Waste tire-macadam semi-constrained flexible base layer structure

Abstract

The invention relates to the technical field of road construction, in particular to a junked tire-macadam semi-constrained flexible base layer structure which comprises a junked tire-macadam flexible base layer arranged on a soil foundation, and an asphalt concrete surface layer is arranged at the end, away from the soil foundation, of the junked tire-macadam flexible base layer; and the waste tire-macadam flexible base layer comprises a waste tire macadam subbase layer and a waste tire macadam middle base layer. Through the double-layer arrangement of the waste tire gravel subbase layer and the waste tire gravel middle base layer, when the waste tire gravel subbase layer and the waste tire gravel middle base layer are subjected to the same load effect, smaller settlement can be generated, and the bearing capacity of the soil foundation is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of road construction, in particular to a waste tire-crushed stone semi-constrained flexible base structure. Background Art

[0002] In recent years, due to the rapid development of the automobile industry, industrialization and urbanization, the number of waste tires will continue to rise year by year. At present, the comprehensive treatment methods of waste tires mainly include refurbishment, material recycling, landfill and energy recovery. Waste tires are difficult to degrade naturally, and conventional landfill will occupy a large amount of valuable land and cause serious environmental pollution. However, due to the characteristics of light weight and good elastic modulus of waste tires, they have broad application prospects in civil engineering; at present, waste tires have been introduced into the engineering field and used in many construction projects such as slope protection, foundation filling and retaining walls; however, the current research on the application of waste tires in engineering has not been in-depth, lacking relevant theoretical basis and applicable standards and specifications, which limits its wide application in large-scale projects. Therefore, it is necessary to apply waste tire-crushed stone flexible base. Summary of the invention

[0003] The purpose of the present invention is to provide a waste tire-gravel semi-constrained flexible base structure to solve the problems existing in the above-mentioned prior art.

[0004] To achieve the above-mentioned object, the present invention provides the following scheme: a waste tire-gravel semi-constrained flexible base structure, comprising a waste tire-gravel flexible base arranged on a soil foundation, wherein an asphalt concrete surface layer is arranged at one end of the waste tire-gravel flexible base away from the soil foundation; the waste tire-gravel flexible base comprises a graded gravel subbase layer laid on the soil foundation, a waste tire gravel subbase layer is laid at one end of the graded gravel subbase layer away from the soil foundation, and the waste tire gravel subbase layer is away from the graded gravel subbase layer. One end of the gravel bottom base layer is paved with a graded gravel middle base layer, the end of the graded gravel middle base layer away from the waste tire gravel bottom base layer is paved with a waste tire gravel middle base layer, the end of the waste tire gravel middle base layer away from the graded gravel middle base layer is paved with a graded gravel upper base layer, the end of the graded gravel upper base layer away from the waste tire gravel middle base layer is paved with an asphalt stabilized gravel mixture upper base layer, and the asphalt concrete surface layer is paved on one end of the asphalt stabilized gravel mixture upper base layer away from the graded gravel upper base layer.

[0005] Preferably, the waste tire gravel bottom base layer and the waste tire gravel middle base layer have the same structure and both include a plurality of waste tires, two adjacent waste tires are connected to each other by high-strength bolts, and the waste tires are filled with graded gravel.

[0006] Preferably, the waste tires are laid in a square shape on the graded crushed stone base layer.

[0007] Preferably, the graded crushed stone subbase is paved with graded crushed stone.

[0008] Preferably, the structures of the graded crushed stone middle base layer and the graded crushed stone upper base layer are the same as those of the graded crushed stone bottom base layer.

[0009] Preferably, the asphalt concrete surface layer includes an asphalt concrete lower layer laid on one end of the asphalt stabilized crushed stone mixture upper base away from the graded crushed stone upper base, and an asphalt concrete upper layer is laid on one end of the asphalt concrete lower layer away from the asphalt stabilized crushed stone mixture upper base.

[0010] The present invention discloses the following technical effects:

[0011] The present invention provides a double-layer waste tire crushed stone base layer and a waste tire crushed stone middle base layer, so that when the waste tire crushed stone base layer and the waste tire crushed stone middle base layer are subjected to the same load, smaller settlement will be generated, thereby effectively improving the bearing capacity of the soil foundation. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0014] Among them, 1. Waste tire-gravel flexible base layer; 2. Asphalt concrete surface layer; 3. Graded gravel subbase layer; 4. Waste tire gravel subbase layer; 5. Graded gravel middle base layer; 6. Waste tire gravel middle base layer; 7. Graded gravel upper base layer; 8. Asphalt stabilized gravel mixture upper base layer; 9. Asphalt concrete lower layer; 10. Asphalt concrete upper layer; 11. Land foundation. DETAILED DESCRIPTION

[0015] The possible implementation schemes found in the art are:

[0016] At present, the waste tire-gravel flexible base layer is to replace the gravel with the same volume of waste tire rubber particles to prepare a rubber particle gravel seal pavement. The application of this material can increase the recycling rate of waste tires and reduce environmental pollution.

[0017] Patent announcement number CN113668314A discloses a medium-grained drainage and crack-resistant flexible base asphalt pavement structure, which includes a semi-rigid base and a surface layer. A flexible base is arranged between the semi-rigid base and the surface layer. The flexible base adopts a medium-grained drainage and crack-resistant asphalt mixture (MSPM-20).

[0018] This patent uses medium-grained asphalt mixture as a flexible base layer, high-viscoelastic modified asphalt as a binder, and uses large-void mixture to discharge moisture laterally. Glass fiber grids are arranged at the bottom of the medium-grained asphalt mixture layer to improve its ability to resist reflective cracks. At the same time, it provides a new structural combination and construction process for preventing reflective cracks in semi-rigid base layers.

[0019] Compared with the existing technology, this patent uses glass fiber grids and large-void asphalt mixtures to prevent reflective cracks from the bottom up in the pavement structure, discharge moisture from the pavement structure laterally, and avoid water damage to the pavement structure. At the same time, it uses large-pore medium-grained drainage and anti-cracking asphalt mixtures to reduce the thickness of the drainage and anti-cracking structure layer, reduce the construction cost, and has great promotion and application value.

[0020] The patented medium-grained drainage and crack-resistant asphalt mixture uses high-viscoelastic modified asphalt, which ensures the high-temperature stability of the mixture and requires that the dynamic stability rutting should not be less than 2600 times / mm.

[0021] This patent uses medium-grained asphalt mixture as a flexible base layer to reduce the thickness of the asphalt pavement, reduce the amount of stone used, and lower the project cost.

[0022] This patent makes full use of the advantages of high-viscoelastic modified asphalt, such as strong adhesion, good elastic recovery performance, and outstanding low-temperature crack resistance, and significantly improves the high-temperature performance, low-temperature performance, water stability and stress absorption capacity of permeable asphalt mixture.

[0023] This patent utilizes the skeleton void structure of the permeable asphalt mixture, which can not only improve the anti-rutting ability, but also quickly discharge the free water inside the pavement structure and the external seepage water, avoiding the occurrence of water damage to the pavement structure.

[0024] This patent arranges glass fiber grids at the bottom of the flexible base layer to enhance the medium-grained flexible base layer's ability to dissipate and absorb base layer reflected stress, eliminate or delay the generation of reflective cracks in the semi-rigid base layer, and prevent the upper structure from cracking, thereby improving the durability of the entire pavement structure and extending its service life, thus achieving significant economic and social benefits.

[0025] Patent publication number CN116971235A discloses a construction method for a flexible asphalt gravel base in the repair and reconstruction of old pavement in severe cold regions, comprising the following steps:

[0026] (1) Pavement survey and RAP performance evaluation: Before milling the old pavement, the technical condition of the old pavement is fully investigated and analyzed. First, the original data of the old pavement, including the type, thickness, gradation of the pavement materials, and the repair and maintenance records, are collected. Then, the milling section is sampled in advance by excavating a pit and drilling a core. The mineral gradation, oil-stone ratio, and asphalt aging degree of different sections are analyzed and evaluated by extraction or Absen method. Specifically, the variability factors of RAP materials after milling are analyzed to analyze the gradation stability and temperature stability of the recycled asphalt mixture. The old pavement is divided into sections and regions based on the survey data obtained, so that the RAP materials of different sections can be classified and recycled to reduce the impact of the variability factors of RAP materials on the stability of the recycled asphalt mixture.

[0027] (2) Cold milling scheme design and milling operation: Before the milling operation, the milling scheme for the old road surface is reasonably determined, and then the milling range, depth, speed and milling water consumption are determined according to the scheme to control the operation; the dirt, water and slag on the surface of the old road surface are cleaned by a road sweeper in combination with manual work, and serious deformation road surface diseases such as rutting and bumps are marked in advance, and excavated in advance when necessary to ensure the cleanliness of the milling and recycling materials;

[0028] (3) RAP aggregate recycling: When recycling RAP materials through pavement milling, base waste, cement concrete waste, sundries and soil impurities must not be mixed in. During milling, the milling machine directly loads the milled materials into the recycling vehicle through the feeding belt and transports them to the asphalt station for crushing and screening. Milled recycled materials from different sources should be piled up according to categories to prevent the mixing of milled materials from different sources, which will affect the stability of the asphalt content and particle size distribution of the RAP materials.

[0029] (4) RAP aggregate crushing and screening: RAP aggregates are subjected to secondary crushing. The moisture content of RAP materials should be checked before crushing and screening. Crushing and screening should be performed when the moisture content is less than 3%. The crushing is performed using a jaw crusher. The crushed RAP recycled asphalt pavement material is screened into two grades of aggregates: 0-8 mm and 8-26 mm. The aggregates are stacked separately and clearly marked to avoid mixing. The stacking height is less than 2 m, and the storage site is flat and free of water accumulation. A rain shelter is installed on the material pile. The screened materials larger than 26 mm are crushed again and screened again and classified into the second grade of aggregates;

[0030] The proportion of RAP aggregate after screening is 0-8mm: 72%, 8-26mm: 25%, and oversized waste: 3%; oversized waste is used as the first layer of filling material in the auxiliary roadbed filling;

[0031] (5) RAP screened aggregate mix design and optimization:

[0032] (a) Based on the investigation of the old pavement and the performance evaluation of RAP collected in this section, different RAP dosages are analyzed and compared, and feasibility tests are conducted. Based on the dosage analysis and comparison and feasibility tests, the mix design of high-dosage recycled asphalt mixture also needs to go through three stages: target mix design, production mix design, and production mix verification. The mix design adopts the Marshall test process to obtain the type of new aggregate, the gradation of ideal mineral materials, and the optimal asphalt dosage;

[0033] The test analysis shows that the stability and dynamic stability of the recycled mixture decrease with the increase of asphalt penetration. This is because the properties of the aged asphalt have changed. The asphalt becomes harder and more brittle. The smaller the penetration, the greater the viscosity of the asphalt. As the penetration decreases, the stability increases, and the dynamic stability also increases, indicating that the high-temperature performance of severely aged asphalt has been improved.

[0034] (b) The RAP aggregate blending ratio was optimized to be 40%, and the mineral composition was designed according to the trial mix method. The ratio of each grade of RAP aggregate was 0-8mm:8-25mm=21:19;

[0035] (c) Selection of regeneration agent: During mix design and verification, the aging degree, old asphalt content, RAP dosage ratio of the regenerated asphalt mixture, and compatibility of the regeneration agent with asphalt should be determined based on the RAP aggregate test analysis, and the type of regeneration agent should be selected comprehensively to meet the aging recovery effect of the old asphalt in the regenerated mixture. After verification, the model XT-2 was selected, with a dosage of 4%;

[0036] (d) Selection of new asphalt type: Through the preliminary design investigation, it was determined that the old asphalt in the RAP aggregate was Grade 90A. The performance and composition of the old asphalt in the RAP material were complex. When designing the mix ratio, the new asphalt grade was selected to determine the asphalt type to be Grade 90A to meet the technical indicators required by the design. The new asphalt type selected was Grade 90A.

[0037] (e) Asphalt dosage: According to the determined mineral aggregate grading composition, five different asphalt dosages were used to prepare Marshall compaction specimens. During the indoor test, the mixing temperature was 165°C, the molding temperature was 155°C, and the front and back sides were compacted 75 times each. Finally, the optimal asphalt dosage was deduced to be 4.1%;

[0038] (6) Target mix ratio of factory-mixed hot recycled asphalt gravel flexible base:

[0039] The weight ratio of each component in the asphalt crushed stone flexible base is: graded crushed stone ratio 0-2.36mm: 2.36-9.5mm: 9.5-19mm: 19-31mm: 0-8mmRAP: 8-25mmRAP: cement: waste carbon fiber filaments: 3-7mm waste tire rubber particles = 7%: 5%: 11%: 30%: 21%: 19%: 3%: 2%: 2%;

[0040] Where RAP is the asphalt mixture recovered from the milling of the old road surface;

[0041] The amount of asphalt is 4.1% of the total weight of all components. The asphalt is 90 grade A road asphalt. The regeneration agent is model XT-2, and the amount is 4%;

[0042] (7) Mixing of recycled mixture:

[0043] (a) The specific mixing process is preheating RAP → mixing regeneration agent and RAP → mixing (mixing time ≥ 10-15S) → adding new aggregate → mixing (mixing time is 10-15S) → adding new asphalt → mixing (mixing time is 15-20S) → adding cement → mixing (mixing time is 20-25S) → adding waste carbon fiber filaments and waste tire rubber particles → mixing (mixing time is 8-10S) → discharging;

[0044] (b) To avoid heating and aging of RAP materials, a second independent heating drum is used to dry and heat the RAP materials. The drying and heating of new and old aggregates are carried out in different drums. The heating temperature of new aggregates is 185-195°C, and the heating temperature of RAP materials is 110-130°C. During the heating process, RAP materials are not in direct contact with open flames. After drying and heating, the new and old materials are hot screened and enter the hot material bin. Finally, they are mixed and stirred according to the proportion of each grade of aggregate in the mixing order. The factory temperature is 170-180°C to form a recycled new asphalt mixture;

[0045] (8) Transportation of recycled new asphalt mixture: When loading the recycled mixture, it should be loaded into the dump truck three times: front, middle and back to avoid segregation. The material transport truck must be cleaned before and after each use. A thin layer of isolation agent or anti-adhesive agent should be applied on the car body to prevent asphalt from sticking, but no excess liquid should be accumulated at the bottom of the car body. When loading the material from the mixer to the material transport truck, the position of the car should be moved several times to balance the loading to reduce the segregation of the mixture. The compartment of the material transport truck should be insulated, and the transported mixture should be covered with tarpaulin to keep it warm, rainproof and pollution-proof.

[0046] (9) Paving of recycled new asphalt mixture:

[0047] (a) Before paving, the quality of the cement-stabilized crushed stone base, including compaction, flatness, longitudinal elevation, width, thickness, cross slope and strength index, should be checked and must meet the paving conditions;

[0048] (b) In order to improve the smoothness and compaction of the regenerated new asphalt mixture, the paver must turn on the screed vibration device while turning on the tamper. The tamper vibration frequency, tamper amplitude, and screed vibration frequency should meet the requirements to ensure that the initial compaction is not less than 80%; the screed preheating temperature of the paver should not be lower than 110°C, and the paving temperature of the regenerated new asphalt mixture should be 5-10°C higher than the corresponding hot mix asphalt mixture paving temperature, and the paving temperature should be 145-150°C;

[0049] (c) The paving of recycled new asphalt mixture should be slow, even, continuous and uninterrupted. The speed should not be changed arbitrarily or stopped during the paving process. The machine should be stopped and started as little as possible, and the paving speed should not exceed 3m / min;

[0050] (d) To reduce segregation, the auger of the paver should be long enough, and the distance between the two ends of the paving boundary should not exceed 25 cm to reduce segregation at both ends; it should rotate continuously during paving, and the mixture level should be higher than the 2 / 3 position of the auger;

[0051] (e) The transport vehicle and the paver should work well together. During the paving process, the transport vehicle should stop 10cm-30cm in front of the paver and wait in neutral. The paver will push forward and slowly unload the material. It is strictly forbidden for the transport vehicle to hit the paver. The transport vehicle should unload the material in multiple times to reduce segregation. The paver should minimize the number of times the bucket is collected and released quickly to maintain the continuity of paving as much as possible;

[0052] (f) The middle of the road width is the junction of two pavers, which is also the location where strip segregation is prone to occur. Since this is the power separation point of the paver's spiral distributor, the resistance is large and the ironing plate is prone to deformation. Spiral blades should be installed on the spiral distributor at this point, and operators should pay attention to this point during daily construction to avoid segregation caused by deformation of the ironing plate;

[0053] (g) Manual patching or replacement of the mixture should be carried out under the guidance of on-site technicians. It is recommended to equip the site with a 10-15mm sieve to screen out the coarse materials in advance when repairs are needed. If the defects are serious, they should be removed, and the paver should be adjusted or the paving process should be improved in time. The paving effect should be observed at any time. If construction cracks, shifting, wheel sticking, wheel marks and other problems are found, feedback should be given in time and solutions should be taken. If they cannot be solved, paving should be suspended;

[0054] (10) Rolling of recycled new asphalt mixture after paving:

[0055] (a) A sufficient number of rollers should be equipped, and a reasonable combination of rollers and the steps of initial, secondary and final compaction should be selected to achieve the best compaction effect. The factory-mixed hot-recycled ATB-25 flexible base should be compacted by no less than 3 double-steel-wheel vibratory rollers and no less than 2 rubber-wheel rollers. The vibratory rollers are double-driven and double-vibrated, with a deadweight of 11t-13t; the rubber-wheel rollers are 26-30t and must be equipped with counterweights. The compaction temperature of the recycled mixture should be 5-10℃ higher than that of ordinary hot-mix asphalt mixtures. The total length of the compaction section should be as short as possible and should not exceed 80m.

[0056] (b) Initial compaction: This should be done immediately after paving. It should be rolled closely after the paver at a high temperature. Use a double-wheel roller or a vibrating roller to compact twice. When compacting, the driving wheels should face the paver. The tire roller should roll at a speed of 2-3 km / h. The steel wheel roller should roll at a speed of 2-3 km / h in a non-vibrating state. After the initial compaction, check the flatness and road camber immediately and make corrections if necessary.

[0057] (c) Recompacting: Recompacting is carried out immediately after the initial compaction, using a vibratory roller and a tire roller. The recompacting is first performed twice with a tire roller and twice with a vibratory roller, with a tire roller rolling at a speed of 3.5-4.5 km / h and a steel wheel roller rolling at a speed of 4-5 km / h in a vibratory state, to achieve the required compaction degree;

[0058] (d) Final compaction: Final compaction is carried out immediately after recompacting, using a double steel wheel roller or a vibratory roller with vibration turned off to roll twice, with the steel wheel roller rolling at a speed of 2-3 km / h in a non-vibrating state, to eliminate wheel marks;

[0059] (11) Health preservation and open transportation:

[0060] After the compaction of the recycled new asphalt mixture layer is completed, traffic should be closed for curing, and traffic can only be opened after the surface temperature of the recycled layer is lower than 50℃.

[0061] While ensuring the performance of asphalt mixture, this patent solves technical problems such as the variability of RAP material grading at high dosages in cold regions, heating and aging of old asphalt, and activation of old asphalt regeneration performance. It completely solves the problem of handling waste materials in the process of old road reconstruction, and significantly reduces construction costs while reducing environmental protection risks. Calculations show that this patent can reduce the cost of construction materials by about 32-35%, which has obvious advantages over traditional old road reconstruction and upgrading construction methods.

[0062] This patent can effectively reduce cracks in traditional asphalt pavements in extremely cold regions, increase the permanent strain of rutting, and overcome the problems of traditional asphalt pavements caused by gradual peeling of the surface due to severe cold, resulting in pavement pumping, base layer damage, pavement network cracking and subsidence. It can achieve crack-free asphalt pavement within 1,000 meters or 1,000 days, and the asphalt pavement meets high-quality standards.

[0063] This patent improves the road surface condition in cold and swampy areas and prolongs the service life of roads. This patent is applicable to road construction in cold areas. Compared with roads built with existing technologies, this patent prolongs the service life by 4-5 times. There is no loss, road cracking, collapse, road pumping, road cracking and subsidence.

[0064] Embodiments that can be added to the present invention are:

[0065] Asphalt concrete surface layer refers to a layer of material used as asphalt concrete as the surface of the road. It is a mixture of mineral materials (such as crushed stone, gravel, sand, etc.) and road asphalt materials in a certain proportion. This mixture is mixed under strictly controlled conditions and then laid on the road base to form a flat and durable driving surface.

[0066] Asphalt concrete pavement can be classified according to different criteria:

[0067] Classification by binder: It can be divided into two categories: petroleum asphalt and coal asphalt. Some areas also use or mix natural asphalt.

[0068] Classification by aggregate type: It can be divided into crushed stone, gravel, sand, slag and other categories, among which crushed stone is the most commonly used.

[0069] Classification by maximum particle size of the mixture: it can be divided into coarse particles (below 35-40 mm), medium particles (below 20-25 mm), fine particles (below 10-15 mm), sand particles (below 5-7 mm) and other categories.

[0070] Classification by density of the mixture: It can be divided into several categories such as dense grading, semi-open grading and open grading. Among them, the hot-mixed and hot-laid dense-graded crushed stone mixture is durable, high in strength and good in integrity. It is a representative material for the construction of high-grade asphalt pavement and is the most widely used.

[0071] The construction process of asphalt concrete surface layer includes the following key steps:

[0072] Preparation: Review the quality of the base and auxiliary structures to confirm that they meet the requirements of the specifications. Construction materials can be used after passing the test, and machinery must be matched and spare, and kept in good condition.

[0073] Asphalt heating temperature and asphalt mixture mixing: The construction temperature should be selected according to the asphalt grade, viscosity, climate conditions, thickness of the paving layer and the thickness of the underlying layer, in accordance with the requirements of the "City Road Engineering Construction and Quality Acceptance Code" (CJJ1-2008). When the asphalt viscosity is high, the temperature is low, and the paving layer thickness is small, the construction temperature should be at the upper limit.

[0074] Trial paving test section: For important asphalt concrete pavement, it is advisable to first build a test section of 100-200 meters, which is mainly divided into two stages: trial mixing and trial paving, to obtain the corresponding parameters.

[0075] Mixing and transportation: Hot mix asphalt concrete mixtures are classified into five types according to the maximum aggregate size: extra coarse, coarse, medium, fine, and sand. The maximum aggregate size of the asphalt concrete surface layer should match the thickness of the layered compaction layer.

[0076] Paving operation: Hot mix asphalt mixture should be spread by crawler or tire asphalt paver. When paving high-grade road asphalt mixture, the paving width of one paver should not exceed 6 (two lanes) - 7.5m (three lanes or more). Usually, two or more pavers are used, staggered 10-20m front and back, and paved synchronously in an echelon manner. There should be an overlap of about 30-60mm between the two sections, and the wheel track of the lane should be avoided. The overlap position of the upper and lower layers should be staggered by more than 200mm.

[0077] Rolling: Asphalt concrete rolling construction is divided into three stages: initial rolling, repeated rolling and final rolling. Steel wheel vibratory rollers, rubber wheel rollers and other equipment are used for back and forth rolling. The rolling rhythm is reasonably controlled, and the flatness of the road surface after rolling is tested to prevent the spread of single rolling defects and cause overall rolling defects.

[0078] During the construction of asphalt concrete surface layer, some quality problems may occur, such as cracks, potholes and looseness. These problems may be related to factors such as inadequate implementation of construction standards, substandard material quality, and insufficient temperature control during construction. To prevent these problems, it is necessary to strictly control material quality and construction temperature during construction, ensure the continuity and uniformity of paving and rolling, and properly handle construction joints.

[0079] Asphalt concrete surface has the following advantages in road construction:

[0080] Easy maintenance: Asphalt concrete can be melted into a liquid mixture at high temperatures, making it easy to maintain.

[0081] Durable: has strong load-bearing capacity and ductility.

[0082] Renewability: Asphalt concrete materials can be reused, reducing construction and maintenance costs.

[0083] Graded crushed stone is a mixture of aggregates of various sizes and particle sizes. When its gradation meets the requirements of technical specifications, it is called graded aggregate. Graded aggregate includes graded crushed stone, graded crushed gravel (a mixture of crushed stone and gravel, and often the oversized particles in gravel are crushed and combined with gravel to form crushed gravel) and graded gravel (or graded gravel).

[0084] Graded crushed stone has a variety of applications in pavement structures:

[0085] Light traffic roads: used as pavement or under a thin asphalt surface layer.

[0086] Heavy traffic roads: used under thick asphalt surface layers. There may be two forms. One is high-quality graded crushed stone with very good construction quality, which is directly used as the base layer under the thick asphalt surface layer. The other is graded aggregate with slightly lower construction quality used in deeper locations, usually under the binder base layer.

[0087] Intermediate layer: Many countries often use graded crushed stone as the intermediate layer between the asphalt surface and the hydraulic binder treated base layer to reduce the shrinkage cracks reflected from the hydraulic binder treated layer to the asphalt surface layer, that is, to reduce reflective cracks, and also help to remove water from the pavement structure layer, reducing or even eliminating the scouring phenomenon of the base layer. This pavement structure is often called "inverted structure".

[0088] The raw materials of graded crushed stone cushion are mainly composed of coarse aggregate, fine aggregate, etc. The quality control indicators of coarse aggregate are mainly crushing value and particle composition of crushed stone. Generally, the crushing value of coarse aggregate is not more than 30%, and the content of needle-like particles is not more than 20%; the fine aggregate is mainly to control the particle composition, mud content and admixture of stone chips to ensure continuous gradation. In order to facilitate the control of the gradation of the mixture, the materials should be prepared in 4 grades, namely: 20-30mm, 10-20mm, 5mm-10mm crushed stone, 0-5mm stone chips. In construction management, targeted measures should be taken to control the quality of raw materials according to the needs of the on-site progress.

[0089] When designing graded crushed stone, the following principles should be followed:

[0090] Continuous grading principle: The particle size of the crushed stone should cover a range from large to small to ensure continuous particle size distribution. Small-sized crushed stone fills the gaps between large-sized crushed stones to improve density.

[0091] Selection of maximum particle size: The limitations of the construction site and usage requirements should be considered to select an appropriate maximum particle size to ensure structural performance.

[0092] Bearing capacity and deformation control: Grading design should meet the bearing capacity requirements while considering deformation control.

[0093] Economical: Under the premise of meeting performance requirements, full use should be made of local resources and cost-effectiveness should be considered.

[0094] The difference between graded crushed stone and water-stabilized layer

[0095] Graded crushed stone is a kind of crushed stone material that has been mechanically crushed and screened to meet certain grading requirements. It is mainly used for the subbase or base of roads, and sometimes also used for drainage and other projects. The main function of graded crushed stone is to bear pressure, disperse loads, and maintain the stability of the roadbed, while ensuring good drainage performance.

[0096] Water-stabilized layer, full name is cement-stabilized crushed stone layer, refers to a hard road base material formed by mixing, paving and compacting crushed stone with appropriate amount of cement and water. It combines the bonding properties of cement and the high bearing capacity of crushed stone to provide higher stability and bearing capacity. Cement-stabilized crushed stone layer is often used in projects such as roads and airport runways that bear heavy loads. The main differences are as follows:

[0097] Material composition: Graded gravel is mainly a mixture of gravel of different particle sizes in a certain proportion, while the water-stabilizing layer contains cement and water in addition to gravel.

[0098] Strength and stability: Because cement is added to the water-stabilized layer, its strength and stability are generally higher than that of the graded crushed stone layer composed only of crushed stone.

[0099] Permeability: Graded crushed stone has better permeability than water-stable layer.

[0100] Economic cost: Since cement needs to be added to the water-stabilizing layer, the cost will be higher than graded crushed stone.

[0101] Application scenarios: Graded crushed stone is suitable for general roads, drainage systems, etc., while water-stabilized layers are more suitable for heavy-loaded roads, airport runways and other occasions that require higher stability and bearing capacity.

[0102] Asphalt-stabilized aggregate (ATB) is a heterogeneous, multi-phase, multi-layered composite system composed of mineral aggregates and asphalt. Aggregates account for about 95% of the mass fraction of the mixture. Therefore, aggregate characteristics (shape, specification, gradation, etc.) determine the volume composition of the asphalt mixture, which in turn affects various road properties of the mixture.

[0103] Asphalt stabilized gravel mixture is divided into three grades: ATB-25, ATB-30, and ATB-40.

[0104] ATB is divided into different types such as densely distributed and open-graded asphalt macadam. In practical applications, more and more road projects are beginning to use asphalt stabilized macadam (ATB) in the lower layers. Due to the large traffic volume, many heavy-loaded vehicles and serious channelized traffic on highways, rutting problems are very likely to occur in hot seasons if the design is not appropriate. Therefore, there are many studies on the high-temperature performance of asphalt mixtures. Although the layer where ATB is used is lower and is not as affected by temperature as the upper and middle layers, if the shear strength of ATB is not high, shear failure will occur and permanent deformation will form; and ATB is generally thicker, so its influence cannot be ignored.

[0105] Asphalt Concrete (AC) is a building material made of asphalt, mineral materials (including crushed stone, sand, mineral powder, etc.) and other additives in a certain proportion. It is widely used in the construction of transportation infrastructure such as roads, airport runways, and parking lots. Asphalt is used as a binder to bond mineral materials together to form a solid pavement structure.

[0106] Common AC specifications include AC-5, AC-10, AC-20, AC-30 and AC-40. The numbers in these specifications represent the standard value of the compressive strength of the mixture, in MPa.

[0107] AC-5: Suitable for low-frequency traffic roads, non-motorized vehicle lanes and sidewalks. This type of asphalt concrete has low strength but good durability, and is suitable for light loads and low-frequency traffic roads.

[0108] AC-10: Suitable for medium-frequency traffic roads, parking lots, airport runways, etc. This model has a higher strength of asphalt concrete and is suitable for medium-load and medium-frequency traffic roads.

[0109] AC-20: Suitable for high-frequency traffic roads, highways, bridges and airport runways. This model has high strength asphalt concrete and is suitable for high-load and high-frequency traffic roads.

[0110] AC-30: Suitable for bridges, tunnels and highways. This type of asphalt concrete has high strength and is suitable for large bridges and highways.

[0111] AC-40: Suitable for large bridges and tunnels on highways. This model has very high asphalt concrete strength and is suitable for special engineering needs.

[0112] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0113] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0114] Embodiment 1

[0115] Reference Figure 1 The present invention provides a waste tire-gravel semi-constrained flexible base structure, comprising a waste tire-gravel flexible base 1 arranged on a soil foundation 11, wherein an asphalt concrete surface layer 2 is arranged at one end of the waste tire-gravel flexible base 1 away from the soil foundation 11; the waste tire-gravel flexible base 1 comprises a graded gravel subbase 3 laid on the soil foundation 11, wherein a waste tire-gravel subbase 4 is laid at one end of the graded gravel subbase 3 away from the soil foundation 11, and the waste tire-gravel subbase 4 is away from the graded gravel subbase One end of the layer 3 is paved with a graded crushed stone middle base layer 5, the end of the graded crushed stone middle base layer 5 away from the waste tire crushed stone bottom base layer 4 is paved with a waste tire crushed stone middle base layer 6, the end of the waste tire crushed stone middle base layer 6 away from the graded crushed stone middle base layer 5 is paved with a graded crushed stone upper base layer 7, the end of the graded crushed stone upper base layer 7 away from the waste tire crushed stone middle base layer 6 is paved with an asphalt stabilized crushed stone mixture upper base layer 8, and the asphalt concrete surface layer 2 is laid on the end of the asphalt stabilized crushed stone mixture upper base layer 8 away from the graded crushed stone upper base layer 7.

[0116] The present invention provides a double-layer waste tire crushed stone bottom base layer 4 and a waste tire crushed stone middle base layer 6, so that when the waste tire crushed stone bottom base layer 4 and the waste tire crushed stone middle base layer 6 are subjected to the same load, they will produce smaller settlement, thereby effectively improving the bearing capacity of the soil foundation 11.

[0117] According to a further optimization scheme, the waste tire gravel bottom base 4 and the waste tire gravel middle base 6 have the same structure and both include a plurality of waste tires. Two adjacent waste tires are connected to each other by high-strength bolts, and the waste tires are filled with graded gravel.

[0118] The waste tires provide circumferential constraints on the crushed stones inside the waste tires, which can effectively improve the bearing capacity of the graded crushed stones when subjected to stress.

[0119] Adjacent waste tires are connected to each other through high-strength bolts to form a whole, which is helpful for filling, compacting and leveling graded gravel during construction.

[0120] In a further optimized solution, waste tires are laid in a square shape on a graded crushed stone base layer 3, so that the outer walls of adjacent waste tires can be closely fitted.

[0121] To further optimize the solution, the graded crushed stone subbase 3 is paved with graded crushed stone, so that the graded crushed stone subbase 3 can effectively provide bearing capacity.

[0122] According to a further optimization scheme, the structures of the graded crushed stone middle base 5 and the graded crushed stone upper base 7 are the same as the graded crushed stone bottom base 3 .

[0123] The graded crushed stone bottom base 3, the graded crushed stone middle base 5, and the graded crushed stone upper base 7 can effectively provide bearing capacity.

[0124] According to a further optimization scheme, the asphalt concrete surface layer 2 includes an asphalt concrete lower layer 9 laid on the asphalt stabilized gravel mixture upper base 8 away from the graded gravel upper base 7, and an asphalt concrete upper layer 10 is laid on the end of the asphalt concrete lower layer 9 away from the asphalt stabilized gravel mixture upper base 8.

[0125] Embodiment 2

[0126] The waste tires are Chaoyang brand radial tires, which have a diameter of 22 inches, a height of 14.5 cm, and a volume of 22 L.

[0127] The thickness of the graded crushed stone subbase 3, the graded crushed stone middle base 5, and the graded crushed stone upper base 7 is 15 cm, the compressive modulus is 400 MPa, and the Poisson's ratio is 0.35.

[0128] The thickness of the graded crushed stone filled in the waste tires is 15 cm, the compressive modulus is 400 MPa, and the Poisson's ratio is 0.35.

[0129] The asphalt stabilized crushed stone mixture upper base 8 adopts ATB-30.

[0130] The asphalt concrete lower layer 9 is made of AC-20 with a thickness of 6 cm.

[0131] The asphalt concrete upper layer 10 is AC-13 with a thickness of 4 cm.

[0132] The waste tire-gravel flexible base layer 1 in the present invention has the advantages of easy control of construction quality and secondary utilization of waste tires. The waste tire-gravel flexible base layer 1 is filled with graded gravel, so that water can be discharged better; at the same time, the waste tire-gravel flexible base layer 1 is in the middle and lower part, and will produce smaller settlement when subjected to the same load.

[0133] When the waste tire-gravel flexible base layer 1 in the present invention is subjected to stress, the waste tires will provide circumferential constraints on the graded gravel under the action of radial load, which not only enables the waste tires to be reused, but also effectively increases the bearing capacity of the graded gravel.

[0134] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0135] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A waste tire-gravel semi-constrained flexible base structure, characterized by: It comprises a waste tire-crushed stone flexible base layer (1) arranged on a soil foundation (11), wherein an asphalt concrete surface layer (2) is arranged at one end of the waste tire-crushed stone flexible base layer (1) facing away from the soil foundation (11); The waste tire-gravel flexible base layer (1) comprises a graded gravel subbase layer (3) laid on the soil foundation (11), a waste tire gravel subbase layer (4) is laid on one end of the graded gravel subbase layer (3) away from the soil foundation (11), a graded gravel middle base layer (5) is laid on one end of the waste tire gravel subbase layer (4) away from the graded gravel subbase layer (3), and a graded gravel middle base layer (5) is laid on one end of the graded gravel middle base layer (5) away from the waste tire gravel subbase layer (4). A waste tire crushed stone middle base layer (6) is paved, and a graded crushed stone upper base layer (7) is paved at one end of the waste tire crushed stone middle base layer (6) away from the graded crushed stone middle base layer (5), and an asphalt stabilized crushed stone mixture upper base layer (8) is paved at one end of the graded crushed stone upper base layer (7) away from the waste tire crushed stone middle base layer (6), and the asphalt concrete surface layer (2) is paved on one end of the asphalt stabilized crushed stone mixture upper base layer (8) away from the graded crushed stone upper base layer (7).

2. The waste tire-gravel semi-constrained flexible base structure according to claim 1 is characterized by: The waste tire gravel bottom base (4) and the waste tire gravel middle base (6) have the same structure and both include a plurality of waste tires. Two adjacent waste tires are connected to each other via high-strength bolts. The waste tires are filled with graded gravel.

3. The waste tire-gravel semi-constrained flexible base structure according to claim 2 is characterized in that: The waste tires are laid in a square shape on the graded crushed stone base layer (3).

4. The waste tire-gravel semi-constrained flexible base structure according to claim 1 is characterized in that: The graded crushed stone subbase (3) is paved with graded crushed stones.

5. The waste tire-gravel semi-constrained flexible base structure according to claim 4 is characterized in that: The structures of the graded crushed stone middle base (5) and the graded crushed stone upper base (7) are the same as those of the graded crushed stone bottom base (3).

6. The waste tire-gravel semi-constrained flexible base structure according to claim 1 is characterized by: The asphalt concrete surface layer (2) comprises an asphalt concrete lower layer (9) laid on one end of the asphalt-stabilized crushed stone mixture upper base (8) away from the graded crushed stone upper base (7), and an asphalt concrete upper layer (10) is laid on one end of the asphalt concrete lower layer (9) away from the asphalt-stabilized crushed stone mixture upper base (8).

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