A construction method for special roadbed in plateau mountainous area

Abstract

The invention discloses a construction method for a special roadbed in a plateau mountainous area, including a karst roadbed treatment construction in a filling section, a karst roadbed treatment construction in a cutting section, and a cave treatment quality control construction; wherein, the karst roadbed treatment construction in the filling section adopts a reinforced concrete cover plate spanning structure, firstly removes the debris in the cave, then backfills and caps it with stone flakes, and then uses a reinforced concrete cover plate to span the cave, covering the cave entrance with 50 to 100 cm around it, ensuring that the cover plate is combined with the original rock as a whole after pouring to form an effective composite foundation. The invention optimizes the special roadbed construction process, reduces the construction cost, and reduces the problem of uneven settlement of the roadbed in the later stage.

Description

Technical Field

[0001] The present invention relates to the field of geotechnical engineering, and more specifically, to a construction method for a special roadbed in a plateau mountainous area. Background Art

[0002] Yunnan and Guizhou are full of mountains and hills, with an altitude of 900-1400 meters. It is a typical karst hilly landform. The karst development is diverse. According to the causes and combined morphological characteristics, it is mainly divided into two types: erosion and dissolution landforms and dissolution landforms. Karst collapse or uneven subsidence occurs under the action of groundwater. The diseases of karst roadbed can be divided into two categories: one is deformation problem and the other is water damage problem. There is not much research data on water damage problems of highway engineering in karst areas in my country. Karst collapse is the primary problem faced by highway roadbeds in karst areas, and it is one of the six major types of geological disasters in my country. Karst roadbeds are generally connected to underground rivers and have abundant groundwater. Therefore, drainage measures in karst areas are key. It is easy to cause environmental protection and ground subsidence due to improper drainage and water diversion. Summary of the invention

[0003] The purpose of the present invention is to provide a construction method for a special roadbed in a plateau mountainous area, optimize the special roadbed construction process, reduce the construction cost, and reduce the problem of uneven settlement of the roadbed in the later stage.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a construction method for a special roadbed in a plateau mountainous area, characterized by comprising the following steps: karst roadbed treatment construction in a filling section, karst roadbed treatment construction in a cutting section, and karst cave treatment quality control construction;

[0005] Among them, the karst roadbed treatment construction of the fill section adopts a reinforced concrete cover spanning structure. First, the debris in the cave is cleared, and then stone slabs are used to backfill and cap the top. Then, a reinforced concrete cover is used to span the cave, covering 50 to 100 cm around the cave entrance to ensure that the cover is combined with the original rock as a whole after pouring to form an effective composite foundation.

[0006] As a further solution of the present invention, the karst roadbed treatment construction of the filling section specifically includes the following steps:

[0007] A1. Construction preparation: remove debris, clean up sediments in the cave, and make a drainage system according to the actual terrain;

[0008] A2. Cave backfill: The thickness of each layer of slab backfill shall not exceed 50cm, and the thickness of the mortar-laid slab cover shall not be less than 50cm; Cave backfill compaction: When the cave is backfilled to 50cm from the top, a tamping machine shall be used for compaction;

[0009] A3. Processing and binding of steel bars;

[0010] A4. Construction of concrete cover: A41 Concrete mixing and transportation: The minimum mixing time of concrete shall be strictly no less than 2 minutes, and concrete shall be transported by mixer trucks; A42 Inspection work before pouring concrete: Before pouring concrete, check the stability and flatness of the formwork. The base surface and formwork should be kept moist without water accumulation; A43 Concrete pouring: 1) Concrete is poured in layers continuously, and the thickness of each layer shall not exceed 30 cm; 2) Concrete vibration is carried out by inserting vibrators, and manual vibration is arranged for local areas that are not vibrated in place; 3) After the concrete pouring is completed, the formwork is kept in place. When the concrete strength reaches 2.5MPa, the formwork can be removed to ensure that it is not disturbed during the strength formation process;

[0011] A5. Concrete curing: After the cover slab is poured, cover the concrete surface with plastic film to retain moisture, and then cover it with a burlap bag to retain moisture. The wet curing period should be maintained for more than 7 days.

[0012] As a further solution of the present invention, in A2, the exposed dry cave is backfilled with stone slabs, the seams are caulked with crushed stones, the upper part is covered with mortar-laid stone slabs, and reinforced concrete cover plates of different thicknesses are used to span according to the span;

[0013] When the top plate of the cave at the bottom of the roadbed is not thick, the top plate is uncovered and then filled with stone slabs, and the cracks are filled with crushed stones. The upper part is covered with mortar-laid stone slabs, and the top reinforced concrete cover plate is spanned;

[0014] For areas where caves are concentrated and cracks are interconnected, blasting is used to uncover the roof, backfill with stone slabs, fill the joints with crushed stones, and block the upper part of the cracks with mortar-laid stone slabs. Then, reinforced concrete cover slabs of different thicknesses are used to span the area depending on the span.

[0015] As a further solution of the present invention, the karst roadbed treatment construction of the excavation section specifically includes the following steps:

[0016] B1. Use an excavator to remove the slag at the bottom of the cave. The bearing capacity of the base after cleaning should meet the design requirements;

[0017] B2. The strength of the backfill mortared stone must be greater than 15MPa, and the maximum particle size of the stone shall not be greater than 2 / 3 of the compacted thickness;

[0018] B3. When filling, adopt layered filling with a thickness of no more than 50cm. Layer by layer, first low and then high, first two sides and then the center, and use a large bulldozer to level it. Individual uneven places should be leveled with fine stones and stone chips in cooperation with manual work. When backfilling with slabs, large stones should be laid first, with the large surface facing down and the small surface facing up, and arranged stably, and then small stones should be used for leveling. The gaps between the stones can be filled with slag and gravel.

[0019] B4. For caves on the slope, the backfilling process in B3 above is adopted, and mud is sprayed on the surface of the road cutting slope, or concrete is poured in the crack development area to ensure the overall stability of the road cutting slope; if there are springs or water flows near the road cutting slope, drainage treatment should be carried out in time.

[0020] As a further solution of the present invention, the cave treatment quality control construction specifically includes the following steps:

[0021] C1. Excavation method: According to the cave treatment method proposed in the design drawings, the slope cave should be excavated horizontally to expose the side of the cave;

[0022] C2. For the exposed caves, the filling materials inside should be removed;

[0023] C3. The cave is backfilled with quarry slag or block stones. Mechanical compaction is used during the filling process. When backfilling to the designed slope surface, M10 mortar and stone are used for the cover. The cover thickness is 30cm, and a reserved PVC pipe drainage hole is set within the cover range;

[0024] C4. Excavation of slope caves should be done during rainy seasons to prevent cave roof collapse and other safety hazards;

[0025] C5. After the mortar surface construction of the cave cover is completed, it should be covered with geotextile in time and watered for curing;

[0026] C6. Slope protection engineering should be carried out immediately after the slope is excavated. After the cave is filled and the strength of the cover mortar and stone reaches 50%, the protection engineering construction can be carried out.

[0027] C7. When dealing with karst caves, first find out whether there are any dangerous sources in the caves, and construction workers need to wear gas masks; when filling the caves with quarrying slag, there should be no construction workers inside the caves;

[0028] C8. Establish a complete drainage system to drain rainwater from the roadbed cave treatment area by setting up drainage ditches, intercepting ditches, water retaining belts, water collection wells and longitudinal drainage ditches.

[0029] As a further solution of the present invention, the karst roadbed treatment construction of the filling section also includes water diversion construction; wherein,

[0030] A2 cave backfill specifically includes:

[0031] A21 Before backfilling, multiple steel casings are uniformly inserted into the cave, and adsorption tubes are coaxially arranged inside the steel casings. The diameter of the adsorption tubes is slightly smaller than the diameter of the steel casings. The steel casings are marked with scales. The bottom end of the adsorption tubes is located a certain distance above the bottom end of the steel casings. The end of the adsorption tubes below the steel casings is inserted into the bottom of the cave. The inner wall of the steel casings is coated with lubricating oil. The adsorption tubes include a hollow flexible tube body and a water-absorbing fiber filling layer filled in the hollow flexible tube body. The part of the hollow flexible tube body located in the cave is provided with a plurality of water inlet holes;

[0032] A22 The thickness of each layer of the slab stone backfill in the cave is not more than 50 cm, and the thickness of the mortared slab stone cover is not less than 50 cm. After compaction and leveling, a part of the steel casing is pulled out to ensure that a part of the steel casing is still in the compacted slab stone, and then the filling, compaction and extraction of the steel casing are repeated layer by layer;

[0033] A23. After the cave is backfilled, the steel casing is completely pulled out, and the adsorption tube is connected to the connecting steel pipe through a joint. The upper end of the connecting steel pipe extends out of the concrete cover plate, and the connecting steel pipe is filled with a water-absorbing fiber filling layer;

[0034] A5 also includes: after the concrete cover is constructed, the upper end of the connecting steel pipe is connected to the bottom end of the water absorption trough, the water absorption trough is provided with a water absorption unit, the water absorption unit includes a water absorption expansion bag and a sponge layer, the sponge layer is coated on the top surface and the surrounding sides of the water absorption expansion bag, the water absorption unit is located in the water absorption trough, and the water absorption expansion bag is opposite to the connecting steel pipe, the outer peripheral cover of the water absorption trough is provided with a water storage tank, the bottom of the water storage tank is sealed and connected to the water absorption trough, the side wall of the water absorption trough is provided with a plurality of water permeable holes, the water storage tank is connected to the water storage barrel through a pipeline, the water storage barrel is provided with a liquid level gauge, the water outlet end of the water storage barrel is connected to the water outlet pipe, the water outlet pipe is installed with an intelligent water pump, and the water of the water outlet pipe is discharged through the drainage system;

[0035] A6. Cover the water tank and water barrel with soil to complete the roadbed structure construction.

[0036] The present invention has at least the following beneficial effects:

[0037] First, through the study of karst roadbed treatment, the special roadbed construction process was optimized, the treatment technology was improved, the construction efficiency was improved, and the construction period was saved by about 1 month.

[0038] Second, through the study of roadbed construction technology for special geological conditions, relevant disposal measures were proposed, and a complete set of construction technology and processes were formed, which provided meaningful reference and reference for the subsequent construction of similar projects.

[0039] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a structural diagram of a concrete cover plate of the present invention;

[0041] Figure 2 It is a schematic diagram of water diversion construction of the present invention.

[0042] Among them, 1-concrete cover plate, 2-steel casing, 3-roadbed structure, 4-soil layer, 5-cavity, 6-hollow flexible pipe body, 7-water-absorbent fiber filling layer, 8-connecting steel pipe, 9-water absorption trough, 10-sponge layer, 11-water absorption expansion bag, 12-water storage tank, 13-water storage barrel, 14-liquid level meter, 15-water outlet pipe. DETAILED DESCRIPTION

[0043] The present invention is described in detail and completely below in conjunction with the accompanying drawings. A person of ordinary skill in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly pointed out that the technical solutions and technical features provided in each part of the present invention, including the following description, can be combined with each other without conflict.

[0044] In addition, the embodiments of the present invention involved in the following description are generally only a part of the embodiments of the present invention, rather than all the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0045] The present invention is further described in detail below in conjunction with the accompanying drawings and implementations, and its specific implementation process is as follows:

[0046] like Figure 1~2 As shown, the present invention provides a construction method for a special roadbed in a plateau mountainous area, including the karst roadbed treatment construction of a filling section, the karst roadbed treatment construction of a cutting section, and the karst cave 5 treatment quality control construction;

[0047] Among them, the karst roadbed treatment construction of the filling section adopts a reinforced concrete cover slab 1 spanning structure. First, the debris in the cave 5 is cleared, and then the stone is backfilled and capped. Then, the reinforced concrete cover slab 1 is used to span the cave 5, covering 50~100 cm around the entrance of the cave 5, ensuring that the cover slab is combined with the original rock as a whole to form an effective composite foundation after pouring, preventing the roadbed from settling in the cave 5 range and ensuring the safety and stability of the roadbed and pavement.

[0048] This technical solution may also include the following technical details to better achieve the technical effect: The karst roadbed treatment construction of the filling section specifically includes the following steps:

[0049] A1. Construction preparation: Strictly follow the principle of "exploring and covering at the same time, combining exploration and covering, and sequential construction" to conduct on-site survey of Cave 5, accurately measure the direction, width, and corresponding mileage of Cave 5, and determine the pile position of the slope foot of the roadbed by measurement and setting out. Clear the debris, clean the sediment in the cave, and make a drainage system according to the actual terrain; determine the construction mix ratio after conducting concrete test mix ratio design according to the specifications and properties of various aggregates on site, and submit it to the supervision engineer for approval together with the mechanical properties test report of the steel bars and the construction plan of Cave 5.

[0050] A2. Backfilling of Cave 5: The thickness of each layer of slabs shall not exceed 50cm, and the thickness of the mortar-laid slabs shall not be less than 50cm; Backfilling and tamping of Cave 5: When Cave 5 is backfilled to 50cm from the top, a tamping machine is used for tamping; the tamping machine is used to tamp once first. If the hole collapses, slabs and crushed stones are backfilled and tamped again, and then fully tamped once. Finally, the top surface of Cave 5 is filled with crushed stones;

[0051] A3. Processing and binding of steel bars: The binding of steel bars must be carried out strictly according to the specifications, models, quantity and spacing of the drawings, so that they are horizontal and vertical with accurate spacing. In order to make the frame have sufficient rigidity, a combination of binding and welding is used for construction;

[0052] A4. Construction of concrete cover 1: A41 Concrete mixing and transportation: The minimum mixing time of concrete shall be strictly no less than 2 minutes, and concrete shall be transported by mixer trucks; A42 Inspection work before pouring concrete: Before pouring concrete, check the stability and flatness of the formwork. The base surface and formwork should be kept moist without water accumulation; A43 Concrete pouring: 1) Concrete is poured in layers continuously, and the thickness of each layer shall not exceed 30 cm; 2) Concrete is vibrated by an inserted vibrator, and manual vibration is arranged for local areas that are not vibrated in place; 3) After the concrete is poured, the formwork is kept in place. When the concrete strength reaches 2.5MPa, the formwork can be removed to ensure that it is not disturbed during the strength formation process;

[0053] A5. Concrete curing: After the cover slab is poured, cover the concrete surface with plastic film to retain moisture, and then cover it with a burlap bag to retain moisture. The wet curing period should be maintained for more than 7 days.

[0054] The technical solution may also include the following technical details to achieve better technical effects: in A2, the exposed shallow and smaller dry cave 5 is backfilled with slabs of stone, the seams are caulked with crushed stones, and the upper part is covered with mortar-laid slabs of stone, and then reinforced concrete cover plates 1 of different thicknesses are used to span according to the span;

[0055] When the top plate of the cave 5 at the bottom of the roadbed is not thick, the top plate is uncovered and then filled with stone slabs, and the cracks are filled with crushed stones. The upper part is covered with mortar-laid stone slabs, and the top reinforced concrete cover 1 is spanned;

[0056] For the areas where the caves 5 are concentrated and the cracks are interconnected, the top plate is opened by blasting, and the slabs are backfilled and the seams are filled with crushed stones. The upper part of the cracks is sealed with mortar-laid slabs, and then reinforced concrete cover plates 1 of different thicknesses are used to span according to the span.

[0057] This technical solution may also include the following technical details to better achieve the technical effect: The excavation section karst roadbed treatment construction specifically includes the following steps:

[0058] B1. Use an excavator to remove the slag at the bottom of cave 5. The bearing capacity of the base after cleaning should meet the design requirements;

[0059] B2. The strength of the backfill mortared stone must be greater than 15MPa, and the maximum particle size of the stone shall not be greater than 2 / 3 of the compacted thickness. If the size exceeds the limit, the stone shall be crushed;

[0060] B3. When filling, adopt layered filling, and the filling thickness should not exceed 50cm. When filling layer by layer, the stone transportation route should be arranged, and a dedicated person should be in charge. The material should be unloaded in layers according to the level, first low and then high, first on the two sides and then in the center, and flattened with a large bulldozer; individual uneven places should be leveled with fine stones and stone chips in cooperation with manual work; when backfilling with stone slabs, large stones should be laid first, with the large surface facing down and the small surface facing up, and arranged stably, and then small stones should be used for leveling. The gaps between the stones can be filled with stone slag and gravel;

[0061] B4. For the cave 5 on the slope, the backfilling process in B3 above is adopted, and mud is sprayed on the surface of the road cutting slope, or concrete is poured in the crack development area to ensure the overall stability of the road cutting slope; if there are springs or water flows near the road cutting slope, drainage treatment should be carried out in time.

[0062] This technical solution may also include the following technical details to better achieve the technical effect: The quality control construction of the cave 5 treatment specifically includes the following steps:

[0063] C1. Excavation method: According to the treatment method of cave 5 proposed in the design drawings, the slope cave 5 should be excavated horizontally to expose the side of cave 5;

[0064] C2. For the exposed cave 5, the filling materials (clay and gravel, etc.) inside it should be removed. After the cleaning is completed, check whether the bedrock characteristics at the bottom of the cave 5 are in accordance with the design drawings and geological survey reports. Report to the supervisor engineer for inspection and confirmation before the filling work can be carried out;

[0065] C3, Cave 5 backfill is made of quarried rock or block with good lithology, and mechanical compaction is used during the filling process. When backfilling to the designed slope surface, M10 mortar and stone are used for cover, with a thickness of 30cm, and reserved PVC pipe drainage holes are set within the cover range;

[0066] C4. Excavation of the slope cave 5 should be done during the rainy season to prevent the collapse of the cave 5 roof and cause potential safety hazards;

[0067] C5. After the mortar finishing of the cover of cave 5 is completed, geotextile shall be covered in time and water shall be sprinkled for curing;

[0068] C6. Slope protection engineering should be carried out immediately after the slope is excavated. After the filling of the 5 caves is completed and the strength of the cover mortar and stone reaches 50%, the protection engineering construction can be carried out.

[0069] C7. When treating Cave 5, first find out whether there are dangerous sources such as gas in Cave 5, and the construction workers need to wear gas masks; when Cave 5 is filled with quarrying slag, there should be no construction workers inside Cave 5;

[0070] C8. Establish a complete drainage system to drain rainwater from the roadbed cave 5 treatment area by setting up drainage ditches, intercepting ditches, water retaining belts, water collection wells, longitudinal drainage ditches, etc.

[0071] This technical solution can also include the following technical details to better achieve the technical effect: karst roadbed is generally connected to underground rivers, and groundwater is relatively abundant, so the drainage measures in karst areas are key. It is easy to cause environmental protection, ground subsidence and other problems due to improper drainage and water diversion. Therefore, the karst roadbed treatment construction of the fill section also includes water diversion construction; Among them,

[0072] The backfilling of A2 cave 5 specifically includes:

[0073] Before backfilling A21, multiple steel casings 2 are uniformly inserted into the cave 5. An adsorption tube is coaxially arranged inside the steel casing 2. The diameter of the adsorption tube is slightly smaller than the diameter of the steel casing 2. The steel casing 2 is marked with scales to facilitate observation of the length of the subsequent extraction of the steel casing 2. The bottom end of the adsorption tube is located a certain distance above the bottom end of the steel casing 2. The end of the adsorption tube below the steel casing 2 is inserted into the bottom of the cave 5. The inner wall of the steel casing 2 is coated with lubricating oil to facilitate smooth separation from the adsorption tube when the steel casing 2 is extracted, leaving the adsorption tube in the cave 5. The adsorption tube includes a hollow flexible tube body 6 and a water-absorbing fiber filling layer 7 filled in the hollow flexible tube body 6. The part of the hollow flexible tube body 6 located in the cave 5 is provided with a plurality of water inlet holes;

[0074] A22 The thickness of each layer of the slab stone backfill in the cave 5 is not more than 50 cm, and the thickness of the mortar slab stone cover is not less than 50 cm. After compaction and leveling, a part of the steel casing 2 is pulled out to ensure that a part of the steel casing 2 is still in the compacted slab stone, thereby ensuring the stability of the steel casing 2, and then repeating the filling, compaction and extraction of the steel casing 2 layer by layer;

[0075] A23. After the cave 5 is backfilled, the steel casing 2 is completely pulled out, and the adsorption tube is connected to the connecting steel pipe 8 through a joint. The upper end of the connecting steel pipe 8 extends out of the concrete cover plate 1, and the connecting steel pipe 8 is filled with a water-absorbing fiber filling layer 7;

[0076] A5 also includes: after the concrete cover 1 is constructed, the upper end of the connecting steel pipe 8 is connected to the bottom end of the water absorption tank 9, and the water absorption tank 9 is provided with a water absorption unit, and the water absorption unit includes a water absorption expansion bag 11 and a sponge layer 10, and the sponge layer 10 is coated on the top surface and the surrounding sides of the water absorption expansion bag 11, and the water absorption unit is located in the water absorption tank 9, and the water absorption expansion bag 11 is opposite to the connecting steel pipe 8, and the outer peripheral cover of the water absorption tank 9 is provided with a water storage tank 12, and the bottom of the water storage tank 12 is connected to the water absorption tank 9. The water absorption trough 9 is sealed and connected, and a plurality of water permeable holes are opened on the side wall of the water absorption trough 9. The water storage tank 12 is connected to the water storage barrel 13 through a pipeline, and a liquid level meter 14 is arranged in the water storage barrel 13. The water outlet end of the water storage barrel 13 is connected to the water outlet pipe 15, and an intelligent water pump is installed on the water outlet pipe 15. The water of the water outlet pipe 15 is discharged through the drainage system. The liquid level meter 14 measures the liquid level in the water storage barrel 13. When the set liquid level is exceeded, the intelligent water pump starts for a certain period of time to discharge the water in time;

[0077] A6. Cover the water tank 12 and the water barrel 13 with a soil layer 4 to complete the construction of the roadbed structure 3.

[0078] In the above technical scheme, when the underground river causes excessive water in the cave 5, the water is absorbed by the adsorption tube arranged in the cave 5. As more and more water is absorbed, the water absorption expansion bag 11 absorbs and expands the sponge on the top and sides, and the liquid in the sponge is discharged through the water-permeable holes of the water absorption trough 9 and enters the water storage tank 12. The water flows through the water storage tank 12 and the pipeline into the water storage barrel 13, and then the water is discharged to the drainage system through the intelligent water pump.

[0079] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A construction method for a special roadbed in a plateau mountainous area, characterized in that: It includes the karst roadbed treatment construction in the filling section, the karst roadbed treatment construction in the excavation section and the karst cave treatment quality control construction; Among them, the karst roadbed treatment construction of the filling section adopts a reinforced concrete cover spanning structure. First, the debris in the cave is cleared, and then the stone is backfilled and capped. Then, a reinforced concrete cover is used to span the cave, covering 50~100 cm around the cave entrance to ensure that the cover is combined with the original rock to form an effective composite foundation after pouring. The karst roadbed treatment construction of the filling section specifically includes the following steps: A1. Construction preparation: remove debris, clean up sediments in the cave, and make a drainage system according to the actual terrain; A2. Cave backfill: The thickness of each layer of slab backfill shall not exceed 50cm, and the thickness of the mortar-laid slab cover shall not be less than 50cm; Cave backfill compaction: When the cave is backfilled to 50cm from the top, a tamping machine shall be used for compaction; A3. Processing and binding of steel bars; A4. Construction of concrete cover: A41 Concrete mixing and transportation: The minimum mixing time of concrete shall be strictly no less than 2 minutes, and concrete shall be transported by mixer trucks; A42 Inspection work before pouring concrete: Before pouring concrete, check the stability and flatness of the formwork. The base surface and formwork should be kept moist without water accumulation; A43 Concrete pouring: 1) Concrete is poured in layers continuously, and the thickness of each layer shall not exceed 30 cm; 2) Concrete vibration is carried out by inserting vibrators, and manual vibration is arranged for local areas that are not vibrated in place; 3) After the concrete pouring is completed, the formwork is kept in place. When the concrete strength reaches 2.5 MPa, the formwork can be removed to ensure that it is not disturbed during the strength formation process; A5. Concrete curing: After the cover plate is poured, the concrete surface should be covered with plastic film to retain moisture, and then covered with burlap bags to retain moisture. The wet curing period should be maintained for more than 7 days; The karst roadbed treatment construction of the filling section also includes water diversion construction; wherein, A2 cave backfill specifically includes: A21 Before backfilling, multiple steel casings are uniformly inserted into the cave, and adsorption tubes are coaxially arranged inside the steel casings. The diameter of the adsorption tubes is slightly smaller than the diameter of the steel casings. The steel casings are marked with scales. The bottom end of the adsorption tubes is located a certain distance above the bottom end of the steel casings. The end of the adsorption tubes below the steel casings is inserted into the bottom of the cave. The inner wall of the steel casings is coated with lubricating oil. The adsorption tubes include a hollow flexible tube body and a water-absorbing fiber filling layer filled in the hollow flexible tube body. The part of the hollow flexible tube body located in the cave is provided with a plurality of water inlet holes; A22 The thickness of each layer of the slab stone backfill in the cave is not more than 50 cm, and the thickness of the mortared slab stone cover is not less than 50 cm. After compaction and leveling, a part of the steel casing is pulled out to ensure that a part of the steel casing is still in the compacted slab stone, and then the filling, compaction and extraction of the steel casing are repeated layer by layer; A23. After the cave is backfilled, the steel casing is completely pulled out, and the adsorption tube is connected to the connecting steel pipe through a joint. The upper end of the connecting steel pipe extends out of the concrete cover plate, and the connecting steel pipe is filled with a water-absorbing fiber filling layer; A5 also includes: after the concrete cover is constructed, the upper end of the connecting steel pipe is connected to the bottom end of the water absorption trough, the water absorption trough is provided with a water absorption unit, the water absorption unit includes a water absorption expansion bag and a sponge layer, the sponge layer is coated on the top surface and the surrounding sides of the water absorption expansion bag, the water absorption unit is located in the water absorption trough, and the water absorption expansion bag is opposite to the connecting steel pipe, the outer peripheral cover of the water absorption trough is provided with a water storage tank, the bottom of the water storage tank is sealed and connected to the water absorption trough, the side wall of the water absorption trough is provided with a plurality of water permeable holes, the water storage tank is connected to the water storage barrel through a pipeline, the water storage barrel is provided with a liquid level gauge, the water outlet end of the water storage barrel is connected to the water outlet pipe, the water outlet pipe is installed with an intelligent water pump, and the water of the water outlet pipe is discharged through the drainage system; A6. Cover the water tank and water barrel with soil to complete the roadbed structure construction.

2. The construction method of special roadbed in plateau mountainous area as claimed in claim 1, characterized in that: The karst roadbed treatment construction of the excavation section specifically includes the following steps: B1. Use an excavator to remove the slag at the bottom of the cave. The bearing capacity of the base after cleaning should meet the design requirements; B2. The strength of the backfill mortared stone must be greater than 15MPa, and the maximum particle size of the stone shall not be greater than 2 / 3 of the compacted thickness; B3. When filling, adopt layered filling with a thickness of no more than 50cm. Layer by layer, first low and then high, first two sides and then the center, and use a large bulldozer to level it. Individual uneven places should be leveled with fine stones and stone chips in cooperation with manual labor. When backfilling with stone slabs, large stones should be laid first, with the large surface facing down and the small surface facing up, and arranged stably, and then small stones should be used for leveling. The gaps between the stones should be filled with stone slag and gravel. B4. For caves on the slope, the backfilling process in B3 above is adopted, and mud is sprayed on the surface of the road cutting slope, or concrete is poured in the crack development area to ensure the overall stability of the road cutting slope; if there are springs or water flows near the road cutting slope, drainage treatment should be carried out in time.

3. The construction method of special roadbed in plateau mountainous area as claimed in claim 1, characterized in that: The cave treatment quality control construction specifically includes the following steps: C1. Excavation method: According to the cave treatment method proposed in the design drawings, the slope cave should be excavated horizontally to expose the side of the cave; C2. For the exposed caves, the filling materials inside should be removed; C3. The cave is backfilled with quarry slag or block stones. Mechanical compaction is used during the filling process. When backfilling to the designed slope surface, M10 mortar and stone are used for the cover. The cover thickness is 30cm, and a reserved PVC pipe drainage hole is set within the cover range; C4. Excavation of slope caves should be done during rainy seasons to prevent cave roof collapse and other safety hazards; C5. After the mortar surface construction of the cave cover is completed, the geotextile should be covered in time and watered for curing; C6. Slope protection engineering should be carried out immediately after the slope is excavated. After the cave is filled and the strength of the cover mortar and stone reaches 50%, the protection engineering construction can be carried out. C7. When dealing with karst caves, first find out whether there are any dangerous sources in the caves, and construction workers need to wear gas masks; when filling the caves with quarrying slag, there should be no construction workers inside the caves; C8. Establish a complete drainage system to drain rainwater from the roadbed cave treatment area by setting up drainage ditches, intercepting ditches, water retaining belts and water collection wells.

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