Anti-settling roadbed structure and construction method

Abstract

The invention discloses an anti-sedimentation roadbed structure and a construction method, and relates to the technical field of roadbeds, the anti-sedimentation roadbed structure comprises rigid piles, pile caps, geogrids and embankment filling soil, and the embankment filling soil is formed by mixing lime and fly ash according to the mass ratio of 1: 2-1: 3. Lateral deformation of filling soil is restrained through friction force and meshing force between the geogrid and the filling soil of the embankment, so that the integrity of the embankment is enhanced, and when the embankment is subjected to a vertical load effect, the reinforced material shares a part of tensile force, so that stress concentration in the filling soil is reduced, differential settlement of the embankment is effectively controlled, and the stability of the embankment is improved. The stability of the embankment is improved, relatively high strength is formed in a relatively short time, the later strength is relatively gentle to increase, the stability is high, and the engineering property of soil can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of roadbed, and in particular to an anti-settlement roadbed structure and a construction method. Background Art

[0002] The roadbed is the basic part of road projects such as highways or railways. It is a strip structure built according to the route location and certain technical requirements, bearing the traffic load and natural factors from the road surface. Simply put, the roadbed is like the "foundation" of the road, providing solid support for the road surface structure. For example, in a highway, the quality of the roadbed is directly related to whether the road surface can stably withstand high-speed vehicle driving for a long time.

[0003] At present, the compaction degree of roadbed fill may not reach the ideal state during the construction process due to factors such as construction technology and compaction machinery. For example, in high embankments, if the compaction is uneven, after the road is put into use, the repeated action of vehicle loads will cause the fill to be further compacted and deformed, resulting in uneven settlement. This uneven settlement will cause cracks and potholes on the road surface, affecting driving comfort and safety. At the same time, differences in the properties of the foundation soil will also cause uneven settlement. For example, in the section where the soft soil foundation and the hard soil foundation meet, the soft soil foundation part will produce a large settlement due to its relatively low bearing capacity, resulting in an uneven road surface. In addition, for some special soil foundations (such as soft soil, collapsible loess, etc.), even if treatment measures are taken during the construction process, they will continue to settle for a period of time after the completion of the project due to drainage consolidation of the soil body, structural remodeling and other processes. This may increase the maintenance cost of the road in the later stage and may also affect the service life of the road.

[0004] Currently, no effective solution has been proposed for the problems in the related technologies. Summary of the invention

[0005] In view of the problems in the related art, the present invention proposes an anti-settlement roadbed structure and a construction method to overcome the above technical problems existing in the existing related art.

[0006] The technical solution of the present invention is achieved in this way:

[0007] In one aspect, the present invention:

[0008] A subsidence prevention roadbed structure, comprising: rigid piles, pile caps, geogrids and embankment fill, wherein;

[0009] Rigid piles pass through the soft soil layer and transfer the embankment load to the deeper harder soil layer. A pile cap is set on the top of the pile to increase the contact area between the pile and the geogrid. The geogrid is laid between the pile cap and the embankment fill. Its grid shape is interlocked with the embankment fill to form a stable reinforced soil structure.

[0010] The embankment fill is a mixture of lime and fly ash in a mass ratio of 1:2 to 1:3.

[0011] Furthermore, the rigid piles are concrete piles, cast-in-place piles or CFG piles.

[0012] Another aspect of the present invention is:

[0013] A roadbed construction method for preventing subsidence comprises the following steps:

[0014] Clean the site in advance, remove vegetation, debris, garbage and unsuitable topsoil within the construction site, and level the site so that the slope of the construction site meets the drainage requirements. The horizontal slope should be no less than 2% to 3% to drain surface water during the construction process.

[0015] Carry out pile foundation construction, including: pile position setting and pile construction;

[0016] Carry out pile cap construction;

[0017] When laying geogrids, cut the geogrids into appropriate lengths and widths according to the width of the embankment and the spacing between pile caps, with a longitudinal overlap length of not less than 300mm and a transverse overlap length of not less than 500mm. Lift the geogrids onto the pile caps with a crane or loader, lay the geogrids evenly on the pile caps, and ensure that the geogrids are in close contact with the pile caps. Tie and fix the geogrids with connecting rods or wires at the overlaps of the geogrids, and fix them to the foundation soil with U-shaped nails or steel bars around the geogrids to prevent them from shifting during the filling process.

[0018] The embankment filling construction includes the following steps:

[0019] Carry out filling and spreading, transport the fill to the construction site, and spread the fill on the geogrid with a bulldozer or loader. The layer thickness of the fill shall not exceed 300-500mm;

[0020] To compact the fill, static rollers and vibratory rollers are used. The compaction sequence is light first, heavy later, slow first, fast later, and the compaction is carried out from the edge of the embankment to the center.

[0021] The pile position surveying includes: according to the construction requirements, using a total station or GPS-RTK surveying equipment to accurately survey the pile positions at the construction site, and the deviation of the position of a single pile does not exceed 100 mm.

[0022] The construction of the piles includes: prefabricated pile construction or CFG pile construction, including the following steps:

[0023] The prefabricated pile construction includes: using a crane to lift the prefabricated pile to the pile position, and then using a static pile driver or a vibrating pile driver to sink the pile into the soil, and the verticality deviation of the pile body shall not exceed 1%;

[0024] The CFG pile construction includes: drilling holes using a long spiral drill, during which the drilling rig must be kept stable and the verticality deviation of the drill rod must not exceed 1%. After drilling to the designed depth, concrete is poured into the hole through the pipe in the drill rod, and the drill rod is slowly lifted to fill the hole with concrete. The slump of the concrete is controlled at 160 to 200 mm to ensure its fluidity and pouring quality.

[0025] Wherein, the pile cap construction comprises the following steps:

[0026] After the pile foundation construction is completed, the pile head should be processed in advance;

[0027] Carry out pile cap reinforcement binding and formwork installation, where the double-sided welding length is not less than 5d, and the single-sided welding length is not less than 10d;

[0028] Install the pile cap formwork, using steel formwork or wooden formwork, the steel formwork is connected with bolts, and the wooden formwork is fixed with tie rods and supports;

[0029] Carry out the pouring and curing of pile cap concrete. When pouring concrete, adopt the layered pouring method, the thickness of each layer shall not exceed 300mm, and use the inserted vibrator to vibrate and compact it.

[0030] The embankment filling is formed by mixing lime and fly ash in a mass ratio of 1:2 to 1:3.

[0031] Beneficial effects of the present invention:

[0032] The rigid piles of the present invention bear most of the vertical load of the embankment, reducing the stress on the foundation soil, while the geogrid coordinates the deformation of the soil between the piles and the piles, making the stress distribution in the embankment fill more uniform. At the same time, the geogrid constrains the lateral deformation of the fill through the friction and bite force between the geogrid and the embankment fill, thereby enhancing the integrity of the embankment. When the embankment is subjected to vertical loads, the reinforcing material shares a part of the tension, thereby reducing the stress concentration in the fill, effectively controlling the uneven settlement of the embankment, and improving the stability of the embankment. In addition, the embankment fill is made of lime and fly ash mixed in a mass ratio of 1:2 to 1:3. The lime can react with the active ingredients of silicon and aluminum oxide in the fly ash to produce a volcanic ash reaction to generate a hydration product with gelling properties, forming a higher strength in a shorter time, and the later strength growth is relatively gentle, with high stability, which can effectively improve the engineering properties of the soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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.

[0034] Figure 1 It is a schematic flow chart of a roadbed construction method for preventing subsidence according to an embodiment of the present invention;

[0035] Figure 2 It is a schematic diagram of geogrid laying in an anti-settlement roadbed construction method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the accompanying 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 belong to the scope of protection of the present invention.

[0037] According to an embodiment of the present invention, an anti-settlement roadbed structure is provided.

[0038] The anti-settlement roadbed structure according to an embodiment of the present invention comprises: a rigid pile, a pile cap, a geogrid and an embankment fill, wherein;

[0039] Rigid piles pass through the soft soil layer and transfer the embankment load to the deeper harder soil layer. A pile cap is set on the top of the pile to increase the contact area between the pile and the geogrid. The geogrid is laid between the pile cap and the embankment fill. Its grid shape is interlocked with the embankment fill to form a stable reinforced soil structure.

[0040] The embankment fill is a mixture of lime and fly ash in a mass ratio of 1:2 to 1:3.

[0041] With the help of the above scheme, the rigid piles bear most of the vertical loads of the embankment, reducing the stress on the foundation soil, while the geogrid coordinates the deformation of the soil between the piles, making the stress distribution in the embankment fill more uniform. At the same time, the geogrid constrains the lateral deformation of the fill through the friction and bite force between the geogrid and the embankment fill, thereby enhancing the integrity of the embankment. When the embankment is subjected to vertical loads, the reinforcing material shares part of the tension, thereby reducing the stress concentration in the fill, effectively controlling the uneven settlement of the embankment, and improving the stability of the embankment. In addition, the embankment fill is mixed with lime and fly ash in a mass ratio of 1:2 to 1:3. The lime can react with the active ingredients of silicon and aluminum oxide in the fly ash to produce a hydration product with gelling properties, forming a higher strength in a shorter time, and the later strength growth is relatively gentle, with high stability, which can effectively improve the engineering properties of the soil.

[0042] Among them, the rigid piles are concrete piles, cast-in-place piles or CFG piles.

[0043] In this technical solution, for the above-mentioned geogrid, a layer of geogrid is laid at a vertical interval of 0.5 to 1 meter, and the geogrid is reversed at the embankment slope.

[0044] According to an embodiment of the present invention, a roadbed construction method for preventing subsidence is provided.

[0045] like Figure 1 As shown, the anti-settlement roadbed construction method according to an embodiment of the present invention includes the following steps:

[0046] Step S1, pre-cleaning the site, removing vegetation, debris, garbage and unsuitable topsoil within the construction site, and leveling the site so that the slope of the construction site meets the drainage requirements, wherein the horizontal slope is not less than 2% to 3% to drain surface water during the construction process;

[0047] This technical solution ensures the purity of the foundation soil and avoids the influence of unfavorable geological conditions such as weak interlayers on the stability of the embankment. Specifically, for sites with a large number of weeds and tree roots, bulldozers and excavators are used to uproot them and then transport them away from the construction site.

[0048] Step S2, performing pile foundation construction, which includes: performing pile position setting and pile construction;

[0049] Step S201, stake out the pile position, according to the construction requirements, use a total station or GPS-RTK (real-time dynamic positioning technology) measuring equipment to accurately stake out the pile position at the construction site, and the single pile position deviation does not exceed 100mm;

[0050] Specifically, when applying, after the pile position is staked out, a wooden stake or steel nail should be driven into the center of the pile position as a mark, and obvious signs should be set up around it to prevent the pile position from being damaged during construction.

[0051] Step S202, wherein the pile construction includes: prefabricated pile construction or CFG pile construction, specifically:

[0052] Among them, for prefabricated pile construction, the prefabricated pile is lifted to the pile position by a crane, and then the pile is sunk into the soil by a static pile driver or a vibrating pile driver. During the pile sinking process, the verticality of the pile must be strictly controlled, which can be monitored by setting a verticality meter on the pile driver. The verticality deviation of the pile body shall not exceed 1%. For example, when static pile sinking, the pile driving speed should be controlled according to the geological conditions and the type of pile. The pile driving speed in soft soil foundation should not be too fast to avoid tilting the pile body or breaking the pile.

[0053] Among them, for CFG pile construction, a long spiral drill is used to drill holes. During the drilling process, the drilling rig must be kept stable and the verticality deviation of the drill rod must not exceed 1%. After drilling to the designed depth, concrete (consisting of cement, fly ash, crushed stone, admixtures and water) is poured into the hole through the pipe in the drill rod, and the drill rod is slowly lifted to fill the hole with concrete. The slump of the concrete is controlled at 160 to 200 mm to ensure its fluidity and pouring quality.

[0054] In addition, when applying, prepare pile materials in advance according to construction requirements, including: precast piles (including precast concrete piles and cast-in-place piles) or CFG (cement fly ash gravel) piles. For precast concrete piles, check their appearance quality to ensure that there are no cracks, corner drops and other defects in the pile body; for cast-in-place piles, prepare steel cage materials and concrete pouring equipment. The concrete strength grade of precast concrete piles must meet the design requirements and can be C30~C40. Check their factory certificates and quality inspection reports when entering the site.

[0055] Step S3, performing pile cap construction, includes the following steps:

[0056] Step S301, after the pile foundation construction is completed, the pile head is processed. Specifically:

[0057] If it is a prefabricated pile, the part of the pile body that is higher than the designed pile top elevation should be cut off, and the pile head should be kept flat when cutting the pile. For CFG piles, the floating slurry part of the pile head should be removed to expose the fresh concrete surface on the pile top. The elevation deviation after the pile head treatment should not exceed ±50mm.

[0058] Step S302, pile cap reinforcement binding and formwork installation, wherein the welding length and quality of the reinforcement must meet the construction requirements, and the double-sided welding length is not less than 5d (d is the reinforcement diameter), and the single-sided welding length is not less than 10d.

[0059] Step S303, installing the pile cap formwork, using a steel formwork or a wooden formwork, the steel formworks are connected with bolts, and the wooden formwork is fixed with tie rods and supports.

[0060] Specifically, the formwork must have sufficient strength and rigidity to withstand the pressure during the concrete pouring process. The formwork must be installed firmly and its joints must be tight to prevent leakage.

[0061] Step S304, pouring and curing the pile cap concrete, wherein the concrete is poured in layers, with each layer not exceeding 300 mm in thickness, and is compacted with an inserted vibrator. The vibration time is based on the concrete surface no longer sinking, no bubbles emerging, and no slurry on the surface.

[0062] This technical solution, specifically, before pouring the pile cap concrete, check whether the debris in the template is cleaned up and whether the thickness of the steel bar protection layer meets the requirements. At the same time, after the concrete pouring is completed, it is necessary to carry out maintenance in time, which can be covered with plastic film and straw mats, and the maintenance time is not less than 7 days to ensure the strength growth of the concrete.

[0063] In addition, when applying, for the above-mentioned pile cap concrete, cement, sand and gravel and other materials are prepared in advance, and trial mix is ​​carried out according to the designed mix ratio. The size and reinforcement of the pile cap should be made strictly according to the design drawings, and its concrete strength grade is slightly higher than that of the pile body concrete, such as C35~C45.

[0064] Step S4, such as Figure 2 As shown, geogrid is laid. According to the width of the embankment and the distance between pile caps, the geogrid is cut into suitable length and width, with the longitudinal overlap length not less than 300mm and the transverse overlap length not less than 500mm. The geogrid is lifted to the pile cap by a crane or a loader, and the geogrid is laid flat on the pile cap to ensure close contact between the geogrid and the pile cap. At the overlap of the geogrid, connecting rods or wires are used for binding and fixing, and U-shaped nails or steel bars are used around the geogrid to fix it to the foundation soil to prevent the geogrid from shifting during the filling process.

[0065] Specifically, the spacing between the U-shaped nails is 1 to 2 meters, and the nailing depth is not less than 300 mm.

[0066] In addition, for the above geogrid, its tensile strength, elongation and other performance indicators meet the design requirements. The width of the geogrid should be reasonably selected according to the width of the embankment, and a variety of specifications of 2 to 6 meters should be adopted. After entering the site, sampling should be carried out for tensile testing to ensure that its tensile strength meets the design standard. At the same time, the geogrid should be protected from damage during storage and transportation to prevent its physical properties from being reduced.

[0067] Step S5, performing embankment filling construction, includes the following steps:

[0068] Step S501, carry out filling and spreading, transport the filling to the construction site, and spread the filling on the geogrid by a bulldozer or loader. The layer thickness of the filling does not exceed 300-500 mm.

[0069] Step S502, compacting the fill soil, using a static roller and a vibratory roller to compact the fill soil, wherein the compaction sequence is light first then heavy, slow first then fast, and compaction is performed from the edge of the embankment to the center.

[0070] This technical solution uses a static roller to press 1 to 2 times at the beginning, then uses a vibratory roller to press 3 to 5 times, and finally uses a static roller to press 1 to 2 times again to achieve the specified compaction degree. The static pressing speed does not exceed 2km / h, and the vibration pressing speed does not exceed 4km / h.

[0071] In addition, during application, the compaction degree of the fill should be checked regularly, and testing methods such as sand filling method or ring knife method should be adopted to ensure that the compaction degree meets the construction requirements.

[0072] Among them, for the above-mentioned embankment filling, lime and fly ash are mixed in a mass ratio of 1:2 to 1:3.

[0073] After compaction, the cementitious material inside the lime-fly ash mixture can fill the pores between soil particles, making the soil structure more compact. At the same time, the mixture can improve the shear strength and bearing capacity of the soil, reduce deformation under load, and effectively prevent embankment settlement. At the same time, the lime-fly ash mixture mixed with a mass ratio of 1:2 to 1:3 can form a higher strength in a shorter time, and the later strength growth is relatively slow, with high stability, which can effectively improve the engineering properties of the soil.

[0074] In summary, with the help of the above technical scheme of the present invention, the rigid piles of the present invention bear most of the vertical loads of the embankment and reduce the stress of the foundation soil, while the geogrid coordinates the deformation of the soil between the piles and the piles, so that the stress distribution in the embankment fill is more uniform. At the same time, the geogrid constrains the lateral deformation of the fill through the friction and bite force between the geogrid and the embankment fill, so that the integrity of the embankment is enhanced. When the embankment is subjected to vertical loads, the reinforcing material shares part of the tension, thereby reducing the stress concentration in the fill, effectively controlling the uneven settlement of the embankment, and improving the stability of the embankment. In addition, a mixture of lime and fly ash with a mass ratio of 1:2 to 1:3 is used for embankment fill. The lime can react with the active ingredients of silicon and aluminum oxide in the fly ash to produce a volcanic ash reaction to generate a hydration product with gelling properties, forming a higher strength in a shorter time, and the later strength growth is relatively gentle, with high stability, which can effectively improve the engineering properties of the soil.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. After considering the disclosure of the specification and the examples, those skilled in the art will easily think of other embodiments of the present disclosure. This application is intended to cover any modification, use or adaptive change of the present disclosure, which follows the principle of the present disclosure and includes common knowledge or customary technical means in the technical field that are not disclosed in the present disclosure. The specification and the examples are only regarded as exemplary, and the true scope and spirit of the present disclosure are indicated by the claims.

[0076] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A subsidence-resistant roadbed structure, characterized in that: include: It consists of rigid piles, pile caps, geogrids and embankment fill, where; Rigid piles pass through the soft soil layer and transfer the embankment load to the deeper harder soil layer. A pile cap is set on the top of the pile to increase the contact area between the pile and the geogrid. The geogrid is laid between the pile cap and the embankment fill. Its grid shape is interlocked with the embankment fill to form a stable reinforced soil structure. The embankment fill is a mixture of lime and fly ash in a mass ratio of 1:2 to 1:

3.

2. The anti-settlement roadbed structure according to claim 1, characterized in that: The rigid piles are concrete piles, cast-in-place piles or CFG piles.

3. A roadbed construction method for preventing subsidence, characterized in that: The construction method for the anti-settlement roadbed according to any one of claims 1 to 2 comprises the following steps: Clean the site in advance, remove vegetation, debris, garbage and unsuitable topsoil within the construction site, and level the site so that the slope of the construction site meets the drainage requirements. The horizontal slope should be no less than 2% to 3% to drain surface water during the construction process. Carry out pile foundation construction, including: pile position setting and pile construction; Carry out pile cap construction; When laying geogrids, cut the geogrids into appropriate lengths and widths according to the width of the embankment and the spacing between pile caps, with a longitudinal overlap length of not less than 300mm and a transverse overlap length of not less than 500mm. Lift the geogrids onto the pile caps with a crane or loader, lay the geogrids evenly on the pile caps, and ensure that the geogrids are in close contact with the pile caps. Tie and fix the geogrids with connecting rods or wires at the overlaps of the geogrids, and fix them to the foundation soil with U-shaped nails or steel bars around the geogrids to prevent them from shifting during the filling process. The embankment filling construction includes the following steps: Carry out filling and spreading, transport the fill to the construction site, and spread the fill on the geogrid with a bulldozer or loader. The layer thickness of the fill shall not exceed 300-500mm; To compact the fill, static rollers and vibratory rollers are used. The compaction sequence is light first, heavy later, slow first, fast later, and the compaction is carried out from the edge of the embankment to the center.

4. The anti-settlement roadbed construction method according to claim 3, characterized in that: The pile position surveying includes: according to the construction requirements, using a total station or GPS-RTK surveying equipment to accurately survey the pile positions at the construction site, wherein the position deviation of a single pile does not exceed 100 mm.

5. The anti-settlement roadbed construction method according to claim 4, characterized in that: The construction of the piles includes: prefabricated pile construction or CFG pile construction, including the following steps: The prefabricated pile construction includes: using a crane to lift the prefabricated pile to the pile position, and then using a static pile driver or a vibrating pile driver to sink the pile into the soil, and the verticality deviation of the pile body shall not exceed 1%; The CFG pile construction includes: drilling holes using a long spiral drill, during which the drilling rig must be kept stable and the verticality deviation of the drill rod must not exceed 1%. After drilling to the designed depth, concrete is poured into the hole through the pipe in the drill rod, and the drill rod is slowly lifted to fill the hole with concrete. The slump of the concrete is controlled at 160 to 200 mm to ensure its fluidity and pouring quality.

6. The anti-settlement roadbed construction method according to claim 3, characterized in that: The pile cap construction comprises the following steps: After the pile foundation construction is completed, the pile head should be processed in advance; Carry out pile cap reinforcement binding and formwork installation, where the double-sided welding length is not less than 5d, and the single-sided welding length is not less than 10d; Install the pile cap formwork, using steel formwork or wooden formwork, the steel formwork is connected with bolts, and the wooden formwork is fixed with tie rods and supports; Carry out the pouring and curing of pile cap concrete. When pouring concrete, adopt the layered pouring method, the thickness of each layer shall not exceed 300mm, and use the inserted vibrator to vibrate and compact it.

7. The anti-settlement roadbed construction method according to claim 3, characterized in that: The embankment filling is formed by mixing lime and fly ash in a mass ratio of 1:2 to 1:3.

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