Garbage landfill structure designed by utilizing long and narrow valley in loess area and construction method of garbage landfill structure

Abstract

The invention provides a refuse landfill structure designed by utilizing a long and narrow valley in a loess area and a construction method of the refuse landfill structure. The refuse landfill structure comprises a refuse landfill area formed by long and narrow valleys in the loess area, a bottom layer anti-seepage structure constructed on the bottom face of the refuse landfill area, reinforcing structures constructed on slope faces on the two sides of the refuse landfill area, and a covering layer laid on the surface layer of the refuse landfill area. The garbage landfill area is a concave area defined by a valley concave groove land, side slopes located on the two sides of the valley concave groove land and a blocking dam located in the valley concave groove land. The bottom layer anti-seepage structure is arranged on the bottom face of a concave area of the valley concave groove land in the length direction of the valley concave groove land and comprises a lower layer underground water collecting main blind ditch and an upper layer percolate collecting main blind ditch. According to the refuse landfill structure, the long and narrow steep valley terrain in the loess area is fully utilized, the construction method is low in engineering cost and small in environmental pollution, and good economic benefits and social benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection technology, in particular to a garbage landfill structure designed using narrow and steep valleys in a loess region and a construction method thereof, aiming to provide an efficient, stable and environmentally friendly garbage landfill solution. Background Art

[0002] With the development of my country's economy and the improvement of people's living standards, the amount of domestic waste has gradually increased. For the treatment of accumulated garbage, the main disposal technologies used in my country are incineration, composting, landfill and recycling. These disposal methods have their own advantages and disadvantages, but at this stage, the most suitable garbage disposal method for China is sanitary landfill. The general design idea of ​​a landfill is to excavate a foundation pit on flat ground at a certain slope and then lay an anti-seepage system to form a composite foundation pit for landfilling garbage.

[0003] According to the natural conditions of the landfill area, in the loess area, due to geological reasons, there are many narrow valleys on site, which can be used to build landfills without the need to excavate foundation pits. Loess valley areas often have complex terrain and gullies. These areas are usually not fully utilized in the process of urbanization, so there are abundant land resources for landfill construction. However, due to the erodibility of loess and the complexity of valley terrain, traditional landfill design structures are difficult to meet the requirements of anti-seepage, reinforcement and environmental protection. Therefore, it is necessary to provide a new comprehensive design structure for landfills to solve the above problems. Summary of the invention

[0004] In view of the defects of the prior art, the present invention provides a landfill structure and a construction method thereof designed using the narrow and long valleys in the loess region. The landfill fully utilizes the narrow and steep valley terrain in the loess region, and can solve the erosion of loess and the complexity of the valley terrain, meeting the requirements of anti-seepage, reinforcement and environmental protection.

[0005] In order to achieve the above technical objectives, the present invention provides a landfill structure designed using narrow and long valleys in loess areas, the landfill structure comprising a landfill area formed using narrow and long valleys in loess areas, a bottom layer anti-seepage structure constructed on the bottom surface of the landfill area, a reinforcement structure constructed on the slopes on both sides of the landfill area, and a covering layer laid on the surface of the landfill area, the landfill area is a concave area formed by a concave trough in the valley, slopes on both sides of the concave trough in the valley, and a retaining dam arranged in the concave trough in the valley; the bottom layer anti-seepage structure is arranged on the bottom surface of the concave area of ​​the concave trough in the valley along the length direction of the concave trough in the valley, including a main blind ditch for collecting groundwater in the lower layer and a main blind ditch for collecting leachate in the upper layer; reinforcement structures are respectively constructed on the slopes on both sides of the concave trough in the valley, The reinforcement structure includes a plurality of soil nails driven into the slope surfaces on both sides, steel meshes hung on the slope surfaces on both sides and a concrete surface layer sprayed on the slope surfaces on both sides, the steel meshes are fixedly welded to the soil nails, and the concrete surface layer covers the steel meshes; a foundation treatment layer is provided on the bottom surface of the concave trough in the valley, and the retaining dam is a dam body structure formed by filling on-site loess, and anti-seepage surface layers are respectively provided on the slope surfaces of the slopes on both sides of the concave trough in the valley, the surface of the foundation treatment layer on the bottom surface of the concave trough in the valley, and the surface of the dam body of the retaining dam; a reinforced cushion layer and a protective surface layer are laid above the anti-seepage layer on the slope surface of the retaining dam, and a toe back-pressure soil layer for back-pressing the anti-seepage surface layer is respectively provided on the toe lines of the slopes on both sides of the concave trough in the valley; after the garbage filling is completed, the covering layer covers the surface of the garbage layer filled in the landfill area.

[0006] A more preferred technical solution of the present invention: the narrow valley in the loess area is divided into multiple adjacent landfill areas by multiple retaining dams, and two adjacent landfill areas share one retaining dam. The retaining dam is an isosceles trapezoidal structure with a flat middle part and sloping surfaces on both sides, and the sloping surfaces on both sides face the two adjacent landfill areas respectively.

[0007] The preferred technical solution of the present invention is as follows: the anti-seepage surface layer is composed of GCL waterproof blanket, HDPE geomembrane and filament geotextile from the inside to the outside, the GCL waterproof blanket is tightly laid on the slope surface of the slopes on both sides of the concave trough in the valley and the slope surface of the retaining dam, and the HDPE geomembrane is seamlessly connected by heat welding technology; the reinforced cushion layer is composed of a lower gravel cushion layer and an upper crushed stone cushion layer, and the protective surface layer is a dry-laid C15 concrete block slope protection layer; the spacing between the soil nails is 1000mm to 1500mm; the thickness of the foundation treatment layer on the bottom surface of the concave trough in the valley is controlled at 250 to 1000mm, and is backfilled with sand and crushed stone materials mixed in loess, and the mixing ratio is controlled at 5% to 30%; the compaction coefficient of the foundation treatment layer should be no less than 0.93.

[0008] The preferred technical solution of the present invention is as follows: the bottom anti-seepage structure is constructed on the midline of the bottom surface of the valley concave trough; the bottom anti-seepage structure includes an inverted trapezoidal blind ditch groove opened on the bottom surface of the valley concave trough, the blind ditch groove extends outside the landfill area and is connected to the bottom anti-seepage structure at the bottom of the next adjacent landfill area, or is connected to the external drainage system; the overall groove depth of the blind ditch groove is 0.8 to 1.2 m, the bottom width is 0.8 to 1.2 m, the top width is 1.8 to 2.2 m, and the slopes on both sides are 1:1; the main blind ditch for collecting groundwater in the lower layer includes a first layer of geotextile anti-filtration layer, a geotextile layer wrapped in the blind ditch groove, and a geotextile anti-filtration layer. A three-flowered pipe wrapped with geotextile, a gravel layer filled in the lower layer of the blind ditch groove and a final protective filter layer laid on the top of the gravel layer; the upper leachate collection main blind ditch includes an impermeable layer laid on the final protective filter layer, an impermeable isolation layer arranged on the impermeable layer, a pebble leachate diversion layer laid on the impermeable isolation layer, a leachate collection and discharge pipe buried in the pebble leachate diversion layer and a geotextile protective layer covering the top of the pebble leachate diversion layer; the impermeable layer and the impermeable surface layer are an integrated structure, and the pebble particle size range of the pebble leachate diversion layer is 20-40mm; the gravel layer is filled with gravel with a diameter of 3-5cm.

[0009] A better technical solution of the present invention: the covering layer includes a clay, sand or gravel base layer laid on the surface of the landfill layer, the thickness of the base layer is 300mm to 350mm, and a HDPE film layer, a 300mm to 350mm compacted clay barrier layer, a geotextile or geomembrane isolation layer, a gravel or expanded clay drainage layer and a nutrient soil layer are laid on the surface of the base layer from bottom to top, and ornamental plants are planted in the nutrient soil layer.

[0010] The preferred technical solution of the present invention is as follows: anchor trenches for fixing the anti-seepage surface layer are provided on both sides of the top surface of the landfill area, the width of the anchor trench is 0.5m-1.0m, and the depth is 0.5m-1.0m. Both sides of the anti-seepage surface layer extend into the corresponding anchor trenches and are fixed by U-shaped nails. A clay layer is backfilled in the anchor trench, and a concrete hardening layer is provided on the top surface of the anchor trench; an intercepting drainage ditch is provided 1 to 2m outside the anchor trench, and the cross-sectional width of the intercepting drainage ditch is 0.5 to 0.8m and the depth is 0.7 to 1m.

[0011] In order to achieve the above technical objectives, the present invention also provides a construction method of a landfill structure designed using narrow and long valleys in the loess region, and the specific steps are as follows:

[0012] S1. Topographic survey and site cleaning: Topographic survey of the narrow valley site in the loess area, drawing topographic maps, providing basic data for subsequent design and construction, leveling the site according to design requirements, and surface treatment and cleaning of the original base soil and slope surface, cleaning plant roots, rocks, pits, steep slopes, etc., cleaning thickness of 50cm, forming a fresh and flat fill base surface;

[0013] S2. Slope treatment: First, according to the overall stability of the slope, determine the equivalent internal friction angle of the slope, calculate the slope repair angle, and cut the slopes on both sides of the valley to make the slope surface flat and without bumps; after the slope cutting treatment is completed, the slope surface is closed and reinforced by driving systematic soil nails into the slope surface, hanging steel mesh, and spraying concrete;

[0014] S3. Site backfill and foundation treatment: When backfilling the site, the loess produced by slope cutting and site leveling should be used first, and the use of cleared topsoil that may damage the surrounding environment should be avoided; when backfilling the foundation in valleys, grooves and depressions, the soil and stone materials should be compacted in layers;

[0015] S4. Construct a retaining dam in the valley as the end plugging of the landfill area, use the loess produced after the slope is cut as the dam material, and fill the loess in layers to the designed height. The thickness of each layer should be controlled within 30cm. During the filling process, control the water content of the loess, and compact each layer after completion;

[0016] S5. Construct a groundwater collection main blind ditch at the bottom of the landfill area as a groundwater drainage system. First, according to the preset control coordinates and elevation data, a main blind ditch for the groundwater drainage main pipe is excavated in a specific area at the bottom of the site, and the inside of the main blind ditch is fully covered with geotextile as the first layer of protective filter layer; then, a groundwater diversion pipe is placed at the bottom of the main blind ditch, and its outer wall is tightly wrapped with woven geotextile. The end of the groundwater diversion pipe is sealed with a special pipe cap, and the end of the groundwater drainage main pipe is reliably connected to the main pipe of the next stage of the groundwater drainage system; then, gravel with a diameter of 3 to 5 cm is filled into the main blind ditch to form an additional filter layer; finally, a layer of geotextile is laid on top of the gravel filter layer as the final protective filter layer;

[0017] S6. Laying of anti-seepage surface layer; the anti-seepage surface layer is laid on the slopes of the slopes on both sides of the valley concave trough, the bottom surface of the valley concave trough and the surface of the dam body of the retaining dam; during the laying process, firstly, a layer of tightly combined GCL waterproof blanket is laid on the foundation layer of the dam body, the slope surface and the bottom surface of the valley concave trough to ensure that it fits tightly with the dam body structure, and then a layer of HDPE geomembrane is covered on the GCL waterproof blanket, and the seamless connection between the membranes is achieved through thermal welding technology, and finally a layer of filament geotextile is laid on the HDPE geomembrane; an anchoring ditch is constructed on the top of the slope, the top of the anti-seepage surface layer is fixed in the anchoring ditch, and the position of the anti-seepage surface layer corresponding to the bottom of the slope is fixed by loess counter pressure;

[0018] Construction of S7 retaining dam protective layer and slope protection; first, a gravel cushion layer was laid on top of the anti-seepage surface layer of the retaining dam, then a crushed stone cushion layer was laid on top of the gravel cushion layer, and finally a dry-laid C15 concrete block slope protection was laid on top of the crushed stone cushion layer.

[0019] S8. Laying a pebble leachate diversion layer; constructing a leachate collection main blind ditch above the groundwater collection main blind ditch in step S4, wherein the leachate collection main blind ditch is located above the impermeable surface layer, including a pebble leachate diversion layer and a leachate collection and discharge pipe buried in the pebble leachate diversion layer, firstly, an impermeable isolation layer is provided on the impermeable surface layer, and then pebbles with a particle size range of 20 to 40 mm are selected to start laying the pebble leachate diversion layer, the pebbles need to be laid tightly and flatly, after laying a certain thickness, the leachate collection and discharge pipe is laid, and then the pebbles are continued to be filled, and finally a geotextile is laid above the pebble leachate diversion layer as a protective layer;

[0020] S9. After the bottom layer of anti-seepage structure at the bottom of the landfill area is fully constructed, garbage is piled in the landfill area. When the garbage is piled to a position flush with the top of the slope, the top surface of the garbage pile is leveled and the base layer is laid. On top of the base layer, HDPE film layer, barrier layer, drainage layer and nutrient soil layer are laid in sequence. Finally, ornamental plants are planted in the nutrient soil layer according to the climate and soil conditions around the landfill to complete the construction of the landfill structure.

[0021] A further technical solution of the present invention: In the step S2, the process of calculating the slope repair angle is as follows:

[0022] Assume the slope is vertical, take the unit width slope, and the rupture angle is Then the slope height AC=h and the sliding surface length BC=l, and the volume of the unstable block per unit width is:

[0023]

[0024] Weight

[0025]

[0026] Normal stress is

[0027]

[0028] From the definition of equivalent internal friction angle, we can know that:

[0029]

[0030] but

[0031] Where: τ-shear stress;

[0032] θ-soil rupture angle,

[0033] -Soil internal friction angle;

[0034] -Equivalent internal friction angle of soil;

[0035] c-cohesion, unit: kPa;

[0036] l-slope sliding surface length, unit: m;

[0037] h-slope height, unit: m;

[0038] The equivalent internal friction angle of the soil can be used to judge the overall stability of the slope: when the slope soil is in a state of limit equilibrium, that is, the sliding force is equal to the anti-sliding force; assuming that the angle between the slope excavation angle and the horizontal is β, then:

[0039]

[0040] but

[0041] Where: β-slope repair angle;

[0042] F S -Safety factor.

[0043] Therefore, according to Slope repair should ensure that the slope is stable in its natural state during the slope repair process.

[0044] The preferred technical solution of the present invention is as follows: in the step S2, a long-arm excavator is used to trim the slope surface. The trimmed slope is required to be smooth and neat without bumps and unevenness, so as to facilitate the laying of the anti-seepage system. The corners and edges are required to be rounded, and the radius of the rounded corner should not be less than 0.3m. The soil nails are hammered into the slope body. The shotcrete is C20 fine stone concrete, which forms a good bond with the steel mesh and soil nails.

[0045] In the step S3, the layer thickness of the backfill soil material of the site is controlled between 150 and 250 mm, 5% to 30% of sand and gravel materials are mixed into the backfill loess, each layer of backfill soil should be tightly combined, the compaction coefficient of the foundation treatment should be not less than 0.93, and after the trough-shaped depression is leveled, the slope along the axial direction of the valley is controlled at 2 to 4‰;

[0046] In the step S4, the moisture content of the backfill loess material of the retaining dam is controlled at 19% to 21%, and the slope of the slopes on both sides of the dam body is 1:2 to 3;

[0047] In the step S5, the first layer and the final protective filter layer are both made of woven geotextiles with a density of 230 g / m2; the groundwater diversion pipe is a high-density polyethylene three-flowered pipe with a diameter of DN300; the inner layer of the gravel layer has a small diameter and the outer layer has a large diameter, and the gravel material is made of sand on the surface of the gravel, and the calcium carbonate content does not exceed 10%;

[0048] In the step S7, the thickness of the gravel cushion layer is 180-220 mm, the thickness of the crushed stone cushion layer is 150-180 mm, and the thickness of the C15 concrete blocks is 150-180 mm.

[0049] The preferred technical solution of the present invention is as follows: the anti-seepage surface layer in step S6 is firstly spliced ​​into a width of 18 to 22 meters in the flat area by GCL waterproof blanket, HDPE geomembrane and filament geotextile; then, in the slope area, it is laid from top to bottom in a direction perpendicular to the axis of the dam; for the laying of the dam body slope, after the dam body slope is accepted, it is slowly unfolded from the top of the dam body to the foot of the dam along a path perpendicular to the axis of the dam body until it forms a T-shaped connection with the geomembrane at the bottom of the dam body at the top of the outer groove of the slope foot; the anti-seepage surface layer is fixed in the anchor trench at the top, and the width of the anchor trench is 0.5m-1 .0m, depth of 0.5m-1.0m, the top edge of the anti-seepage surface layer extends to the bottom of the anchor trench and is fixed by U-shaped nails, and then the soil layer is backfilled in the anchor trench to ensure that the compaction coefficient of the backfill soil layer is not less than 0.93; an intercepting drainage ditch is set at a position 1.5m to 2m outside the anchor trench, and the area between the top of the slope and the intercepting drainage ditch is hardened with 80-120mm thick C30 concrete; loess counter pressure is used at the foot of the slope to make the anti-seepage surface layer close to the inner side of the soil pile, and the counter pressure body is trapezoidal, with a top width of 0.8-1.2m, a bottom width of 1.8-2.2m, a height of 0.8-1.2m, and a slope gradient of 1:1.

[0050] The purpose of the slope surface closure reinforcement in the present invention is to enhance the stability of the slope and prevent the occurrence of geological disasters such as soil erosion and slope landslides; soil nails, as the main load-bearing components of slope reinforcement, form a complex with the surrounding soil to jointly bear the lateral soil pressure of the slope. In order to further improve the integrity and shear resistance of the slope surface, the steel mesh is hung on the slope surface to effectively disperse and transfer the load on the slope surface, prevent soil peeling and crack expansion caused by natural factors such as rain erosion and freeze-thaw cycles. At the same time, the steel mesh also provides a reliable attachment basis for the subsequent shotcrete, enhancing the integrity and durability of the slope protection layer; finally, the slope surface is shotcrete to ensure good bonding between the shotcrete layer and the steel mesh and soil nails, thereby improving the overall stiffness and stability of the entire protective structure.

[0051] When backfilling the site, the loess produced by slope cutting and site leveling should be given priority, and the use of cleared topsoil that may cause damage to the surrounding environment should be avoided; when backfilling the foundation of the valley trough, the soil and stone materials should be compacted layer by layer to ensure that the thickness of each layer is moderate to improve the density and stability of the foundation. For foundation treatment, natural sand, gravel and other materials with uniform particles, hard texture, no weathering and no impurities should be mixed into the loess; according to the original particle grading of the loess and the requirements of the project, the proportion of sand and gravel should be reasonably determined to improve its physical and mechanical properties and improve the bearing capacity and deformation resistance of the foundation. Ensure that each layer of backfill soil is closely combined to avoid stratification or overhead phenomena, and ensure the integrity and stability of the foundation.

[0052] The anti-seepage surface layer in the present invention is composed of GCL (natural sodium-based bentonite waterproof blanket), HDPE (high-density polyethylene) geomembrane and filament geotextile from the inside to the outside, aiming to effectively prevent the occurrence of side wall leakage; the GCL waterproof blanket can fit closely with the slope surface and the dam structure, thereby establishing a preliminary and crucial anti-seepage barrier, and the HDPE geomembrane further plays an anti-seepage effect. In order to further enhance the protective effect of the geomembrane, a layer of filament geotextile is laid, which has excellent mechanical strength and UV resistance, and can effectively prevent external factors from damaging the geomembrane. In view of the stability problem of the covering layer caused by the low shear strength contact surface inside the closure system in the slope terrain, in engineering practice, it is often adopted to set an anchor ditch at the top of the slope and lay an anti-seepage layer, strictly control the compaction quality of the backfill soil, anchor the anti-seepage layer at the bottom of the slope, and adopt loess back pressure measures to enhance the stability of the slope of the closure system and the reliability of the anti-seepage layer. These measures together ensure that the anti-seepage system can give full play to its anti-seepage, isolation and reinforcement functions. A layer of gravel cushion and crushed stone cushion is laid outside the anti-seepage surface layer of the retaining dam. The gravel cushion ensures that the cushion has good permeability and bearing capacity, providing a solid foundation for subsequent construction. The addition of the crushed stone cushion further enhances the bearing capacity and stability of the dam body. At the same time, its rough surface provides a good friction basis for the laying of subsequent slope protection materials. The dry-laid C15 concrete block slope protection provides a solid slope protection layer for the retaining dam, effectively resisting damage from natural factors such as rain scouring and wind erosion.

[0053] The pebble leachate diversion layer of the present invention should be selected to meet the particle size range of 20 to 40 mm to ensure good water permeability, pressure resistance and durability. The pebbles should be laid tightly and flat to avoid gaps or uneven stacking to ensure the diversion effect. A layer of woven geotextile is laid above the pebble diversion layer as a protective layer to prevent garbage from directly pressing the pebble layer. The design of the diversion layer needs to be combined with the overall anti-seepage system of the landfill to ensure that the leachate can be discharged smoothly. An anti-seepage isolation layer is set below the diversion layer to prevent the leachate from leaking into the groundwater. A collection pipe and a discharge pipe are set above the diversion layer to transport the collected leachate to the treatment facility. The covering layer in the present invention includes a base layer, which provides stable support for the subsequent covering layer. On the base layer, a HDPE film layer is laid, which is made of high-density polyethylene material and has good anti-seepage and aging resistance, and is used to prevent the leakage of garbage leachate and the diffusion of odor; on the HDPE film layer, a barrier layer is set, which is made of materials such as geotextiles or geomembranes to further block the diffusion of odors and pollutants. On the barrier layer, a drainage layer is set, which is made of materials with good water permeability such as crushed stone and ceramsite, which is used to collect and discharge the accumulated water on the surface of the landfill and keep the covering layer dry and stable. On the drainage layer, a nutrient layer is laid, which is made of mixed materials such as soil and fertilizer, etc., to provide nutrients and a growth environment for green plants. Greening and beautification are carried out around the landfill, and suitable plant species are selected. According to the climate, soil and other conditions around the landfill, plants with strong adaptability, rapid growth and ornamental value are planted.

[0054] This application has the following beneficial effects:

[0055] (1) The present invention builds on the slope surface without further excavation, so there will be no land red line, which solves the land use problem and protects the environment; the slope surface is provided with a backfill anti-seepage structure, which not only plays the effect of trimming the slope surface, but also effectively prevents the garbage leachate from penetrating into the slope. When facing the existing steep valley, the slope surface and the bottom of the slope are trimmed using the technical solution of this application, and the existing slope can be reused without digging another pit; and the existing slope does not meet the requirements of the landfill, which is conducive to reducing costs.

[0056] (2) The present invention divides the retaining dam system into several independent sections according to the phased construction and operation plan of the landfill, and each section is designed and constructed separately; this not only reduces the difficulty of construction, but also allows the position and height of the retaining dam to be flexibly adjusted according to the actual operation of the landfill to adapt to the continuous expansion of the landfill; at the same time, the retaining dam system constructed in sections is easier to maintain and overhaul, ensuring the long-term stable operation of the system.

[0057] (3) The present invention uses the narrow valleys in the loess region as landfills, which have the advantages of rich land resources, suitable geological conditions, less environmental impact, low cost, and is conducive to garbage treatment and resource utilization. Dams are set up at both ends of the loess valley to form storage capacity, which is simple to operate and manage, with low investment and low operating costs. It can reduce the impact on residents' lives and reduce the risk of environmental pollution generated during garbage treatment. The specific composition of the anti-seepage layer structure is further optimized, and a new anti-seepage system is constructed with the cooperation of layers of different materials and specifications, so as to have a better self-defense effect, slow down the penetration of garbage leachate, and be beneficial to protecting the slope surface.

[0058] (4) The present invention provides an anti-seepage group, which can protect the HDPE geomembrane layer through the bentonite waterproof blanket and the non-woven fabric layer, reduce the damage rate of the HDPE geomembrane layer, and further increase the anti-seepage effect. The slope is set at the bottom of the valley reservoir, which can introduce the garbage liquid into the middle concrete infiltration pipe. The garbage liquid is discharged by being concentrated in the main pipeline, thereby reducing the corrosion of the garbage liquid on the anti-seepage group and reducing the impact of garbage odor on the surrounding environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 is a plan view of the landfill site in the first phase of the gully in the embodiment;

[0060] Figure 2 yes Figure 1 Middle aa section view;

[0061] Figure 3 yes Figure 1 Middle bb section;

[0062] Figure 4 is a plan view of the slope reinforcement structure in the embodiment;

[0063] Figure 5 is a cross-sectional view of a slope reinforcement structure in an embodiment;

[0064] Figure 6 This is a structural diagram of the main blind ditch for collecting leachate and groundwater in the embodiment;

[0065] Figure 7 It is a structural diagram of the anti-seepage surface layer in the embodiment;

[0066] Figure 8 It is a structural diagram of the slope top anchoring trench in the embodiment;

[0067] Fig. 9 It is a structural diagram of the landfill cover layer and surface greening in the embodiment.

[0068] In the figure: 1-slope, 1-1-slope top line, 1-2-slope foot line, 2-retaining dam, 3-valley concave trough, 4-anti-seepage surface layer, 5-reinforcement structure, 5-1-soil nails, 5-2-steel mesh, 5-3-concrete surface layer, 6-slope foot counter-pressure soil layer, 7-cover layer, 7-1-foundation layer, 7-2-HDPE membrane layer, 7-3-compacted clay barrier layer, 7-4-isolation layer, 7-5-drainage layer, 7-6-nutrient soil layer, 8-foundation treatment, 9-bottom anti-seepage structure, 9-1-groundwater collection main blind ditch, 9-2-groundwater collection main blind ditch, 9-3-groundwater collection main blind ditch, 9-4-groundwater collection main blind ditch, 9-5-groundwater collection main blind ditch, 9-1 ... -11—first geotextile filter layer, 9-12—three-flower pipe, 9-13—gravel layer, 9-14—final protective filter layer, 9-2—main blind ditch for leachate collection, 9-21—pebble leachate diversion layer, 9-22—leachate collection and discharge pipe, 9-23—geotextile protective layer, 9-24—anti-seepage isolation layer, 10—landfill area, 11—intercepting drainage ditch, 12—reinforced cushion layer, 13—protective surface layer, 14—anchor ditch, 15—U-shaped nails, 16—clay layer, 17—concrete hardening layer, 18—landfill layer. DETAILED DESCRIPTION

[0069] In order to further understand the content, features and effects of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments. Figures 1 to 8 The drawings are all of embodiments, which are drawn in a simplified manner and are only used for the purpose of clearly and concisely illustrating the embodiments of the present invention. The technical solutions shown in the following drawings are specific solutions of the embodiments of the present invention and are not intended to limit the scope of the invention claimed for protection. 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.

[0070] The present invention is further described below in conjunction with the accompanying drawings. The embodiment provides a landfill structure designed using narrow valleys in loess regions, such as Figure 1 and Figure 2As shown, it includes a landfill area 10 formed by a narrow valley in a loess area, a bottom anti-seepage structure 9 constructed on the bottom surface of the landfill area, a reinforcement structure 5 constructed on the slopes on both sides of the landfill area, and a covering layer 7 laid on the surface of the landfill area 10. The landfill area 10 is a concave area formed by a concave trough 3 in the valley, side slopes 1 located on both sides of the concave trough 3 in the valley, and a retaining dam 2 located in the concave trough 3 in the valley; the narrow valley in the loess area is divided into multiple adjacent landfill areas 10 by multiple retaining dams 2, and two adjacent landfill areas 10 share a retaining dam 2, and the retaining dam 2 is an isosceles trapezoidal structure with a flat middle part and sloped surfaces on both sides, and the sloped surfaces on both sides face the two adjacent landfill areas 10 respectively. Reinforcement structures 5 are constructed on the slopes 1 on both sides of the valley concave trough 3. The bottom surface of the valley concave trough 3 is provided with a foundation treatment layer 8. The thickness of the foundation treatment layer 8 on the bottom surface of the valley concave trough 3 is controlled to be 250-1000mm, and the sand and gravel materials mixed in the loess are used for backfilling, and the mixing ratio is controlled to be 5%-30%; the compaction coefficient of the foundation treatment layer 8 should be not less than 0.93. Anti-seepage surface layers 4 are respectively provided on the slopes 1 on both sides of the valley concave trough 3, the surface of the foundation treatment layer 8 on the bottom surface of the valley concave trough 3, and the dam body surface of the retaining dam 2.

[0071] The embodiment provides a landfill structure designed using narrow valleys in loess regions, such as Figure 1 to Figure 2 As shown, the bottom anti-seepage structure 9 is arranged on the bottom surface of the concave area of ​​the valley concave trough 3 along the length direction of the valley concave trough 3. The bottom anti-seepage structure 9 is constructed on the midline of the bottom surface of the valley concave trough 3, including the main blind ditch 9-1 for collecting groundwater in the lower layer and the main blind ditch 9-2 for collecting leachate in the upper layer. The bottom anti-seepage structure 9 extends outside the landfill area 10 and is connected to the bottom anti-seepage structure 9 at the bottom of the next adjacent landfill area 10, or is connected to the external drainage system to discharge groundwater and leachate. Figure 6As shown, the bottom anti-seepage structure 9 includes an inverted trapezoidal blind ditch groove opened on the bottom surface of the valley concave trough 3, the blind ditch groove extends outside the landfill area 10, and is connected to the bottom anti-seepage structure 9 at the bottom of the next adjacent landfill area 10, or is connected to the external drainage system; the overall groove depth of the blind ditch groove is 0.8-1.2m, the bottom width is 0.8-1.2m, the top width is 1.8-2.2m, and the slope of the two sides is 1:1; the lower groundwater collection main blind ditch 9-1 includes a first layer of geotextile filter layer 9-11 laid in the blind ditch groove, a three-flowered pipe 9-12 wrapped with geotextile, and a gravel layer 9 filled in the lower layer of the blind ditch groove. -13 and a final protective filter layer 9-14 laid on the top surface of the gravel layer; the upper leachate collection main blind ditch 9-2 includes an impermeable layer laid above the final protective filter layer 9-14, an impermeable isolation layer 9-24 arranged above the impermeable layer, a pebble leachate diversion layer 9-21 laid on the impermeable isolation layer 9-24, a leachate collection and discharge pipe 9-22 buried in the pebble leachate diversion layer and a geotextile protective layer 9-23 covering the top surface of the pebble leachate diversion layer; the impermeable layer and the impermeable surface layer 4 are an integrated structure, and the pebble particle size range of the pebble leachate diversion layer is 20 to 40 mm; the gravel layer is filled with gravel with a diameter of 3 to 5 cm.

[0072] In the embodiment, Figure 4 and Figure 5 As shown, the reinforcement structure 5 includes a plurality of soil nails 5-1 driven on the slope surfaces of the two side slopes 1, a steel mesh 5-2 hung on the slope surfaces of the two side slopes 1, and a concrete surface layer 5-3 sprayed on the slope surfaces of the two side slopes 1, the steel mesh 5-2 is fixedly welded to the soil nails 5-1, and the concrete surface layer 5-3 covers the steel mesh 5-2; the spacing between the soil nails 5-1 is 1000mm to 1500mm.

[0073] In the embodiment, the retaining dam 2 is a dam structure formed by filling on-site loess. Figure 3 As shown, a reinforcement cushion layer 12 and a protective surface layer 13 are laid above the slope anti-seepage layer 4 of the retaining dam 2. The reinforcement cushion layer 12 is composed of a lower gravel cushion layer and an upper crushed stone cushion layer, and the protective surface layer 13 is a dry-laid C15 concrete block slope protection layer. Figure 7 As shown, the anti-seepage surface layer 4 is composed of GCL waterproof blanket 4-1, HDPE geomembrane 4-2 and filament geotextile 4-3 from the inside to the outside. The GCL waterproof blanket 4-1 is tightly laid on the slope 1 and the slope of the retaining dam 2 on both sides of the valley concave trough 3, and the HDPE geomembrane 4-2 is seamlessly connected by thermal welding technology. Figure 8As shown, anchor trenches 14 for fixing the anti-seepage surface layer 4 are provided on both sides of the top surface of the landfill area 10, the width of the anchor trench 14 is 0.5m-1.0m, and the depth is 0.5m-1.0m. Both sides of the anti-seepage surface layer 4 extend into the corresponding anchor trenches 14 and are fixed by U-shaped nails 15. A clay layer 16 is backfilled in the anchor trench 14, and a concrete hardening layer 17 is provided on the top surface of the anchor trench 14; an intercepting drainage ditch 11 is provided 1 to 2m outside the anchor trench 14, and the cross-sectional width of the intercepting drainage ditch 11 is 0.5 to 0.8m and the depth is 0.7 to 1m.

[0074] The embodiment provides a landfill structure designed using narrow valleys in loess regions, such as Figure 1 and Fig. 9 As shown, the foot lines of the slopes 1 on both sides of the valley concave trough 3 are respectively provided with foot anti-pressure soil layers 6; the cover layer 7 covers the surface of the garbage layer landfilled in the landfill area 10 after the garbage landfill is completed. The cover layer 7 includes a clay, sand or gravel base layer 7-1 laid on the surface of the garbage landfill layer 18, the thickness of the base layer 7-1 is 300mm to 350mm, and the HDPE film layer 7-2, 300mm to 350mm compacted clay barrier layer 7-3, geotextile or geomembrane isolation layer 7-4, gravel or ceramsite drainage layer 7-5 and nutrient soil layer 7-6 are laid on the surface of the base layer 7-1 from bottom to top, and ornamental plants are planted in the nutrient soil layer.

[0075] In the embodiment, the proposed project site is located in a loess area in Shaanxi Province with convenient transportation. The site geomorphic unit is the second-level terrace on the north bank of Shichuan River, and the overall terrain trend is high in the east and low in the west. The ground elevation of the exploration borehole is between 230 and 218 meters, with a maximum height difference of 12 meters. The engineering geological characteristics of each rock and soil layer from top to bottom are as follows:

[0076] ①-2 Plain fill Q 4 ml : Yellowish brown, uneven soil, loose, mainly clay soil, containing a small amount of plant roots, thickness 0 to 1m.

[0077] ② Loess Q 2 eol :Brown-yellow, relatively uniform soil, macropores, calcium streaks, tubercles, snail shells, plant roots and worm holes, etc. Hard plastic to plastic (some soil samples are hard), with slight collapsibility and self-weight collapsibility, belonging to medium compressible soil. Loess layer gravity γ = 17.5kN / m 3 , cohesion c is 30kPa, internal friction angle The temperature is 35 degrees and the thickness is 10 to 20 m.

[0078] The strata within the gully depth range in this area are mainly loess layers, and the gully depth is about 10m.

[0079] The specific construction steps for the above landfill are as follows:

[0080] S1. Topographic survey and site cover cleaning: Conduct detailed topographic survey of the site and draw a topographic map to provide basic data for subsequent design and construction. First, treat the original base soil and slope surface, clean up plant roots, rocks, pits, steep slopes, etc., with a cleaning thickness of 50cm to form a fresh and flat base surface. The site excavation and cleaning work should be completed from top to bottom at one time. It can be carried out in stages, but measures should be proposed to ensure quality and not affect the construction period. All the removed waste should be transported to the designated soil dump.

[0081] S2. Slope treatment

[0082] a. Calculate the overall stability of the slope, determine the equivalent internal friction angle of the slope, determine the area and amount of slope cutting required, and perform slope cutting treatment;

[0083] Assume the slope is vertical, take the unit width slope, and the rupture angle is Then the slope height AC=h and the sliding surface length BC=l, so the volume of the unstable block per unit width is

[0084]

[0085] Weight

[0086]

[0087] Normal stress is

[0088]

[0089] The equivalent internal friction angle of soil is widely used in engineering and is also accepted by the majority of engineering technicians. From the definition of the equivalent internal friction angle, we can know that:

[0090]

[0091] but

[0092] Where: τ-shear stress;

[0093] θ-soil rupture angle,

[0094] -Soil internal friction angle;

[0095] -Equivalent internal friction angle of soil;

[0096] c-cohesion, unit: kPa;

[0097] l-slope sliding surface length, unit: m;

[0098] h-slope height, unit: m;

[0099] The soil equivalent internal friction angle can be used to judge the overall stability of the slope: when the slope soil is in a limit equilibrium state, that is, the sliding force is equal to the anti-sliding force; assuming that the slope safety level is level 1, the safety factor is 1.35, and the angle between the slope excavation angle and the horizontal is β:

[0100]

[0101] but

[0102]

[0103] Where: β-slope repair angle;

[0104] F S -Safety factor.

[0105] Therefore, the slope is repaired according to β = 60° to ensure that the slope is stable in its natural state during the repair process.

[0106] b. Figure 1 As shown, the slopes on both sides of the valley are repaired: during construction, the slopes around the landfill after closure are first shaped and repaired by mechanical equipment according to the design requirements. For the parts that cannot be handled by mechanical equipment, manual repair can be used to make the slopes flat and without bumps. The slope repair equipment uses a long-arm excavator. The repaired slopes are required to be smooth and tidy, without bumps and unevenness, to facilitate the laying of the anti-seepage system. The corners and edges are required to be rounded, and the radius of the rounded corner should not be less than 0.3m.

[0107] c. Close and reinforce the slope surface, as follows: Figure 2 , Figure 4 and Figure 5As shown in the figure, the reinforcement structure adopts the soil nailing system driven into the slope surface + shotcrete; the slope surface closure is intended to enhance the stability of the slope and prevent the occurrence of geological disasters such as soil erosion and slope landslide; the soil nailing system 5-1 driven into the slope surface, as the main load-bearing component of the slope reinforcement, is hammered into the soil nails until the slope and the surrounding soil form a composite body, which jointly bears the lateral earth pressure of the slope; the soil nail 5-1 is a Φ16 steel bar of HRB400 grade, with high yield strength and good ductility, the soil nail L=1m, and the spacing is arranged at 1m×1m; in order to further improve the integrity and shear resistance of the slope surface, a steel mesh 5-2 is hung on the slope surface, which effectively disperses and transmits the load on the slope surface, improves the integrity and shear resistance of the slope surface, and also provides for subsequent The shotcrete provides a reliable attachment foundation and enhances the integrity and durability of the slope protection layer. The steel mesh 5-2 is 6.5mm@200x200mm in diameter. The soil nails 5-1 are welded to the steel mesh to prevent soil peeling and crack expansion caused by natural factors such as rain erosion and freeze-thaw cycles. Finally, the slope shotcrete 5-3 is C20 with a thickness of 100mm to ensure good bonding between the shotcrete layer and the steel mesh and soil nails. C20 fine stone concrete has high compressive strength and good workability, and forms good bonding with the steel mesh and soil nails, thereby improving the overall stiffness and stability of the entire protective structure, protecting the slope from wind and rain erosion, further reinforcing the slope and improving the safety factor.

[0108] S3. Site backfill and foundation treatment; The site backfill shall give priority to the loess produced by slope cutting and site leveling, and avoid the use of cleared topsoil that may cause damage to the surrounding environment. For the foundation treatment of gully-shaped depressions, natural sand, gravel and other materials with uniform particles, hard texture, no weathering and no impurities shall be mixed into the loess. The layered thickness of the site backfill soil material is controlled between 150 and 250 mm to ensure the density and stability of the foundation; 5% to 30% of sand, gravel and other materials are mixed into the loess. According to the original particle grading of the loess and the engineering requirements, the mixing ratio of sand and gravel is reasonably determined to improve its physical and mechanical properties and improve the bearing capacity and deformation resistance of the foundation. Each layer of backfill soil should be tightly combined to avoid stratification or overhead phenomena to ensure the integrity and stability of the foundation. The compaction coefficient of foundation treatment should be no less than 0.93 to ensure that the density and stability of the foundation meet the design requirements; after the trough-shaped depression is leveled, the slope along the axial direction of the valley should be controlled at around 3‰ to ensure the stability and safety of the landfill.

[0109] S4. The end of the valley is blocked by a retaining dam 2; a large amount of loess produced after the slope is cut can be used as the dam body material of the retaining dam 2. The structure of the retaining dam 2 is as follows: Figure 3As shown in the figure, the loess is filled in layers to the designed height, and the slope is set to 1:2.5. The thickness of each layer should be controlled within a reasonable range (generally not more than 30cm) to ensure the compaction effect and the overall stability of the dam. During the filling process of retaining dam 2, the water content of the loess must be strictly controlled at 19% to 21% to avoid excessive moisture or dryness affecting the compaction effect. After each layer is filled, it needs to be compacted; the compaction equipment should be a vibrating roller or a tamping machine, and the number of compaction passes should be determined according to the characteristics of the loess and the compaction requirements. During the compaction process, the compaction degree needs to be monitored in real time to ensure that the compaction degree of each layer of loess is not less than 0.94.

[0110] S5. Construct the main blind ditch 9-1 for collecting groundwater as the groundwater drainage system; Figure 2 and Figure 6 As shown, after the site is leveled, the construction of the groundwater drainage system is carried out in accordance with the following steps: ① Excavation of the main blind ditch groove: According to the preset control coordinates and elevation data, the main blind ditch of the groundwater drainage main pipe is excavated in a specific area at the bottom of the site. The main blind ditch has a depth of 1.0 m, a lower bottom width of 1.0 m, an upper bottom width of 2.0 m, and a slope design of 1:1; ② Laying the first layer of protective filter layer 9-11: A layer of woven geotextile is fully covered inside the main blind ditch groove as the first layer of protective filter layer. The first layer of filter material and the final protective and filter layer are all made of woven geotextile with a density of 230 g / m2; ③ Place and wrap the three-flowered pipe 9-12: A high-density polyethylene (HDPE) three-flowered pipe is accurately placed at the center of the bottom of the main blind ditch, and its outer wall is tightly wrapped with woven geotextile. The diameter of the three-flowered pipe is DN300 high-density polyethylene (HDPE) PE) three-flower pipe, as the main drainage pipeline for groundwater, passes through the foundation of the retaining dam and extends to the valley of the second phase landfill to be built in the future; ④ Seal the end of the pipeline and connect the system: The end of the pipeline is sealed with a special pipe cap, and the end of the groundwater drainage main pipe is reliably connected to the main pipe of the groundwater drainage system in the next stage. The diameter of the filled gravel is 3 to 5 cm, the inner layer is fine and the outer layer is coarse, naturally forming an additional anti-filter layer. The gravel material needs to be cleaned of the surface sediment before entering the site, and ensure that its calcium carbonate content does not exceed 10% to ensure the quality and applicability of the material; ⑤ Fill the gravel layer 9-13: Fill the main blind ditch groove with gravel with a diameter of 3 to 5 cm to form an additional anti-filter layer with a filling height of 50 cm; ⑥ Lay the final protective anti-filter layer 9-14: Lay another layer of woven geotextile on the surface of the gravel layer 9-13 as the final protective anti-filter layer.

[0111] S6. Laying of the anti-seepage surface layer 4; the anti-seepage surface layer 4 covers the bottom of the valley, the slopes on both sides of the valley, and the slope area of ​​the retaining dam. The anti-seepage surface layer 4 adopts a multi-layer structure, which is composed of GCL (natural sodium-based bentonite waterproof blanket), HDPE (high-density polyethylene) geomembrane and filament geotextile from the inside to the outside, aiming to effectively prevent the occurrence of side wall leakage. Laying method: The laying of the dam body anti-seepage surface layer 4 requires that the width be spliced ​​and welded into a 20m wide width on the flat ground, and then laid from top to bottom on the slope, perpendicular to the axis of the dam; after the slope surface is accepted, the dam body slope is laid, and it is slowly spread from the top of the embankment to the foot of the embankment in a direction perpendicular to the axis of the embankment to the outer top of the tooth groove at the foot of the slope, and connected with the geomembrane at the bottom of the reservoir in a T-shaped manner. After the excavation of the bottom of the reservoir is accepted, the laying of the bottom of the garbage landfill area 10 is slowly spread from the outer top of the tooth groove to the inside of the reservoir in a direction perpendicular to the axis of the embankment foot to 25m inside the reservoir. GCL natural sodium-based bentonite blanket, HDPE geomembrane and filament geotextile are laid from bottom to top on the slopes on both sides of the landfill area 10 to ensure that the side walls are impermeable. A leakage detection system is set up around the anti-seepage surface layer 4 to regularly check whether the anti-seepage layer is intact and to promptly detect and deal with leakage problems. The foot of the slope inside the dam and the slope of the reservoir area are cleaned and leveled to the clay layer, or filled and tamped to the clay layer, and then a layer of HDPE anti-seepage membrane and a layer of filament geotextile (300g / m 2 ).

[0112] like Figure 8 As shown, an anchoring ditch 14 is set at the top of the slope to fix the composite anti-seepage surface layer; the width and depth of the anchoring ditch 14 should be determined according to the use conditions and stress conditions of the anti-seepage layer, generally the width is 0.5m-1.0m, and the depth is 0.5m-1.0m. The edge of the anti-seepage surface layer 4 is buried in the anchoring ditch 14 and anchored with U-shaped nails 15. The U-shaped nails 15 have a steel bar diameter of 8mm, a length of 0.5m, and a spacing of 0.5m, and then the soil layer is backfilled in the anchoring ditch 14. When backfilling the soil in the anchoring ditch 14 at the top of the slope, the compaction quality of the backfill soil must be strictly controlled to ensure that the compaction coefficient of the backfill soil layer is not less than 0.93. The increase in the compaction coefficient helps to enhance the density and shear strength of the backfill soil, thereby further improving the overall stability of the anchoring ditch 14 and its internal anti-seepage surface layer. An intercepting drainage ditch 11 is set 1.5m outside the anchoring ditch 14. The area between the top of the slope and the intercepting drainage ditch 11 is hardened with 100mm C30 concrete. The cross-sectional dimensions of the intercepting drainage ditch are 0.5m wide and 0.7m deep. It intercepts the water flow from the outside of the slope to the inside of the slope, protects the slope and the foot of the slope, maintains the stability of the slope, and reduces soil erosion. Loess counterpressure measures are adopted at the foot of the slope, so that the anti-seepage material should be close to the inside of the soil pile to ensure good contact and adhesion with the soil, so as to give full play to its anti-seepage, isolation and reinforcement functions. The anti-pressure soil layer 6 at the foot of the slope is trapezoidal, with a top width of 1m, a bottom width of 2m, a height of 1m, and a slope gradient of 1:1.

[0113] S7. Construction of the retaining dam protective layer and slope protection; First, a 200mm thick gravel cushion layer was laid on top of the filament geotextile of the retaining dam's anti-seepage layer. This step ensures that the cushion layer has good permeability and bearing capacity, providing a solid foundation for subsequent construction; then, a 150mm thick crushed stone cushion layer was laid on top of the gravel cushion layer. The addition of the crushed stone cushion layer further enhances the bearing capacity and stability of the dam body, and its rough surface provides a good friction foundation for the subsequent laying of slope protection materials; finally, A layer of dry-laid C15 concrete block slope protection was laid. The C15 concrete block is 150mm thick and has high compressive strength and durability. It is connected by dry-laying, that is, no bonding materials such as mortar are used, but the overall stability is maintained by the fit and friction between the stones. It is not only easy to construct, but also can adapt to the slight deformation of the slope, improving the adaptability and durability of the slope protection. This step provides a solid slope protection layer for the retaining dam, effectively resisting damage from natural factors such as rain scouring and wind erosion, and facilitating vehicle passage and garbage unloading.

[0114] S8. Construction of leachate collection main blind ditch 9-2, such as Figure 6 As shown in the figure, after the anti-seepage surface layer of the trough-shaped valley is laid in step S6, the pebble leachate diversion layer is laid on the anti-seepage layer; the selection of pebbles should meet the particle size range of 20-40 mm to ensure good permeability, pressure resistance and durability. The pebbles should be laid tightly and flat to avoid gaps or uneven stacking to ensure the diversion effect. A layer of woven geotextile is laid above the pebble diversion layer as a protective layer to prevent garbage from directly pressing the pebble layer. The design of the diversion layer needs to be combined with the overall anti-seepage system of the landfill to ensure that the leachate can be discharged smoothly. An anti-seepage isolation layer is set below the diversion layer to prevent the leachate from leaking into the groundwater. A dn315HDPE leachate collection pipe is set above the diversion layer to transport the collected leachate to the treatment facility.

[0115] S9. Construction of covering layer and surface greening, the specific structure is as follows Fig. 9As shown, the construction process is as follows: first, after the garbage is filled in the landfill area 10, the surface of the garbage landfill layer 18 is leveled, and then a base layer 7-1 is laid with a thickness of 300mm. Its main materials usually include clay, sand and gravel, etc., to provide stable support for the subsequent covering layer; on the base layer 7-1, a HDPE film layer 7-2 with a thickness of 0.5mm is laid. The film layer is made of high-density polyethylene material and has good anti-seepage and aging resistance. It is used to prevent the leakage of garbage leachate and the diffusion of odor. On the HDPE film layer 72, a barrier layer 7-3 is set, which is composed of 300mm thick compacted clay to further block the diffusion of odor and pollutants. A geotextile or geomembrane isolation layer 7-4 is laid on the barrier layer 7-3, and then a drainage layer 7-5 is set. The drainage layer 7-5 is made of materials with good water permeability such as gravel and ceramsite, which is used to collect and discharge the accumulated water on the surface of the landfill and keep the covering layer dry and stable. A nutrient layer 7-6 is laid on the drainage layer 7-5. The thickness of the nutrient layer 7-6 is 1000 mm and it is made of mixed materials such as soil and fertilizer to provide nutrients and a growth environment for green plants. Greening and beautification are carried out around the landfill, and suitable plant species are selected. According to the climate, soil and other conditions around the landfill, plants with strong adaptability, rapid growth and ornamental value are planted.

[0116] The present invention uses the narrow valleys in the loess region as landfills, which have the advantages of rich land resources, suitable geological conditions, less environmental impact, low cost, and is conducive to garbage treatment and resource utilization. The slope surface and the bottom of the slope are trimmed, and the existing slope can be reused without digging another pit. It also overcomes the problem that the existing slope does not meet the requirements of the landfill, which is conducive to reducing costs. According to the phased construction and operation plan of the landfill, the retaining dam system is divided into several independent sections, and each section is designed and constructed separately. This not only reduces the difficulty of construction, but also allows the position and height of the retaining dam to be flexibly adjusted according to the actual operation of the landfill to adapt to the continuous expansion of the landfill.

[0117] In summary, the content of the present invention is not limited to the above-mentioned embodiments, and people with insight in the same field can easily propose other embodiments within the technical guiding ideology of the present invention, but such embodiments are all included in the scope of the present invention.

Claims

1. A landfill structure designed using narrow valleys in loess regions, characterized by: The landfill structure comprises a landfill area (10) formed by a narrow valley in a loess region, a bottom anti-seepage structure (9) constructed on the bottom surface of the landfill area, a reinforcement structure (5) constructed on the slopes on both sides of the landfill area, and a covering layer (7) laid on the surface of the landfill area (10). The landfill area (10) is surrounded by a valley concave trough (3), side slopes (1) located on both sides of the valley concave trough (3), and a retaining dam (2) located in the valley concave trough (3). A concave area is formed; the bottom anti-seepage structure (9) is arranged on the bottom surface of the concave area of ​​the valley concave trough (3) along the length direction of the valley concave trough (3), including a main blind ditch (9-1) for collecting groundwater in the lower layer and a main blind ditch (9-2) for collecting leachate in the upper layer; reinforcement structures (5) are respectively constructed on the slope surfaces of the side slopes (1) on both sides of the valley concave trough (3), and the reinforcement structures (5) include a plurality of soil nails (5-1) driven on the slope surfaces of the two side slopes (1), and a plurality of soil nails (5-1) hung on the two side slopes (1 ) and a concrete surface layer (5-3) sprayed on the slope surfaces of the two side slopes (1), the steel mesh (5-2) and the soil nails (5-1) are fixedly welded, and the concrete surface layer (5-3) covers the steel mesh (5-2); the bottom surface of the valley concave trough (3) is provided with a foundation treatment layer (8), the retaining dam (2) is a dam body structure formed by filling on-site loess, and the slope surfaces of the two side slopes (1) of the valley concave trough (3) and the valley concave trough (3) are provided with a foundation treatment layer (8). The surface of the bottom foundation treatment layer (8) and the surface of the dam body of the retaining dam (2) are respectively provided with an anti-seepage surface layer (4); a reinforcing cushion layer (12) and a protective surface layer (13) are laid above the anti-seepage layer (4) on the slope surface of the retaining dam (2); and the foot lines of the slopes (1) on both sides of the concave trough (3) are respectively provided with foot back pressure soil layers (6) for back pressure on the anti-seepage surface layer (4); after the garbage is landfilled, the covering layer (7) covers the surface of the garbage layer landfilled in the garbage landfill area (10).

2. The landfill structure designed by utilizing the narrow valleys in the loess region according to claim 1 is characterized by: The narrow valley in the loess region is divided into a plurality of adjacent landfill areas (10) by a plurality of retaining dams (2), and two adjacent landfill areas (10) share one retaining dam (2). The retaining dam (2) is an isosceles trapezoidal structure with a plane in the middle and sloping surfaces on both sides, and the sloping surfaces on both sides face the two adjacent landfill areas (10) respectively.

3. A landfill structure designed using narrow valleys in loess regions according to claim 1 or 2, characterized in that: The anti-seepage surface layer (4) is composed of a GCL waterproof blanket (4-1), a HDPE geomembrane (4-2) and a filament geotextile (4-3) from the inside to the outside. The GCL waterproof blanket (4-1) is tightly laid on the slope surface of the side slope (1) and the slope surface of the retaining dam (2) on both sides of the valley concave trough (3). The HDPE geomembrane (4-2) is seamlessly connected by heat welding technology. The reinforcing cushion layer (12) is composed of a lower gravel cushion layer and an upper The protective surface layer (13) is a dry-laid C15 concrete block slope protection layer; the spacing between the soil nails (5-1) is 1000mm to 1500mm; the thickness of the foundation treatment layer (8) at the bottom of the valley concave trough (3) is controlled to be 250 to 1000mm, and the backfill is made of sand and gravel materials mixed in loess, and the mixing ratio is controlled to be 5% to 30%; the compaction coefficient of the foundation treatment layer (8) should be not less than 0.

93.

4. A landfill structure designed using narrow valleys in loess regions according to claim 1 or 2, characterized in that: The bottom anti-seepage structure (9) is constructed on the midline of the bottom surface of the valley concave trough (3); the bottom anti-seepage structure (9) includes an inverted trapezoidal blind ditch groove opened on the bottom surface of the valley concave trough (3), the blind ditch groove extends outside the landfill area (10), and is connected to the bottom anti-seepage structure (9) at the bottom of the next adjacent landfill area (10), or is connected to the external drainage system; the overall groove depth of the blind ditch groove is 0.8 to 1.2 meters, the bottom width is 0.8 to 1.2 meters, the top width is 1.8 to 2.2 meters, and the slope of the two sides is 1:1; the lower groundwater collection main blind ditch (9-1) includes a first layer of geotextile filter layer (9-11) laid in the blind ditch groove, a three-flowered pipe (9-12) wrapped with geotextile, and a blind ditch groove filled with geotextiles. A gravel layer (9-13) in the lower layer of the groove and a final protective filter layer (9-14) laid on the top of the gravel layer; the upper layer leachate collection main blind ditch (9-2) comprises an impermeable layer laid on the top of the final protective filter layer (9-14), an impermeable isolation layer (9-24) arranged on the impermeable layer, a pebble leachate diversion layer (9-21) laid on the impermeable isolation layer (9-24), a leachate collection and discharge pipe (9-22) buried in the pebble leachate diversion layer, and a geotextile protective layer (9-23) covering the top of the pebble leachate diversion layer; the impermeable layer and the impermeable surface layer (4) are an integrated structure, and the pebble particle size range of the pebble leachate diversion layer is 20 to 40 mm; the gravel layer is filled with gravel with a diameter of 3 to 5 cm.

5. A landfill structure designed using narrow valleys in loess regions according to claim 1 or 2, characterized in that: The covering layer (7) comprises a clay, sand or gravel base layer (7-1) laid on the surface of the landfill layer (18), the base layer (7-1) having a thickness of 300 mm to 350 mm, and a HDPE film layer (7-2), a 300 mm to 350 mm compacted clay barrier layer (7-3), a geotextile or geomembrane isolation layer (7-4), a gravel or ceramsite drainage layer (7-5) and a nutrient soil layer (7-6) laid in sequence from bottom to top on the surface of the base layer (7-1), and ornamental plants are planted in the nutrient soil layer.

6. A landfill structure designed using narrow valleys in loess regions according to claim 1 or 2, characterized in that: Anchor trenches (14) for fixing an impermeable surface layer (4) are arranged on both sides of the top surface of the landfill area (10), the width of the anchor trenches (14) is 0.5m-1.0m, and the depth is 0.5m-1.0m. Both sides of the impermeable surface layer (4) extend into the corresponding anchor trenches (14) and are fixed by U-shaped nails (15). A clay layer (16) is backfilled in the anchor trench (14), and a concrete hardening layer (17) is arranged on the top surface of the anchor trench (14); an intercepting drainage trench (11) is arranged 1-2m outside the anchor trench (14), and the cross-sectional width of the intercepting drainage trench (11) is 0.5-0.8m, and the depth is 0.7-1m.

7. A method for constructing a landfill structure using a narrow valley design in a loess region as described in claims 1 to 6, characterized in that: The specific steps are as follows: S1. Topographic survey and site cleaning: Topographic survey and topographic map drawing are carried out on the narrow valley sites in the loess area to provide basic data for subsequent design and construction. The site is leveled according to the design requirements, and the surface of the original base soil and slope is treated and cleaned to form a fresh and flat fill base surface; S2. Slope treatment: First, according to the overall stability of the slope, determine the equivalent internal friction angle of the slope, calculate the slope repair angle, and cut the slopes on both sides of the valley to make the slope surface flat and without bumps; after the slope cutting treatment is completed, the slope surface is closed and reinforced by driving systematic soil nails into the slope surface, hanging steel mesh, and spraying concrete; S3. Site backfill and foundation treatment: When backfilling the site, the loess produced by slope cutting and site leveling should be used first, and the use of cleared topsoil that may damage the surrounding environment should be avoided; when backfilling the foundation in valleys, grooves and depressions, the soil and stone materials should be compacted in layers; S4. Construct a retaining dam in the valley as the end plugging of the landfill area, use the loess produced after the slope is cut as the dam material, and fill the loess in layers to the designed height. The thickness of each layer should be controlled within 30cm. During the filling process, control the water content of the loess, and compact each layer after completion; S5. Construct a groundwater collection main blind ditch at the bottom of the landfill area as a groundwater drainage system. First, according to the preset control coordinates and elevation data, a main blind ditch for the groundwater drainage main pipe is excavated in a specific area at the bottom of the site, and the inside of the main blind ditch is fully covered with geotextile as the first layer of protective filter layer; then, a groundwater diversion pipe is placed at the bottom of the main blind ditch, and its outer wall is tightly wrapped with woven geotextile. The end of the groundwater diversion pipe is sealed with a special pipe cap, and the end of the groundwater drainage main pipe is reliably connected to the main pipe of the next stage of the groundwater drainage system; then, gravel with a diameter of 3 to 5 cm is filled into the main blind ditch to form an additional filter layer; finally, a layer of geotextile is laid on top of the gravel filter layer as the final protective filter layer; S6. Laying of anti-seepage surface layer; the anti-seepage surface layer is laid on the slopes of the slopes on both sides of the valley concave trough, the bottom surface of the valley concave trough and the surface of the dam body of the retaining dam; during the laying process, firstly, a layer of tightly combined GCL waterproof blanket is laid on the foundation layer of the dam body, the slope surface and the bottom surface of the valley concave trough to ensure that it fits tightly with the dam body structure, and then a layer of HDPE geomembrane is covered on the GCL waterproof blanket, and the seamless connection between the membranes is achieved through thermal welding technology, and finally a layer of filament geotextile is laid on the HDPE geomembrane; an anchoring ditch is constructed on the top of the slope, the top of the anti-seepage surface layer is fixed in the anchoring ditch, and the position of the anti-seepage surface layer corresponding to the bottom of the slope is fixed by loess counter pressure; Construction of S7 retaining dam protective layer and slope protection; first, a gravel cushion layer was laid on top of the anti-seepage surface layer of the retaining dam, then a crushed stone cushion layer was laid on top of the gravel cushion layer, and finally a dry-laid C15 concrete block slope protection was laid on top of the crushed stone cushion layer. S8. Laying a pebble leachate diversion layer; constructing a leachate collection main blind ditch above the groundwater collection main blind ditch in step S4, wherein the leachate collection main blind ditch is located above the impermeable surface layer, including a pebble leachate diversion layer and a leachate collection and discharge pipe buried in the pebble leachate diversion layer, firstly, an impermeable isolation layer is provided on the impermeable surface layer, and then pebbles with a particle size range of 20 to 40 mm are selected to start laying the pebble leachate diversion layer, the pebbles need to be laid tightly and flatly, after laying a certain thickness, the leachate collection and discharge pipe is laid, and then the pebbles are continued to be filled, and finally a geotextile is laid above the pebble leachate diversion layer as a protective layer; S9. After the bottom layer of anti-seepage structure at the bottom of the landfill area is fully constructed, garbage is piled in the landfill area. When the garbage is piled to a position flush with the top of the slope, the top surface of the garbage pile is leveled and the base layer is laid. On top of the base layer, HDPE film layer, barrier layer, drainage layer and nutrient soil layer are laid in sequence. Finally, ornamental plants are planted in the nutrient soil layer according to the climate and soil conditions around the landfill to complete the construction of the landfill structure.

8. The method for constructing a landfill structure using a narrow valley design in a loess region according to claim 7, characterized in that: In step S2, the process of calculating the slope repair angle is as follows: Assume the slope is vertical, take the unit width slope, and the rupture angle is Then the slope height AC=h and the sliding surface length BC=l, and the volume of the unstable block per unit width is: Weight Normal stress is From the definition of equivalent internal friction angle, we can know that: but Where: τ-shear stress; θ-soil rupture angle, -Soil internal friction angle; -Equivalent internal friction angle of soil; c-cohesion, unit: kPa; l-slope sliding surface length, unit: m; h-slope height, unit: m; The equivalent internal friction angle of the soil can be used to judge the overall stability of the slope: when the slope soil is in a state of limit equilibrium, that is, the sliding force is equal to the anti-sliding force; assuming that the angle between the slope excavation angle and the horizontal is β, then: but Where: β-slope repair angle; F S -Safety factor. Therefore, according to Slope repair should ensure that the slope is stable in its natural state during the slope repair process.

9. The method for constructing a landfill structure using a narrow valley design in a loess region according to claim 7, characterized in that: In the step S2, a long-arm excavator is used to trim the slope surface. The trimmed slope is required to be smooth and neat without bumps and unevenness to facilitate the laying of the anti-seepage system. The corners and edges are required to be rounded, and the radius of the rounded corner should not be less than 0.3m. The soil nails are hammered into the slope body. The shotcrete is C20 fine stone concrete, which forms good bonding with the steel mesh and soil nails; In the step S3, the layer thickness of the backfill soil material of the site is controlled between 150 and 250 mm, 5% to 30% of sand and gravel materials are mixed into the backfill loess, each layer of backfill soil should be tightly combined, the compaction coefficient of the foundation treatment should be not less than 0.93, and after the trough-shaped depression is leveled, the slope along the axial direction of the valley is controlled at 2 to 4‰; In the step S4, the moisture content of the backfill loess material of the retaining dam is controlled at 19% to 21%, and the slope of the slopes on both sides of the dam body is 1:2 to 3; In the step S5, the first layer and the final protective filter layer are both made of woven geotextiles with a density of 230 g / m2; the groundwater diversion pipe is a high-density polyethylene three-flowered pipe with a diameter of DN300; the inner layer of the gravel layer has a small diameter and the outer layer has a large diameter, and the gravel material is made of sand on the surface of the gravel, and the calcium carbonate content does not exceed 10%; In the step S7, the thickness of the gravel cushion layer is 180-220 mm, the thickness of the crushed stone cushion layer is 150-180 mm, and the thickness of the C15 concrete blocks is 150-180 mm.

10. The method for constructing a landfill structure using a narrow valley design in a loess region according to claim 7, characterized in that: In the flat area, the anti-seepage surface layer in step S6 is firstly spliced ​​into a width of 18 to 22 meters by GCL waterproof blanket, HDPE geomembrane and filament geotextile; then, in the slope area, it is laid from top to bottom in a direction perpendicular to the axis of the dam; for the laying of the dam body slope, after the dam body slope is accepted, it is slowly unfolded from the top of the dam body to the foot of the dam along a path perpendicular to the axis of the dam body until it forms a T-shaped connection with the geomembrane at the bottom of the dam body at the top of the outer groove of the slope foot; the anti-seepage surface layer is fixed in the anchor trench at the top, the width of the anchor trench is 0.5m-1.0m, and the depth is 1.0m. The depth is 0.5m-1.0m, the top edge of the anti-seepage surface layer extends to the bottom of the anchor trench and is fixed by U-shaped nails, and then the soil layer is backfilled in the anchor trench to ensure that the compaction coefficient of the backfill soil layer is not less than 0.93; an intercepting drainage ditch is set at a position 1.5m-2m outside the anchor trench, and the area between the top of the slope and the intercepting drainage ditch is hardened with 80-120mm thick C30 concrete; loess counter pressure is used at the foot of the slope to make the anti-seepage surface layer close to the inner side of the soil pile. The counter pressure body is trapezoidal, with a top width of 0.8-1.2m, a bottom width of 1.8-2.2m, a height of 0.8-1.2m, and a slope gradient of 1:1.

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