A method for constructing development stages of large debris flow accumulation fan and disaster history

Abstract

The large-scale debris flow accumulation fan development period and disaster history construction method comprises the following steps: 1, field division of debris flow deposition structure and period unit; 2, analysis of debris flow thick fan degree change and boulder distribution by geophysical prospecting; 3, based on steps 1 and 2, complete the sampling of debris flow fan horizontal and longitudinal section layout; 4, based on the collected information, complete the dating analysis and age constraint; 5, according to the test analysis result of step 4, complete the establishment of debris flow fan development period and age sequence; 6, based on the above steps, complete the debris flow fan evolution process and disaster history construction; the method can complete the dating of the top of the accumulation fan and the overlying colluvial soil system and the dating of the bottom of the accumulation fan and the river-lake facies sand layer system; through debris flow numerical simulation, the long-time-scale debris flow development period can be reconstructed, the short-term observation disaster data deficiency can be supplemented, and the practical needs of major debris flow fan history reconstruction and disaster prevention and mitigation engineering can be met.

Description

Technical Field

[0001] This invention relates to the field of ancient debris flow fan mixed sediment dating technology, and in particular to a method for constructing the development stages and catastrophic history of large debris flow fans. Background Technology

[0002] Debris flow fans are the final product of debris flow activities. Major engineering projects develop diverse types of debris flow fans with complex formations. These large debris flow fans are limited spaces that are difficult to avoid during route planning and engineering site selection and construction.

[0003] Most debris flow gullies lack effective observation or have short observation periods. Large debris flow depositional fans record major catastrophic events with low frequency over long geological periods. How to reveal the developmental stages of debris flow deposition in the past history of large debris flow depositional fans has become an important issue in engineering site selection.

[0004] The developmental stages and disaster history of debris flow fans can provide long-term data for the future risk assessment of major debris flow disasters such as railway projects crossing debris flow fans and urban settlements. Based on the data of historical major disaster events, reasonable disaster prevention and mitigation strategies can be proposed.

[0005] In the existing technology, optically stimulated luminescence (OSL) dating is used to directly measure the age of mixed debris flow deposits. However, this existing technology is difficult to use directly because the debris flow deposits have a short transport distance and the OSL signal is not completely faded. As a result, the results obtained by this technology are prone to overestimating the age of the debris flow deposits.

[0006] Furthermore, in practical applications, most studies using existing technologies simply sample and date mixed debris flow deposits directly, lacking detailed analysis of the debris flow deposit structure, making it difficult to obtain accurate debris flow dating results.

[0007] In existing technologies, radioactive carbon-14 (carbon tetrachloride) is used. 14 C) Dating techniques are used for dating various sediments, but dating materials specifically for organic materials such as charcoal in debris flows are not easily found and obtained in the field; existing debris flow sediments 14 The acquisition of organic materials for C-dating is highly random, and it is extremely easy to encounter situations where no organic materials are available, making the process impossible. 14 The results of the C-test annual test;

[0008] The existing technology for establishing the chronological sequence and disaster history of debris flow fans is inaccurate, thus failing to guide the practical needs of disaster prevention and mitigation projects.

[0009] Therefore, those skilled in the art are dedicated to developing a method for constructing the development stages and catastrophic history of large debris flow deposit fans, aiming to solve the defects existing in the prior art. Summary of the Invention

[0010] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is that in the current prior art, direct OSL measurement of debris flows faces the problems of large signal residue and overestimation of age; 14 C-dating makes it difficult to find organic dating materials in debris flow deposits, as it is highly random. The dating of all organic matter in debris flow deposits tends to be too high or too low, making it impossible to accurately establish the chronological sequence of debris flow fans and the history of the disaster.

[0011] To achieve the above objectives, the present invention provides a method for constructing the development stages and catastrophic history of large debris flow depositional fans, comprising the following steps:

[0012] Step 1: Field delineation of debris flow depositional structures and phase units;

[0013] Step 2: Geophysical analysis of the thickness and distribution of debris flows;

[0014] Step 3: Based on steps 1 and 2, complete the sampling of the horizontal and vertical profiles of the debris flow fan;

[0015] Step 4: Based on the collected information, complete the dating analysis and age constraints;

[0016] Step 5: Based on the test and analysis results of Step 4, establish the development stages and chronological sequence of debris flow fans.

[0017] Step 6: Based on the above steps, complete the construction of the debris flow fan evolution process and disaster history;

[0018] Step 1, dividing debris flow depositional structures and phase units in the field, requires selecting well-exposed ancient debris flow fan profiles, conducting stratigraphic structure, tectonics, grain order and stratigraphic relationships observations, clarifying the macroscopic features of the depositional fan such as boulders, stone line structures and bottom mud-mixed structures, and then dividing debris flow phase units based on the above features.

[0019] Step 2 involves using ground-penetrating radar depth sounding to obtain the thickness variation of unexposed debris flow depositional fans, especially the distribution of debris flow boulders.

[0020] Step 3 involves conducting a systematic site survey and sampling of the work sites from the transverse and longitudinal profiles of the stacked fan.

[0021] Step 4: Based on the above steps, complete the dating analysis and age constraints;

[0022] The dating analysis in step 4 includes: OSL dating analysis of debris flow lens sand layers and analysis of organic matter encased in debris flow gravel. 14 C-term dating analysis;

[0023] The age constraints in step 4 include: minimum age constraints for the overlying strata of the debris flow and maximum age constraints for the underlying strata of the debris flow.

[0024] The dating analysis in step 4 involves collecting OSL samples from the lenticular sand layer within the debris flow fan, based on the structural characteristics of the sedimentary profile of each debris flow fan, and collecting samples from the bottom mud layer within the "mud-encased gravel" structure. 14 Organic materials dated by C2D; comprehensive analysis of the two dating results to determine the age of the debris flow event layer;

[0025] The chronological constraints in step 4 constrain the chronology of the upper and lower interlayers at the top and bottom of the debris flow depositional fan, obtain the upper and lower limits of the debris flow depositional fan, analyze the debris flow event layer and the upper and lower limit chronological framework, and determine the development stages of the debris flow.

[0026] Step 5: Based on the test and analysis results of Step 4, establish the development stages and chronological sequence of debris flow fans.

[0027] In step 5, for debris flow fans older than 50,000 to 100,000 years, additional testing of cosmogenic nuclides in the surface boulders of the debris flow fan can be performed. 10 Be、 36 Cl、 26 A1) dating was used to obtain the exposure age and burial age of debris flow depositional fans;

[0028] In step 5, if travertine deposits are present on the surface of the debris flow gravel, uranium (U) series dating can be carried out.

[0029] Step 6: Based on the above steps, complete the construction of the debris flow fan evolution process and disaster history;

[0030] In step 6, the scale of the flash flood and debris flow can be estimated based on the boulder records obtained by ground-penetrating radar sounding in step 2.

[0031] Step 6 involves reconstructing debris flow data from different historical periods using geophysical exploration and numerical simulation.

[0032] Step 6 can be based on the dating of debris flow mixed sediments in the sedimentary structure to determine the development stages of debris flows, thereby completing the numerical simulation and reconstruction of the evolution process of debris flows in different stages.

[0033] By adopting the above scheme, the method for constructing the development stages and catastrophic history of large debris flow depositional fans disclosed in this invention has the following advantages:

[0034] (1) The method for constructing the development stages and catastrophic history of large debris flow deposit fans in this invention is based on a systematic analysis of debris flow sedimentary structures and proposes a new method for dating debris flow event layers. Compared with existing technologies, this method innovatively utilizes the alluvial-diluvial characteristics of debris flow lens sand layers, which exhibit certain sorting, thus making them ideal OSL dating materials in debris flow deposits. Furthermore, the fine-grained mud bodies in the "mud-encased gravel" structure of debris flows are covered with... 14 The organic dating material C enables simultaneous dating of the top of the colluvial fan and its overlying colluvial soil system, as well as the bottom of the colluvial fan and its fluvial-lacustrine sand layer system.

[0035] (2) The method for constructing the development stages and catastrophic history of large debris flow depositional fans in this invention involves analyzing the landforms, geological geophysical exploration, sediment structure, OSL dating, and other factors of the debris flow depositional fan. 14 Starting with the C-terminal dating technology, and through debris flow numerical simulation, it is possible to reconstruct long-term debris flow development stages, analyze the history of low-frequency debris flow disasters, and supplement the lack of short-term observation disaster data. This can provide long-term data for the future risk assessment of major debris flow disasters such as railway projects crossing debris fans and urban settlements, thus meeting the practical needs of major debris flow fan development stages and disaster prevention and mitigation projects.

[0036] In summary, the method for constructing the development stages and disaster history of large debris flow fans disclosed in this invention can simultaneously complete the dating of the top of the debris flow fan and its overlying colluvial soil system, as well as the dating of the bottom of the debris flow fan and its fluvial and lacustrine sand layer system. Through debris flow numerical simulation, the development stages of debris flows over long time scales can be reconstructed, supplementing the lack of short-term observational disaster data, thereby meeting the practical needs of major debris flow fan development stages and disaster prevention and mitigation projects.

[0037] The following will further explain the concept, specific technical solution and technical effects of the present invention in conjunction with specific embodiments, so as to fully understand the purpose, features and effects of the present invention. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the process for constructing the development stages and disaster history of large debris flow depositional fans according to the present invention.

[0039] Figure 2 This is a schematic diagram of the debris flow fan geophysical exploration, sampling point layout, and geochronological sample collection layout in Embodiment 1 of the present invention.

[0040] Figure 3 This is a schematic diagram of the age-constrained technical solution based on debris flow depositional structure in Embodiment 1 of the present invention;

[0041] Figure 4This is the present invention, Example 1, showing the phase division and age-based sample collection diagram of the outcrop profile of the debris flow depositional fan;

[0042] Figure 5 This is the result diagram of the debris flow fan development stages and disaster history obtained in step 6 of embodiment 1 of the present invention. Detailed Implementation

[0043] The following describes several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, which are described exemplarily, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0044] Example 1: Using the method of the present invention, the development stages and disaster history of debris flow depositional fans in a certain region were constructed.

[0045] As shown in the figure Figure 1 This is a schematic diagram of the process for constructing the development stages and disaster history of large debris flow depositional fans according to the present invention.

[0046] First, step 1 is to divide the debris flow depositional structure and phase units in the field;

[0047] Step 1, dividing debris flow depositional structures and phase units in the field, requires selecting well-exposed ancient debris flow fan profiles, conducting stratigraphic structure, tectonics, grain order and stratigraphic relationships observations, clarifying the macroscopic features of the depositional fan such as boulders, stone line structures and bottom mud-mixed structures, and then dividing debris flow phase units based on the above features.

[0048] Then, step 2 was carried out, and geophysical analysis was conducted to examine the changes in the thickness fan of the debris flow and the distribution of boulders.

[0049] Step 2 involves using ground-penetrating radar depth sounding to obtain the thickness variation of unexposed debris flow depositional fans, especially the distribution of debris flow boulders.

[0050] Based on steps 1 and 2, step 3 is carried out to complete the sampling of the horizontal and vertical profiles of the debris flow fan.

[0051] Step 3 involves conducting a systematic site survey and sampling of the work sites from the transverse and longitudinal profiles of the stacked fan.

[0052] In specific implementation, the site survey and layout sampling in Example 1 are as follows: Figure 2 As shown, Figure 2 This is a schematic diagram of the debris flow fan geophysical exploration, sampling point layout, and geochronological sample collection layout in Embodiment 1 of the present invention.

[0053] Then proceed to step 4: Based on the collected information, complete the dating analysis and age constraints;

[0054] In practical implementation, this method is based on the fact that debris flow lens sand layers have alluvial-diluvial characteristics and exhibit a certain degree of sorting, making them relatively ideal OSL dating materials in debris flow deposits; while the fine-grained soil within the "mud-encased gravel" structure of debris flows contains... 14 C organic dating materials;

[0055] The dating analysis in step 4 includes: OSL dating analysis of debris flow lens sand layers and analysis of organic matter encased in debris flow gravel. 14 C-term dating analysis;

[0056] The dating analysis in step 4 involves collecting OSL samples from the lenticular sand layer within the debris flow fan, based on the structural characteristics of the sedimentary profile of each debris flow fan, and collecting samples from the bottom mud layer within the "mud-encased gravel" structure. 14 Organic materials dated by C2D; comprehensive analysis of the two dating results to determine the age of the debris flow event layer;

[0057] As shown in the figure Figure 3 This is a schematic diagram of the age-constrained technical solution based on debris flow depositional structure in Embodiment 1 of the present invention; Figure 3 Figure I in the text shows a boulder. 10 A schematic diagram of Be dating; Figure 3 Figure II in the diagram is a schematic diagram of U-series dating of travertine. Figure 3 Figure III in the diagram is a schematic diagram of OSL dating of lenticular sand layers; Figure 3 Figure IV in the diagram represents organic matter encased in mud and gravel. 14 Schematic diagram of C-dating;

[0058] The age constraints in step 4 include: minimum age constraints for the overlying strata of the debris flow and maximum age constraints for the underlying strata of the debris flow.

[0059] The chronological constraints in step 4 constrain the chronology of the upper and lower interlayers at the top and bottom of the debris flow depositional fan, obtain the upper and lower limits of the debris flow depositional fan, analyze the debris flow event layer and the upper and lower limit chronological framework, and determine the development stages of the debris flow.

[0060] As shown in the figure Figure 3 Figure V in the diagram is a schematic diagram indicating the minimum age of the overlying strata; Figure 3 Figure VI in the diagram is a schematic diagram indicating the maximum age of the underlying strata;

[0061] Step 5: Based on the test and analysis results of Step 4, establish the development stages and chronological sequence of debris flow fans.

[0062] In step 5, for debris flow fans older than 50,000 to 100,000 years, additional testing of cosmogenic nuclides in the surface boulders of the debris flow fan can be performed. 10 Be、 36 Cl、 26A1) dating was used to obtain the exposure age and burial age of debris flow depositional fans;

[0063] In step 5, if travertine deposits are present on the surface of the debris flow gravel, uranium (U) series dating can be carried out.

[0064] In practice, it is as shown in the figure. Figure 4 This is the present invention, Example 1, showing the phase division and age-based sample collection diagram of the outcrop profile of the debris flow depositional fan;

[0065] Finally, perform step 6: Based on the above steps, complete the construction of the debris flow fan evolution process and disaster history;

[0066] In step 6, the scale of the flash flood and debris flow can be estimated based on the boulder records obtained by ground-penetrating radar sounding in step 2.

[0067] Step 6 involves reconstructing debris flow data from different historical periods using geophysical exploration and numerical simulation.

[0068] Step 6 can be based on the dating of debris flow mixed sediments in the sedimentary structure to determine the development stages of debris flows, thereby completing the numerical simulation reconstruction of the evolution process of debris flows in different stages, and thus completing the construction of the development stages of debris flow fans and the history of disasters.

[0069] As shown in the figure Figure 5 The debris flow fan development stages and disaster history construction result diagram obtained in step 6 of embodiment 1 of this invention means that the debris flow fan development stages and disaster history in this region are constructed through this method, which can provide an important reference for disaster prevention and mitigation projects in this region.

[0070] In summary, this patented technical solution, based on a systematic analysis of debris flow depositional structures, proposes a novel method for dating debris flow event layers. Compared to existing technologies, this method innovatively utilizes the alluvial-diluvial characteristics of debris flow lens sand layers, which exhibit a certain degree of sorting, thus making them ideal OSL dating materials within debris flow deposits. Furthermore, it utilizes fine-grained mud within the "mud-encased gravel" structure of debris flows. 14 Organic dating materials (C) enable simultaneous dating of the top of debris flow fan and its overlying colluvial soil system; as well as the bottom of the debris flow fan and its fluvial-lacustrine sand layer system; and can be used for dating based on debris flow fan geomorphology, geological geophysical exploration, sediment structure analysis, OSL dating, and... 14 Starting with the C-terminal dating technology, and through debris flow numerical simulation, it is possible to reconstruct long-term debris flow development stages, analyze the history of low-frequency debris flow disasters, and supplement the lack of short-term observation disaster data. This can provide long-term data for the future risk assessment of major debris flow disasters such as railway projects crossing debris fans and urban settlements, thus meeting the practical needs of major debris flow fan development stages and disaster prevention and mitigation projects.

[0071] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for constructing the development stages and catastrophic history of large debris flow depositional fans, characterized in that, Includes the following steps: Step 1: Field delineation of debris flow depositional structures and phase units; Step 2: Geophysical analysis of the thickness and distribution of debris flows; Step 3: Based on steps 1 and 2, complete the sampling of the horizontal and vertical profiles of the debris flow fan; Step 4: Based on the collected information, complete the dating analysis and age constraints; The dating analysis in step 4 includes: OSL dating analysis of debris flow lens sand layers and analysis of organic matter encased in debris flow gravel. 14 C-term dating analysis; The dating analysis in step 4 involves collecting OSL samples from the lenticular sand layer within the debris flow fan, based on the structural characteristics of the sedimentary profile of each debris flow fan, and collecting samples from the bottom mud layer within the mud-covered gravel structure. 14 Organic materials dated by C2D; comprehensive analysis of the two dating results to determine the age of the debris flow event layer; The age constraints in step 4 include: minimum age constraints for the "overlying strata" of the debris flow and maximum age constraints for the "underlying strata" of the debris flow. The chronological constraints in step 4 constrain the chronology of the upper and lower interlayers at the top and bottom of the debris flow depositional fan, obtain the upper and lower limits of the debris flow depositional fan, analyze the debris flow event layer and the upper and lower limit chronological framework, and determine the development stages of the debris flow. Step 5: Based on the test and analysis results of Step 4, establish the development stages and chronological sequence of debris flow fans. Step 6: Based on the above steps, complete the construction of the debris flow fan evolution process and disaster history.

2. The method for constructing the development stages and disaster history of large debris flow depositional fans as described in claim 1, characterized in that, Step 1, the field delineation of debris flow depositional structures and phase units, requires selecting well-exposed ancient debris flow fan profiles, conducting stratigraphic structure, tectonics, grain sequence and stratigraphic relationships observations, clarifying the characteristics of boulders, stone lines and bottom mud-mixed structures of the depositional fan, and then delineating debris flow phase units based on the above characteristics.

3. The method for constructing the development stages and disaster history of large debris flow depositional fans as described in claim 1, characterized in that, Step 2 involves using ground-penetrating radar depth measurement to obtain the thickness variation of unexposed debris flow depositional fans and the distribution of debris flow boulders.

4. The method for constructing the development stages and disaster history of large debris flow depositional fans as described in claim 1, characterized in that, Step 3 involves conducting on-site site surveys and sampling of the layout of work sites from the transverse and longitudinal profiles of the stacked fan.

5. The method for constructing the development stages and disaster history of large debris flow depositional fans as described in claim 1, characterized in that, In step 5, for debris flow fans older than 50,000 to 100,000 years, additional testing is conducted on the cosmological nuclides of the surface boulders of the debris flow fan. 10 Be、 36 Cl、 26 Al dating was used to obtain the exposure and burial ages of debris flow depositional fans. In step 5, if travertine deposits are present on the surface of the debris flow gravel, uranium U-series dating is carried out.

6. The method for constructing the development stages and disaster history of large debris flow depositional fans as described in claim 1, characterized in that, In step 6, the scale of the flash flood and debris flow is estimated based on the boulder records obtained by ground-penetrating radar depth sounding in step 2.

7. The method for constructing the development stages and disaster history of large debris flow depositional fans as described in claim 1, characterized in that, Step 6 involves reconstructing debris flow data from different historical periods using geophysical exploration and numerical simulation. Step 6 involves dating the mixed sediments of debris flows based on the sedimentary structure to determine the developmental stages of debris flows, thereby completing the numerical simulation and reconstruction of the evolution process of debris flows in different stages.

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