction of granite residual soil roadbed slopes with filling and protection, effectively avoiding slope erosion damage. Therefore, the design of granite residual soil roadbed type should be comprehensively determined based on the pavement structure, central median drainage, and the excellence of various protection measures. Summary of the invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides a granite residual soil roadbed structure and a construction method thereof.

[0004] A granite residual soil roadbed structure comprises five parts, namely a bottom isolation layer, a granite residual soil filling area, a geocell protection area, a strength compensation layer and a pavement structure layer. The bottom of the granite residual soil filling area is a bottom isolation layer, the two sides of the granite residual soil filling area are geocell protection areas respectively, the geocell protection area comprises a left geocell slope protection and a right geocell slope protection, the top of the granite residual soil filling area is a strength compensation layer and a pavement structure layer, the subbase and base layer of the pavement structure layer are cement stabilized crushed stone layers, and the subbase and base layer are a full-width paved structure.

[0005] The top of the bottom isolation layer is filled with granite residual soil, and the loose thickness of each layer of granite residual soil is less than 30cm.

[0006] The left geocell slope protection and the right geocell slope protection are composed of geocells respectively. The geogrid is made of high-strength HDPE or PP copolymer wide bands, which are strongly welded or riveted to form a mesh cell structure. The copolymer wide bands are perforated, and the geocells are stretched to form an inner cavity space. The surrounding walls of the geocells are fixed to the ground with U-shaped nails.

[0007] The subbase and base of the pavement structure layer are cement-stabilized gravel layers. The subbase and base are full-width paved structures, and there is a closed central dividing strip on the pavement structure layer.

[0008] A construction method for a granite residual soil roadbed structure comprises the following steps:

[0009] Before filling the granite residual soil roadbed, verify its distribution and quantity and determine a reasonable roadbed soil and stone allocation plan.

[0010] Secondly, typical granite residual soil was selected for geotechnical tests such as moisture content, compaction, liquid limit, plastic limit, screening, CBR, etc., to determine the natural moisture content, optimum moisture content, maximum dry density, liquid limit, plastic limit, particle grading and CBR of the granite residual soil, and draw the relationship curve between CBR and moisture content. According to the control standard of CBR of the granite residual soil filling site, the rolling moisture content range of the granite residual soil in each part was determined respectively.

[0011] A typical fill roadbed construction site was selected to pave a test section of granite residual soil roadbed, the drying method and drying rate of the granite residual soil were determined, and the mechanical combination, compaction machinery specifications, loose paving thickness, number of rolling times, rolling speed and compaction quality control standard construction process parameters of the granite residual soil roadbed were summarized.

[0012] Strength compensation layers of different thicknesses are paved in the test section of the granite residual soil roadbed, and the thickness of the strength compensation layer can be controlled and determined based on the deflection value of the top surface of the strength compensation layer; before large-scale construction of granite residual soil, construction measurement and layout are carried out, and the surface is cleared and compacted according to design requirements.

[0013] It also contains the following steps:

[0014] A layer of crushed stone soil, gravel soil, quarrying slag and other materials with large porosity and good water stability with a thickness of not less than 50cm is filled on the surface after clearing and compaction. The first layer of granite residual soil is loaded on it. The loose thickness of the granite residual soil is controlled by drawing gray grids and hanging lines. After loading, the bulldozer is used for rough leveling and the grader is used for fine leveling. The test section is rolled and tested according to the construction technology and compaction standards determined. After meeting the compaction standards, the second layer of granite residual soil roadbed is loaded, spread, leveled, rolled and tested.

[0015] After that, the third, fourth and Nth layers of granite residual soil will be loaded, spread, leveled, rolled and tested in turn.

[0016] The slope surface is shaped every 2m of granite residual soil, and geocell protection is laid in time until the granite residual soil is filled to the designed elevation of the bottom surface of the strength compensation layer.

[0017] The first layer of strength compensation layer is loaded, spread, leveled and rolled above the granite residual soil filling area until it is rolled layer by layer to the top surface elevation of the strength compensation layer in accordance with relevant specifications, and the roadbed is handed over for acceptance.

[0018] Finally, the pavement structure layer is paved. Before the pavement structure layer is paved, the granite residual soil roadbed must experience at least one complete rainy season or a 6-month natural settlement stabilization period.

[0019] The advantages of the present invention are: the roadbed structure of the present invention can maximize the use of granite residual soil to fill the roadbed, and can avoid the erosion of the granite residual soil slope. The bottom isolation layer 2 of the granite residual soil roadbed structure can prevent the migration of water caused by the rise of groundwater level or capillary water to the granite residual soil filling area 3, and can increase the stability of the roadbed. The geocell protection area can prevent the slope runoff from eroding the slope under rainfall conditions, and improve the embankment stability of the granite residual soil slope. The cast-in-place or precast concrete guardrail closed central dividing strip 7 can prevent the water in the middle dividing strip from infiltrating the roadbed, and prevent the uneven settlement deformation and strength attenuation of the granite residual soil roadbed. The strength compensation layer can ensure that the roadbed has sufficient structural strength and provide a bearing foundation for the pavement structure layer.

[0020] The granite residual soil roadbed structure of the present invention can effectively prevent rainfall runoff from eroding the granite residual soil slope, prevent water from infiltrating the granite residual soil roadbed, ensure the humidity stability of the granite residual soil filling area 3, ensure the long-term performance stability of the granite residual soil roadbed, make the construction more convenient, and have a low cost, and can maximize the use of the granite residual soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] When considered in conjunction with the accompanying drawings, the present invention can be more completely and better understood and many of the accompanying advantages can be easily known by referring to the detailed description below, but the drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention, as shown in the figure:

[0022] Figure 1 It is a schematic diagram of the granite residual soil roadbed structure of the present invention.

[0023] Figure 2It is a schematic diagram of the construction process of the granite residual soil roadbed structure of the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0025] Obviously, many modifications and changes made by those skilled in the art based on the purpose of the present invention belong to the protection scope of the present invention.

[0026] It will be understood by those skilled in the art that, unless expressly stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when an element or component is said to be "connected" to another element or component, it may be directly connected to the other element or component, or there may be an intermediate element or component. The term "and / or" used herein includes any unit and all combinations of one or more associated listed items.

[0027] It should 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 generally understood by those skilled in the art.

[0028] To facilitate the understanding of the embodiments, further explanations will be given below, and each embodiment does not constitute a limitation of the present invention.

[0029] Example 1: Figure 1 As shown, a granite residual soil roadbed structure includes five parts: a bottom isolation layer 2, a granite residual soil filling area 3, a geocell protection area, a strength compensation layer 5 and a pavement structure layer 6.

[0030] The bottom of the granite residual soil filling area 3 is the bottom isolation layer 2. The original surface 1 is cleared and compacted before the bottom isolation layer 2 is filled. The granite residual soil is filled on the top of the bottom isolation layer 2. The loose thickness of each layer of granite residual soil does not exceed 30 cm until it is filled to the design elevation of the bottom surface of the strength compensation layer 5; the strength compensation layer 5 is filled above the granite residual soil filling area 3, and finally an asphalt concrete pavement is laid above the strength compensation layer 5. The two sides of the granite residual soil filling area 3 are geocell protection areas respectively. The geocell protection area includes a left geocell slope protection area 4 and a right geocell slope protection area 8. There is a closed central dividing strip 7 on the pavement structure layer 6. The top of the granite residual soil filling area 3 is the strength compensation layer 5 and the pavement structure layer 6.

[0031] The left geocell slope protection 4 and the right geocell slope protection 8 are respectively composed of geocells, the peripheral walls of the geocells are arranged with holes, the peripheral walls between the geocells are connected to each other, the geocells are stretched to form an inner cavity space, and the peripheral walls of the geocells are fixed to the ground surface 1 with U-shaped nails.

[0032] Example 2: Figure 1 and Figure 2 As shown in the figure, a granite residual soil roadbed structure and construction method are aimed at solving the problem of rational utilization of granite residual soil as roadbed filling material. By comprehensively considering rainfall, roadbed and pavement drainage, pavement structure and slope protection measures, a more scientific, more convenient construction, higher utilization rate, and the ability to avoid slope erosion and ensure long-term stability of roadbed performance are proposed.

[0033] The present invention provides a granite residual soil roadbed structure, such as Figure 1 And shown in Example 1.

[0034] The granite residual soil filling part in the granite residual soil roadbed structure is the area between the bottom isolation layer 2 and the strength compensation layer 5. The filling height does not exceed 15m, and the slope is 1:1.5 to 1:1.75.

[0035] The filler of strength compensation layer 5 can be improved granite residual soil such as cement and lime, or coarse-grained soil with good water stability such as crushed stone soil, gravel soil, and mountain slag. The thickness of strength compensation layer 5 shall not be less than 50cm, which can be determined through test sections according to the representative value of design deflection, the filler of strength compensation layer 5, etc.

[0036] The central dividing strip on the pavement structure layer 6 of the asphalt concrete pavement is a closed central dividing strip 7 of cast-in-place or precast concrete guardrail.

[0037] The subbase and base of the pavement structure layer are cement-stabilized gravel layers, and are a full-width paved structure.

[0038] The bottom isolation layer 2 is a crushed stone soil, gravel soil or mountain slag filling layer with a filling thickness of not less than (greater than) 50 cm. The crushed stone in the crushed stone soil, gravel soil, mountain slag, etc. is a hard, medium-hard stone with good water stability.

[0039] The geocell protection area is a granite residual soil roadbed slope surface fully paved with geocells, anchored by hook-shaped rivet piles or U-shaped steel bars with a fixed spacing of about 1m; the cell space is filled with planting soil.

[0040] The geocell protection area is constructed simultaneously with the granite residual soil roadbed, so that protection can be achieved as the filling is completed, thus avoiding erosion and damage to the granite residual soil slope.

[0041] Example 3: Figure 2As shown, a granite residual soil roadbed structure and construction method comprises the following steps:

[0042] Before filling the granite residual soil roadbed, verify its distribution and quantity and determine a reasonable roadbed soil and stone allocation plan.

[0043] Secondly, typical granite residual soil was selected for geotechnical tests such as moisture content, compaction, liquid limit, plastic limit, screening, CBR, etc., to determine the natural moisture content, optimum moisture content, maximum dry density, liquid limit, plastic limit, particle grading and CBR of the granite residual soil, and draw the relationship curve between CBR and moisture content. According to the control standard of CBR of the granite residual soil filling site, the rolling moisture content range of the granite residual soil in each part was determined respectively; typical fill roadbed construction sites were selected to pave the granite residual soil roadbed test section, the drying method and drying rate of the granite residual soil were determined, and the construction process parameters such as the mechanical combination of granite residual soil roadbed, compaction machinery specifications, loose paving thickness, number of rolling times, rolling speed and compaction quality control standards were summarized.

[0044] Strength compensation layers 5 of different thicknesses are paved in the test section of the granite residual soil roadbed, and the thickness of the strength compensation layer 5 can be controlled and determined based on the deflection value of the top surface of the strength compensation layer 5; before large-scale construction of granite residual soil, construction measurement and layout are carried out, and the surface is cleared and compacted according to the design requirements.

[0045] A layer of crushed stone soil, gravel soil, quarrying slag and other materials with large porosity and good water stability with a thickness of not less than 50cm is filled on the surface after clearing and compaction. The first layer of granite residual soil is loaded on it. The loose thickness of the granite residual soil is controlled by drawing gray grids and hanging lines. After loading, the bulldozer is used for rough leveling and the grader is used for fine leveling. The test section is rolled and tested according to the construction technology and compaction standards determined. The second layer of granite residual soil roadbed can be loaded, spread, leveled, rolled and tested only after the compaction standards are met.

[0046] After that, the third, fourth, ..., Nth layer of granite residual soil will be loaded, spread, leveled, rolled and tested in turn.

[0047] The slope surface is shaped every 2 m of granite residual soil, and geocell protection is laid in time until the granite residual soil is filled to the designed elevation of the bottom surface of the strength compensation layer 5.

[0048] The first strength compensation layer 5 is loaded, spread, leveled and rolled above the granite residual soil filling area 3 until it is rolled layer by layer to the top surface elevation of the strength compensation layer 5 according to relevant specifications, and the roadbed is handed over for acceptance.

[0049] Finally, the pavement structure layer 6 is paved. Before the pavement structure layer 6 is paved, the granite residual soil roadbed must experience at least one complete rainy season or a 6-month natural settlement stabilization period.

[0050] As described above, the embodiments of the present invention are described in detail, but it is obvious to those skilled in the art that many variations are possible without departing from the inventive point and effect of the present invention. Therefore, all such variations are also included in the protection scope of the present invention.

Claims

1. A construction method for a granite residual soil roadbed structure, characterized in that: It includes a granite residual soil roadbed structure, which includes five parts: a bottom isolation layer, a granite residual soil filling area, a geocell protection area, a strength compensation layer and a pavement structure layer. The bottom of the granite residual soil filling area is the bottom isolation layer, and the two sides of the granite residual soil filling area are geocell protection areas respectively. The geocell protection area includes a left geocell slope protection and a right geocell slope protection. The top of the granite residual soil filling area is a strength compensation layer and a pavement structure layer. The subbase and base of the pavement structure layer are cement stabilized gravel layers. The subbase and base are full-width paved structures. There is a closed central dividing strip on the pavement structure layer. The top of the bottom isolation layer is filled with granite residual soil. The loose thickness of each layer of granite residual soil is less than 30cm. The left geocell slope protection and the right geocell slope protection are composed of geocells. The geocell is a mesh cell structure formed by high-strength HDPE or PP copolymer wide bands through strong welding or riveting. The copolymer wide bands are perforated, and the geocell is stretched to form an inner cavity space. The surrounding walls of the geocell are fixed to the ground with U-shaped nails. Contains the following steps: Before filling the granite residual soil roadbed, verify its distribution and quantity to determine a reasonable roadbed soil and stone allocation plan; Secondly, typical granite residual soil was selected for water content, compaction, liquid limit, screening, CBR geotechnical tests to determine the natural water content, optimum water content, maximum dry density, liquid limit, particle size distribution and CBR of granite residual soil, and the relationship curve between CBR and water content was drawn. According to the control standard of CBR of granite residual soil filling site, the rolling water content range of granite residual soil in each site was determined respectively. Select typical fill roadbed construction sites to pave granite residual soil roadbed test sections, determine the drying method and drying rate of granite residual soil, and summarize the mechanical combination, compaction machinery specifications, loose paving thickness, rolling times, rolling speed and compaction quality control standard construction process parameters of granite residual soil roadbed; Strength compensation layers of different thicknesses are laid in the test section of granite residual soil roadbed. The thickness of the strength compensation layer can be controlled and determined based on the deflection value of the top surface of the strength compensation layer. Before large-scale construction of granite residual soil, construction measurement and layout are carried out, and the surface is cleared and compacted according to the design requirements. A layer of crushed stone soil, gravel soil, and quarried rock slag with a thickness of not less than 50cm and high porosity and good water stability is filled on the surface after clearing and compaction, and the first layer of granite residual soil is loaded on it. The loose thickness of the granite residual soil is controlled by drawing gray grids and hanging lines. After loading, the bulldozer is used for rough leveling and the grader is used for fine leveling. According to the construction technology and compaction standards determined by the test section, rolling and testing are carried out. After meeting the compaction standards, the second layer of granite residual soil roadbed is loaded, spread, leveled, rolled and tested; After that, the third, fourth and Nth layers of granite residual soil are loaded, spread, leveled, rolled and tested in turn; The slope surface is shaped every 2m of granite residual soil, and geocell protection is laid in time until the granite residual soil is filled to the designed elevation of the bottom surface of the strength compensation layer; Load, spread, level and roll the first strength compensation layer above the granite residual soil filling area until it is rolled layer by layer to the top elevation of the strength compensation layer according to relevant specifications, and then conduct the roadbed acceptance inspection; Finally, the pavement structure layer is paved. Before the pavement structure layer is paved, the granite residual soil roadbed must experience at least one complete rainy season or a 6-month natural settlement stabilization period; The granite residual soil filling part in the granite residual soil roadbed structure is the area between the bottom isolation layer and the strength compensation layer, the filling height does not exceed 15m, and the slope is 1:1.5~1:1.75; the strength compensation layer filler uses cement and lime to improve the granite residual soil, or crushed stone soil, gravel soil, and coarse-grained soil with good water stability; the thickness of the strength compensation layer is not less than 50cm, and the geocell protection area is the granite residual soil roadbed slope surface fully paved with geocells, anchored by hook-shaped rivets or U-shaped steel bars, with a fixed spacing of about 1m; the cell space is filled with planting soil; the geocell protection area is constructed simultaneously with the granite residual soil roadbed to achieve protection as it is filled to avoid erosion and damage to the granite residual soil slope.

2. The construction method of a granite residual soil roadbed structure according to claim 1, characterized in that: The subbase and base layers of the pavement structure layer are cement-stabilized crushed stone layers, and are full-width paved structures; the bottom isolation layer is a crushed stone soil, gravel soil or mountain slag filling layer with a filling thickness greater than 50cm; the crushed stone in the crushed stone soil, gravel soil and mountain slag is hard or medium-hard stone with good water stability.

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