Drainage system for large-area high-fill site and use method of drainage system

Abstract

The invention relates to the technical field of geotechnical engineering, and aims to provide a drainage system for a large-area high-fill site and a use method thereof.The main body of the drainage system is backfill soil, and the backfill soil is arranged in a stepped and layered mode and comprises a plurality of main blind ditches correspondingly arranged at the bottoms of all layers of backfill soil; the open trench is formed in the slope surface of the backfill soil body; the water-resisting layers are correspondingly laid on the top sides of all the layers of backfill soil bodies, and the water-resisting layers are arranged in a manner of avoiding the open trenches; a plurality of water guide slopes are arranged on the top side of the water-resisting layer, and a plurality of water collecting depressions are defined by the water guide slopes; the plurality of vertical seepage wells are respectively buried in each layer of backfill soil body, and the vertical seepage wells are correspondingly arranged below the water collecting depression; wherein a plurality of secondary blind ditches extend on the main blind ditch, and water diversion strips are arranged in the main blind ditch and the secondary blind ditches; the method has efficient drainage capacity, and the problems of site water and soil loss, settlement deformation, slope instability and the like can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering, and particularly to a drainage system for large-area high-fill sites and a method for using the same. Background Art

[0002] Fujian is located on the southeast coast of China. Its topography and landform present typical characteristics of "eight mountains, one water and one field". Mountains and hills account for more than 80% of the total land area of the province, and the plain area is narrow, only accounting for about 10%. This unique geographical pattern results in extremely limited flat land resources available for direct development and utilization. With the continuous advancement of the national urbanization and industrialization processes, the demand for construction land in the Fujian region is increasing day by day, and the contradiction of tight land resources has become increasingly prominent. To expand the development space, a large number of valley areas that were originally unsuitable for construction have been transformed into construction land by filling and leveling, forming large-area high-fill sites. These high-fill sites have been widely used in the fields of urban construction, industrial park development, transportation infrastructure construction, etc., effectively alleviating the problem of land shortage.

[0003] The Fujian region belongs to the subtropical monsoon climate, with abundant rainfall. The annual average rainfall can reach 1400 - 2000 millimeters, and the rainfall is concentrated, with many rainstorm days. During the construction and use of high-fill sites, the drainage problem is particularly important. However, at present, for such large-area high-fill sites, the drainage measures mainly focus on the surface layer, and usually only conventional surface drainage ditches are set. This traditional drainage method has obvious defects. For the drainage requirements of large-area high-fill sites, the collection and drainage capabilities of surface drainage ditches are very limited.

[0004] A large amount of rainwater cannot be drained in time through the surface drainage ditches and instead infiltrates into the soil mass. In the case of no special underground drainage system being set, continuous water infiltration will cause a series of serious engineering problems. On the one hand, rainwater infiltration will lead to increased soil erosion in the site. The fine-grained substances in the soil mass migrate with the water flow, causing damage to the soil structure, uneven surface settlement, and subsequent potential dangers such as depressions and cracks in the site, affecting the normal use of the site and the safety of buildings. On the other hand, for the filling slope area, rainwater infiltration will increase the water content of the soil mass, increase the self-weight of the soil, and at the same time significantly reduce the shear strength of the soil. Under the action of water seepage force, the slope stability is seriously threatened, and disasters such as slope instability, landslides and even collapses are extremely likely to occur, which will not only damage the surrounding buildings, roads, pipelines, etc., but may also endanger people's lives and property safety.

[0005] At present, regarding the drainage problem of high fill sites, although there are some targeted treatment measures in some local areas or small fill projects, for large-area high fill sites, there is a lack of systematic and effective drainage system design and construction technology. Existing research mainly focuses on surface drainage and the diversion of shallow groundwater, and there is insufficient research on the movement law and control method of deep groundwater. At the same time, in the drainage system design of high fill sites, the special climatic conditions, topography and landform, and soil properties in Fujian region are often not fully considered, resulting in poor drainage effects and the inability to fundamentally solve a series of problems caused by underwater seepage.

[0006] With the continuous expansion of the construction scale of high fill sites, the drainage problem has become a key factor restricting project construction and the safe use of the site. The traditional surface drainage method can no longer meet the drainage requirements of large-area high fill sites, and there is an urgent need to invent a drainage system and its usage method that can effectively collect and discharge rainwater and groundwater in the site. This drainage system should be able to adapt to the special environmental conditions of large-area high fills, have high drainage capacity, form a complete drainage network from the surface to the underground, achieve all-round control of rainwater and groundwater, so as to solve problems such as soil erosion, settlement deformation, and slope instability in the site, and ensure the safety, stability, and long-term use of high fill sites.

[0007] In summary, aiming at the drainage problem of large-area high fill sites, developing a new type of drainage system and its usage method has important practical significance and engineering application value, and plays an important role in promoting the national urbanization and industrialization processes and ensuring the safety and sustainable development of project construction. Summary of the Invention

[0008] The purpose of the present invention is to provide a drainage system and its usage method for large-area high fill sites, which has high drainage capacity, forms a complete drainage network from the surface to the underground, and achieves all-round control of rainwater and groundwater, thereby solving problems such as soil erosion, settlement deformation, and slope instability in the site.

[0009] One of the purposes of the present invention is achieved through the following technical solutions:

[0010] A drainage system for large-area high fill sites, the main body is backfilled soil, the backfilled soil is arranged in a stepped layer, and the height of the backfilled soil decreases from front to back, including:

[0011] A number of main blind ditches, correspondingly arranged at the bottom of each layer of backfilled soil, and the main blind ditches extend obliquely downward from front to back;

[0012] An open ditch, opened on the slope surface of the backfilled soil, is connected to the external drainage channel at the outlet of the lowest main blind ditch, and the outlets of the remaining main blind ditches are all connected to the open ditch;

[0013] A number of water - proof layers are correspondingly laid on the top sides of the backfill soil layers of each layer, and the water - proof layers are arranged to avoid the open ditches; there are a number of water - guiding slopes on the top sides of the water - proof layers, and a number of water - collecting depressions are formed by enclosing between the water - guiding slopes;

[0014] A number of vertical infiltration wells are respectively buried in the backfill soil layers of each layer, and the vertical infiltration wells are correspondingly arranged below the water - collecting depressions;

[0015] Among them, a number of secondary blind ditches extend from the main blind ditch, and water - guiding strips are arranged in both the main blind ditch and the secondary blind ditches; the lower end of the vertical infiltration well is connected to the main blind ditch or the secondary blind ditch, and its upper end is connected to the corresponding water - collecting depression.

[0016] The second object of the present invention is achieved through the following technical solutions:

[0017] A construction method for a drainage system of a large - area high - fill site, comprising the following steps:

[0018] S1. Excavate the main blind ditch, secondary blind ditches and branch blind ditches on the surface of the original site that has not been backfilled, and connect the main blind ditch to the external drainage channel; then lay water - guiding strips along the extending directions of the main blind ditch, secondary blind ditches and branch blind ditches;

[0019] S2. Support vertical infiltration wells at preset positions in the main blind ditch and secondary blind ditches, and backfill the backfill soil in layers to the predetermined elevation;

[0020] S3. Lay a water - proof layer on the top side of this layer of backfill soil, and construct a number of water - guiding slopes on the top side of the water - proof layer, so that a number of water - collecting depressions are formed by enclosing between the water - guiding slopes, and the water - collecting depressions are connected to the corresponding vertical infiltration wells;

[0021] S4. Carry out the construction of the soil backfill of the upper layer. Among them, first backfill part of the soil to the elevation position of the top sides of the main blind ditch, secondary blind ditches and branch blind ditches of this layer, and then excavate the main blind ditch, secondary blind ditches and branch blind ditches on the surface of the backfilled part of the soil; then lay water - guiding strips along the extending directions of the main blind ditch, secondary blind ditches and branch blind ditches, and support vertical infiltration wells at preset positions in the main blind ditch and secondary blind ditches; continue to backfill the remaining soil, and then lay a water - proof layer on the top side of this layer of backfill soil, and construct a number of water - guiding slopes on the top side of the water - proof layer. The water - guiding slopes enclose a number of water - collecting depressions, and the water - collecting depressions are connected to the corresponding vertical infiltration wells;

[0022] S5. Repeat step S4 according to the number of backfill layers until all backfill operations and the hierarchical layout of the drainage system are completed;

[0023] S6. Excavate an open ditch along a predetermined path on the surface of the backfill soil after all backfilling is completed, so that the open ditch is successively connected to the main blind ditches of each layer to achieve step - by - step diversion and drainage.

[0024] Compared with the prior art, the advantages of the present invention are as follows:

[0025] By providing a clay layer, vertical infiltration wells, main blind ditches, secondary blind ditches and open ditches, a multi-level drainage path is formed in the backfill soil body. When the rainfall is small, the rainwater is successively guided by the clay layer into the vertical infiltration wells, and then enters the blind ditches. Under the connection effect of the open ditches, it is discharged into the external drainage channel through the main blind ditch at the lowest layer, realizing efficient hierarchical drainage and avoiding waterlogging retention. In addition, when the rainfall intensity is large, the infiltrated rainwater can gradually infiltrate into the next-level backfill soil body, and then be guided by the water-conducting slope to the main blind ditches, secondary blind ditches and branch blind ditches in their respective layers. The rainwater is drained dispersedly through the multi-level blind ditches, avoiding problems such as soil erosion, settlement deformation and slope instability on large-area high-fill sites. Brief Description of the Drawings

[0026] Figure 1 It is a longitudinal sectional schematic view of an embodiment of a drainage system for a large-area high-fill site of the present invention;

[0027] Figure 2 It is a partial structural sectional view of an embodiment of a drainage system for a large-area high-fill site of the present invention;

[0028] Figure 3 It is a structural top view of an embodiment of a drainage system for a large-area high-fill site of the present invention;

[0029] Figure 4 It is Figure 1 a schematic diagram of the highest-level blind ditch in

[0030] Figure 5 It is Figure 1 a schematic diagram of the intermediate-level blind ditch in

[0031] Figure 6 It is Figure 1 a schematic diagram of the lowest-level blind ditch in

[0032] Label Description: 1 Backfill soil body, 100 Slope indication line, 2 Main blind ditch, 3 Open ditch, 4 Impervious layer, 41 Water-conducting slope, 42 Water-collecting depression, 5 Vertical infiltration well, 51 Prefabricated concrete pipe, 52 Gravel filter, 53 Annular water-stop part, 6 Secondary blind ditch, 71 Sand and gravel filter, 72 Geotextile, 8 Branch blind ditch, 9 Dry-laid rubble Detailed Embodiment

[0033] The content of the present invention will be described in detail below with reference to the accompanying drawings of the specification and embodiments:

[0034] As Figures 1-6 shown, it is a schematic diagram of an embodiment of a drainage system for a large-area high-fill site provided by the present invention:

[0035] A drainage system for a large-area high-fill site, with the main body being the backfill soil mass 1. The backfill soil mass 1 is arranged in stepped layers, and the height of the backfill soil mass 1 decreases from front to back, including:

[0036] A number of main blind ditches 2, which are correspondingly arranged at the bottom of each layer of the backfill soil mass 1. The main blind ditches 2 extend obliquely downward from front to back;

[0037] Open ditches 3 are opened on the slope surface of the backfill soil mass 1. Specifically, since the backfill soil mass 1 is in a stepped shape with a decreasing height from front to back, the tread surface and the riser surface of each layer of steps can be regarded as a continuous slope surface. In this embodiment, the backfill soil mass 1 is arranged in three layers, and the riser surfaces between each layer are all sloped, as Figures 3-6 shown, that is, the open ditches 3 are arranged on the tread surface of the middle layer, the tread surface of the lowest layer, and the riser surface between the middle layer and the lowest layer. The outlet of the lowest main blind ditch 2 is connected to the external drainage channel, while the outlets of the other main blind ditches 2 are all connected to the open ditches 3;

[0038] Furthermore, the side walls of the trenches of the open ditches 3 are treated with cement hardening.

[0039] A number of water-proof layers 4 are correspondingly laid on the top side of each layer of the backfill soil mass 1, and the water-proof layers 4 are arranged to avoid the open ditches 3; there are a number of water-conducting slopes 41 on the top side of the water-proof layers 4, and a number of water-collecting depressions 42 are formed by enclosing between the water-conducting slopes 41;

[0040] Specifically, the water-conducting slopes 41 are constructed manually to ensure that rainwater can smoothly enter the water-collecting depressions 42.

[0041] A number of vertical infiltration wells 5 are respectively buried in each layer of the backfill soil mass 1, and the vertical infiltration wells 5 are correspondingly arranged below the water-collecting depressions 42;

[0042] Among them, a number of secondary blind ditches 6 extend on the main blind ditches 2, and water diversion strips are arranged in both the main blind ditches 2 and the secondary blind ditches 6; the lower end of the vertical infiltration well 5 is connected to the main blind ditch 2 or the secondary blind ditch 6, and its upper end is connected to the corresponding water-collecting depression 42.

[0043] The vertical infiltration well 5 includes a precast concrete pipe 51 and gravel filter material 52 filled in the pipe cavity of the precast concrete pipe 51. The upper end of the precast concrete pipe 51 is connected to the water-collecting depression 42, and the lower part of the precast concrete pipe 51 extends into the main blind ditch 2 or the secondary blind ditch 6.

[0044] The gravel filter material 52 is gravel with a particle size within 10mm - 60mm, and the gravel filter material 52 is filled with a gradually decreasing particle size from top to bottom.

[0045] The lower end of the precast concrete pipe 51 is further provided with an annular water stop portion 53, and the annular water stop portion 53 is used to seal the gap at the joint of the lower end of the precast concrete pipe 51 and the main blind ditch 2 and the secondary blind ditch 6.

[0046] Preferably, the annular water stop portion 53 is made of clay.

[0047] The water diversion strip is in a strip shape and includes sand and gravel filter material 71 and a geotextile 72 wound around the outer peripheral side of the sand and gravel filter material 71. The water diversion strip is arranged throughout the main blind ditch 2 and the secondary blind ditch 6.

[0048] Preferably, the water barrier layer 4 is a clay layer. Due to the aggregation, low permeability and pore structure of the clay, when the rainfall is small or the groundwater is scarce, the clay layer can effectively prevent water from penetrating into the underlying backfill soil 1, playing a role in water barrier protection; at the same time, in the case of heavy rainfall or long duration of rain, part of the water can seep in along the pores between the clay particles, and thus can achieve diversion or infiltration according to the size of the water flow.

[0049] The vertical infiltration wells 5 in the upper and lower adjacent backfill soil layers are arranged in a staggered manner.

[0050] A number of branch blind ditches 8 extend from the secondary blind ditch 6, and water diversion strips are arranged throughout the branch blind ditches 8.

[0051] Dry-laid riprap 9 is provided on the side walls of the main blind ditch 2, the secondary blind ditch 6 and the branch blind ditch 8.

[0052] A construction method of a drainage system for a large-area high-fill site as described above includes the following steps:

[0053] S1. Excavate the main blind ditch 2, the secondary blind ditch 6 and the branch blind ditch 8 on the surface of the original site that has not been backfilled, and connect the main blind ditch 2 with an external drainage channel; then lay water diversion strips along the extending directions of the main blind ditch 2, the secondary blind ditch 6 and the branch blind ditch 8;

[0054] S2. Support vertical infiltration wells 5 at preset positions in the main blind ditch 2 and the secondary blind ditch 6, and backfill the backfill soil 1 in layers to a predetermined elevation;

[0055] S3. Lay a water barrier layer 4 on the top side of this layer of backfill soil 1, and construct a number of water diversion slopes 41 on the top side of the water barrier layer 4, so that a number of water collection depressions 42 are formed by enclosing among the water diversion slopes 41, and the water collection depressions 42 are communicated with the correspondingly arranged vertical infiltration wells 5;

[0056] S4. Carry out the construction of backfilling the soil layer above. Among them, first backfill part of the soil to the top elevation position of the main blind ditch 2, secondary blind ditch 6 and branch blind ditch 8 of this layer. Subsequently, excavate the main blind ditch 2, secondary blind ditch 6 and branch blind ditch 8 on the surface of the backfilled part of the soil. Then lay the water diversion strips along the extension directions of the main blind ditch 2, secondary blind ditch 6 and branch blind ditch 8, and support the vertical infiltration wells 5 at the preset positions of the main blind ditch 2 and secondary blind ditch 6. Continue to backfill the remaining soil. Subsequently, lay the water-proof layer 4 on the top side of the backfilled soil layer 1 of this layer, and construct a number of water guiding slopes 41 on the top side of the water-proof layer 4. The water guiding slopes 41 enclose a number of water collecting depressions 42, and the water collecting depressions 42 are connected to the corresponding vertical infiltration wells 5.

[0057] S5. Repeat step S4 according to the number of backfilled layers until the completion of all backfilling operations and the layered layout of the drainage system.

[0058] S6. Excavate an open ditch 3 on the surface of the backfilled soil 1 after all backfilling is completed along the predetermined path, so that the open ditch 3 is sequentially connected to the main blind ditches 2 of each layer to achieve step-by-step diversion and drainage.

[0059] The drainage principle of the present invention is roughly as follows:

[0060] When the rainfall is small, the rainwater falls on the clay layer on the top side of the backfilled soil layer 1 of each layer, and flows along the water guiding slope 41 to the water collecting depression 42, thereby entering the vertical infiltration well 5. Subsequently, it flows into the secondary blind ditch 6 or the main blind ditch 2, and flows out of the outlet of the main blind ditch 2 of each layer into the open ditch 3, and finally is discharged into the external drainage ditch through the outlet of the main blind ditch 2 of the lowest layer.

[0061] When the rainfall is large, part of the rainwater still flows into the vertical infiltration well 5 through the diversion of the clay layer, while the remaining rainwater penetrates downward to the clay layer on the top side of the lower backfilled soil layer 1. Part of the penetrated rainwater is diverted by the clay layer of this layer and enters the main blind ditch 2 or secondary blind ditch 6 of this layer. Another part of the penetrated rainwater directly flows into the branch blind ditch 8 or continues to penetrate downward and flows into the branch blind ditch 8. The rainwater flowing into the branch blind ditch 8 is re-converged into the main blind ditch 2 through the secondary blind ditch 6, and finally enters the open ditch 3 or is discharged into the external drainage ditch through the outlet of the main blind ditch 2 of this layer.

[0062] The above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A drainage system for a large-area high-fill site, with the main body being the backfill soil mass (1). The backfill soil mass (1) is arranged in a stepped layer-by-layer manner, and the height of the backfill soil mass (1) decreases from front to back. It is characterized in that, Including: A number of main blind ditches (2), which are correspondingly arranged at the bottom of each layer of backfill soil body (1), and the main blind ditches (2) extend obliquely downward from front to back; An open ditch (3) is opened on the slope surface of the backfill soil body (1), and is located at the outlet of the lowermost main blind ditch (2) and is connected to the external drainage ditch, while the outlets of the remaining main blind ditches (2) are all connected to the open ditch (3); A number of waterproof layers (4), which are correspondingly laid on the top side of each layer of backfill soil body (1), and the waterproof layers (4) are arranged to avoid the open ditch (3); there are a number of water guiding slopes (41) on the top side of the waterproof layer (4), and a number of water collecting depressions (42) are formed by enclosing between the water guiding slopes (41); A number of vertical infiltration wells (5) are respectively buried in each layer of backfill soil body (1), and the vertical infiltration wells (5) are correspondingly arranged below the water collecting depressions (42); Wherein, a number of secondary blind ditches (6) extend on the main blind ditch (2), and water guiding strips are arranged in both the main blind ditch (2) and the secondary blind ditches (6); the lower end of the vertical infiltration well (5) is connected to the main blind ditch (2) or the secondary blind ditch (6), and its upper end is connected to the corresponding water collecting depression (42).

2. The drainage system for large-area high-fill sites according to claim 1, characterized in that: The vertical infiltration well (5) includes a precast concrete pipe (51) and gravel filter material (52) filled in the pipe cavity of the precast concrete pipe (51), the upper end of the precast concrete pipe (51) is connected to the water collecting depression (42), and the lower part of the precast concrete pipe (51) extends into the main blind ditch (2) or the secondary blind ditch (6).

3. The drainage system for large-area high-fill sites according to claim 2, wherein: The gravel filter material (52) is gravel with a particle size within 10mm - 60mm, and the gravel filter material (52) is filled with gradually decreasing particle size from top to bottom.

4. The drainage system for large-area high-fill sites according to claim 2, wherein: The lower end of the precast concrete pipe (51) is also provided with an annular water stop part (53), and the annular water stop part (53) is used to seal the gap at the junction of the lower end of the precast concrete pipe (51) and the main blind ditch (2) and the secondary blind ditches (6).

5. The drainage system for large-area high-fill sites according to claim 1, characterized in that: The water guiding strip is in a strip shape, and includes gravel filter material (71) and a geotextile (72) wound around the outer peripheral side of the gravel filter material (71), and the water guiding strip is arranged throughout the main blind ditch (2) and the secondary blind ditches (6).

6. The drainage system for large-area high-fill sites according to claim 1, characterized in that: The waterproof layer (4) is a clay layer.

7. The drainage system for large-area high-fill sites according to claim 1, characterized in that: The vertical infiltration wells (5) in two adjacent upper and lower backfill soil layers are arranged in a staggered manner.

8. The drainage system for large-area high-fill sites according to any one of claims 1 to 7, characterized in that: A number of branch blind ditches (8) extend on the secondary blind ditch (6), and water guiding strips are arranged throughout the branch blind ditches (8).

9. The drainage system for large-area high fill sites according to claim 8, characterized in that: Dry-laid split stones (9) are arranged on the side walls of the main blind ditch (2), the secondary blind ditches (6) and the branch blind ditches (8).

10. A construction method for a drainage system for a large-area high-fill site as described in claim 9, characterized in that, Including the following steps: S1. Excavate the main blind ditch (2), the secondary blind ditches (6) and the branch blind ditches (8) on the surface of the original site that has not been backfilled, and connect the main blind ditch (2) to the external drainage ditch; then lay water guiding strips along the extending directions of the main blind ditch (2), the secondary blind ditches (6) and the branch blind ditches (8); S2. Support the vertical infiltration wells (5) at the preset positions of the main blind ditch (2) and the secondary blind ditches (6), and backfill the backfill soil body (1) layer by layer to the predetermined elevation; S3. Lay a water-proof layer (4) on the top side of the backfilled soil body (1) of this layer, and construct a number of water-conducting slopes (41) on the top side of the water-proof layer (4), so that a number of water-collecting depressions (42) are enclosed between the water-conducting slopes (41), and the water-collecting depressions (42) are communicated with the correspondingly arranged vertical infiltration wells (5); S4. Carry out the soil backfilling construction of the upper layer. Among them, first backfill part of the soil to the top elevation position of the main blind ditch (2), secondary blind ditch (6) and branch blind ditch (8) of this layer, and then excavate the main blind ditch (2), secondary blind ditch (6) and branch blind ditch (8) on the surface of the backfilled part of the soil; then lay water diversion strips along the extension directions of the main blind ditch (2), secondary blind ditch (6) and branch blind ditch (8), and support vertical infiltration wells (5) at preset points of the main blind ditch (2) and secondary blind ditch (6); continue to backfill the remaining soil, and then lay a water-proof layer (4) on the top side of the backfilled soil body (1) of this layer, and construct a number of water-conducting slopes (41) on the top side of the water-proof layer (4), and the water-conducting slopes (41) enclose a number of water-collecting depressions (42) therebetween, and the water-collecting depressions (42) are communicated with the correspondingly arranged vertical infiltration wells (5); S5. Repeat step S4 according to the number of backfill layers until all backfill operations and the hierarchical layout of the drainage system are completed; S6. Excavate an open ditch (3) on the surface of the backfilled soil body (1) after all backfilling is completed along a predetermined path, so that the open ditch (3) is communicated with the main blind ditches (2) of each layer in sequence to achieve step-by-step diversion drainage.

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