An altered mapping data-driven tunnel unfavorable altered body prediction method and system

Abstract

This application provides a method and system for predicting adverse alteration features in tunnels based on alteration mapping data, relating to the field of tunnel exploration. The method includes: delineating the target area of ​​the magma intrusion contact zone based on topography and conducting field geological surveys to clarify the spatial relationship between the magma intrusion contact zone and the proposed tunnel route; deploying standardized artificial trenches at the surface intersection of the magma intrusion contact zone and the proposed tunnel route, measuring the spatial distribution information of altered rock masses on the trench sidewalls, and dividing alteration zones; identifying adverse alteration minerals within the alteration zones and determining the original rock mineral replacement ratio; calculating the retention degree of the original rock structure; classifying adverse alteration levels based on the original rock mineral replacement ratio and retention degree; and predicting the spatial distribution and scale of adverse alteration geological bodies underground based on the correlation criterion between adverse alteration levels and high-density electrical resistivity. This application combines geological mapping and geophysical interpretation techniques to provide a scientific basis for tunnel route selection.

Description

Technical Field

[0001] This application relates to the field of tunnel exploration, and in particular to a method and system for predicting adverse alteration types in tunnels driven by alteration mapping data. Background Technology

[0002] When tunnel projects traverse mountainous areas, they often encounter unfavorable altered geological bodies developed from magma intrusion contact zones. These geological bodies contain large amounts of unfavorable altered minerals such as sericite, chlorite, kaolin, and montmorillonite, which significantly degrade the strength of the rock mass. During construction, they are prone to geological disasters such as mudslides, water inrushes, and large deformations, which seriously threaten construction safety, affect project progress, and control investment.

[0003] Currently, in the tunnel engineering route selection phase, the prediction of potential adverse altered geological bodies mainly relies on two technical means: limited geological drilling verification and geophysical exploration. Although geological drilling can directly obtain core samples, it has the limitation of "one-hole view," making it difficult to fully reflect the three-dimensional spatial distribution characteristics of altered geological bodies, and it is also costly and has a long construction period. Geophysical methods such as high-density electrical resistivity tomography can cover a large area, but their interpretation results are ambiguous, making it difficult to accurately identify the spatial distribution and scale of adverse altered geological bodies underground.

[0004] During the construction phase, the main reliance is on advanced geological forecasting to predict the geological conditions ahead. However, due to the lack of obvious differences in physical properties between adverse altered geological bodies and surrounding rocks, coupled with the strong dependence on interpretation experience, it is often difficult to effectively identify adverse altered geological bodies, which often leads to geological disaster threats during the construction process.

[0005] Therefore, existing technologies lack a comprehensive prediction method that can economically, efficiently, and accurately identify adverse altered geological bodies during the tunnel alignment stage. There is an urgent need to develop a technical means that organically combines alteration geological surveys, engineering exploration, and geophysical interpretation to provide a scientific basis for tunnel alignment. Summary of the Invention

[0006] The purpose of this invention is to fill the technological gap in the economical, efficient, and rapid identification of adversely altered geological bodies, and to provide a method and system for predicting adversely altered tunnel bodies driven by alteration mapping data.

[0007] The above-mentioned objective of this application is achieved through the following technical solution:

[0008] S1: Based on aerial 3D geomorphological images and topographic maps, delineate the target area of ​​the magma intrusion contact zone;

[0009] S2: Conduct field geological surveys of the target area based on the contact zone to clarify the surface orientation of the magma intrusion contact zone and its spatial relationship with the proposed tunnel route;

[0010] S3: At the intersection of the magma intrusion contact zone and the proposed tunnel route on the ground surface, a standardized artificial trench is set up to expose fresh bedrock and measure the spatial distribution information of the altered rock mass on the sidewall of the trench; based on the spatial distribution information, the alteration zones from the intrusive rock to the pre-existing rock mass are identified and divided on the sidewall of the artificial trench.

[0011] S4: Systematically identify undesirable alteration minerals in alteration zones and determine the alteration rocks and the proportion of original mineral replacement in the contact zone;

[0012] S5: Identify the structural features of altered rocks and determine the degree of preservation of the original rock structure;

[0013] S6: Based on the ratio of original rock mineral replacement and the degree of original rock structure retention, a classification standard for adverse alteration levels is established.

[0014] S7: Based on the correlation criteria between adverse alteration levels and high-density electrical geophysical data, combined with structural features, the spatial distribution and scale of adversely altered geological bodies underground are predicted; based on the spatial distribution and scale, the tunnel engineering route is selected.

[0015] Optionally, step S1 includes:

[0016] Based on aerial 3D geomorphological images and topographic maps, the target area of ​​the magma intrusion contact zone was initially delineated by identifying geomorphological differences and abrupt topographic changes.

[0017] Optionally, step S2 includes:

[0018] By examining the differences in color and lithology of exposed rocks on the Earth's surface, we can trace the abrupt lithological transition zones between magmatic intrusive rocks and pre-existing rock masses.

[0019] Investigate the rock masses on both sides of the lithological abrupt change zone to determine the magma intrusion contact zone. Specifically, if one or more geological phenomena such as baking rim, cooling rim, transition vein, flow cleavage, and xenoliths are developed, it is determined to be a magma intrusion contact zone.

[0020] The tracing method was used to trace the extension of the magma intrusion contact zone along its development direction, mark key points, and draw them on a topographic map to determine the surface orientation of the magma intrusion contact zone and the spatial relationship between the proposed tunnel route and the magma intrusion contact zone.

[0021] Optionally, step S3 includes:

[0022] S31: At the intersection of the magma intrusion contact zone and the proposed tunnel route on the ground, an artificial trench shall be excavated along the tunnel axis. The length of the artificial trench shall pass through the unaltered magma intrusion rock and the unaltered pre-existing rock mass, and the depth shall penetrate the surface weathering crust and expose the fresh bedrock.

[0023] S32: Clean, number, and photograph the sidewalls of the trench to obtain high-definition digital images, and then stitch, correct, and enhance them;

[0024] S33: Conduct geological mapping of the trench sidewalls. The specific steps are as follows:

[0025] A two-dimensional coordinate system is established based on the sidewall of the trench;

[0026] Based on a two-dimensional coordinate system, the width of the altered rock mass is measured using a tape measure on the sidewall of the artificial trench, and the strike, dip and dip angle of the altered rock mass are measured using a geological compass to determine the spatial distribution information of the altered rock mass.

[0027] Based on the spatial distribution information of altered rock masses, the boundaries of rock zones with different colors, structures and lithologies are observed and delineated on the sidewalls of artificial trenches; based on the rock zone boundaries, the specific boundaries of alteration zones are clearly marked on the sidewalls of artificial trenches using spray paint and labels, and the spatial distribution information of each alteration zone is recorded.

[0028] S34: An alteration geological map is obtained based on high-definition digital images, spatial distribution information of altered rock masses, and spatial distribution information of alteration zones.

[0029] Optionally, step S4 includes:

[0030] Using a magnifying glass, a knife, and dilute hydrochloric acid, the altered rocks are systematically identified on the sidewall of the artificial trench, following the order from the intrusive rock mass to the pre-existing rock mass, based on the physical properties of the minerals. This process helps to determine the altered rocks.

[0031] Physical properties include: shape, color, luster, hardness, and joints;

[0032] Undesirable alteration minerals include one or more of the following: sericite, chlorite, epidote, kaolinite, montmorillonite, and illite.

[0033] The replacement ratio of adverse alteration minerals to protolith minerals is calculated as follows:

[0034]

[0035] In the formula, The volume content of undesirable altered minerals; This represents the volumetric content of the original rock minerals.

[0036] Optionally, step S5 includes:

[0037] On the sidewall of the artificial trench, along the sequence from the intrusive rock mass to the pre-existing rock strata, the structure, mineral cementation degree, porosity and joint and fracture development of the magmatic intrusive rocks, contact zone altered rocks and pre-existing strata rocks are described respectively.

[0038] Manual specimens were collected from each alteration zone, and the differences between the structure of each altered rock and the original rock structure were delineated using a magnifying glass to obtain the preservation degree of the original rock structure.

[0039] Structural features include: mineral grain morphology and size, spatial arrangement of mineral aggregates, degree of cementation between minerals, porosity, and degree of joint and fracture development.

[0040] Optionally, step S6 includes:

[0041] Undesirable alteration grades are classified as follows:

[0042] Strong adverse alteration: the proportion of original rock mineral replacement >75%; the retention of original rock structure <25%, and the structure is loose and sandy or earthy;

[0043] Moderately unfavorable alteration: the proportion of original rock mineral replacement is 25%–75%; the preservation of original rock structure is 25%–75%.

[0044] Weak and undesirable alteration: the proportion of original rock mineral replacement is <25%; the original rock structure is preserved >75%; and altered minerals are distributed only along the fractures.

[0045] Step S7 includes:

[0046] Establish a correlation criterion between adverse alteration levels and high-density electrical resistivity. Under the constraints of this correlation criterion, interpret surface high-density electrical resistivity data to predict the spatial distribution and scale of adversely altered geological bodies underground.

[0047] A tunnel adverse erosion type prediction system driven by erosion mapping data, the system comprising: a data acquisition module, a data processing module, and a display module;

[0048] The data acquisition module includes: aerial photography equipment, high-resolution digital cameras, and high-density electrical resistivity tomography (EDT) surface geophysical exploration equipment;

[0049] The data acquisition module is used to acquire aerial 3D geomorphological images, topographic maps, and high-density electrical resistivity tomography data;

[0050] The data processing module is used to delineate the target area of ​​the magma intrusion contact zone based on aerial 3D geomorphological images and topographic maps;

[0051] The data processing module is also used to conduct field geological surveys of the target area based on the contact zone, clarifying the surface orientation of the magma intrusion contact zone and its spatial relationship with the proposed tunnel route;

[0052] The data processing module is also used to deploy standardized artificial trenches at the surface intersection of the magma intrusion contact zone and the proposed tunnel route, expose fresh bedrock, and measure the spatial distribution information of the altered rock mass on the sidewall of the trench; based on the spatial distribution information, it identifies and divides the alteration zones from the intrusive rock to the pre-existing rock mass on the sidewall of the artificial trench.

[0053] The data processing module is also used to systematically identify undesirable alteration minerals in alteration zones and determine the alteration rocks and the proportion of original mineral replacement in the contact zone.

[0054] The data processing module is also used to identify the structural features of altered rocks and determine the degree of preservation of the original rock structure;

[0055] The data processing module is also used to classify the grading standards for adverse alteration levels based on the original rock mineral replacement ratio and the original rock structure retention.

[0056] The data processing module is also used to predict the spatial distribution and scale of the adverse alteration geological body underground based on the correlation criteria between the adverse alteration level and high-density electrical geophysical data, combined with structural features; and to select the route for tunnel engineering based on the spatial distribution and scale.

[0057] The display module is used to visualize the spatial distribution and scale of adversely altered geological bodies underground.

[0058] The beneficial effects of the technical solution provided in this application are:

[0059] This application proposes a prediction methodology system of "artificial trenching + alteration mapping + geophysical fusion." It organically combines traditional geological surveys, standardized artificial trench excavation, systematic identification of alteration minerals and structural features, classification of adverse alteration levels, and fusion interpretation of high-density electrical resistivity tomography (EDT) data to form a complete prediction process. This invention, with alteration geological mapping and fusion interpretation as its core, is the first to systematically use adverse alteration levels as the core basis and prior knowledge for prediction. By meticulously characterizing the "fingerprint" information of the alteration itself, it provides robust geological model constraints for geophysical anomalies, greatly reducing the ambiguity and uncertainty in the interpretation process, and making the prediction results closer to geological reality.

[0060] This application proposes a method and system for predicting adversely altered geological bodies in tunnels, driven by alteration mapping data. It organically integrates traditional geological surveys, artificial trenching, systematic identification of altered minerals and their structures, classification of adverse alteration levels, and high-density electrical resistivity tomography (EDT) surface geophysical data to form a complete prediction method for adversely altered geological bodies in tunnels. This invention focuses on alteration geological mapping and geophysical data-constrained interpretation. For the first time, it uses the adverse alteration level based on the original rock mineral replacement ratio and the retention degree of the original rock structure as the basis for prediction and prior knowledge. It establishes a correlation criterion between the adverse alteration level and high-density EDT resistivity, and interprets surface high-density EDT data under the constraints of this correlation criterion, greatly suppressing the ambiguity and uncertainty of the interpretation, making the prediction results closer to geological reality. Attached Figure Description

[0061] The present application will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0062] Figure 1 This is a flowchart of an embodiment of this application;

[0063] Figure 2 This is a schematic diagram of the arrangement of artificial trenches in the embodiments of this application;

[0064] Figure 3 This is a sketch of the alteration zoning in the embodiments of this application;

[0065] Figure 4 This is a schematic diagram of the predicted distribution of alteration zones in the embodiments of this application;

[0066] Figure 5 This is a comparison diagram of alteration mineral characteristics in the embodiments of this application. Detailed Implementation

[0067] To provide a clearer understanding of the technical features, objectives, and effects of this application, the specific embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0068] Embodiments of this application provide a method for predicting adverse erosion types in tunnels driven by erosion mapping data.

[0069] Please refer to Figure 1 , Figure 1 This is a flowchart of a method for predicting adverse erosion types in tunnels driven by erosion mapping data, as described in an embodiment of this application, including:

[0070] S1: Based on aerial 3D geomorphological images and topographic maps, delineate the target area of ​​the magma intrusion contact zone;

[0071] S2: Conduct field geological surveys of the target area based on the contact zone to clarify the surface orientation of the magma intrusion contact zone and its spatial relationship with the proposed tunnel route;

[0072] S3: At the intersection of the magma intrusion contact zone and the proposed tunnel route on the ground surface, a standardized artificial trench is set up to expose fresh bedrock and measure the spatial distribution information of the altered rock mass on the sidewall of the trench; based on the spatial distribution information, the alteration zones from the intrusive rock to the pre-existing rock mass are identified and divided on the sidewall of the artificial trench.

[0073] S4: Systematically identify undesirable alteration minerals in alteration zones and determine the alteration rocks and the proportion of original mineral replacement in the contact zone;

[0074] S5: Identify the structural features of altered rocks and determine the degree of preservation of the original rock structure;

[0075] S6: Based on the ratio of original rock mineral replacement and the degree of original rock structure retention, a classification standard for adverse alteration levels is established.

[0076] S7: Based on the correlation criteria between adverse alteration levels and high-density electrical geophysical data, combined with structural features, the spatial distribution and scale of adversely altered geological bodies underground are predicted; based on the spatial distribution and scale, the tunnel engineering route is selected.

[0077] As one example, the prediction of existing adversely altered geological bodies mainly relies on advanced geological forecasting during tunnel construction, which has the following problems:

[0078] 1. In the tunnel engineering route selection stage, geological drilling is often used to verify potential adverse altered geological bodies. This invention provides a novel method for predicting adverse altered geological bodies based on artificial trenching, altered geological mapping, and fusion interpretation. This method is less expensive than traditional geological drilling and avoids additional drilling work on the proposed tunnel route. Excavating artificial trenches is faster, easier to organize, and easier to implement than geological drilling. Furthermore, this method expands the exposure of altered geological information from the point-like exposure of drilling to the overall exposure of the three-dimensional altered structure of intrusive contact structures, revealing more complete and representative altered geological information than drilling alone.

[0079] 2. In the tunnel engineering route selection stage, there is a lack of effective prediction methods for adverse altered geological bodies, relying entirely on advanced geological forecasts during construction. However, due to the ambiguity of interpreting advanced geological forecast results, it is difficult to effectively identify adverse altered geological bodies, leading to frequent threats of disasters such as mudslides, water inrushes, and large deformations induced by these bodies during construction. The technology of this invention can identify strongly adverse altered geological bodies during the route selection stage and allow for detours. For moderately and weakly adverse altered geological bodies, it can provide geological "fingerprints" for interpreting advanced geological forecast results during the construction stage, effectively guiding the interpretation of advanced geological forecast results and reducing their ambiguity.

[0080] 3. Establishing a correspondence between alteration levels and geophysical response parameters has fundamentally transformed alteration geological information from "indirect detection and empirical judgment" to "feature-driven and quantitative prediction," improving the prediction accuracy of major adverse alteration geological bodies during the route selection stage. Traditional methods rely excessively on the indirect interpretation of geophysical data, making multiple interpretations unavoidable.

[0081] Step S1 includes:

[0082] Based on aerial 3D geomorphological images and topographic maps, the target area of ​​the magma intrusion contact zone was initially delineated by identifying geomorphological differences and abrupt topographic changes.

[0083] As one example, aerial 3D geomorphological images and topographic maps are collected. Differences in landforms are identified in the images. Magmatic intrusions often form mountains or highlands (such as granite mountains), while pre-existing rock masses are generally easily weathered, forming valleys or plains. Secondly, topographic abrupt change zones are analyzed on the topographic maps. Steep cliffs are generally developed near magmatic intrusion contact zones, resulting in significant topographic differences. Through these differences in geomorphology and topography, the magmatic intrusion contact zone is preliminarily delineated, and key target areas, potential locations, and possible trends for field investigations are constructed.

[0084] Step S2 includes:

[0085] By examining the differences in color and lithology of exposed rocks on the Earth's surface, we can trace the abrupt lithological transition zones between magmatic intrusive rocks and pre-existing rock masses.

[0086] Investigate the rock masses on both sides of the lithological abrupt change zone to determine the magma intrusion contact zone. Specifically, if one or more geological phenomena such as baking rim, cooling rim, transition vein, flow cleavage, and xenoliths are developed, it is determined to be a magma intrusion contact zone.

[0087] The tracing method was used to trace the extension of the magma intrusion contact zone along its development direction, mark key points, and draw them on a topographic map to determine the surface orientation of the magma intrusion contact zone and the spatial relationship between the proposed tunnel route and the magma intrusion contact zone.

[0088] As one example, a field geological survey of magma intrusion contact structures is conducted in the aforementioned preliminarily delineated key areas and locations. First, by observing the color and lithological differences of exposed rocks at the surface, the lithological abrupt change zone between the magma intrusion rock and the pre-existing rock mass is traced. Second, the rock masses on both sides of the lithological abrupt change zone are investigated. If one or more geological phenomena such as baked rims, cooled rims, transition veins, flow cleavage, and xenoliths are developed, it can be identified as a magma intrusion contact zone. Finally, the extension range of the magma intrusion contact zone is traced along its development direction using a tracing method, key points are marked, and plotted on a topographic map to determine the surface orientation of the magma intrusion contact zone and its spatial relationship with the proposed tunnel route.

[0089] Step S3 includes:

[0090] S31: At the intersection of the magma intrusion contact zone and the proposed tunnel route on the ground, an artificial trench shall be excavated along the tunnel axis. The length of the artificial trench shall pass through the unaltered magma intrusion rock and the unaltered pre-existing rock mass, and the depth shall penetrate the surface weathering crust and expose the fresh bedrock.

[0091] S32: Clean, number, and photograph the sidewalls of the trench to obtain high-definition digital images, and then stitch, correct, and enhance them;

[0092] S33: Conduct geological mapping of the trench sidewalls. The specific steps are as follows:

[0093] A two-dimensional coordinate system is established based on the sidewall of the trench;

[0094] Based on a two-dimensional coordinate system, the width of the altered rock mass is measured using a tape measure on the sidewall of the artificial trench, and the strike, dip and dip angle of the altered rock mass are measured using a geological compass to determine the spatial distribution information of the altered rock mass.

[0095] As one example, at the intersection of the magma intrusion contact zone and the proposed tunnel route on the surface, an artificial trench is excavated along the tunnel axis. The length of the artificial trench must penetrate the unaltered magma intrusion rock and the unaltered pre-existing rock mass, and the depth must penetrate the surface weathering crust and expose fresh bedrock. The width of the trench is 2-3 meters. The sidewalls of the trench are cleaned, numbered, photographed, and sketched to establish a two-dimensional coordinate system for the trench, providing precise spatial positioning for all observation points. Inside the artificial trench, the width of the altered rock mass is measured using a tape measure, and the strike, dip, and angle of the altered rock mass are measured using a geological compass.

[0096] Based on the spatial distribution information of altered rock masses, the boundaries of rock zones with different colors, structures and lithologies are observed and delineated on the sidewalls of artificial trenches; based on the rock zone boundaries, the specific boundaries of alteration zones are clearly marked on the sidewalls of artificial trenches using spray paint and labels, and the spatial distribution information of each alteration zone is recorded.

[0097] S34: An alteration geological map is obtained based on high-definition digital images, spatial distribution information of altered rock masses, and spatial distribution information of alteration zones.

[0098] As one example, such as Figure 2 As shown, macroscopic color and lithological boundary identification involves observing and delineating the boundaries of rock zones with different colors, structures, and lithologies on the sidewalls of the artificial trench. For example, magmatic intrusive rocks are typically lighter in color (e.g., grayish-white, flesh-colored), with high mineral crystallinity and a uniform structure; while pre-existing rocks vary in color and structure. Near the contact zone, areas where color, structural characteristics, and mineral composition change gradually or abruptly are identified. Zoning boundary determination and marking: The specific boundaries of alteration zones are clearly marked on the sidewalls of the artificial trench using spray paint and labels, and the spatial distribution and width of each zone are recorded.

[0099] In one specific embodiment of this application, an artificial trench perpendicular to the direction of alteration development was excavated on the surface in the area where the alteration zone was developed. The sidewalls of the trench were cleaned and photographed. Then, a detailed alteration geological mapping was conducted on the sidewalls, including the types and contents of alteration minerals, and the structure of alteration rocks. Finally, an alteration geological map was obtained based on the high-resolution photographs and the results of the alteration geological mapping, completing the alteration geological mapping of the artificial trench. The above steps have the following beneficial effects:

[0100] High efficiency: High-definition images and digital processing enable rapid acquisition and organization of geological information, reducing fieldwork time.

[0101] High precision: Combining images and field mapping reduces subjective errors and improves the accuracy and continuity of geological data.

[0102] Strong visualization: Generates digital alteration geological maps, which are easy to store, share and analyze, and support tunnel route selection decisions.

[0103] Low cost: It utilizes conventional equipment (such as digital cameras) and software, requiring no expensive specialized instruments, and is easy to promote.

[0104] Step S4 includes:

[0105] Using a magnifying glass, a knife, and dilute hydrochloric acid, the altered rocks are systematically identified on the sidewall of the artificial trench, following the order from the intrusive rock mass to the pre-existing rock mass, based on the physical properties of the minerals. This process helps to determine the altered rocks.

[0106] Physical properties include: shape, color, luster, hardness, and joints;

[0107] Undesirable alteration minerals include one or more of the following: sericite, chlorite, epidote, kaolinite, montmorillonite, and illite.

[0108] As one example, such as Figure 5 As shown, the identification of undesirable alteration minerals involves using a magnifying glass, a knife, and dilute hydrochloric acid to systematically identify the presence, disappearance, and content changes of undesirable alteration minerals such as sericite, chlorite, calcite, kaolinite, montmorillonite, and illite that cause the deterioration of rock mass strength on the sidewall of the artificial trench, following the sequence from the intrusive rock mass to the pre-existing rock mass, based on the physical properties of the minerals, such as morphology, color, luster, hardness, and joints.

[0109] Rapid field identification of altered sericite minerals mainly relies on the following characteristics: the color is white, light grayish-white, pale yellow or pale green, and under a magnifying glass it has a silky luster and fine scaly texture; in terms of hardness, it can be scratched with a fingernail and feels noticeably slippery when rubbed between the fingers; macroscopically, it often develops into clusters, bands, or scaly aggregates, and its size can be measured with a ruler.

[0110] Rapid field identification of altered chlorite minerals mainly relies on the following characteristics: green color, scaly texture, dull luster, commonly found in phyllostite, under magnification it appears as fine scaly or leaf-like structures with directional arrangement of the fine scaly flakes, and a dull, non-reflective luster, clearly distinguishable from the silky luster of sericite; in terms of hardness, it can be easily scratched with a knife, and the resulting fracture surface is thin and flaky, with a slightly slippery feel when rubbed between the fingers; macroscopically, it often occurs as platy, thin-layered, or massive aggregates, and its band width, patch area, and other scale parameters can be measured with a ruler.

[0111] Rapid field identification of altered epidote minerals mainly relies on the following characteristics: yellowish-green, columnar, vitreous luster; under magnification, it appears as typical long columnar or needle-like crystals; some crystal aggregates are arranged radially or in bundles; the vitreous luster is significant; and a slight transparency can be seen at the crystal edges. In terms of hardness, it does not react when scratched with a fingernail, but leaves a scratch when scratched with a knife; it does not feel slippery when rubbed between fingers; and the crystals have a distinct granular feel. Macroscopically, it often occurs as veinlets, lenses, or masses; the size information such as the width of the veinlets and the diameter of the masses can be measured with a ruler.

[0112] Rapid field identification of altered clay minerals mainly relies on the following characteristics: earthy appearance, slippery feel, strong water absorption, and white or grayish-white color; under magnification, it has an earthy luster, no obvious crystal morphology, and is a fine powder or cryptocrystalline structure without a granular feel; in terms of hardness, it can be easily scratched with a fingernail and can be crushed into powder by fingers without leaving any lumps; in terms of feel, it has an extremely slippery feel when rubbed between fingers, and the slipperiness intensifies after wetting, and it is extremely absorbent, and can be kneaded into a ball after wetting; macroscopically, it often appears as earthy, loose lumps or thin layers covering the rock surface, or filling the cracks and pores of the rock mass, and its distribution layer thickness, coverage area and other scale parameters can be measured with a measuring tape.

[0113] The ratio of adverse alteration minerals to protolith minerals can be calculated by their volume content in hand specimens. Then, by calculating the proportion of adverse alteration minerals in the total minerals, the proportion of protolith minerals replaced by secondary adverse alteration minerals can be determined.

[0114] The replacement ratio of adverse alteration minerals to protolith minerals is calculated as follows:

[0115]

[0116] In the formula, The volume content of undesirable altered minerals; This represents the volumetric content of the original rock minerals.

[0117] Step S5 includes:

[0118] On the sidewall of the artificial trench, along the sequence from the intrusive rock mass to the pre-existing rock strata, the structure, mineral cementation degree, porosity and joint and fracture development of the magmatic intrusive rocks, contact zone altered rocks and pre-existing strata rocks are described respectively.

[0119] Manual specimens were collected from each alteration zone, and the differences between the structure of each altered rock and the original rock structure were delineated using a magnifying glass to obtain the preservation degree of the original rock structure.

[0120] Structural features include: mineral grain morphology and size, spatial arrangement of mineral aggregates, degree of cementation between minerals, porosity, and degree of joint and fracture development.

[0121] As an example, magmatic intrusive rocks generally exhibit typical euhedral to subhedral granular textures and massive structures, while altered rocks generally exhibit metamorphic (scaly, fibrous, granular), relict (porphyritic, granitic), and metasomatic structures, as well as porphyritic, sandy, earthy, and vein-like textures.

[0122] Step S6 includes:

[0123] Undesirable alteration grades are classified as follows:

[0124] Strong adverse alteration: the proportion of original rock mineral replacement >75%; the retention of original rock structure <25%, and the structure is loose and sandy or earthy;

[0125] Moderately unfavorable alteration: the proportion of original rock mineral replacement is 25%–75%; the preservation of original rock structure is 25%–75%.

[0126] Weak and undesirable alteration: the proportion of original rock mineral replacement is <25%; the original rock structure is preserved >75%; and altered minerals are distributed only along the fractures.

[0127] Step S7 includes:

[0128] Establish a correlation criterion between adverse alteration levels and high-density electrical resistivity. Under the constraints of this correlation criterion, interpret surface high-density electrical resistivity data to predict the spatial distribution and scale of adversely altered geological bodies underground.

[0129] A tunnel adverse erosion type prediction system driven by erosion mapping data, the system comprising: a data acquisition module, a data processing module, and a display module;

[0130] The data acquisition module includes: aerial photography equipment, high-resolution digital cameras, and high-density electrical resistivity tomography (EDT) surface geophysical exploration equipment;

[0131] The data acquisition module is used to acquire aerial 3D geomorphological images, topographic maps, and high-density electrical resistivity tomography data;

[0132] The data processing module is used to delineate the target area of ​​the magma intrusion contact zone based on aerial 3D geomorphological images and topographic maps;

[0133] The data processing module is also used to conduct field geological surveys of the target area based on the contact zone, clarifying the surface orientation of the magma intrusion contact zone and its spatial relationship with the proposed tunnel route;

[0134] The data processing module is also used to deploy standardized artificial trenches at the surface intersection of the magma intrusion contact zone and the proposed tunnel route, expose fresh bedrock, and measure the spatial distribution information of the altered rock mass on the sidewall of the trench; based on the spatial distribution information, it identifies and divides the alteration zones from the intrusive rock to the pre-existing rock mass on the sidewall of the artificial trench.

[0135] The data processing module is also used to systematically identify undesirable alteration minerals in alteration zones and determine the alteration rocks and the proportion of original mineral replacement in the contact zone.

[0136] The data processing module is also used to identify the structural features of altered rocks and determine the degree of preservation of the original rock structure;

[0137] The data processing module is also used to classify the grading standards for adverse alteration levels based on the original rock mineral replacement ratio and the original rock structure retention.

[0138] The data processing module is also used to predict the spatial distribution and scale of the adverse alteration geological body underground based on the correlation criteria between the adverse alteration level and high-density electrical geophysical data, combined with structural features; and to select the route for tunnel engineering based on the spatial distribution and scale.

[0139] The display module is used to visualize the spatial distribution and scale of adversely altered geological bodies underground.

[0140] As one example, Table 1 shows the correspondence between the degree of adverse alteration and typical geophysical results of high-density electrical resistivity tomography.

[0141] Table 1

[0142]

[0143] The resistivity range is based on the field measurement patterns of "high-density electrical resistivity (Wenner device, electrode spacing 5~10 m)" during the tunnel route selection stage. The stronger the alteration, the higher the clay mineral content, the greater the porosity, and the easier it is to contain water, resulting in a lower resistivity.

[0144] As one example, during the route selection process for a certain tunnel, complete alteration geological data was obtained through systematic geological mapping and testing. This data can be used to verify the scientific validity and operability of the prediction process for adverse alteration geological bodies. The specific process is as follows:

[0145] During the route selection process, the project team collected 1:2000 aerial 3D geomorphological images and 1:5000 topographic maps along the tunnel route. Geomorphological feature analysis revealed that the light pink crystalline granite intrusion in the area, due to its strong resistance to weathering, formed distinct mountain highlands; while the surrounding grayish-white tuff was easily weathered and eroded, forming valleys and plains, with a clear geomorphic boundary between the two. Further analysis of the topographic maps showed that steep cliffs and abrupt topographic changes occurred at the contact point between the granite and tuff. Based on this, a 1.2 km long magma intrusion contact zone was initially delineated as a key area for field investigation, clarifying the potential location and extension direction of this area.

[0146] Subsequently, a surface geological survey was conducted along the delineated area, and the geological boundary was identified using the "lithological tracing method": based on the lithological differences between the light pink crystalline pavonica granite and the grayish-white tuff, continuously distributed baked rims (5-15 cm wide) and granite xenoliths (20-50 cm in diameter) were found on survey line L2, confirming that the area was a magmatic intrusion contact zone. The attitude of the contact zone was measured to be 315°∠42° using a geological compass, and 12 key control points were marked using GPS and plotted on a topographic map. Finally, it was determined that the contact zone intersected the proposed tunnel route at a 35° angle, suggesting that tunnel construction might traverse the contact zone and the altered areas within its influence range.

[0147] To obtain deep alteration information of the contact zone, an artificial trench (numbered TC01) was excavated along the tunnel axis in the core area where the contact zone intersects with the tunnel route. The trench adopted an inverted trapezoidal design, with an opening width of 2.5m, a bottom width of 0.8m, a length of 6m, and a depth of 2.8m. After penetrating a 2.0m thick layer of residual slope deposits, it successfully exposed 0.8m thick fresh bedrock. After construction, the trench sidewalls were cleaned, numbered, and subjected to panoramic photography. A baseline was established on the north wall (starting coordinates X=32568.2m, Y=48952.6m). Distances were measured with a tape measure, GPS was used to locate the baseline point, and a compass was used to measure the baseline azimuth at 30°. Simultaneously, the strike, dip, and dip angle of each geological interface were recorded to provide precise spatial positioning for subsequent alteration analysis.

[0148] On the north wall of trench TC01, five clear geological boundaries were identified from the granite intrusion towards the tuff surrounding rock through visual observation and spray-paint markings. These boundaries delineated five alteration zones, which were then labeled: TC01-S1 (unaltered vuggraviate zone), TC01-S2 (albitized granite zone), TC01-S3 (sericite-albitized granite zone), TC01-S4 (clay zone, subdivided into the inner kaolinized subzone S4-1 and the outer montmorillonite subzone S4-2), and TC01-S5 (silicified tuff zone and unaltered tuff zone). A 1:40 scale sketch of the trench was drawn; see details below. Figure 3The widths of each alteration zone were measured and recorded: S1 was 1.2m wide, S2 was 0.8m wide, S3 was 1.5m wide, S4 was 0.9m wide, and S5 was 1.6m wide, clearly showing the spatial distribution characteristics of the alteration zones. Table 2 shows the alteration characteristics and mineral composition of the rock and soil.

[0149] Table 2

[0150]

[0151] Using a 10x magnifying glass and a knife, mineral identification was conducted along each alteration zone: In zone TC01-S2, granular albite was visible under magnification as vein-like fillings (vein width 1-3mm), easily broken when scratched with a knife; in zone TC01-S3, sericite appeared as silky-lustered, scaly aggregates, feeling slippery to the touch, accompanied by dark green chlorite (scale diameter 0.1-0.3mm), easily scratched with a knife, with a thin, flaky cross-section; in zone TC01-S4, kaolinite appeared as white, earthy material, highly absorbent, and could be clumped together when wet, while montmorillonite appeared light white and slightly expanded in volume when wet. Based on volume estimation of hand specimens, undesirable alteration minerals accounted for 85.6% of the minerals in zone TC01-S4, indicating significant replacement of the original rock minerals. Table 3 shows the alteration processes and intensity of the rock and soil; thicker lines indicate stronger alteration, while thinner lines indicate weaker alteration.

[0152] Table 3

[0153]

[0154] Meanwhile, detailed observations were conducted on the rock structure of each alteration zone: Zone TC01-S1 exhibits an euhedral to subhedral granular structure and massive texture, with uniform crystal grains and no obvious fractures; Zone TC01-S2 shows a metamorphic structure with a porosity of approximately 12%, and localized fine fractures; Zone TC01-S3 develops a lepidic metamorphic structure, with sericite arranged in a directional manner to form foliation, accompanied by a vein-like structure; Zone TC01-S4 has a typical earthy structure, with the original rock structure completely destroyed, exhibiting a loose texture that crumbles easily when touched. The degree of structural damage gradually intensifies with increasing alteration and shows a clear positive correlation with the degree of mineral replacement.

[0155] Based on the mineral replacement ratio and the degree of structural damage, the adverse alteration levels of each alteration zone were classified as follows: Zone TC01-S4 (clay zone) has a mineral replacement ratio of >75% and a loose, earthy structure, and is classified as strongly adverse alteration; Zone TC01-S3 (sericite-albitized granite zone) has a replacement ratio of 48.3% and partial structural damage, and is classified as moderately adverse alteration; Zone TC01-S2 (albitized granite zone) has a replacement ratio of 18.7% and the structure is basically preserved, and is classified as weakly adverse alteration. This provides a clear basis for the design of subsequent construction support schemes.

[0156] To further investigate the distribution of underground alteration zones, high-density electrical resistivity tomography (EDT) was conducted around the trench using a Wenner instrument with an electrode spacing of 5m and a detection depth of 30m. The results showed that the strongly altered TC01-S4 zone corresponds to a low resistivity anomaly (50-150 Ω·m), the moderately altered TC01-S3 zone exhibits a medium-low resistivity anomaly (150-300 Ω·m), the weakly altered TC01-S2 zone shows medium resistivity characteristics (300-500 Ω·m), and the unaltered zone exhibits high resistivity (>500 Ω·m). Based on previous geological data, a geological model of the underground alteration zone was constructed, predicting that the tunnel will traverse a strongly altered zone in the K12+350-K12+380 section, approximately 30m in length and 385m in depth. See details below. Figure 4 .

[0157] During subsequent tunnel excavation, the actual distribution of alteration zones, mineral assemblage, and alteration grade revealed matched the preliminary predictions. In the strongly altered sections, the risk of collapse and mudslide was successfully avoided by employing advanced small-diameter pipe support in advance. The alteration geological data, exploration procedures, and prediction results obtained from this tunnel exploration and construction practice all conform to the requirements of each stage of the method for predicting adverse alteration geological bodies, fully verifying the scientific validity, operability, and engineering applicability of this method.

[0158] The above are merely exemplary embodiments of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure.

[0159] This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described in this disclosure. The specification and embodiments are to be considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

Claims

1. A method for predicting adverse erosion types in tunnels driven by erosion mapping data, characterized in that, The method includes the following steps: S1: Based on aerial 3D geomorphological images and topographic maps, delineate the target area of ​​the magma intrusion contact zone; S2: Conduct field geological surveys of the target area based on the contact zone to clarify the surface orientation of the magma intrusion contact zone and its spatial relationship with the proposed tunnel route; S3: At the intersection of the magma intrusion contact zone and the proposed tunnel route on the ground surface, a standardized artificial trench is set up to expose fresh bedrock and measure the spatial distribution information of the altered rock mass on the sidewall of the trench; based on the spatial distribution information, the alteration zones from the intrusive rock to the pre-existing rock mass are identified and divided on the sidewall of the artificial trench. S4: Systematically identify undesirable alteration minerals in alteration zones and determine the alteration rocks and the proportion of original mineral replacement in the contact zone; S5: Identify the structural features of altered rocks and determine the degree of preservation of the original rock structure; S6: Based on the ratio of original rock mineral replacement and the degree of original rock structure retention, a classification standard for adverse alteration levels is established. S7: Based on the correlation criteria between adverse alteration levels and high-density electrical geophysical data, combined with structural features, the spatial distribution and scale of adversely altered geological bodies underground are predicted; based on the spatial distribution and scale, the tunnel engineering route is selected.

2. The method for predicting adverse erosion types in tunnels driven by erosion mapping data as described in claim 1, characterized in that, Step S1 includes: Based on aerial 3D geomorphological images and topographic maps, the target area of ​​the magma intrusion contact zone was initially delineated by identifying geomorphological differences and abrupt topographic changes.

3. The method for predicting adverse erosion types in tunnels driven by erosion mapping data as described in claim 1, characterized in that, Step S2 includes: By examining the differences in color and lithology of exposed rocks on the Earth's surface, we can trace the abrupt lithological transition zones between magmatic intrusive rocks and pre-existing rock masses. Investigate the rock masses on both sides of the lithological abrupt change zone to determine the magma intrusion contact zone. Specifically, if one or more geological phenomena such as baking rim, cooling rim, transition vein, flow cleavage, and xenoliths are developed, it is determined to be a magma intrusion contact zone. The tracing method was used to trace the extension of the magma intrusion contact zone along its development direction, mark key points, and draw them on a topographic map to determine the surface orientation of the magma intrusion contact zone and the spatial relationship between the proposed tunnel route and the magma intrusion contact zone.

4. The method for predicting adverse erosion types in tunnels driven by erosion mapping data as described in claim 1, characterized in that, Step S3 includes: S31: At the intersection of the magma intrusion contact zone and the proposed tunnel route on the ground, an artificial trench shall be excavated along the tunnel axis. The length of the artificial trench shall pass through the unaltered magma intrusion rock and the unaltered pre-existing rock mass, and the depth shall penetrate the surface weathering crust and expose the fresh bedrock. S32: Clean, number, and photograph the sidewalls of the trench to obtain high-definition digital images, and then stitch, correct, and enhance them; S33: Conduct geological mapping of the trench sidewalls. The specific steps are as follows: A two-dimensional coordinate system is established based on the sidewall of the trench; Based on a two-dimensional coordinate system, the width of the altered rock mass is measured using a tape measure on the sidewall of the artificial trench, and the strike, dip and dip angle of the altered rock mass are measured using a geological compass to determine the spatial distribution information of the altered rock mass. Based on the spatial distribution information of altered rock masses, the boundaries of rock zones with different colors, structures and lithologies are observed and delineated on the sidewalls of artificial trenches; based on the rock zone boundaries, the specific boundaries of alteration zones are clearly marked on the sidewalls of artificial trenches using spray paint and labels, and the spatial distribution information of each alteration zone is recorded. S34: An alteration geological map is obtained based on high-definition digital images, spatial distribution information of altered rock masses, and spatial distribution information of alteration zones.

5. The method for predicting adverse erosion types in tunnels driven by erosion mapping data as described in claim 1, characterized in that, Step S4 includes: Using a magnifying glass, a knife, and dilute hydrochloric acid, the altered rocks are systematically identified on the sidewall of the artificial trench, following the order from the intrusive rock mass to the pre-existing rock mass, based on the physical properties of the minerals. This process helps to determine the altered rocks. Physical properties include: shape, color, luster, hardness, and joints; Undesirable alteration minerals include one or more of the following: sericite, chlorite, epidote, kaolinite, montmorillonite, and illite. The replacement ratio of adverse alteration minerals to protolith minerals is calculated as follows: In the formula, The volume content of undesirable altered minerals; This represents the volumetric content of the original rock minerals.

6. The method for predicting adverse erosion types in tunnels driven by erosion mapping data as described in claim 1, characterized in that, Step S5 includes: On the sidewall of the artificial trench, along the sequence from the intrusive rock mass to the pre-existing rock strata, the structure, mineral cementation degree, porosity and joint and fracture development of the magmatic intrusive rocks, contact zone altered rocks and pre-existing strata rocks are described respectively. Manual specimens were collected from each alteration zone, and the differences between the structure of each altered rock and the original rock structure were delineated using a magnifying glass to obtain the preservation degree of the original rock structure. Structural features include: mineral grain morphology and size, spatial arrangement of mineral aggregates, degree of cementation between minerals, porosity, and degree of joint and fracture development.

7. The method for predicting adverse erosion types in tunnels driven by erosion mapping data as described in claim 1, characterized in that, Step S6 includes: Undesirable alteration grades are classified as follows: Strong adverse alteration: the proportion of original rock mineral replacement > 75%; the retention of original rock structure < 25%, and the structure is loose and sandy or earthy; Moderately unfavorable alteration: the proportion of original rock mineral replacement is 25%–75%; the preservation of original rock structure is 25%–75%. Weak and undesirable alteration: the proportion of original rock mineral replacement is < 25%; the original rock structure is preserved > 75%; and altered minerals are distributed only along fractures.

8. The method for predicting adverse erosion types in tunnels driven by erosion mapping data as described in claim 1, characterized in that, Step S7 includes: Establish a correlation criterion between adverse alteration levels and high-density electrical resistivity. Under the constraints of this correlation criterion, interpret surface high-density electrical resistivity data to predict the spatial distribution and scale of adversely altered geological bodies underground.

9. A tunnel adverse alteration type prediction system driven by alteration mapping data, used to implement the tunnel adverse alteration type prediction method driven by alteration mapping data as described in any one of claims 1-8, characterized in that, The system includes: a data acquisition module, a data processing module, and a display module; The data acquisition module includes: aerial photography equipment, high-resolution digital cameras, and high-density electrical resistivity tomography (EDT) surface geophysical exploration equipment; The data acquisition module is used to acquire aerial 3D geomorphological images, topographic maps, and high-density electrical resistivity tomography data; The data processing module is used to delineate the target area of ​​the magma intrusion contact zone based on aerial 3D geomorphological images and topographic maps; The data processing module is also used to conduct field geological surveys of the target area based on the contact zone, clarifying the surface orientation of the magma intrusion contact zone and its spatial relationship with the proposed tunnel route; The data processing module is also used to deploy standardized artificial trenches at the surface intersection of the magma intrusion contact zone and the proposed tunnel route, expose fresh bedrock, and measure the spatial distribution information of the altered rock mass on the sidewall of the trench; based on the spatial distribution information, it identifies and divides the alteration zones from the intrusive rock to the pre-existing rock mass on the sidewall of the artificial trench. The data processing module is also used to systematically identify undesirable alteration minerals in alteration zones and determine the alteration rocks and the proportion of original mineral replacement in the contact zone. The data processing module is also used to identify the structural features of altered rocks and determine the degree of preservation of the original rock structure; The data processing module is also used to classify the grading standards for adverse alteration levels based on the original rock mineral replacement ratio and the original rock structure retention. The data processing module is also used to predict the spatial distribution and scale of the adverse alteration geological body underground based on the correlation criteria between the adverse alteration level and high-density electrical geophysical data, combined with structural features; and to select the route for tunnel engineering based on the spatial distribution and scale. The display module is used to visualize the spatial distribution and scale of adversely altered geological bodies underground.

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