Three-dimensional water seepage prevention and treatment structure for gully high-fill engineering

Abstract

The utility model belongs to the technical field of collapsible foundation reinforcement, and relates to a three-dimensional water seepage prevention and treatment structure for gully high-fill engineering, which comprises an original slope body, a fill body, a gully, a plurality of staggered underground soil layers and opposite water-resisting layers which penetrate through the ground level of the original slope body along the height direction, and isolation cushion layers which are attached to the gully and are arranged at the bottom and the side direction of the gully, the filling body and the original slope body are isolated on the inner side and the outer side of the isolation cushion layer through the isolation cushion layer. The isolation cushion layer sequentially comprises a cushion soil layer, a fine grain layer and a coarse grain layer in the thickness direction from inside to outside. The three-dimensional anti-seepage structure is adopted, the hidden danger of water seepage of the filling body is eliminated, it is guaranteed that the filling body is not threatened by surrounding water seepage, and the problem that after filling is completed, slope water seepage causes large-area differential settlement of a filling project, and project operation is difficult is effectively solved; therefore, the quality of a filling project is guaranteed, and large-area differential settlement in the later period is avoided.

Description

Technical Field

[0001] The utility model belongs to the technical field of collapsible ground reinforcement, and relates to a three-dimensional seepage prevention structure for high fill projects in gully areas. Background Technique

[0002] The three-dimensional anti-seepage technology of the fill body is based on the correct understanding of the environmental changes caused by filling in the gully area, considering and designing the anti-seepage problem of the fill body with the concept of dynamic thinking. At the same time, it is also based on the in-depth analysis of previous fill seepage cases and the research on the water seepage mechanism, accurately grasping the seepage problem induced by the environmental changes in the original gully area caused by filling. In addition, the concept of time scale is introduced into the anti-seepage design, paying attention to the characteristics of slope seepage during the long rainy season with a long time span, and emphasizing the accumulation and time effect of seepage. When determining the possible seepage positions, according to the lithological changes of the slope, the existence of the impermeable layer is determined by using the difference in the permeability coefficients of the rock layers, and the possible seepage paths of the seepage in the slope are analyzed in combination with the structural distribution of the slope to accurately judge the possible seepage positions of the slope. Combining the meteorological historical data of the site, the maximum seepage volume is estimated, and on this basis, the layout and design of the anti-seepage measures are considered.

[0003] However, the current general design and specification requirements mainly focus on the collection and drainage of seepage water at the bottom of the gully, without considering the seepage water on the slope. At the same time, designers have insufficient understanding of the environmental changes caused by filling, especially in arid regions, and lack a correct understanding of the gullies that are determined to be dry all year round or without groundwater in the geological exploration report, and do not realize that the environmental changes caused by filling will lead to the exudation of groundwater on the post-construction slope. Therefore, the lateral incoming water of the slope is basically ignored in the anti-seepage design of the gully fill body, which is also one of the main reasons for frequent incidents after the completion of the filling project.

[0004] Moreover, the existing blind ditch design draws on the architecture of building water supply and drainage, without considering the gully landform, lithology and gully seepage and other characteristics. The water may not flow smoothly into the pipeline. In addition, the blind ditch is complex to set up, costly, and has durability problems.

[0005] Therefore, a method or structure is needed to avoid large-area uneven settlement of the filling project caused by slope seepage after the completion of the filling to solve the above technical problems. Content of the Utility Model

[0006] The utility model aims at the problem that the slope body after the filling is completed causes large-area uneven settlement of the filling project due to water seepage. It has carried out systematic innovation in terms of design concept, understanding of water seepage in the filling project, and specific setting of blind ditches. It uses common graded pebbles and arranges them in a paving form. In order to make the seepage flow out of the bottom of the ditch quickly and smoothly, it uses the original slope surface to collect the seepage water and let the seepage water flow out naturally along the bottom of the ditch. Only the drainage ditch at the bottom of the ditch is appropriately dredged to make the water flow smoothly, and no artificial drainage blind ditch is designed separately, which better solves the anti-seepage problem around the filling and ensures the long-term safe operation of the filling project.

[0007] The utility model can well solve the problem of lateral water seepage in the original gully slope of high fill. By setting up three-dimensional anti-seepage measures, the lateral water seepage of the slope body is transported to the bottom of the ditch to prevent the filling body from being soaked by water, ensuring the stability of the filling project and completely solving the anti-seepage problem of the filling body.

[0008] The technical solution adopted by the utility model to solve the technical problem is: a three-dimensional water seepage prevention and control structure for a gully high fill project, including: the original slope body, the filling body, and the gully. The gully is located below the ground plane of the original slope body. The gully passes through multiple staggered underground soil layers and relatively water-resistant layers below the ground plane of the original slope body in the height direction. The bottom and sides of the gully are provided with an isolation cushion layer that fits the gully. The isolation cushion layer separates the filling body and the original slope body on the inner and outer sides of the isolation cushion layer respectively. The filling body is filled in the isolation cushion layer;

[0009] The isolation cushion layer sequentially includes, along the thickness direction from the filling body side to the original slope body side: a cushion soil layer, a fine-grained layer, and a coarse-grained layer;

[0010] The cushion soil layer is used to prevent water from seeping from the original slope body side to the filling body side, forming an isolation layer between the filling body and the underground seepage water, preventing the filling body from sinking or deforming; the fine-grained layer is used as a transition layer between the cushion soil layer and the coarse-grained layer, reducing water seepage while protecting the cushion soil layer from being damaged by larger particles in the coarse-grained layer; the coarse-grained layer is used to drain the seepage water to prevent water accumulation, and the coarse-grained layer is also used to protect the fine-grained layer and the cushion soil layer from external damage;

[0011] The cushion soil layer is composed of clay or soil with good anti-seepage performance. The fine-grained layer and the coarse-grained layer are respectively composed of gravel or crushed stone. The particle size of the fine-grained layer is smaller than that of the coarse-grained layer.

[0012] Preferably, the relatively water-resistant layer includes: mudstone, marl.

[0013] Preferably, the cross-section of the gully is in the shape of an arc-shaped groove.

[0014] Preferably, the selected granular material of the coarse-grained layer at the bottom of the isolation cushion layer is graded 25# and 30#, and the thickness of the coarse-grained layer at the bottom of the isolation cushion layer is not less than 50 cm.

[0015] Preferably, the fine-grained layer aggregate at the bottom of the isolation cushion layer selects 17# aggregate, and the thickness of the fine-grained layer at the bottom of the isolation cushion layer is not less than 50 cm.

[0016] Preferably, the lateral thickness of the isolation cushion layer is not less than 1 m, the aggregate gradation of the lateral part of the isolation cushion layer selects 25# aggregate, and the lateral part of the isolation cushion layer is arranged along the valley slope form.

[0017] The beneficial effects of the present utility model are as follows:

[0018] Based on the actual situation of the environmental changes in the filled valley, the present utility model adopts a three-dimensional anti-seepage structure to eliminate the potential seepage hazards of the filled body, ensure that the filled body is not threatened by seepage from all around, effectively avoid the problem that large-area uneven settlement occurs in the filled project due to slope seepage after the filling is completed, resulting in difficulties in the operation of the project; therefore, the present utility model guarantees the quality of the filled project and avoids large-area uneven settlement in the later stage. Description of the Drawings

[0019] Figure 1 is a cross-sectional schematic view of a three-dimensional seepage prevention and control structure for a gully high-filled project of the present utility model;

[0020] Figure 2 is a schematic diagram of the aggregate gradation at the bottom of the valley of the present utility model.

[0021] In the figure, 1, original slope; 2, filled body; 3, valley; 4, underground soil layer; 5, relatively water-resistant layer; 6, isolation cushion layer; 7, cushion layer; 8, fine-grained layer; 9, coarse-grained layer. Specific Embodiments

[0022] Next, the relevant technologies in the present utility model will be clearly and completely described in conjunction with the drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0023] Refer to Figures 1 - 2 , the lateral seepage prevention and control structure of the gully high-filled project in this embodiment includes: original slope 1, filled body 2, valley 3. The valley 3 is located below the ground plane of the original slope 1. The valley 3 passes through multiple staggered underground soil layers 4 and relatively water-resistant layers 5 below the ground plane of the original slope 1 along the height direction. The bottom and lateral sides of the valley 3 are provided with an isolation cushion layer 6 that fits the valley 3. The isolation cushion layer 6 separates the filled body 2 and the original slope 1 on the inner and outer sides of the isolation cushion layer 6 respectively. The filled body 2 is filled in the isolation cushion layer 6; the isolation cushion layer 6 is used to separate the original slope 1 from the filled body 2 and prevent the seepage water from the seepage emergence points at different positions on the original slope 1 from entering the filled body 2;

[0024] The isolation cushion layer 6 sequentially includes, along the thickness direction from one side of the filled body 2 to one side of the original slope body 1: a cushion soil layer 7, a fine-grained layer 8, and a coarse-grained layer 9;

[0025] The cushion soil layer 7 is used to prevent water from seeping from one side of the original slope body 1 to one side of the filled body 2, form an isolation layer between the filled body 2 and the underground seepage water, and prevent the filled body 2 from sinking or deforming; the fine-grained layer 8 is used as a transition layer between the cushion soil layer 7 and the coarse-grained layer 9, reducing water seepage while protecting the cushion soil layer 7 from being damaged by larger particles in the coarse-grained layer 9; the coarse-grained layer 9 is used to drain the seepage water to prevent water accumulation, and the coarse-grained layer 9 is also used to protect the fine-grained layer 8 and the cushion soil layer 7 from external force damage; the cushion soil layer 7 is used to isolate the seepage water from the filled body 2, the fine-grained layer 8 is used to transition between the cushion soil layer 7 and the coarse-grained layer 9, and the coarse-grained layer 9 is used to drain the seepage water in time. Therefore, when seepage occurs at the seepage point on one side of the original slope body 1, the lateral seepage water converges to the bottom through the coarse-grained layer 9, and the bottom seepage water is drained through the coarse-grained layer 9, so that the seepage water cannot seep into the filled body 2 through the cushion soil layer 7, ensuring that the filled body 2 will not have large-area uneven settlement due to seepage water in the filling project;

[0026] The cushion soil layer 7 is composed of clay or soil with good anti-seepage performance, and the fine-grained layer 8 and the coarse-grained layer 9 are respectively composed of gravel or crushed stone, and the particle size of the fine-grained layer 8 is smaller than that of the coarse-grained layer 9.

[0027] Further, the relatively water-resistant layer 5 includes: mudstone, marl.

[0028] Further, the cross-section of the gully 3 is in an arc-shaped trough shape.

[0029] Further, the selected aggregate of the coarse-grained layer 9 at the bottom of the isolation cushion layer 6 is graded 25# and 30#, and the thickness of the coarse-grained layer 9 at the bottom of the isolation cushion layer 6 is not less than 50 cm.

[0030] Further, the selected aggregate of the fine-grained layer 8 at the bottom of the isolation cushion layer 6 is 17# aggregate, and the thickness of the fine-grained layer 8 at the bottom of the isolation cushion layer 6 is not less than 50 cm; the aggregate material of the fine-grained layer 8 is hard stone and is not easily weathered when exposed to water.

[0031] Further, the lateral thickness of the isolation cushion layer 6 is not less than 1 m, the lateral aggregate grading of the isolation cushion layer 6 is selected as 25# aggregate, and the lateral side of the isolation cushion layer 6 is arranged along the slope body shape of the gully 3.

[0032] Before the design and construction of the three-dimensional anti-seepage project for the gully filled body, when determining the seepage position, the construction thickness and ratio of the isolation cushion layer, the following steps are further included:

[0033] Step 1: Determine the seepage position of the slope body.

[0034] Vertical direction:

[0035] Ⅰ: Determine the existence of the relatively water - impermeable layer based on the layered permeability coefficients of the slope strata. In this embodiment, the permeability coefficient data of each rock stratum is obtained through the indoor experimental method of the layered permeability coefficient of the strata. The permeability coefficient of the strata is used to distinguish whether there is a water - impermeable layer according to the difference of the order of magnitude of 10ˉ2. When the permeability coefficient of the lower stratum is less than that of the upper stratum by up to 10ˉ2, this layer is considered as the water - impermeable layer;

[0036] Ⅱ: The existence of the water - impermeable layer can also be determined by lithological differences. Mudstone and argillaceous shale are both water - impermeable layers.

[0037] Horizontal direction:

[0038] Determine the possible water - discharging positions of the slope according to the distribution of faults and fractures. Tensile faults and vertical fractures are both the positions of lateral water inflow. The fracture zones developed with mudstone and argillaceous cements are all the positions where water seeps out.

[0039] Step 2: Determine the groundwater seepage field situation, possible seepage paths and the positions of specific water - discharging points after filling the gully.

[0040] ⑴ According to the geological exploration report of the filling area, understand the basic geological conditions such as stratum distribution, lithological characteristics, permeability coefficient characteristics, fault and fracture development conditions, etc.

[0041] ⑵ Collect or conduct hydro - geological surveys to understand the occurrence conditions of groundwater, water - level dynamics, recharge - discharge relationships, etc.

[0042] ⑶ Obtain the groundwater seepage field situation, possible seepage paths and the positions of specific water - discharging points after filling the gully.

[0043] Step 3: Calculate the rainfall received for recharge according to the meteorological data and the outcropping area of the slope strata after filling, determine the actual catchment area of the strata. The calculation of the catchment area is not limited to the vicinity of the filling. Determine the actual catchment area of the strata according to the regional hydro - geological data, basically determine the annual water catchment volume of the slope strata, and measure the volume of lateral water inflow at different positions.

[0044] The amount of water Pr infiltrating and recharging groundwater is Pr = P×α, where Pr is the amount of water infiltrating and recharging groundwater, P is the precipitation, and α is the precipitation infiltration recharge coefficient, with a value between 0 and 1, and different values are taken according to different regions.

[0045] Step 4: Determine the height and scope of the design of the water - seeping material layer of the slope.

[0046] ① Seepage height: Determine the maximum height that seepage may reach according to the groundwater level and seepage path. Considering the rainfall intensity and frequency, as well as the drainage capacity of the slope, comprehensively determine the seepage design height.

[0047] ② Seepage range: Based on the geological exploration results, determine the diffusion range of seepage within the slope body. Considering factors such as the permeability of the slope body and rainfall intensity, reasonably delimit the area affected by seepage.

[0048] ③ Taking the principle of laying the seepage material layer to cover the seepage emergence points within the fill, ensure that seepage in the slope body cannot enter the fill body after filling. For the area near the permeable fault, the width design of the seepage material layer should be thickened.

[0049] Step Five: Design the thickness of the graded gravel at the bottom of the gully. According to the amount of water, the bottom can select graded materials of No. 25 and No. 30. The thickness is determined but not less than 50 cm. The second layer of gravel selects graded material of No. 17 with a thickness of 50 cm. The material of the gravel is hard stone and is not easily weathered by water. The thickness of the lateral anti-seepage stone wall is considered as 1 meter, and the graded material is designed according to No. 25. The layout of the lateral anti-seepage stone wall is arranged according to the slope body shape. During the construction process, it is not easy to accurately control the thickness of the stone wall. Taking not less than 1 meter as the principle.

[0050] In this embodiment, Step Five is as Figure 2 shown. For the first layer of gravel, select graded material of No. 25 with a thickness of 50 cm. For the second layer of gravel, select graded material of No. 17 with a thickness of 50 cm. The material of the gravel is hard stone and is not easily weathered by water. The thickness of the lateral anti-seepage stone wall is considered as 1 meter, and the graded material is designed according to No. 25. The layout of the lateral anti-seepage stone wall is arranged according to the slope body shape.

[0051] Example

[0052] Example 1: For a coal mine resettlement project, the filling depth is 25 meters. The filled gully belongs to a natural erosion gully composed of a main gully and secondary gullies. The two sides of the gully slope are fractured rock layers, mostly mudstone and muddy sandstone, with silty loess covering the mudstone. The filling material is also silty soil. The gully is a seasonal river, dry except during the rainy season, but the gully has a large catchment area, the catchment divide is more than 100 meters high, and there is occasionally a small amount of seepage at the bottom of the gully usually. According to the topographic and geomorphic analysis, there is a possibility of seepage on both sides of the gully after filling, so a three-dimensional waterproof design is adopted. At the back edge of the filling, that is, at the confluence of the secondary gully and the main gully on the southeast side of the gully, there is a fault approximately perpendicular to the gully. The bottom of this secondary gully is higher than the filling ground level. During the rainy season, the runoff will be directly discharged, and the infiltrated part will seep into the main gully, that is, the filling body, along the fracture zone. Therefore, the diversion measure for seepage here is the key point of the three-dimensional anti-seepage of the filling body. Similarly, at the joint of the bedrock and the filling in the upper reaches of the gully, the bedrock is layered mudstone with developed fissures, and the seepage positions are different. Vertical anti-seepage measures must be taken to ensure that no water seeps into the filling body. On the northwest side of the gully, it belongs to a single mountain ridge landform, with a small rainwater catchment area, and a deep gully with smooth drainage on the other side. Therefore, for the anti-seepage design here, only a seepage gravel layer is set at the bottom of the gully.

[0053] Embodiment 2: A high fill project at an airport, which belongs to an ultra-high fill body, with a maximum depth of 74 meters and a fill volume of more than 24 million cubic meters. It involves multiple gullies. The upper part of the site is loess with a maximum thickness of more than 40 meters, and the lower part is an interlayer of mudstone and mudstone sandstone. The overall dip of the rock formation is to the southeast, and there is no water in the gully all year round. Through the analysis of the surrounding topography, geologic lithology and hydrogeological characteristics of the site, after filling, the main source of seepage in the site is at the horizon of argillaceous mudstone below the loess cover layer. Therefore, the vertical anti-seepage measures are mainly arranged on both sides of the gully slopes where the mudstone outcrops. According to the distribution characteristics of the fault fracture zone of the site, there is a nearly north-south fracture zone in the middle of the filling depth. The fracture zone is gray-green thin-sheet mudstone, which is easy to weather when exposed to water, with a thickness of 5 - 10 meters and has good water isolation performance. According to on-site analysis, this fracture zone is the largest seepage layer of the fill body and is the key anti-seepage part of the entire filling project. The anti-seepage measures here adopt enhanced design to increase the thickness of the granular layer to ensure that seepage water is quickly drained. The assessment of the seepage possibility of this fracture zone is both crucial and accurate, which was verified in the second rainy season during construction. After the thickness of the filling operation is greater than the height here, a large amount of seepage water was found at the fracture zone, which verified the necessity of the three-dimensional anti-seepage design from the side.

[0054] To sum up, starting from the actual situation of the environmental changes in the filling gully, the utility model adopts a three-dimensional anti-seepage structure to eliminate the seepage hidden danger of the fill body, ensure that the fill body is not threatened by seepage from all around, and effectively avoid the problem that large-area uneven settlement occurs in the filling project due to slope seepage after the filling is completed, resulting in difficulties in the operation of the project; the utility model guarantees the quality of the filling project, avoids large-area uneven settlement in the later stage, and brings obvious economic and social benefits. Therefore, the utility model has a wide application prospect.

[0055] It should be emphasized that the above are only the preferred embodiments of the utility model, and do not impose any form of limitation on the utility model. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the utility model still belong to the scope of the technical solution of the utility model.

Claims

1. A three-dimensional seepage prevention structure for high fill projects in gullies, characterized in that Including: The original slope body (1), the filled body (2), and the gully (3). The gully (3) is located below the ground plane of the original slope body (1). The gully (3) passes through multiple intersecting underground soil layers (4) and relatively water - impermeable layers (5) below the ground plane of the original slope body (1) in the height direction. The bottom and sides of the gully (3) are provided with an isolation cushion layer (6) that fits the gully (3). The isolation cushion layer (6) separates the filled body (2) and the original slope body (1) on the inner and outer sides of the isolation cushion layer (6) respectively, and the filled body (2) is filled in the isolation cushion layer (6). The isolation cushion layer (6) sequentially includes, in the thickness direction from the side of the filled body (2) to the side of the original slope body (1): a cushion soil layer (7), a fine - grained layer (8), and a coarse - grained layer (9). The cushion soil layer (7) is used to prevent water from seeping from the side of the original slope body (1) to the side of the filled body (2), forming an isolation layer between the filled body (2) and the underground seepage water, and preventing the filled body (2) from sinking or deforming. The fine - grained layer (8) is used as a transition layer between the cushion soil layer (7) and the coarse - grained layer (9), reducing water seepage while protecting the cushion soil layer (7) from damage by larger particles in the coarse - grained layer (9). The coarse - grained layer (9) is used to drain the seepage water to prevent water accumulation, and the coarse - grained layer (9) is also used to protect the fine - grained layer (8) and the cushion soil layer (7) from external force damage. The cushion soil layer (7) is composed of clay or soil with good anti - seepage performance. The fine - grained layer (8) and the coarse - grained layer (9) are respectively composed of gravel or crushed stone. The particle size of the particles in the fine - grained layer (8) is smaller than that of the particles in the coarse - grained layer (9).

2. The three-dimensional seepage prevention structure for high fill project in gully according to claim 1, characterized in that The relatively water - impermeable layer (5) includes: mudstone, marl.

3. The three-dimensional seepage prevention structure for high-fill projects in gully areas according to claim 1, characterized in that, The cross - section of the gully (3) is in the shape of an arc - shaped trough.

4. The three-dimensional seepage prevention structure for high-fill projects in gully areas according to claim 1, characterized in that, The selected aggregate of the coarse - grained layer (9) at the bottom of the isolation cushion layer (6) is graded 25# and 30#, and the thickness of the coarse - grained layer (9) at the bottom of the isolation cushion layer (6) is not less than 50 cm.

5. A three-dimensional seepage prevention structure for a high-fill project in a gully, characterized in that, The selected aggregate of the fine - grained layer (8) at the bottom of the isolation cushion layer (6) is 17# aggregate, and the thickness of the fine - grained layer (8) at the bottom of the isolation cushion layer (6) is not less than 50 cm.

6. The three-dimensional seepage prevention structure for high-fill projects in gullies according to claim 1, characterized in that, The lateral thickness of the isolation cushion layer (6) is not less than 1 m. The lateral aggregate grading of the isolation cushion layer (6) selects 25# aggregate, and the lateral part of the isolation cushion layer (6) is arranged according to the slope form of the gully (3).

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