A debris flow source blocking system and design method suitable for large-volume debris flow ditch slag field protection

Abstract

The present invention provides a debris flow source blocking system and design method suitable for the protection of debris flow ditch slag dump with large flood volume, including a slag blocking dam, a slag dump, an open drainage channel, a drainage cushion layer and a slag retaining wall; the slag blocking dam is arranged on the upstream side of the slag dump; the upstream of the slag blocking dam is surrounded by a silt retention and water collection area; the silt retention and water collection area has the function of intercepting and storing debris flow solid matter and floods, forming a debris flow source silt retention area and a water collection area; the open drainage channel is arranged on the periphery of the slag dump, and the water inlet of the open drainage channel is connected to the flood discharge port of the slag blocking dam, which is used to discharge flood water from the debris flow ditch. The present invention not only solves the problem of difficulty in timely drainage of debris flow sources, but also can greatly reduce the scale of blocking and drainage facilities. It can be widely used in projects for building slag dumps in debris flow ditch with large flood volume.

Description

Technical Field

[0001] The invention belongs to the technical field of water conservancy and hydropower engineering, and in particular relates to a debris flow source blocking system and a design method suitable for protecting a debris flow ditch slag field with a large amount of flood. Background Art

[0002] In recent years, due to the restrictions of terrain conditions, ecological red lines and other factors, some water conservancy and hydropower projects have set up slag dumps in large-volume debris flow ditches near the project area in order to dispose of engineering waste. This arrangement requires the management of large-volume debris flow ditches, making the protection of large slag dumps difficult. On the one hand, if no protection is carried out or the debris flow is not properly handled, the safety risk will be greatly increased; on the other hand, in order to manage the debris flow, there are problems such as the large amount of engineering work required for blocking and drainage measures.

[0003] In the prior art, when debris flows occur in the rainy season, they carry a large amount of rocks and silt, which makes it difficult to drain them in time, or the drainage cost is too high. Therefore, how to achieve the debris flow blocking and drainage of large-volume debris flow ditch slag fields while reducing engineering investment is a difficult problem that needs to be solved urgently. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a debris flow source blocking system and design method suitable for the protection of large-volume debris flow ditch slag yards, which effectively solves the problems of the prior art that large-volume debris flow is difficult to drain in time and the large amount of engineering work of blocking facilities, thereby achieving safe prevention and control of debris flow ditch and greatly reducing project investment.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] The present invention provides a debris flow source blocking system suitable for protecting large-volume debris flow ditch slag fields, comprising a slag blocking dam (1), a slag field (4), an open drainage channel (5), a drainage cushion layer (6) and a slag retaining wall (7);

[0007] The slag dump (4) is arranged in the debris flow ditch; the slag retaining dam (1) is arranged on the upstream side of the slag dump (4); the upstream of the slag retaining dam (1) forms a silt retention and water collection area; the silt retention and water collection area has the function of retaining solid matter and floods of the debris flow, forming a debris flow source silt retention area and a water collection area; the drainage open channel (5) is arranged on the periphery of the slag dump (4), and the water inlet of the drainage open channel (5) is connected to the flood discharge outlet of the slag retaining dam (1) for discharging floods from the debris flow ditch;

[0008] The drainage cushion layer (6) is arranged at the bottom of the channel of the slag field (4); the slag retaining wall (7) is arranged downstream of the slag field (4); and the downstream side of the drainage cushion layer (6) is connected to the reinforced concrete culvert on the upstream side of the slag retaining wall (7), so that the water inside the slag field (4) is discharged to the downstream of the slag retaining wall (7) through the drainage cushion layer (6).

[0009] Preferably, an anti-seepage layer (2) is provided on the upstream side of the slag retaining dam (1); a concrete base (3) connected to the bedrock is provided at the foot of the slope of the slag retaining dam (1);

[0010] The anti-seepage layer (2) comprises a filter layer (8), a composite geomembrane (9) and mortar masonry (10); the filter layer (8) is arranged in two layers, namely: a first filter layer and a second filter layer;

[0011] The first filter layer, the composite geomembrane (9), the second filter layer and the mortar masonry (10) are laid in sequence on the upstream surface of the slag retaining dam (1); wherein the composite geomembrane (9) is connected to the concrete base (3) in an embedded manner, and the composite geomembrane (9) is embedded in the concrete base (3) by pouring the concrete base (3) in stages.

[0012] Preferably, the concrete base (3) is constructed in three phases and the composite geomembrane (9) is pre-buried; the concrete base (3) comprises a first-phase concrete part (11), a second-phase concrete part (12), a third-phase concrete part (13) and C22 steel bars (14);

[0013] First, the first-phase concrete portion (11) is cast, and after the casting is completed, the composite geomembrane (9) is pre-buried and covered with the C22 steel bars (14); then, the second-phase concrete portion (12) is cast; after the second-phase concrete solidifies, the composite geomembrane (9) is folded; and finally, the third-phase concrete portion (13) is cast.

[0014] The present invention also provides a design method for a debris flow source blocking system suitable for protecting a large-volume debris flow ditch slag field, comprising the following steps:

[0015] Step 1: Slag dump (4) site selection and image determination:

[0016] Based on the planned waste slag capacity, actual terrain conditions and hydrological data, the specific location of the slag dump (4) and the image of the slag dump (4) are determined; wherein the image of the slag dump (4) includes the outer edge of the slag dump;

[0017] Step 2: Planning and design of slag retaining dam (1):

[0018] According to the specific location and shape of the slag dump (4) and the flood control calculation results of the siltation and water collection field, the specific location and shape of the slag retaining dam (1) are determined;

[0019] Step 3: Planning and design of open drainage channels (5):

[0020] Determine the starting water level and the starting elevation of the drainage channel (5) according to the flood control calculation results; determine the maximum peak flow that needs to be discharged by the drainage channel (5) according to the flood control calculation results, and determine the axis, longitudinal slope and size of the drainage channel (5) in combination with the outer edge of the slag dump determined in step 1 and the actual terrain conditions;

[0021] Step 4: Slag yard protection and internal drainage planning and design:

[0022] Construct slag retaining wall (7) and drainage cushion layer (6) as water conservation and protection engineering measures.

[0023] Preferably, step 1 is specifically:

[0024] Step 1.1, determine the site of the slag dump (4): determine the site of the slag dump (4) within the project area, avoiding sensitive factors;

[0025] Step 1.2, determine the capacity of the slag dump (4): determine the capacity of the slag dump (4) according to the engineering excavation and filling engineering quantities and engineering schedule;

[0026] Step 1.3, determining the slope ratio of the slag field (4): determining the slope ratio of the slag field (4) according to the slag source of the slag field (4) and its physical and mechanical properties;

[0027] Step 1.4, determine the location and elevation of the slag dump (4):

[0028] Make full use of the natural topography upstream to ensure that the storage capacity of the siltation catchment area upstream of the slag dump (4) is sufficient to intercept and store the total amount of solid matter and flood volume of the debris flow at least once, and determine the location and elevation of the slag dump (4); when steps 1.2 and 1.3 are met, determine the outer edge of the slag dump (4).

[0029] Preferably, step 2 is specifically:

[0030] Step 2.1, determine the location of the slag retaining dam (1): according to the location and shape of the slag dump (4), the slag retaining dam (1) is arranged in combination with the slag dump (4) at the upstream of the slag dump (4);

[0031] Step 2.2, determining the slope ratio of the slag retaining dam (1): determining the slope ratio of the slag retaining dam (1) according to the natural repose angle of the dam body building materials;

[0032] Wherein: in consideration of the fact that the slag field (4) covers the back slope of the slag retaining dam (1), the dam slope stability of the slag retaining dam (1) is improved, and the back slope ratio of the slag retaining dam (1) is steepened;

[0033] Step 2.3, determine the top elevation of the slag retaining dam (1) by calculating the flood control results of the siltation catchment area:

[0034] Specifically, flood flow process lines, flood control storage capacity curves of the siltation catchment area, and discharge capacity of the open drainage channel (5) are used for flood control calculations, and the top elevation of the slag retaining dam (1) is determined by taking safety overheight into consideration;

[0035] Step 2.4, an anti-seepage layer (2) is provided on the upstream side of the slag retaining dam (1), and a concrete foundation (3) is provided at the foot of the slope to connect with the bedrock.

[0036] Preferably, step 2.3 is specifically as follows:

[0037] Assuming that under the extreme working condition, after the silt retention water collection field in front of the slag retaining dam (1) is filled with debris flow solid matter and flood, the constructed drainage channel (5) is used to discharge the flood again. In this process, the top elevation of the slag retaining dam (1) needs to be higher than the highest water level. The highest water level in front of the slag retaining dam (1) is determined by flood control calculation:

[0038] Step 2.3.1, determine the flood flow process line: determine the 24-hour flood flow process line of a flood according to the hydrological data;

[0039] Step 2.3.2, determining the flood control storage capacity curve: determining the storage capacity curve of the flood control storage capacity in front of the slag retaining dam (1) according to the actual terrain and the layout of the slag dump (4);

[0040] Step 2.3.3, determine the discharge capacity of the proposed open drainage channel (5): the discharge capacity is determined according to the hydraulic weir flow calculation formula (1);

[0041] Q=δ s δ c mnb(2g)^0.5H0 3 / 2 Formula 1

[0042] Where: c is the lateral contraction coefficient, which reflects the effect of the lateral contraction of the weir flow due to the channel width, the reduction of the effective flow width and the increase of local energy loss on the discharge capacity; δ s is the flooding coefficient. Assuming that the downstream water level does not affect the discharge capacity of the open drainage channel, it is a free weir flow. At this time, δ s =1.0; m is the discharge coefficient of gravity overflow; n is the number of open drainage channels; b is the net width of the open drainage channel (m); H0 is the head before the weir including the approaching velocity head, that is, the head above the bottom plate of the drainage channel;

[0043] Step 2.3.4, flood control calculation:

[0044] Flood control calculation is performed based on the flood flow process line, the flood control storage capacity curve, and the discharge capacity of the open drainage channel (5), and the highest water level in front of the slag retaining dam (1) is determined.

[0045] Preferably, step 3 is specifically:

[0046] Step 3.1, determining the starting elevation of the bottom plate of the drainage channel (5): determining the starting elevation of the bottom plate of the drainage channel (5) according to the flood control calculation result in step 2;

[0047] Step 3.2, according to the outer edge of the slag dump determined in step 1, determine the axis of the drainage open channel (5), and determine the longitudinal section of the drainage open channel (5) according to the terrain;

[0048] Step 3.3, according to the determined plan layout and longitudinal section design of the drainage open channel, based on the maximum flood peak flow determined by the flood control calculation results, the water surface line is deduced according to hydraulics to determine the size of the drainage open channel (5).

[0049] Preferably, step 4 is specifically:

[0050] Step 4.1: Before the construction of water conservation engineering measures in the slag field and slag stacking, the surface clearing work in the slag stacking area must be completed;

[0051] Step 4.2, for the slag dump site treated in step 4.1, a drainage cushion layer (6) is provided at the bottom of the slag dump channel;

[0052] Step 4.3, constructing a slag retaining wall (7) downstream of the slag site, the upstream of the slag retaining wall (7) is connected to the drainage cushion layer (6) through a reinforced concrete culvert, so that the water inside the slag site (4) passes through the drainage cushion layer (6) and then through the reinforced concrete culvert to the downstream of the slag retaining wall (7);

[0053] Step 4.4, when the excavated slag is transported to the slag dump, the slag is piled up in layers from bottom to top. After each level of slag is removed from the bridleway, the slope is cut and graded from top to bottom to form a slag dump (4).

[0054] Preferably, step 4.2 is specifically as follows:

[0055] Excavate a foundation pit at the bottom of the slag dump site with a depth of not less than 0.5m, level the base with an undulation of not more than 20cm, and backfill to form a continuous drainage cushion layer (6);

[0056] The cross-sectional area of ​​the drainage cushion layer (6) at the bottom of the ditch shall not be less than 14m 2The filling material is excavated weakly weathered rock or fresh rock excavated from the cave, with good gradation, the maximum particle size is 600mm, the content of particles less than 5m is not more than 20%, the content of particles less than 0.075m is not more than 5%, the unevenness coefficient is greater than 10, and the permeability coefficient is greater than 10 -1 cm / s; after laying the drainage cushion layer (6), the top is leveled and rolled with a 13t vibrating roller, and the corners are rolled with a hand-held vibrating roller, and the number of rolling times is 6 to 8 times;

[0057] After the drainage cushion layer (6) is laid and rolled, a 30 cm thick filter material is laid. The cushion layer material is made of sand and gravel with the following particle size requirements: the maximum particle size is 80 m, the content of particles smaller than 5 m is not more than 20%, the content of particles smaller than 0.075 mm is less than 5%, and the non-uniformity coefficient is greater than 12; the material is weakly weathered crushed stone with continuous grading;

[0058] Geotextile is laid on the filter material, the nominal breaking strength of the geotextile is 15kN / m, and the unit area mass is 400g / m;

[0059] Step 4.3 is as follows:

[0060] The slag retaining wall (7) is located on a solid foundation, with a base burial depth of not less than 1.2m and a foundation bearing capacity of not less than 180kPa. If the requirements are not met, it is necessary to use a vibrating roller to compact or replace with a crushed stone cushion layer of not less than 30cm; the particle size of the backfill slag of the slag retaining wall (7) is not less than 300mm, and the particle size below 500m is not more than 60% of the total backfill; the particle size requirements of the filter material of the slag retaining wall (7) are: the maximum particle size is 80mm, the content of particles less than 5mm is not more than 20%, and the content of particles less than 0.075m is less than 5%. The unevenness coefficient is greater than 12, and the gradation is continuous.

[0061] The present invention provides a debris flow source blocking system and design method suitable for protecting large-volume debris flow ditch slag fields, which has at least the following technical effects and advantages:

[0062] (1) This application effectively solves the problem of difficulty in timely drainage of debris flow sources. By making full use of the natural terrain upstream of the slag dump to create a silt retention and water collection area, the debris flow is intercepted and stored in the reserved storage space in front of the slag retaining dam. After the debris flow activity ends, the corresponding cleaning and treatment work is carried out, thereby reducing the overflow pressure of the drainage facilities when the debris flow occurs, thereby achieving safe prevention and control of the debris flow ditch;

[0063] (2) The present application utilizes a slag yard in combination with a slag retaining dam, which has the functions of both a slag retaining dam and a retaining dam, blocking both upstream solid matter and upstream flooding, thereby reducing the amount of retaining structure engineering specifically used to block debris flows; at the same time, slag is piled behind the slag retaining dam, which is conducive to improving the stability of the slag retaining dam and the safety of the siltation-stopping water collection field;

[0064] (3) This application combines the terrain conditions upstream of the slag dump and utilizes the silt retention and water collection field in front of the slag retaining dam to effectively reduce the peak flow and reduce the scale of the drainage system.

[0065] The realization of these technical effects and advantages not only improves the efficiency and safety of debris flow prevention and control, but also reduces engineering costs, reflecting the innovation and practicality of the technical solution of this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic plan view of the overall protection layout of the debris flow ditch slag dump in the embodiment of the present application.

[0067] Figure 2 This is a schematic diagram of the slag retaining dam structure in the embodiment of the present application;

[0068] Figure 3 This is a schematic diagram of the structure of the anti-seepage material in the embodiment of the present application;

[0069] Figure 4 This is a schematic diagram of the concrete base structure in the embodiment of the present application;

[0070] In the figure: 1---slag retaining dam; 2---anti-seepage layer; 3---concrete base; 4---slag yard; 5---open drainage channel; 6---drainage cushion layer; 7---slag retaining wall; 8---filter layer; 9---composite geomembrane; 10---mortar masonry; 11---first phase concrete part; 12---second phase concrete part; 13---third phase concrete part; 14---C22 steel bar. DETAILED DESCRIPTION

[0071] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred implementation scheme of the present invention is described below in combination with specific examples. However, it should be understood that the drawings are only for illustrative purposes and cannot be understood as a limitation on this patent: In order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product: For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted. The positional relationship described in the drawings is only for illustrative purposes and cannot be understood as a limitation on this patent.

[0072] See also Figure 1 to Figure 4 The present invention provides a debris flow source blocking system suitable for protecting large-volume debris flow ditch slag yards, including a slag blocking dam 1, a slag yard 4, an open drainage channel 5, a drainage cushion layer 6 and a slag retaining wall 7;

[0073] The slag field 4 is arranged in the debris flow ditch; a slag retaining dam 1 is arranged on the upstream side of the slag field 4; a silt retention field is formed upstream of the slag retaining dam 1; the silt retention field has the function of retaining solid matter and floods of the debris flow, forming a silt retention field and a water collection area of ​​the debris flow source; an open drainage channel 5 is arranged outside the slag field 4, and the water inlet of the open drainage channel 5 is connected with the flood discharge port of the slag retaining dam 1, so as to discharge floods from the debris flow ditch;

[0074] A drainage cushion layer 6 is arranged at the bottom of the channel of the slag yard 4; a slag retaining wall 7 is arranged downstream of the slag yard 4; and the downstream side of the drainage cushion layer 6 is connected to the reinforced concrete culvert on the upstream side of the slag retaining wall 7, so that the water inside the slag yard 4 is discharged to the downstream of the slag retaining wall 7 through the drainage cushion layer 6.

[0075] For the slag retaining dam 1, in order to enhance its anti-seepage capability and structural stability, an anti-seepage layer 2 is provided on the upstream side of the slag retaining dam 1; a concrete foundation 3 connected to the bedrock is provided at the slope foot of the slag retaining dam 1;

[0076] The anti-seepage layer 2 includes a filter layer 8, a composite geomembrane 9 and mortar masonry 10; wherein the filter layer 8 is arranged in two layers, namely: a first filter layer and a second filter layer;

[0077] On the upstream surface of the slag retaining dam 1, the first filter layer, the composite geomembrane 9, the second filter layer and the mortar masonry 10 are laid in sequence; wherein the composite geomembrane 9 is connected to the concrete base 3 by an embedded type, and the composite geomembrane 9 is embedded in the concrete base 3 by pouring the concrete base 3 in stages.

[0078] Specifically, the concrete base 3 is constructed in three phases and the composite geomembrane 9 is pre-buried; the concrete base 3 includes a first-phase concrete part 11, a second-phase concrete part 12, a third-phase concrete part 13 and C22 steel bars 14;

[0079] First, the first-phase concrete part 11 is cast, and after the casting is completed, the composite geomembrane 9 is pre-buried and covered with C22 steel bars 14; then, the second-phase concrete part 12 is cast; after the second-phase concrete solidifies, the composite geomembrane 9 is folded; and finally, the third-phase concrete part 13 is cast.

[0080] The present invention also provides a design method for a debris flow source blocking system suitable for protecting a debris flow ditch slag field with a large amount of flood, comprising the following steps:

[0081] Step 1: Site selection and image determination of slag dump 4:

[0082] Based on the planned waste slag capacity, actual terrain conditions and hydrological data, the specific location and image of the slag dump 4 are determined; wherein the image of the slag dump 4 includes the outer edge of the slag dump;

[0083] Step 2: Planning and design of slag retaining dam 1:

[0084] According to the specific location and shape of the slag dump 4 and the flood control calculation results of the siltation and water collection field, the specific location and shape of the slag retaining dam 1 are determined;

[0085] Step 3: Planning and design of open drainage channel 5:

[0086] Determine the starting water level and the starting elevation of the open drainage channel 5 according to the flood control calculation results; determine the maximum peak flow that needs to be drained by the open drainage channel 5 according to the flood control calculation results, and determine the axis, longitudinal slope and size of the open drainage channel 5 in combination with the outer edge of the slag dump determined in step 1 and the actual terrain conditions;

[0087] Step 4: Slag yard protection and internal drainage planning and design:

[0088] Construct slag retaining wall 7 and drainage cushion layer 6 water conservation and protection engineering measures.

[0089] The following is a detailed description of steps 1 to 4:

[0090] Step 1: Site selection and image determination of slag dump 4:

[0091] Based on the planned waste dump capacity, actual terrain conditions and hydrological data, the natural terrain upstream of the dump is fully utilized to create a siltation and water collection area, and the specific location and image of the dump 4 are determined; the image of the dump 4 includes the outer edge of the dump;

[0092] Step 1 is as follows:

[0093] Step 1.1, determine the site of slag dump 4: within the project area, avoid sensitive factors such as ecological red lines, basic farmland, and ecological protection areas, and determine the site of slag dump 4;

[0094] Step 1.2, determine the capacity of the slag field 4: according to the excavation and filling engineering quantities and engineering schedule of the project, determine the capacity of the slag field 4 to meet the requirements of the project;

[0095] Step 1.3, determining the slope ratio of the slag field 4: determining the slope ratio of the slag field 4 according to the slag source and its physical and mechanical properties of the slag field 4;

[0096] Step 1.4, determine the location and elevation of slag dump 4:

[0097] Make full use of the natural terrain upstream to ensure that the flood control storage capacity of the siltation catchment area upstream of slag dump 4 is sufficient to intercept and store the total amount of solid matter and flood volume of debris flow at least once, and determine the location and elevation of slag dump 4; determine the outer edge of slag dump 4 when steps 1.2 and 1.3 are met.

[0098] Step 2: Planning and design of slag retaining dam 1:

[0099] According to the specific location and shape of the slag dump 4 and the flood control calculation results of the siltation and water collection field, the specific location and shape of the slag retaining dam 1 are determined;

[0100] Step 2 is as follows:

[0101] Step 2.1, determine the position of the slag retaining dam 1: according to the position and shape of the slag dump 4, the slag retaining dam 1 is arranged in combination with the slag dump 4 at the upstream position of the slag dump 4;

[0102] Step 2.2, determining the slope ratio of the slag retaining dam 1: determining the slope ratio of the slag retaining dam 1 according to the natural repose angle of the dam body building materials;

[0103] Among them: considering that the slag field 4 covers the back slope of the slag retaining dam 1, the stability of the dam slope of the slag retaining dam 1 can be improved, and the back slope ratio of the slag retaining dam 1 can be appropriately steepened to save engineering workload;

[0104] Step 2.3, determine the top elevation of the slag retaining dam 1 through the flood control calculation results of the siltation catchment area:

[0105] Specifically, the flood flow process line, the flood control storage capacity curve of the siltation catchment field, and the discharge capacity of the open drainage channel 5 are calculated, and the top elevation of the slag retaining dam 1 is determined by considering the safety overheight;

[0106] Step 2.3 is as follows:

[0107] Assuming that under the extreme working condition, after the flood control storage capacity in front of the slag retaining dam 1 is filled with debris flow solid materials and flood, the constructed drainage channel 5 is used to discharge the flood again. In this process, the top elevation of the slag retaining dam 1 needs to be higher than the highest water level; the highest water level in front of the slag retaining dam 1 is determined by flood control calculation:

[0108] Step 2.3.1, determine the flood flow process line: determine the 24-hour flood flow process line of a flood according to the hydrological data;

[0109] Step 2.3.2, determine the flood control storage capacity curve: determine the storage capacity curve of the flood control storage capacity in front of the slag retaining dam 1 according to the actual terrain and the layout of the slag dump 4;

[0110] Step 2.3.3, determine the discharge capacity of the proposed drainage open channel 5: the discharge capacity is determined according to the hydraulic weir flow calculation formula 1;

[0111] Q=δ s δ c mnb2g^0.5H0 3 / 2 Formula 1

[0112] Where: cis the lateral contraction coefficient, which reflects the effect of the lateral contraction of the weir flow due to the channel width, the reduction of the effective flow width and the increase of local energy loss on the discharge capacity; δ s is the flooding coefficient. Assuming that the downstream water level does not affect the discharge capacity of the open drainage channel, it is a free weir flow. At this time, δ s =1.0; m is the discharge coefficient of gravity overflow; n is the number of open drainage channels; b is the net width of the open drainage channel (m); H0 is the head before the weir including the approaching velocity head, that is, the head above the bottom plate of the drainage channel (m);

[0113] Step 2.3.4, flood control calculation:

[0114] Flood control calculation is performed based on the flood flow process line, the flood control storage capacity curve, and the discharge capacity of the open drainage channel 5 to determine the maximum water level in front of the slag retaining dam 1.

[0115] When a flood flows through a silted catchment, the water level, flow rate, cross-section, and velocity along the silted catchment change with time, and its flow pattern belongs to open channel unsteady flow. According to hydraulics, the basic equation of open channel unsteady flow, namely the Saint-Venant equations, is:

[0116]

[0117] Where ω is the cross-sectional area of ​​the water flow (m 2 ); t is time (s); Q is flow rate (m 3 / s); s is the distance along the water flow direction (m); Z is the water level (m); g is the acceleration of gravity (m / s2); υ is the average flow velocity of the section (m / s); K is the flow modulus (m 3 / s).

[0118] It is difficult to obtain an accurate analytical solution by directly solving the partial differential equation group 2. Usually, a simplified approximate solution is used. In engineering practice, the transient method is generally used to replace the differential value with a finite difference, and the basic formula is simplified in combination with the unique conditions of the siltation catchment field to obtain a practical formula specifically used for flood control calculations in the siltation catchment field - the water balance equation:

[0119]

[0120] Where Q1 and Q2 are the inflow flow at the beginning and end of the calculation period (m 3 / s; q1 and q2 are the discharge flow at the beginning and end of the calculation period (m 3 / s; V1 and V2 are the water storage capacity of the catchment area at the beginning and end of the calculation period (m 3) ; △t is the calculation period, generally 1 to 6 hours, and the unit is converted to seconds. This formula shows that in a calculation period, the difference between the inflow and the discharge is the change in the storage capacity of the siltation catchment during that period.

[0121] When the flood process line of the desilting catchment into the reservoir is known, Q1 and Q2 are both known; q1 and q2 are the initial conditions for the calculation of the start of the period △t. Therefore, the only unknowns in formula 3 are V2 and q2. After V2 and q2 of the current period are calculated, their values ​​become the values ​​of V1 and q1 of the next period, so that the calculation can be carried out continuously from period to period. Of course, it is impossible to use one formula 3 to solve the two unknowns V2 and q2. However, the volume characteristics of the desilting catchment V = f(Z) and the discharge capacity relationship curve q = f(Z) can indirectly express the relationship curve between the discharge flow q and the reservoir capacity V, that is:

[0122] q = f (V) Formula 4

[0123] The unknowns V2 and q2 can be solved by using the simultaneous equations 3 and 4. Therefore, by solving the water storage V2 of the water catchment area at the end of each calculation period △t, the maximum water storage capacity can be obtained, thereby obtaining the highest water level in front of the dam 1.

[0124] According to the highest water level obtained by flood control, the top elevation of the slag retaining dam 1 is determined after reserving a safe overheight.

[0125] Step 2.4, an impermeable layer 2 is set on the upstream side of the slag retaining dam 1, and a concrete foundation 3 is set at the foot of the slope to connect with the bedrock.

[0126] Specifically, an anti-seepage layer 2 of a filter layer 8, a composite geomembrane 9 and mortar masonry 10 is arranged on the upstream side of the slag retaining dam 1, and a concrete foundation 3 is arranged at the foot of the slope to connect with the bedrock.

[0127] In this step, the crushed stone material of the filter layer 8 is sand and gravel, and the particle size requirements are: the maximum particle size is 80mm, the content of particles less than 5mm is not more than 20%, the content of particles less than 0.075mm is less than 5%, the unevenness coefficient is greater than 12, and the material requirements are weakly weathered crushed stone with continuous grading;

[0128] In this step, the mortar masonry 10 uses MU30 blocks, and the weight of a single block is not less than 30kg; the construction should meet the relevant requirements of the "Code for Construction of Masonry Structure Engineering" (GB 50924-2014); the mortar masonry 10 should be built with fresh and solid stones, and the cement mortar should be M10. A joint is set every 6 to 10m, the joint width is 1cm, and the joint is filled with closed-cell foam board.

[0129] In this step, the geomembrane adopts a composite geomembrane 9, and the specifications of two cloths and one membrane are 350g / 0.5mm / 350g; the geomembrane is connected to the bedrock by an embedded type, and the geomembrane is embedded by pouring a concrete base 3 in stages. The length of the geomembrane embedded in the base should be not less than 80cm; before laying the geomembrane, the surface of the cushion material should be leveled first, and the protrusions, pits, cracks and other parts of the concrete in each stage must be leveled or filled, and the surface unevenness should not be greater than 3cm; the geomembrane is manually rolled and laid, and the laying should be smooth and moderately tight. The geomembrane is embedded in each section, and the joints between the sections are embedded in the first-stage concrete trough. The joints are covered with geomembranes of the same material, and the overlap width is not less than 10cm.

[0130] In this step, the anti-seepage layer 2 is constructed along with the progress of the dam body filling of the slag retaining dam 1. The top elevation of the anti-seepage layer 2 on the upstream side of the slag retaining dam 1 needs to be higher than the highest water level after flood control calculation, and some safety overheight should be reserved.

[0131] In this step, the dam body of the slag retaining dam 1 is filled with well-graded weak and slightly weathered fresh rocks, and the designed dry density after compaction is >2.0t / m 3 The designed porosity should be ≤21%; the thickness of the layered filling material and the number of layered compaction times of the slag retaining dam 1 should be determined through tests based on the compaction equipment. The filling and rolling of each part must be strictly supervised on site, and leakage of pressure is not allowed.

[0132] In this step, the concrete base 3 adopts C20F150, secondary grade; the depth into the bedrock should be no less than 50cm.

[0133] In this step, the concrete base 3 for pre-embedded composite geomembrane 9 is constructed in three phases. The first phase concrete part 11 is poured first, and after the pouring is completed, the composite geomembrane 9 is pre-embedded, and two C22 steel bars 14 are arranged to press and cover the geomembrane to ensure the flatness of the geomembrane, and then the second phase concrete part 12 is poured, and after the second phase concrete solidifies, the composite geomembrane 9 is folded, and finally the third phase concrete part 13 is poured.

[0134] Step 3: Planning and design of open drainage channel 5:

[0135] Determine the starting water level and the starting elevation of the open drainage channel 5 according to the flood control calculation results; determine the maximum peak flow that needs to be drained by the open drainage channel 5 according to the flood control calculation results, and determine the axis, longitudinal slope and size of the open drainage channel 5 in combination with the outer edge of the slag dump determined in step 1 and the actual terrain conditions;

[0136] Step 3 is as follows:

[0137] Step 3.1, determining the starting elevation of the bottom plate of the drainage channel 5: determining the starting elevation of the bottom plate of the drainage channel 5 according to the flood control calculation result in step 2;

[0138] Step 3.2, according to the outer edge of the slag dump determined in step 1, determine the axis of the drainage open channel 5, and determine the longitudinal section of the drainage open channel 5 according to the terrain;

[0139] Step 3.3, according to the determined plan layout and longitudinal section design of the drainage open channel, based on the maximum flood peak flow determined by the flood control calculation results, and the water surface line is deduced according to hydraulics, the size of the drainage open channel 5 is determined.

[0140] Step 4: Slag yard protection and internal drainage planning and design:

[0141] Construct slag retaining wall 7 and drainage cushion layer 6 and other water conservation and protection engineering measures.

[0142] Step 4 is as follows:

[0143] Step 4.1: Before the construction of water conservation engineering measures in the slag dump and the slag dumping, the surface clearing work in the slag dumping area must be completed; specifically, tree roots, weeds, garbage, waste slag and other obstacles specified by the supervisor must be removed, and the cleared vegetation should not be abandoned in the slag dumping area;

[0144] Step 4.2, for the slag dump site treated in step 4.1, a drainage cushion layer 6 is provided at the bottom of the slag dump channel;

[0145] Step 4.2 is as follows:

[0146] A foundation pit is excavated at the bottom of the slag site with a depth of not less than 0.5m, and the base is leveled with an undulation of not more than 20cm, and backfilled to form a continuous drainage cushion layer 6;

[0147] The cross-sectional area of ​​the drainage cushion layer 6 at the bottom of the ditch shall not be less than 14m 2 The filling material is excavated weakly weathered rock or fresh rock excavated from the cave, with good gradation, maximum particle size of 600mm, particle size less than 5m content not more than 20%, particle size less than 0.075m content not more than 5%, uneven coefficient greater than 10, permeability coefficient greater than 10 -1 cm / s; After laying the drainage cushion layer 6, the top is leveled and rolled with a 13t vibrating roller, and the corners are rolled with a hand-held vibrating roller, and the number of rolling times is 6 to 8 times;

[0148] After the drainage cushion layer 6 is laid and rolled, a 30cm thick filter material is laid. The cushion material is gravel with the following particle size requirements: the maximum particle size is 80m, the content of particles smaller than 5m is not more than 20%, the content of particles smaller than 0.075mm is less than 5%, and the unevenness coefficient is greater than 12; the material is required to be weakly weathered crushed stone with continuous grading;

[0149] Geotextile is laid on the filter material, the nominal breaking strength of the geotextile is 15kN / m, and the unit area mass is 400g / m;

[0150] Step 4.3, construct a slag retaining wall 7 downstream of the slag site, and the upstream of the slag retaining wall 7 is connected to the drainage cushion layer 6 through a reinforced concrete culvert, so that the water inside the slag site 4 passes through the drainage cushion layer 6 and then through the reinforced concrete culvert to the downstream of the slag retaining wall 7;

[0151] Step 4.3 is as follows:

[0152] The slag retaining wall 7 is located on a solid foundation, with a base burial depth of not less than 1.2m and a foundation bearing capacity of not less than 180kPa. If the requirements are not met, it is necessary to use a vibrating roller to compact or replace with a crushed stone cushion layer of not less than 30cm; the particle size of the backfill slag of the slag retaining wall 7 is not less than 300mm, and the particle size below 500m is not more than 60% of the total backfill; the particle size requirements of the filter material of the slag retaining wall 7 are: the maximum particle size is 80mm, the content of particles less than 5mm is not more than 20%, and the content of particles less than 0.075m is less than 5%. The unevenness coefficient is greater than 12, and the gradation is continuous.

[0153] Step 4.4, when the excavated slag is transported to the slag dump, the slag is piled up in layers from bottom to top. After each level of slag at the horse trail elevation is completed, the slope is cut and graded from top to bottom to ensure the stability of the slag body and form a slag dump 4.

[0154] The present invention provides a debris flow source blocking system and design method suitable for protecting large-volume debris flow ditch slag fields, which has the following advantages:

[0155] (1) This application effectively solves the problem of difficulty in timely drainage of debris flow sources. By making full use of the natural terrain upstream of the slag dump to create a silt retention and water collection area, the debris flow is intercepted and stored in the reserved storage space in front of the slag retaining dam. After the debris flow activity ends, the corresponding cleaning and treatment work is carried out, thereby reducing the overflow pressure of the drainage facilities when the debris flow occurs, thereby achieving safe prevention and control of the debris flow ditch;

[0156] (2) The present application utilizes a slag field combined with a slag retaining dam, which has the functions of both a slag retaining dam and a retaining dam, blocking both upstream solid matter and upstream flooding, thereby reducing the engineering workload of a slag retaining dam specifically used to block debris flows and a retaining dam specifically used to block upstream flooding; at the same time, slag is piled behind the slag retaining dam, which is beneficial to the stability of the slag retaining dam and the safety of the siltation-stopping water collection field;

[0157] (3) This application combines the terrain conditions upstream of the slag dump and utilizes the silt retention and water collection field in front of the slag retaining dam to effectively reduce the peak flow and reduce the scale of the drainage system.

[0158] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A design method for a debris flow source blocking system suitable for protecting large-volume debris flow ditch slag fields, characterized in that: The debris flow source blocking system suitable for protecting large-volume debris flow ditch slag dumps comprises a slag blocking dam (1), a slag dump (4), an open drainage channel (5), a drainage cushion layer (6) and a slag retaining wall (7); The slag dump (4) is arranged in the debris flow ditch; the slag retaining dam (1) is arranged on the upstream side of the slag dump (4); the upstream of the slag retaining dam (1) forms a silt retention and water collection area; the silt retention and water collection area has the function of retaining solid matter and floods of the debris flow, forming a debris flow source silt retention area and a water collection area; the drainage open channel (5) is arranged on the periphery of the slag dump (4), and the water inlet of the drainage open channel (5) is connected to the flood discharge outlet of the slag retaining dam (1) for discharging floods from the debris flow ditch; The drainage cushion layer (6) is arranged at the bottom of the channel of the slag field (4); the slag retaining wall (7) is arranged downstream of the slag field (4); and the downstream side of the drainage cushion layer (6) is connected to the reinforced concrete culvert on the upstream side of the slag retaining wall (7), so that the water inside the slag field (4) is discharged to the downstream of the slag retaining wall (7) through the drainage cushion layer (6); The method comprises the following steps: Step 1: Slag dump (4) site selection and image determination: Based on the planned waste slag capacity, actual terrain conditions and hydrological data, the specific location of the slag dump (4) and the image of the slag dump (4) are determined; wherein the image of the slag dump (4) includes the outer edge of the slag dump; Step 2: Planning and design of slag retaining dam (1): According to the specific location and shape of the slag dump (4) and the flood control calculation results of the siltation and water collection field, the specific location and shape of the slag retaining dam (1) are determined; Step 2 is as follows: Step 2.1, determine the location of the slag retaining dam (1): according to the location and shape of the slag dump (4), the slag retaining dam (1) is arranged in combination with the slag dump (4) at the upstream of the slag dump (4); Step 2.2, determining the slope ratio of the slag retaining dam (1): determining the slope ratio of the slag retaining dam (1) according to the natural repose angle of the dam body building materials; Wherein: in consideration of the fact that the slag field (4) covers the back slope of the slag retaining dam (1), the dam slope stability of the slag retaining dam (1) is improved, and the back slope ratio of the slag retaining dam (1) is steepened; Step 2.3, determine the top elevation of the slag retaining dam (1) by calculating the flood control results of the siltation catchment area: Specifically, flood flow process lines, flood control storage capacity curves of the siltation catchment area, and discharge capacity of the open drainage channel (5) are used for flood control calculations, and the top elevation of the slag retaining dam (1) is determined by taking safety overheight into consideration; Step 2.3 is as follows: Assuming that under the extreme working condition, after the silt retention water collection field in front of the slag retaining dam (1) is filled with debris flow solid matter and flood, the constructed drainage channel (5) is used to discharge the flood again. In this process, the top elevation of the slag retaining dam (1) needs to be higher than the highest water level. The highest water level in front of the slag retaining dam (1) is determined by flood control calculation: Step 2.3.1, determine the flood flow process line: determine the 24-hour flood flow process line of a flood according to the hydrological data; Step 2.3.2, determining the flood control storage capacity curve: determining the storage capacity curve of the flood control storage capacity in front of the slag retaining dam (1) according to the actual terrain and the layout of the slag dump (4); Step 2.3.3, determine the discharge capacity of the proposed open drainage channel (5): the discharge capacity is determined according to the hydraulic weir flow calculation formula (1); Where: c is the lateral contraction coefficient, which reflects the effect of the lateral contraction of the weir flow due to the channel width, the reduction of the effective flow width and the increase of local energy loss on the discharge capacity; δ s is the flooding coefficient. Assuming that the downstream water level does not affect the discharge capacity of the open drainage channel, it is a free weir flow. At this time, δ s =1.0; m is the discharge coefficient of gravity overflow; n is the number of open drainage channels; b is the net width of the open drainage channel (m); H0 is the head before the weir including the approaching velocity head, that is, the head above the bottom plate of the drainage channel; Step 2.3.4, flood control calculation: Flood control calculation is performed according to the flood flow process line, the flood control storage capacity curve, and the discharge capacity of the drainage open channel (5), and the maximum water level in front of the slag retaining dam (1) is determined; Step 2.4, providing an anti-seepage layer (2) on the upstream side of the slag retaining dam (1), and providing a concrete foundation (3) at the foot of the slope to connect with the bedrock; Step 3: Planning and design of open drainage channels (5): Determine the starting water level and the starting elevation of the drainage channel (5) according to the flood control calculation results; determine the maximum peak flow that needs to be discharged by the drainage channel (5) according to the flood control calculation results, and determine the axis, longitudinal slope and size of the drainage channel (5) in combination with the outer edge of the slag dump determined in step 1 and the actual terrain conditions; Step 4: Slag yard protection and internal drainage planning and design: Construct slag retaining wall (7) and drainage cushion layer (6) as water conservation and protection engineering measures.

2. The design method of a debris flow source blocking system suitable for protecting a large-volume debris flow ditch slag field according to claim 1 is characterized in that: Step 1 is as follows: Step 1.1, determine the site of the slag dump (4): determine the site of the slag dump (4) within the project area, avoiding sensitive factors; Step 1.2, determine the capacity of the slag dump (4): determine the capacity of the slag dump (4) according to the engineering excavation and filling engineering quantities and engineering schedule; Step 1.3, determining the slope ratio of the slag field (4): determining the slope ratio of the slag field (4) according to the slag source of the slag field (4) and its physical and mechanical properties; Step 1.4, determine the location and elevation of the slag dump (4): Make full use of the natural topography upstream to ensure that the flood control storage capacity of the siltation and water collection field upstream of the slag dump (4) is sufficient to intercept and store the total amount of solid matter and flood volume of the debris flow at least once, and determine the location and elevation of the slag dump (4); when steps 1.2 and 1.3 are met, determine the outer edge of the slag dump (4).

3. The design method of a debris flow source blocking system suitable for protecting large-volume debris flow ditch slag fields according to claim 1 is characterized in that: Step 3 is as follows: Step 3.1, determining the starting elevation of the bottom plate of the drainage channel (5): determining the starting elevation of the bottom plate of the drainage channel (5) according to the flood control calculation result in step 2; Step 3.2, according to the outer edge of the slag dump determined in step 1, determine the axis of the drainage open channel (5), and determine the longitudinal section of the drainage open channel (5) according to the terrain; Step 3.3, according to the determined plan layout and longitudinal section design of the drainage open channel, based on the maximum flood peak flow determined by the flood control calculation results, the water surface line is deduced according to hydraulics to determine the size of the drainage open channel (5).

4. The design method of a debris flow source blocking system suitable for protecting large-volume debris flow ditch slag dump according to claim 1 is characterized in that: Step 4 is as follows: Step 4.1: Before the construction of water conservation engineering measures in the slag field and slag stacking, the surface clearing work in the slag stacking area must be completed; Step 4.2, for the slag dump site treated in step 4.1, a drainage cushion layer (6) is provided at the bottom of the slag dump channel; Step 4.3, constructing a slag retaining wall (7) downstream of the slag site, the upstream of the slag retaining wall (7) is connected to the drainage cushion layer (6) through a reinforced concrete culvert, so that the water inside the slag site (4) passes through the drainage cushion layer (6) and then through the reinforced concrete culvert to the downstream of the slag retaining wall (7); Step 4.4, when the excavated slag is transported to the slag dump, the slag is piled up in layers from bottom to top. After each level of slag at the horse trail elevation is completed, the slope is cut and graded from top to bottom to form a slag dump (4).

5. The design method of a debris flow source blocking system suitable for protecting large-volume debris flow ditch slag fields according to claim 4 is characterized in that: Step 4.2 is as follows: Excavate a foundation pit at the bottom of the slag dump site with a depth of not less than 0.5m, level the base with an undulation of not more than 20cm, and backfill to form a continuous drainage cushion layer (6); The cross-sectional area of ​​the drainage cushion layer (6) at the bottom of the ditch shall not be less than 14m 2 The filling material is excavated weakly weathered rock or fresh rock excavated from the cave, with good gradation, the maximum particle size is 600mm, the content of particles less than 5m is not more than 20%, the content of particles less than 0.075m is not more than 5%, the unevenness coefficient is greater than 10, and the permeability coefficient is greater than 10 -1 cm / s; after laying the drainage cushion layer (6), the top is leveled and rolled with a 13t vibrating roller, and the corners are rolled with a hand-held vibrating roller, and the number of rolling times is 6 to 8 times; After the drainage cushion layer (6) is laid and rolled, a 30 cm thick filter material is laid. The cushion layer material is made of sand and gravel with the following particle size requirements: the maximum particle size is 80 m, the content of particles smaller than 5 m is not more than 20%, the content of particles smaller than 0.075 mm is less than 5%, and the non-uniformity coefficient is greater than 12; the material is weakly weathered crushed stone with continuous grading; Geotextile is laid on the filter material, the nominal breaking strength of the geotextile is 15kN / m, and the unit area mass is 400g / m; Step 4.3 is as follows: The slag retaining wall (7) is located on a solid foundation, with a base buried depth of not less than 1.2m and a foundation bearing capacity of not less than 180kPa. If the requirements are not met, it is necessary to use a vibrating roller to compact or replace with a crushed stone cushion layer of not less than 30cm; the particle size of the backfill slag of the slag retaining wall (7) is not less than 300mm, and the particle size below 500m is not more than 60% of the total backfill volume; the particle size requirements of the filter material of the slag retaining wall (7) are: the maximum particle size is 80mm, the content of particles less than 5mm is not more than 20%, the content of particles less than 0.075m is less than 5%, the unevenness coefficient is greater than 12, and the gradation is continuous.

6. The design method of a debris flow source blocking system suitable for protecting large-volume debris flow ditch slag dump according to claim 1 is characterized in that: An anti-seepage layer (2) is provided on the upstream side of the slag retaining dam (1); a concrete base (3) connected to the bedrock is provided at the slope foot of the slag retaining dam (1); The anti-seepage layer (2) comprises a filter layer (8), a composite geomembrane (9) and mortar masonry (10); the filter layer (8) is arranged in two layers, namely: a first filter layer and a second filter layer; The first filter layer, the composite geomembrane (9), the second filter layer and the mortar masonry (10) are laid in sequence on the upstream surface of the slag retaining dam (1); wherein the composite geomembrane (9) is connected to the concrete base (3) in an embedded manner, and the composite geomembrane (9) is embedded in the concrete base (3) by pouring the concrete base (3) in stages.

7. The design method of a debris flow source blocking system suitable for protecting a large-volume debris flow ditch slag field according to claim 6 is characterized in that: The concrete base (3) is constructed in three phases and the composite geomembrane (9) is pre-buried; the concrete base (3) comprises a first-phase concrete part (11), a second-phase concrete part (12), a third-phase concrete part (13) and C22 steel bars (14); First, the first-phase concrete portion (11) is cast, and after the casting is completed, the composite geomembrane (9) is pre-buried and covered with the C22 steel bars (14); then, the second-phase concrete portion (12) is cast; after the second-phase concrete solidifies, the composite geomembrane (9) is folded; and finally, the third-phase concrete portion (13) is cast.

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