A method for restoring the original form and scale of a residual alluvial deposit

Abstract

The application provides a method for restoring the original form and scale of residual alluvial deposits, comprising the following steps: S1, establishing a three-dimensional model of a deposition area base by using a deposition area plan, coordinates of deposition boundary observation points, slope direction angle and slope curve function, and adjusting the model by using the extension direction of low ground to make the extension direction of low ground of the model consistent with the main development direction of the deposit; S2, dividing the deposit into stages, analyzing the river channel to obtain the source direction of each stage, and detecting the thickness of each stratum by ground penetrating radar; S3, taking the information obtained in 2) as a spatial distribution rule, introducing the three-dimensional model of the base in 1) by stages to obtain a series of sections; connecting the upper curves of the sections into a smooth surface which is tangent to the base surface in the model, and the model cut by the surface is the model of the deposit of each stage; and constructing the original deposit model stage by stage.

Description

Technical Field

[0001] This invention provides a method for restoring the original morphology and scale of residual alluvial deposits, belonging to the field of alluvial deposit technology. Background Technology

[0002] Alluvial deposits are an important type of sediment in sedimentology, such as... Figure 1 As shown, its formation process is as follows: At the exit of the mountain, due to the steep drop in terrain, mountain sediments are carried out of the mountain by water flow and deposited in a fan shape. The sedimentary body has a steep slope and fast water flow, resulting in numerous braided channels. Each channel is scattered and points in the opposite direction towards the source of the sediment. Based on the distribution pattern of the sediments, the alluvial deposits can be divided into the fan root, fan center, and fan edge, corresponding to different sedimentary characteristics. From the fan root to the fan edge, the grain size of the sediment decreases; the smaller the grain size, the weaker the resistance to weathering and erosion, and the easier it is to be eroded and destroyed. Finally, a residual alluvial deposit body is formed, mainly composed of the fan root and part of the fan center, such as... Figure 2 As shown.

[0003] Current research on residual alluvial deposits mainly focuses on two aspects. One is geological exploration, which involves observing profile sedimentary characteristics to determine sedimentary facies, subfacies, and microfacies types. This method can identify the type of sedimentary body but cannot predict its original morphology and scale. The other is flume experiments, which can visually demonstrate the evolution of alluvial deposits. However, existing flume experiments have limited control factors, typically including provenance, water flow, and slope. The actual sedimentary process is highly complex, and setting limited variables makes it difficult to simulate real-world sedimentation. Therefore, a method is needed that can reconstruct the original morphology and scale of existing residual alluvial deposits without the need for flume experiment simulations. Summary of the Invention

[0004] This invention provides a method for restoring the original morphology and scale of residual alluvial deposits, comprising the following steps:

[0005] S1, Topographical Study

[0006] 1) Observe the satellite map of the study area, confirm the boundaries of the mountainous area and sedimentary area, the source outlet, and the extent of the sedimentary area, and draw an abstract planar map of the sedimentary area, marking the scale.

[0007] 2) Conduct a complete horizontal aerial photograph of the existing sedimentary area profile from left to right using a drone. Then, use computer graphics processing software to horizontally stitch together a series of photographs to obtain a complete stitched plan view of the profile.

[0008] By observing the trend of sediment thickness variation in the plane, the thickest part of the profile sediment is found. The line connecting this thickest part to the smooth curve at the exit of the mountain is the main development direction of the sedimentary body, which is also the direction of extension of the low-lying terrain.

[0009] 3) Analyze the distribution characteristics of the sedimentary area obtained in 1), and rationally select a series of sedimentary edge exploration points at a certain interval ratio. Upon reaching the exploration point, record the GPS three-dimensional coordinates. By identifying lithology and structural characteristics, confirm the sedimentary edge boundary, further observe and confirm the boundary trend, and calculate the azimuth angle of the vertical boundary direction. Along the vertical boundary direction, i.e., towards the center of the sedimentary area, use ground-penetrating radar (GPR) for multiple probes. GPR detects the subsurface stratigraphic interface by emitting high-frequency electromagnetic waves, and the generated image is the stratigraphic trend map. As the sediment thickness increases, the GPR image becomes increasingly blurry. Using the farthest and clearest probe as the standard, abstract the interface curve between the sediment and the basement in the image into a smooth profile curve, and then import it into computer simulation software to simulate the basement profile curve functions f1(x), f2(x), ... f1(x) at each point. n (x).

[0010] 4) Import the plan view of the sedimentary area in 1), the coordinates of a series of sedimentary boundary observation points in 3), the slope direction angle and the slope curve function f(x) into the computer modeling software, establish a spatial rectangular coordinate system, and a three-dimensional model of the sedimentary area basement can be generated. Based on the extension direction of the terrain area obtained in 2), adjust the model so that the low terrain extension direction of the model is consistent with the main development direction of the sedimentary body.

[0011] S2, Sectional Study

[0012] 1) By observing the cross-section and identifying the contact relationships at stratigraphic boundaries, as well as the lithology, facies, and sedimentary structures above and below, different phases of alluvial deposits can be determined, thus classifying the sedimentary bodies into stages. Each phase is a small alluvial sedimentary unit, with strata divided into fan root, fan middle, and fan edge subfacies from bottom to top, further subdivided into corresponding microfacies. The first phase is the first deposition on the basement, sometimes located below the cross-section; the second phase is above it, and so on, determining the chronological order of the sedimentary bodies. The thickness of each phase in the observed section of the cross-section is measured using a laser rangefinder.

[0013] 2) The development direction of each phase of alluvial deposition is determined by the direction of its main channel, which may deviate from the overall development direction of the alluvial body. Finally, they superimpose to form the overall alluvial deposit body. A single phase of alluvial deposition starts from the exit of the mountain pass and develops a main channel along the development direction of the sedimentary body. Due to the steep terrain, the main channel often branches off, resulting in the widespread development of branch channels. The branch channels disperse the sediments of the main channel, and eventually, the main channel can be identified in the profile, or only various branch channels can be seen.

[0014] For a profile with a main channel, the direction of the main channel can be determined by observing its sedimentary characteristics, including the channel cross-section morphology, internal sedimentary structures, and its positional relationship with the exit facies.

[0015] For profiles without a main channel, it is necessary to analyze the flow direction of each distributary channel. The sedimentary morphology of channels developed in different parts of the alluvial body is inconsistent, and their profile characteristics show that the thickest part tends to be biased towards the main channel.

[0016] Based on this characteristic, the distributary channels at different locations of the sedimentary body profile are statistically analyzed, and their flow directions are determined sequentially according to their spatial morphology. Finally, the results are summarized into a coordinate system for fitting, which is the direction of the main channel.

[0017] 3) The spatial distribution pattern of sedimentary alluvial bodies in a certain period is as follows: along the main source direction, the stratum thickness gradually decreases to both sides in the transverse direction until it tapers out, while the stratum thickness increases from zero in the longitudinal direction and then gradually tapers out. The change pattern of the cross section is defined by the relationship between the changes of the upper and lower curves.

[0018] Using the exit of the mountain pass as the origin, determine the GPS coordinates of the origin. Establish the main source direction as the baseline L0. Take a series of rays spaced 10° apart to the east and west, continuing until the strata pinch out. The westward rays are designated as odd-numbered lines L1, L3, L5…, and the eastward rays as even-numbered lines L2, L4, L6… Taking ray L0 as an example, locate the GPS coordinates of the middle and top (section) of the ray. Use ground-penetrating radar to probe a 50-100m long section along the ray direction, thus obtaining two stratigraphic sections, a and b. Extract the upper and lower curves a from these two sections. 上 a 下 and b 上 b 下 By combining the coordinates of the origin and the probe point, and importing them into computer simulation software, the upper and lower curve functions f0(x1) and f0(x2) of the cross-section can be simulated. Repeating this step, the upper and lower curve functions f0(x1) of the cross-section corresponding to all rays are finally obtained. n (x1) and f n (x2).

[0019] First-stage thickness calculation: At the intersection of a certain ray and the profile, the ratio of the first-stage deposition thickness to the profile thickness can be obtained from the spacing of the strata in the ground penetrating radar image. Substitute the actual thickness value of the profile into the value to calculate the first-stage deposition thickness.

[0020] S3, 3D modeling

[0021] 1) Use computer modeling software to create a scaled-down model of the sedimentary zone's basement;

[0022] 2) First-stage sedimentation. The provenance direction of the first-stage sedimentation is taken as the direction of the low elevation of the basin. The upper curve functions of all ray sections of the first-stage sedimentary body are imported into the model to obtain a series of sections. The upper curves of the sections are connected to form a smooth surface. This surface is tangent to the basement surface in the model, and the resulting model is the model of the first-stage sedimentary body.

[0023] 3) Later-stage sedimentation. Based on the provenance direction determined by the river channel, the upper ray curve of the nth-stage sedimentary body is imported into the model to obtain a series of cross-sections. The upper curves of the cross-sections are connected into a smooth surface, which is tangent to the upper surface and the basement surface of the n-1th-stage sedimentary body. The resulting model is the model of the nth-stage sedimentary body.

[0024] 4) This process is repeated until the final stage, which is when the original sedimentary body model is constructed. Attached Figure Description

[0025] Figure 1 Original alluvial deposits;

[0026] Figure 2 Residual alluvial deposits;

[0027] Figure 3 Mind map of this invention;

[0028] Figure 4 This is a diagram showing the extent of the sedimentation zone in the embodiment.

[0029] Figure 5 This is a drone aerial photograph stitched together as an example.

[0030] Figure 6 Image showing the thickest point of a single-stage deposition (indicating the source direction) in the example;

[0031] Figure 7 Sampling detection of depositional boundaries is used as an example;

[0032] Figure 8 The example is a detection of a sedimentary boundary base slope;

[0033] Figure 9 The three-dimensional model of the sedimentary zone substrate is shown in the example.

[0034] Figure 10 The cross-sectional phases for the embodiment;

[0035] Figure 11 This is a cross-sectional view of the main channel of an example river.

[0036] Figure 12 This is a cross-sectional view without a main channel, as shown in the example.

[0037] Figure 13 The examples illustrate the sedimentary morphology characteristics of river channels at different locations.

[0038] Figure 14 The results of the examples are summarized into a coordinate system for fitting.

[0039] Figure 15 The spatial distribution pattern of sedimentary alluvial bodies in the example;

[0040] Figure 16 This is a schematic diagram of the GPS coordinates of the measurement origin in an embodiment.

[0041] Figure 17 The first deposition thickness in this embodiment;

[0042] Figure 18 A scale model of the sedimentary zone substrate was created for the embodiment.

[0043] Figure 19 This is the first sedimentary model used in the embodiment;

[0044] Figure 20 This is a sedimentary model of the nth phase in the example.

[0045] Figure 21 The original sediment model is used as an example. Detailed Implementation

[0046] The specific technical solutions of the present invention will be described with reference to the embodiments.

[0047] like Figure 3 As shown, a method for restoring the original morphology and scale of residual alluvial deposits includes the following steps:

[0048] S 1, Topographical Study

[0049] 1) Observe the satellite map of the study area to confirm the boundaries of the mountainous area and sedimentary zone, the source outlet, and the extent of the sedimentary zone. Draw an abstract planar map of the sedimentary zone, such as... Figure 4 As shown, the scale is marked.

[0050] 2) Conduct a complete horizontal aerial photograph of the existing sedimentary profile from left to right using a drone. Then, use computer graphics processing software to horizontally stitch together a series of photographs. The final result is a complete stitched plan view of the profile, as shown below. Figure 5 As shown.

[0051] Observe the trend of sediment thickness variation in the plane and find the thickest part of the sediment profile, such as... Figure 6 As shown, the line connecting it to the smooth curve at the exit of the mountain is the main development direction (source direction) of the sedimentary body, and it is also the extension direction of the low-lying terrain.

[0052] 3) Analyze the distribution characteristics of the sedimentary area obtained in 1), and rationally select a series of sedimentary boundary exploration points at a certain interval ratio. Upon reaching the exploration points, record the GPS three-dimensional coordinates, and confirm the sedimentary boundary boundaries by identifying lithology and structural characteristics, such as... Figure 7As shown, further observation confirms the boundary direction, and the azimuth angle of the vertical boundary direction is calculated. Multiple probes are conducted using ground-penetrating radar (GPR) along the vertical boundary direction, i.e., towards the center of the sedimentary area. GPR detects subsurface interfaces by emitting high-frequency electromagnetic waves, generating images that form the stratigraphic trend map. As the sediment thickness increases, the GPR images become increasingly blurry. Using the farthest and clearest probe as the benchmark, the interface curve between the sediment and the substrate in the image is abstracted into a smooth profile curve. This curve is then imported into computer simulation software to simulate the substrate profile curve functions f1(x), f2(x), ... f2(x) at each point. n (x), such as Figure 8 As shown.

[0053] 4) Import the depositional area plan from 1), the coordinates of a series of depositional boundary observation points from 3), the slope direction angle, and the slope curve function f(x) into computer modeling software, establish a spatial rectangular coordinate system, and a three-dimensional model of the depositional area basement can be generated, such as... Figure 9 As shown. Based on the terrain extension direction obtained in 2), the model is reasonably adjusted so that the low terrain extension direction of the model is consistent with the main development direction of the sedimentary body.

[0054] S2, Sectional Study

[0055] 1) Observe the cross-section, identify alluvial deposits of different periods by examining the contact relationships at stratigraphic boundaries, the lithology and facies above and below, and sedimentary structures, and then classify the sedimentary bodies into different periods. For example... Figure 10 Each phase is a small alluvial sedimentary unit, and the strata can be divided into fan root, fan middle, and fan edge subfacies from bottom to top, and further subdivided into corresponding microfacies. The first phase is the first deposition on the basement, sometimes below the profile, the second phase is above it, and so on, to determine the sequence of sedimentary phases. The thickness of each phase in the observable part of the profile is measured using a laser rangefinder.

[0056] 2) The development direction of each phase of alluvial deposition is determined by the direction of its main channel, which may deviate from the overall development direction of the alluvial body. Finally, they superimpose to form the overall alluvial deposit body. A single phase of alluvial deposition starts from the exit of the mountain pass and develops a main channel along the development direction of the sedimentary body (the direction of low-lying extension). Due to the steep terrain, the main channel often branches off, resulting in the widespread development of branch channels. The branch channels disperse the sediments of the main channel. In the end, on the profile, it is possible to identify the main channel, or it may only show various branch channels.

[0057] like Figure 11 For a profile with a main channel, the direction of the main channel can be determined by observing its profile sedimentary characteristics, including the channel cross-section morphology, internal sedimentary structures, and its positional relationship with the exit facies.

[0058] like Figure 12For profiles without a main channel, it is necessary to analyze the flow direction of each distributary channel. The sedimentary morphology of channels developed in different parts of the alluvial body is inconsistent; their profile characteristics show that the thickest parts tend to gravitate towards the main channel. Figure 13 As shown.

[0059] Based on this characteristic, the distributary channels at different locations within the sedimentary profile were statistically analyzed. Their flow directions were determined sequentially according to spatial morphology, and finally, these results were aggregated into a coordinate system for fitting, thus identifying the main channel direction. Figure 14 .

[0060] 3) The spatial distribution pattern of alluvial deposits in a certain period is as follows: (e.g.) Figure 15 Along the main source (main river channel), the stratum thickness gradually decreases laterally until it tapers out, while the stratum thickness increases from zero and then gradually tapers out. The variation pattern of the cross section is defined by the relationship between the upper and lower curves.

[0061] like Figure 16 Using the exit of the mountain pass as the origin, the GPS coordinates of the origin are determined. The direction of the main source is set as the baseline L0. A series of rays with a spacing of 10° are taken to the east and west sides until the strata pinch out. The westward rays are odd-numbered lines L1, L3, L5..., and the eastward rays are even-numbered lines L2, L4, L6... Taking ray L0 as an example, the GPS coordinates of the middle and top (section) of the ray are located. A 50-100m long section is detected along the ray direction using ground-penetrating radar. This yields two stratigraphic sections, a and b. The upper and lower curves a of the two sections are then extracted. 上 a 下 and b 上 b 下 By combining the coordinates of the origin and the probe point, and importing them into computer simulation software, the upper and lower curve functions f0(x1) and f0(x2) of the cross-section can be simulated. Repeating this step, the upper and lower curve functions f0(x1) of the cross-section corresponding to all rays are finally obtained. n (x1) and f n (x2).

[0062] Calculation of the first stage of sedimentary thickness: At the intersection of a ray and the profile, the ratio of the first stage sedimentary thickness to the profile thickness can be obtained from the spacing of strata in the ground-penetrating radar image. Substituting this ratio into the actual profile thickness value, the first stage sedimentary thickness can be calculated. Figure 17 .

[0063] h 1真实 =(h2+h3) 真实 *(h1 / h2+h3) 雷达 .

[0064] S3, 3D modeling

[0065] 1) Using computer modeling software, create a scaled-down model of the sedimentary basement, such as... Figure 18 .

[0066] 2) First-stage sedimentation. The provenance direction of the first-stage sedimentation is taken as the direction of the basin's low elevation (the main development direction of the sedimentary body). The upper curve functions of all ray sections of the first-stage sedimentary body are imported into the model to obtain a series of sections. The upper curves of the sections are connected to form a smooth surface. This surface is tangent to the basement surface in the model, and the resulting model is the model of the first-stage sedimentary body, such as... Figure 19 .

[0067] 3) Later Deposits. Based on the provenance direction determined by the river channel, the upper ray curve of the nth stage sedimentary body is imported into the model to obtain a series of cross-sections. The upper curves of these cross-sections are connected to form a smooth surface. This surface is tangent to the upper surface and the basement surface of the (n-1)th stage sedimentary body. The resulting model is the model of the nth stage sedimentary body, such as... Figure 20 .

[0068] 4) This process is repeated until the final stage, which completes the construction of the original sedimentary body model, such as... Figure 21 .

Claims

1. A method for restoring the original morphology and scale of residual alluvial deposits, characterized in that, Includes the following steps: S1. Topographical study, including the following sub-steps: 1) Observe the satellite map of the study area, confirm the boundaries of the mountainous area and sedimentary area, the source outlet, and the extent of the sedimentary area, and draw an abstract planar map of the sedimentary area, marking the scale; 2) Conduct a complete horizontal aerial photograph of the existing sedimentary area profile from left to right using a drone. Then, use computer graphics processing software to horizontally stitch together a series of photographs to obtain a complete cross-sectional mosaic plan view. Observe the trend of sediment thickness variation in the plane, find the thickest part of the profile sediment, and connect it with the smooth curve of the exit of the mountain to indicate the main development direction of the sedimentary body, which also corresponds to the extension direction of the low terrain. 3) Analyze the distribution characteristics of the sedimentary area obtained in 1), and rationally select a series of sedimentary edge exploration points at a certain interval ratio; upon reaching the exploration points, record the GPS three-dimensional coordinates, and confirm the sedimentary edge boundary by judging lithology and structural characteristics. Further observe and confirm the boundary trend, and calculate the azimuth of the vertical boundary trend; along the vertical boundary direction, i.e., towards the center of the sedimentary area, use ground-penetrating radar to conduct multiple probes; ground-penetrating radar detects the underground stratigraphic interface by releasing high-frequency electromagnetic waves, and the generated image is the stratigraphic distribution map; as the sediment thickness increases, the ground-penetrating radar image becomes increasingly blurry; based on the farthest and clearest probe, abstract the interface curve between the sediment and the basement in the image into a smooth profile curve, and then import it into computer simulation software to simulate the basement profile curve functions f1(x), f2(x), ... f at each point. n (x); 4) Establish a three-dimensional model of the sedimentary basement using the plan view of the sedimentary area, the coordinates of the observation points at the sedimentary boundary, the slope direction angle, and the slope curve function. Adjust the model using the extension direction of the low-lying terrain so that the extension direction of the low-lying terrain in the model is consistent with the main development direction of the sedimentary body. S2. Sectional study, including the following sub-steps: 1) Observe the profile and identify alluvial deposits of different phases by examining the contact relationships of stratigraphic boundaries, lithology, facies, and sedimentary structures above and below. Then, classify the sedimentary bodies into phases. Each phase is a small alluvial sedimentary unit. The strata are divided into fan root, fan middle, and fan edge subfacies from bottom to top, and then further subdivided into corresponding microfacies. The first phase is the first phase of deposition on the basement. Sometimes it is below the profile, and the second phase is above it, and so on, to determine the chronological order of the sedimentary bodies. Use a laser rangefinder to measure the thickness of each phase in the profile observation section. 2) The development direction of each phase of alluvial deposition is determined by the direction of its main channel, which deviates from the overall development direction of the alluvial body, i.e. the direction of low-lying extension. Finally, they are superimposed to form the overall alluvial deposit body. A single phase of alluvial deposition starts from the exit of the mountain pass and develops a main channel along the development direction of the sedimentary body. The main channel has the largest flow and the deepest and widest channel deposition. Due to the steep terrain, the main channel often diverts, resulting in the widespread development of diversion channels. Diversion channels weaken the deposition of the main channel. In the end, on the profile, sometimes the main channel can be identified, and sometimes only a series of diversion channels can be identified. For a profile with a main channel, observing its profile sedimentary characteristics, including the channel cross-section morphology, internal sedimentary structures, and its positional relationship with the exit facies, can determine the direction of the main channel. For profiles without a main channel, it is necessary to analyze the flow direction of each distributary channel. The sedimentary morphology of channels developed in different parts of the alluvial deposit is inconsistent, and the profile characteristics show that the thickest part will be biased towards the main channel. Based on this characteristic, the distributary channels at different locations of the sedimentary body profile are statistically analyzed, and their flow directions are determined sequentially according to their spatial morphology. Finally, the results are summarized into a coordinate system for fitting, which is the direction of the main channel. 3) Ground-penetrating radar detects the thickness of various strata; S3. 3D modeling, including the following sub-steps: 1) Use computer modeling software to create a scaled-down model of the sedimentary zone's basement; 2) First stage of sedimentation; The source direction of the first stage sedimentary body is taken from the low-lying direction of the basin. The upper curve functions of all ray sections of the first stage sedimentary body are imported into the model to obtain a series of sections. The upper curves of the sections are connected into a smooth surface. This surface is tangent to the base surface in the model. The model obtained by cutting is the model of the first stage sedimentary body. 3) Later sedimentation; Based on the source direction determined by the river channel, the upper part of the ray curve of the nth stage sedimentary body is imported into the model to obtain a series of cross-sections; The upper part of the cross-sections is connected into a smooth surface, which is tangent to the upper surface and the base surface of the n-1 stage. The model obtained is the model of the nth stage sedimentary body. 4) This process is repeated until the final stage, which is when the original sedimentary body model is constructed.

2. The method for restoring the original morphology and scale of residual alluvial deposits according to claim 1, characterized in that, The specific method of sub-step 4) in S1 is as follows: import the plan view of the sedimentary area in 1), the coordinates of a series of sedimentary boundary observation points in 3), the slope direction angle and the slope curve function f(x) into the computer modeling software, establish a spatial rectangular coordinate system, that is, generate a three-dimensional model of the sedimentary area basement. According to the extension direction of the terrain area obtained in 2), adjust the model so that the low terrain extension direction of the model is consistent with the main development direction of the sedimentary body.

3. The method for restoring the original morphology and scale of residual alluvial deposits according to claim 2, characterized in that, Sub-step 3) in S2 is specifically as follows: The spatial distribution pattern of a certain period of sedimentary alluvial body is as follows: along the main source direction, the stratum thickness gradually decreases to both sides in the transverse direction until it tapers out, and the stratum thickness increases from zero in the longitudinal direction and then gradually tapers out. The change pattern of the cross section is defined by the relationship between the changes of the upper and lower curves. Using the exit of the mountain pass as the origin, determine the GPS coordinates of the origin and define the direction of the main source as the baseline L0. Take a series of rays spaced 10° apart to the east and west, until the strata pinch out. The westward rays are odd-numbered lines L1, L3, L5…, and the eastward rays are even-numbered lines L2, L4, L6…. Locate the GPS coordinates of two detection points at the middle and top of the rays using the baseline L0. Along the ray direction, use ground-penetrating radar to detect a 50-100m long section at these two points, thus obtaining two stratigraphic sections, a and b. Extract the upper and lower curves a from these two sections. 上 a 下 and b 上 b 下 Combining the coordinates of the origin and the two probe points, the data is imported into computer simulation software to simulate the upper and lower curve functions f0(x1) and f0(x2) of the cross-section. This step is repeated to finally obtain the upper and lower curve functions f0(x1) of the cross-section corresponding to all rays. n (x1) and f n (x2); First-stage thickness calculation: At the intersection of a certain ray and the profile, the ratio of the first-stage deposition thickness to the profile thickness is obtained from the distance between the strata in the ground penetrating radar image. Substitute this value into the actual thickness of the profile to calculate the first-stage deposition thickness.

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