Identification method for interlayer type weathering of metamorphic sandstone stock ground

Abstract

The invention discloses an identification method for interlayer type weathering of a metamorphic sandstone stock ground, and belongs to the technical field of rock-fill dam material preparation processes. The invention provides the identification method for the interlayer type weathering of the metamorphic sandstone stock ground, which can effectively identify the interlayer type weathering condition of the metamorphic sandstone. The method comprises the following steps: firstly, carrying out lithology and spatial distribution exploration on a metamorphic sandstone stock ground, then analyzing and judging whether interlayer type weathering exists in the metamorphic sandstone stock ground through regional geologic causes, and when the interlayer type weathering exists, introducing a saturated uniaxial compressive strength statistical analysis tool to carry out secondary judgment. When it is judged that the interlayer type weathering condition exists in the metamorphic sandstone stock ground again, a pre-rolling test is conducted on rockfill materials mined in the metamorphic sandstone stock ground through the pre-rolling test technology, final judgment is conducted, and finally the blasting mining mode is determined according to the final judgment conclusion and the characteristics of the interlayer type weathering sandstone stock ground. Therefore, the dam material which meets the required characteristics and is good in gradation is obtained.

Description

Technical Field

[0001] This invention relates to an identification method, and more particularly to an identification method for interlayered weathering of metamorphic sandstone quarries, belonging to the technical field of rockfill dam material preparation process. Background Technology

[0002] Statistics show that the tallest dams in the world, both completed and under construction, are all gravel-soil core rockfill dams, reaching heights of 310 meters. Dam slope stability, seepage stability, and stress-deformation are three key factors ensuring the reliable operation of gravel-soil core rockfill dams. Among these, the frequent drop in reservoir water levels leading to the accumulation, wetting, and creep deformation of the rockfill material is the primary cause of longitudinal cracks appearing on the crest of ultra-high gravel-soil core rockfill dams. Therefore, although the gravel-soil core plays a seepage-prevention role, the key factor determining the success or failure of a dam is the rockfill material, which accounts for more than 80% of the total dam fill.

[0003] Sandstone is generally considered to have high saturated compressive strength, is a hard rock, has a large softening coefficient, and exhibits relatively small differences in anisotropy. Therefore, metamorphic sandstone is a relatively ideal material for dam construction. However, quarries with strong interlayered weathering exhibit engineering characteristics such as uneven sandstone strength, significant anisotropy, poor particle shape after crushing, high stone powder content after excavation and compaction, and significant deformation after wetting.

[0004] Studies have shown that the wetting and creep deformation of the upstream rockfill material of the dam cannot be ignored. The evolution of its deformation over time is closely related to the dam material zoning and water storage planning. Some projects have not properly coordinated the spatiotemporal evolution contradictions of settlement between the core wall area and the upstream and downstream rockfill areas. At a certain time, due to the large settlement difference between the upstream rockfill area and the core wall area, the upstream rockfill area exhibits a "nodding effect" or a "reverse arch effect" in the gravel-soil core wall dam, which weakens the slope effect of the upstream rockfill area relative to the core wall and even causes a tension effect, resulting in longitudinal cracks at the top of the dam.

[0005] It is evident that identifying interlayered weathering in metamorphic sandstone quarries is crucial. This allows for proactive planning of dam structure zoning and material sources, studies on reducing long-term dam deformation and the risk of longitudinal cracks in the core wall, and enhanced reverse-filtration drainage design to ensure dam seepage stability.

[0006] Existing exploration standards classify quarry types according to topographic and geological conditions, categorizing them into Class I, II, and III from simple to complex. They also set requirements and regulations for engineering geological mapping in terms of scale, surveying scope, surveying content, and techniques. Furthermore, they specify the spacing, exploration types, and descriptions of exploration points during the general, preliminary, and detailed survey stages of riprap quarries. Finally, they stipulate the number of sampling groups, sampling methods, and test content for the design stages of general, preliminary, and detailed surveys of riprap quarries. However, current problems include a lack of specific requirements for identifying interlayered weathering in metamorphic sandstone quarries, and the absence of specific mining planning requirements for interlayered weathered metamorphic sandstone quarries. Practice has shown that conventional methods such as surface mapping, caving, drilling, and sampling for indoor saturated uniaxial compressive strength tests, compression tests, and triaxial tests are insufficient to reveal the interlayered weathering development characteristics of metamorphic sandstone quarries. Furthermore, it is even more difficult to reveal the true physical and mechanical properties of excavated rockfill materials from metamorphic sandstone quarries dominated by interlayered weathering development. For the design of ultra-high gravel-soil core rockfill dams, this characteristic cannot be ignored. If this rockfill material characteristic is only discovered during the detailed construction design stage, it will bring significant trouble and challenges to project construction and safety. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for identifying interlayered weathering in metamorphic sandstone quarries, which can effectively identify the interlayered weathering state of metamorphic sandstone.

[0008] The technical solution adopted to solve the above-mentioned technical problems is: a method for identifying interlayered weathering in metamorphic sandstone quarries. This method identifies interlayered weathering in metamorphic sandstone quarries and determines their mining and utilization methods through the following steps. S1. Use general exploration techniques for material yards to determine the lithology and spatial distribution of metamorphic sandstone material yards. S2. Based on S1, first conduct a regional geological genesis analysis, and then, based on the analysis conclusions, preliminarily determine whether there is interlayered weathering in the metamorphic sandstone quarry. S3. When it is initially determined that interlayered weathering exists in the metamorphic sandstone quarry, a saturated uniaxial compressive strength statistical analysis tool is introduced to conduct saturated uniaxial compressive strength tests on the samples and analyze the test statistical data. Based on the analysis results, a secondary determination is made as to whether interlayered weathering exists in the metamorphic sandstone quarry. S4. When it is determined again that interlayered weathering exists in the metamorphic sandstone quarry, a pre-compaction test process is introduced to conduct a pre-compaction test on the riprap material mined from the metamorphic sandstone quarry. Based on the pre-compaction test data, the interlayered weathering status of the metamorphic sandstone quarry is finally determined. S5. Based on the characteristics of metamorphic sandstone quarries with interlayered weathering, such as distinct bedding planes, easy cutting into smaller blocks by blasting, and poor gas-holding effect during blasting, the proposed mining method is to use vertical bedding drilling to obtain dam material with better gradation.

[0009] Furthermore, the S4 step confirmed that rockfill dams constructed from quarried metamorphic sandstone with interlayered weathering exhibit permeability anisotropy, with the vertical permeability coefficient being significantly lower than the horizontal permeability coefficient. When constructing such rockfill dams, regional planning should be carried out first, and horizontal drainage measures that are connected to the vertical drainage measures should be set up to ensure the seepage stability of the dam.

[0010] The preferred approach to the above scheme is that the general exploration techniques for the material yard include using surface mapping, drilling, tunneling, and geophysical exploration to explore the metamorphic sandstone material yard. Drilling is arranged in a grid pattern, and horizontal tunnels and drilling are combined.

[0011] Furthermore, the regional geological genesis analysis includes at least the following aspects: collecting data on the distribution characteristics and changes of strata or rock layers, rocks, and landforms from a macroscopic to a microscopic perspective; collecting data on the geometric morphology of deformation structures and the evolution sequence of deformation and geological events; systematically collecting representative strata or rock layers, rocks, structures, river valleys and their terrace deposits along the main route, and systematically preparing, identifying and testing samples; and systematically collecting field measurement data and information on the macroscopic structure and geometric morphology of folds, faults and joints in the work area, and performing quantitative calculation analysis and phased matching by computer.

[0012] The preferred method of the above scheme is to preliminarily determine whether there is interlayered weathering in the metamorphic sandstone quarry based on the obtained regional geological genesis analysis data. This is done according to the following requirements: if there is a metamorphic sandstone quarry formed by dynamic thermal flow metamorphism and / or thermal contact metamorphism in the adjacent area, and granitic igneous rocks are interbedded in the metamorphic sandstone, and the metamorphic sandstone rock mass is significantly compressed and deformed due to the intrusion of igneous rock mass and geological structure, and the rock strata change significantly, then it is preliminarily determined that the metamorphic sandstone quarry has the general characteristics of interlayered weathering.

[0013] Furthermore, the statistical analysis of saturated uniaxial compressive strength was performed according to the following steps: First, core samples were prepared in three mutually perpendicular directions (X, Y, and Z), with at least five core samples in each direction. Saturated uniaxial compressive strength tests were then conducted on each core sample, and the average and range of strength in each direction were calculated, denoted as X. 均 X 极 Y 均 Y 极 Z 均 Z 极 Find the coefficients X=X respectively. 极 / X 均 Y=Y 极 / Y均 Z=Z 极 / Z 均 And calculate the statistical average T. 均 = (X 均 +Y 均 +Z 均 ) / 3,T 极 =max(X 均 Y 均 Z 均 )-min(X 均 Y 均 Z 均 ), calculate the statistical coefficient T=T 极 = / T 均 If the coefficients min(X, Y, Z) and T are all greater than 0.8, and most core samples are described as having well-developed or extremely well-developed fissures, with many fractures and interlayers, it indicates that the metamorphic sandstone field is uneven and has obvious anisotropy. Therefore, it is re-judged that there is interlayered weathering in the metamorphic sandstone field.

[0014] The preferred method for the above scheme is that the statistical analysis of saturated uniaxial compressive strength is carried out according to the following steps: rock blocks are taken from the exploratory cavern and numbered X1, X2, ..., X n For each rock block, at least five core samples were prepared, and saturated uniaxial compressive strength tests were conducted. The average strength and range of each rock block were calculated and denoted as X. 1均 X 1极 X 2均 X 2极 ... X n均 X n极 Find the coefficients X1=X respectively. 1极 / X 1均 X2=X 2极 / X 2均 ... X n =X n极 / X n均 And calculate the statistical average T. 均 = (X 1均 +X 2均 +…+X n均 ) / n,T 极 =max(X 1均 X 2均 ... X n均 )-min(X 1均 X 2均 ... X n均 ), calculate the statistical coefficient T=T 极 = / T 均 If the coefficients min(X1, X2, ..., X...) nBoth T and T are greater than 0.8. Most core samples are described as having well-developed or extremely well-developed fissures, with many fractures and interlayers, indicating that the metamorphic sandstone field is uneven and has obvious anisotropy. Therefore, it is re-judged that there is interlayered weathering in the metamorphic sandstone field.

[0015] Furthermore, the prepared core samples should ensure that the weathering degree and lithology of the samples are consistent, and avoid faults and influence zones; in addition, whether a layer of fine powder is produced when the geological hammer is used to strike the surface of fresh metamorphic sandstone in the tunnel during sample preparation can be used as evidence of interlayer weathering.

[0016] The preferred approach to the above scheme is to obtain the following three test criteria through pre-compaction tests, and to determine the presence of interlayered weathering in the metamorphic sandstone quarry based on these criteria. Blasting tests were conducted according to the general blasting parameters for rockfill, and the gradation of the blasted rockfill was determined. If the content of particles smaller than 5mm was greater than 20%, it was used as test criterion 1. If, after paving and compaction, there is obvious concentration of fine powder on the surface, and after compaction, there is a concentrated and compacted fine powder layer with a thickness of 8-15 cm on the surface, this is used as test criterion 2. The compacted rockfill was excavated along the vertical direction. Visual inspection revealed obvious stratification. The particle size distribution of the finer surface layer and the coarser lower layer was analyzed separately, and seepage, compression, and triaxial tests were carried out. If the difference in the content of particles smaller than 5 mm between the finer and coarser layers was greater than 10%, the permeability coefficient difference was more than two orders of magnitude, and there were also significant differences in the deformation modulus and triaxial test mechanical parameters, these were used as test criterion 3.

[0017] Furthermore, conventional triaxial test studies should be conducted by scaling down the sample preparation based on the characteristics of the S4 rockfill field compaction test; When conventional triaxial tests are insufficient to accurately reflect the true mechanical properties of interlayered weathered and metamorphic sandstone riprap, original gradation tests without scaling up are conducted to reveal its true mechanical characteristics. Parameters are then reasonably obtained to perform dam slope stability calculations and stress-strain calculations considering cumulative wetting and creep, which guide dam design and ensure dam safety.

[0018] The beneficial effects of this invention are as follows: The technical solution provided in this application first conducts lithological and spatial distribution surveys of metamorphic sandstone quarries using general quarry exploration and control technology. Then, based on this, it determines whether interlayered weathering exists in the metamorphic sandstone quarry through regional geological genesis analysis. When it is initially determined that interlayered weathering exists in the metamorphic sandstone quarry, a saturated uniaxial compressive strength statistical analysis tool is introduced for a second determination. When it is determined again that interlayered weathering exists in the metamorphic sandstone quarry, a pre-compaction test process is introduced to conduct a pre-compaction test on the riprap material mined from the metamorphic sandstone quarry and make a final determination. Finally, based on the final determination conclusion, the blasting mining method is determined according to the characteristics of the metamorphic sandstone quarry, such as obvious bedding planes, easy cutting into smaller blocks by blasting, and poor gas-holding effect during blasting, in order to obtain dam material with good gradation that meets the required characteristics. The comprehensive identification method proposed in this application can effectively identify the interlayered weathering condition of metamorphic sandstone and determine the mining method, providing a new approach for the exploration of metamorphic sandstone and ensuring the acquisition of high-quality riprap. This avoids the troubles and challenges to engineering construction and safety caused by discovering the special characteristics of riprap only during the detailed design stage of construction drawings. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the identification process of the method for identifying interlayered weathering in metamorphic sandstone quarries according to the present invention. Detailed Implementation

[0020] like Figure 1 This invention illustrates a method for identifying interlayered weathering in metamorphic sandstone quarries, which effectively identifies the interlayered weathering condition of metamorphic sandstone. The method identifies the interlayered weathering in metamorphic sandstone quarries and determines their mining and utilization methods through the following steps. S1. Use general exploration techniques for material yards to determine the lithology and spatial distribution of metamorphic sandstone material yards. S2. Based on S1, first conduct a regional geological genesis analysis, and then, based on the analysis conclusions, preliminarily determine whether there is interlayered weathering in the metamorphic sandstone quarry. S3. When it is initially determined that interlayered weathering exists in the metamorphic sandstone quarry, a saturated uniaxial compressive strength statistical analysis tool is introduced to conduct saturated uniaxial compressive strength tests on the samples and analyze the test statistical data. Based on the analysis results, a secondary determination is made as to whether interlayered weathering exists in the metamorphic sandstone quarry. S4. When it is determined again that interlayered weathering exists in the metamorphic sandstone quarry, a pre-compaction test process is introduced to conduct a pre-compaction test on the riprap material mined from the metamorphic sandstone quarry. Based on the pre-compaction test data, the interlayered weathering status of the metamorphic sandstone quarry is finally determined. S5. Based on the characteristics of metamorphic sandstone quarries with interlayered weathering, such as distinct bedding planes, easy cutting into smaller blocks by blasting, and poor gas-holding effect during blasting, the proposed mining method is to use vertical bedding drilling to obtain dam material with better gradation. The technical solution provided in this application first conducts lithological and spatial distribution surveys of metamorphic sandstone quarries using general quarry exploration and control techniques. Then, based on this, it determines whether interlayered weathering exists in the metamorphic sandstone quarry through regional geological genesis analysis. When it is initially determined that interlayered weathering exists in the metamorphic sandstone quarry, a statistical analysis tool for saturated uniaxial compressive strength is introduced for a second determination. When it is determined again that interlayered weathering exists in the metamorphic sandstone quarry, a pre-compaction test process is introduced to conduct a pre-compaction test on the riprap material mined from the metamorphic sandstone quarry and make a final determination. Finally, based on the final determination, the blasting mining method is determined according to the characteristics of the metamorphic sandstone quarry, such as obvious bedding planes, easy cutting into smaller blocks by blasting, and poor gas-holding effect during blasting, in order to obtain dam material with good gradation that meets the required characteristics. The comprehensive identification method proposed in this application can effectively identify the interlayered weathering condition of metamorphic sandstone and determine the mining method, providing a framework for metamorphic sandstone exploration and ensuring the acquisition of high-quality rockfill. This avoids the difficulties and challenges caused by discovering the unique characteristics of rockfill only during the detailed construction design stage, which can hinder engineering construction and safety. Specifically, in the detailed construction design of this application, the S4 step confirms that rockfill dams constructed from rockfill mined from metamorphic sandstone quarries with interlayered weathering exhibit permeability anisotropy, with a vertical permeability coefficient significantly lower than the horizontal permeability coefficient. When constructing such rockfill dams, regional planning should be conducted first, and horizontal drainage measures connected to the vertical drainage measures should be implemented to ensure the dam's permeability stability.

[0021] Accordingly, to maximize the accuracy of identification and facilitate its application in actual exploration work, the general exploration technology for material yards in this application includes the use of surface mapping, drilling, tunneling, and geophysical exploration to explore metamorphic sandstone material yards. Drilling is arranged in a grid pattern, with a combination of adits and drilling. The regional geological genesis analysis in this application includes at least the following aspects: collecting data on the distribution characteristics and changes of strata or rock layers, rocks, and landforms from a macroscopic to a microscopic perspective; collecting data on the geometric morphology of deformation structures and the evolution sequence of deformation and geological events; systematically collecting representative strata or rock layers, rocks, structures, river valleys, and their terrace deposits along the main route, and systematically preparing, identifying, and testing samples; and systematically collecting field measurement data and information on the macroscopic structure and geometric morphology of folds, faults, and joints in the working area, and performing quantitative calculations and analysis by computer and phased matching. More specifically, the preliminary judgment on whether there is interlayered weathering in metamorphic sandstone quarries based on the obtained regional geological genesis analysis data is carried out according to the following requirements: if there are metamorphic sandstone quarries formed by dynamic thermal flow metamorphism and / or thermal contact metamorphism in the associated area, and granitic igneous rocks are interbedded in the metamorphic sandstone, and the metamorphic sandstone rock mass is significantly compressed and deformed due to the intrusion of igneous rock mass and geological structure, and the rock strata have large variations in attitude, then it is preliminarily judged that the metamorphic sandstone quarry has the general characteristics of interlayered weathering.

[0022] Furthermore, the statistical analysis tool for saturated uniaxial compressive strength introduced in this application can be performed in two ways. One method involves preparing core samples in three mutually perpendicular directions (X, Y, and Z), with at least five core samples in each direction. A saturated uniaxial compressive strength test is then conducted on each core sample, and the average and range of the strength in each direction are calculated and denoted as X. 均 X 极 Y 均 Y 极 Z 均 Z 极 Find the coefficients X=X respectively. 极 / X 均 Y=Y 极 / Y 均 Z=Z 极 / Z 均 And calculate the statistical average T. 均 = (X 均 +Y 均 +Z 均 ) / 3,T 极 =max(X 均 Y 均 Z 均 )-min(X 均 Y 均 Z 均 ), calculate the statistical coefficient T=T极 = / T 均 If the coefficients min(X, Y, Z) and T are all greater than 0.8, and most core samples are described as having well-developed or extremely well-developed fractures, numerous fractures, and many interlayers, it indicates that the metamorphic sandstone deposit is heterogeneous and exhibits significant anisotropy. Therefore, it is re-judged that the metamorphic sandstone deposit contains interlayered weathering. Another method is the statistical analysis of saturated uniaxial compressive strength, which is conducted as follows: rock blocks are collected from the exploratory tunnel and numbered X1, X2, ..., X... n For each rock block, at least five core samples were prepared, and saturated uniaxial compressive strength tests were conducted. The average strength and range of each rock block were calculated and denoted as X. 1均 X 1极 X 2均 X 2极 ... X n均 X n极 Find the coefficients X1=X respectively. 1极 / X 1均 X2=X 2极 / X 2均 ... X n =X n极 / X n均 And calculate the statistical average T. 均 = (X 1均 +X 2均 +…+X n均 ) / n,T 极 =max(X 1均 X 2均 ... X n均 )-min(X 1均 X 2均 ... X n均 ), calculate the statistical coefficient T=T 极 = / T 均 If the coefficients min(X1, X2, ..., X...) n Both T and T are greater than 0.8. Most core samples are described as having well-developed or extremely well-developed fractures, numerous fractures, and many interlayers, indicating that the metamorphic sandstone deposit is heterogeneous and exhibits significant anisotropy. Therefore, it is re-evaluated that interlayered weathering exists in the metamorphic sandstone deposit. In this case, the prepared core samples should ensure that the weathering degree and lithology of the samples are consistent, and avoid faults and influence zones. Furthermore, whether a layer of fine powder is produced when the geological hammer is used to strike the surface of the fresh metamorphic sandstone in the exploratory tunnel during sample preparation can serve as supporting evidence of interlayered weathering.

[0023] Accordingly, this application obtained the following three test criteria through pre-compaction tests, and based on these criteria, determined that interlayered weathering exists in the metamorphic sandstone quarry. Blasting tests were conducted according to the general blasting parameters for rockfill, and the gradation of the blasted rockfill was determined. If the content of particles smaller than 5mm was greater than 20%, it was used as test criterion 1. If, after paving and compaction, there is obvious concentration of fine powder on the surface, and after compaction, there is a concentrated and compacted fine powder layer with a thickness of 8-15 cm on the surface, this is used as test criterion 2. The compacted rockfill was excavated along its vertical direction. Visual inspection revealed distinct stratification. Particle size distribution analysis was performed on the surface (finer layer) and the underlying (coarser layer), and seepage, compression, and triaxial tests were conducted. If the difference in the content of particles smaller than 5mm between the finer and coarser layers exceeded 10%, the permeability coefficient differed by more than two orders of magnitude, and there were significant differences in deformation modulus and triaxial mechanical parameters, this was used as test criterion 3. Based on test criteria 1-3, it was determined that interlayered weathering existed in the metamorphic sandstone quarry. Specific requirements for triaxial tests when obtaining identification criteria are as follows: conventional triaxial test studies should be conducted using scaled-down samples based on the characteristics of the S4 rockfill field compaction test. When conventional triaxial tests are insufficient to accurately reflect the true mechanical properties of interlayered weathered and metamorphic sandstone riprap, original gradation tests without scaling up are conducted to reveal its true mechanical characteristics. Parameters are then reasonably obtained to perform dam slope stability calculations and stress-strain calculations considering cumulative wetting and creep, which guide dam design and ensure dam safety.

[0024] In summary, this application provides a method for identifying interlayered weathering in metamorphic sandstone quarries, which includes steps such as regional geological genesis analysis, statistical analysis of saturated uniaxial compressive strength, and pre-compaction tests. It also proposes a research method for the mining and utilization of stone in metamorphic sandstone quarries dominated by interlayered weathering. For metamorphic sandstone quarries that may exhibit interlayered weathering, it is recommended to conduct compaction tests in the early stages, such as feasibility studies, to verify and study the characteristics of excavated stone under fractured weathering conditions, formulate targeted excavation and blasting processes, and arrange layered simulation tests and original aggregate mechanical property tests to obtain more realistic physical and mechanical performance indicators to guide dam material design.

[0025] The technical solution of this application will be further described below through specific embodiments: The technical problem to be solved by this invention is to provide a method for identifying interlayered weathering in metamorphic sandstone quarries, including steps such as regional geological genesis analysis, statistical analysis of saturated uniaxial compressive strength, and pre-compaction test, and to propose a research method for the mining and utilization of stone in metamorphic sandstone quarries dominated by interlayered weathering.

[0026] To solve the above-mentioned technical problems, the technical solution adopted by the present invention includes the following steps: S1. General material yard exploration steps, which are to explore the rockfill material yard by means of surface mapping, drilling, tunneling and geophysical exploration. The exploration is arranged in a grid pattern, and the horizontal tunnel and drilling are combined to determine the lithology and spatial distribution of the material yard. Geophysical exploration includes in-hole television and acoustic wave to determine the integrity of the rock mass. S2. Based on S1, conduct a regional geological genetic analysis. S2-1 collects data on the distribution characteristics and changes of strata, rocks, and landforms, as well as the geometric morphology of deformation structures and the evolution sequence of deformation and geological events from a macroscopic to a microscopic perspective through methods such as typical profile measurements, geological point analysis along the route, and geological mapping.

[0027] S2-2, systematically collects representative strata, rocks, structures, river valleys and their terrace deposits along the main route, and systematically prepares, identifies and tests the samples.

[0028] S2-3: The system collects field measurement data and information on the macroscopic structural geometry of folds, faults, joints, etc. in the working area (complex), and performs quantitative calculation and analysis by microcomputer and phased matching.

[0029] S2-4. Based on the results of S2-1 to S2-3, if the metamorphic sandstone quarry is formed by metamorphic processes such as regional dynamic thermal flow metamorphism and thermal contact metamorphism, and if the metamorphic sandstone contains igneous rocks such as granite, and the metamorphic sandstone is significantly deformed by compression due to the intrusion of igneous rock bodies and geological structures, and the strata exhibit large variations in attitude, then it can be preliminarily judged that the quarry exhibits the general characteristics of interlayered weathering.

[0030] S3. Statistical analysis of saturated uniaxial compressive strength: Prepare core samples drilled in three mutually perpendicular directions (X, Y, and Z), with no fewer than 5 core samples in each direction. Perform saturated uniaxial compressive strength tests and calculate the average and range of strength in each direction, denoted as X. 均 X 极 Y 均 Y 极 Z 均 Z 极 Find the coefficients X=X respectively. 极 / X 均 Y=Y 极 / Y 均 Z=Z 极 / Z 均 And calculate the statistical average T. 均 = (X 均 +Y 均 +Z 均 ) / 3,T 极 =max(X 均 Y 均 Z 均 )-min(X 均 Y 均 Z 均 ), calculate the statistical coefficient T=T 极 = / T 均If the coefficients min (X, Y, Z) and T are all greater than 0.8, and most core samples are described as having well-developed or extremely well-developed fissures, numerous fractures, and many interlayers, it indicates that the metamorphic sandstone quarry is uneven and has obvious anisotropy, and it can be re-judged that there is interlayered weathering in the quarry.

[0031] The above tests can also be conducted by collecting rock blocks inside the cave, numbered X1, X2, ..., X n For each rock block, at least five core samples were prepared, and saturated uniaxial compressive strength tests were conducted. The average strength and range of each rock block were calculated and denoted as X. 1均 X 1极 X 2均 X 2极 ... X n均 X n极 Find the coefficients X1=X respectively. 1极 / X 1均 X2=X 2极 / X 2均 ... X n =X n极 / X n均 And calculate the statistical average T. 均 = (X 1均 +X 2均 +…+X n均 ) / n,T 极 =max(X 1均 X 2均 ... X n均 )-min(X 1均 X 2均 ... X n均 ), calculate the statistical coefficient T=T 极 = / T 均 If the coefficients min(X1, X2, ..., X...) n Both T and T are greater than 0.8. Most core samples are described as having well-developed or extremely well-developed fissures, with many fractures and interlayers, indicating that the metamorphic sandstone quarry is uneven and has obvious anisotropy. Therefore, it can be determined that there is interlayered weathering in the quarry.

[0032] To eliminate interference from other factors on the above test results, the weathering degree and lithology of the samples should be consistent, and faults and influence zones should be avoided.

[0033] In addition, striking the surface of fresh metamorphic sandstone inside the cave with a geological hammer will produce a layer of fine powder, which can serve as evidence of interlayered weathering.

[0034] S4. Preliminary compaction test: Based on the initial assessment in S2 and the secondary assessment in S3, there is a metamorphic sandstone quarry with interlayered weathering. It is recommended to conduct a compaction test during the feasibility study stage. Blasting tests were conducted according to the general blasting parameters for rockfill, and the gradation of the blasted rockfill was determined. If the content of particles smaller than 5mm was greater than 20%, it was used as test criterion 1. If, after paving and compaction, there is obvious concentration of fine powder on the surface, and after compaction, there is a concentrated and compacted fine powder layer with a thickness of 8-15 cm on the surface, this is used as test criterion 2. The compacted rockfill was excavated along the vertical direction. Visual inspection revealed obvious stratification. The finer surface layer and the coarser lower layer were analyzed for particle size distribution. Seepage, compression, and triaxial tests were conducted. If the difference in the content of particles smaller than 5 mm between the finer and coarser layers was greater than 10%, the permeability coefficient difference was more than two orders of magnitude, and the deformation modulus and triaxial test mechanical parameters were also significantly different, these were used as test criteria 3. Based on experimental criteria 1-3, it was determined that interlayered weathering exists in the metamorphic sandstone quarry.

[0035] S5. Mining and utilization methods: Generally, rockfill quarries are mined by vertical hole blasting. However, metamorphic sandstone quarries dominated by interlayer weathering have obvious strata. In addition, the rock mass is cut into smaller blocks by interlayer weathering, resulting in poor gas-holding effect during blasting. Vertical strata drilling should be used to obtain dam material with better gradation.

[0036] According to S4, metamorphic sandstone dominated by interlayered weathering is used as the material source. After the rockfill is compacted, the layers are obvious. The test and calculation analysis should focus on the anisotropic characteristics of its vertical permeability coefficient being significantly smaller than the horizontal permeability coefficient. The utilization area should be rationally planned and the vertical drainage measures should be reasonably set up to connect with the horizontal drainage measures to ensure the seepage stability of the dam.

[0037] Conventional triaxial test studies should be conducted by scaling down the sample preparation based on the characteristics of the S4 rockfill field compaction test.

[0038] Conventional triaxial tests are difficult to accurately reflect the true mechanical properties of interlayered weathered and metamorphic sandstone riprap. It is recommended to conduct unscaled original gradation tests to reveal its true mechanical characteristics, obtain reasonable parameters for dam slope stability calculations and stress-strain calculations considering cumulative wetting and creep, guide dam design and ensure dam safety.

[0039] Furthermore, the impact of interlayer weathering on metamorphic sandstone quarries is global and will persist throughout the entire mining process. It will not lead to a significant improvement in the quality of dam material as the surface layer of the quarry is stripped away. Dam material planning should take this characteristic into account.

[0040] Example 1 One of the quarries for a certain project consists mainly of metamorphic sandstone with highly developed interlayered weathering. Exploration and testing were conducted according to specifications during the feasibility study and detailed construction drawing review stages, but the characteristics of interlayered weathering were not revealed. The following steps were taken to gradually reveal these characteristics.

[0041] (1) According to the analysis, the material yard is a metamorphic sandstone material yard formed by the dynamic thermal flow metamorphism and thermal contact metamorphism in the region. Furthermore, igneous rocks such as granite are interbedded in the metamorphic sandstone. Due to the intrusion of igneous rock bodies and the influence of geological structures, the metamorphic sandstone rock bodies are significantly squeezed and deformed, and the rock strata exhibit large variations in their occurrence.

[0042] (2) The results of the saturated uniaxial compressive strength test of some rock blocks are shown in Table 1. It can be seen that for individual rock blocks, the range / average of the saturated uniaxial compressive strength of most rock blocks is greater than 1.4, and the strength difference between different rock blocks is also very large. The sample descriptions are all about well-developed or extremely well-developed fissures, many fracture phenomena, many interlayers, etc., and it is common for samples to be unavailable. When the bedding plane of fresh metamorphic sandstone is struck with a geological hammer, a layer of fine powder will be produced.

[0043] The results of the saturated uniaxial compressive strength test of rock blocks in a sandwich-type weathered metamorphic sandstone quarry of a certain project are shown in Table 1.

[0044] Table 1

[0045] (3) Extensive blasting tests have shown that the stone gradation is best when drilling and blasting at vertical planes. The gradation test results of the stone after blasting show that the content of coarse and fine particles is relatively high, while the content of medium-sized particles is relatively low, and the content of particles smaller than 5 mm is generally greater than 20%.

[0046] (4) After the stone is laid on the dam face according to the common process of riprap, the layers are obvious when viewed from the vertical surface, and the fine powder layer is concentrated on the surface. After compaction, the concentration of fine powder layer is even more obvious. After the vertical surface is excavated, it is found that the thickness of the concentrated and hardened fine powder layer on the surface after compaction can reach 8 to 15 cm.

[0047] (5) The typical gradation of the concentrated compacted fine powder layer of the surface layer of 8-15cm is shown in Table 2. During the filling period, the maximum particle size is 80mm-20mm, the content of particles with a diameter <5mm is 30.7%-61.5%, and the permeability coefficient k20=8.07×10-4cm / s. The design requirement gradation is shown in Table 3. After filling and compaction, the particle gradation after removing the concentrated compacted fine powder layer is between the upper envelope and the average line in Table 3. The content of particles with a diameter <5mm is 17%-25%, and the permeability coefficient k20>1×10-2cm / s. The combined permeability test shows that the vertical permeability coefficient is significantly smaller than the horizontal permeability coefficient, and the permeability anisotropy is very obvious. Therefore, a plum blossom-shaped vertical permeable body with a spacing of 30m-40m and a diameter of 5m was set up, and fresh high-quality materials were selected for filling.

[0048] The results of physical tests on the fine powder layer after compaction of the dam material are shown in Table 2.

[0049] Table 2

[0050] The results of physical tests on the non-fine powder layer after dam material compaction are shown in Table 3.

[0051] Table 3 (6) The results of the conventional triaxial test are shown in Table 4. According to the design requirements, the riprap... Its properties should be significantly better than those of rubble. However, the experimental parameters showed that the riprap material Superior to rubble This situation is clearly unreasonable; that is, conventional triaxial tests cannot reflect the true mechanical properties of dam materials. Table 5 shows the test results simulating the stratification after on-site filling. It can be seen that the test parameters are significantly lower than those without considering stratification. Therefore, it is recommended that conventional triaxial tests should simulate the stratification of the filling.

[0052] Duncan model parameters for conventional triaxial tests of dam materials (without separate simulation of the slab layer).

[0053] Table 4

[0054] Duncan model parameters for conventional triaxial tests of dam materials (simulating slab layer).

[0055] Table 5

[0056] (7) Due to the weathering and cutting of the interlayered metamorphic sandstone, the maximum particle size of the blasted riprap is mostly less than 60cm. Therefore, the project is conducting compression tests and direct shear tests on the original graded riprap with a diameter of 3m in accordance with the specifications, in order to obtain more realistic physical and mechanical parameters of the interlayered weathered metamorphic sandstone riprap, so as to carry out relevant calculation and analysis research.

[0057] (8) The excavation slope of the material yard is nearly 500m high, but interlayer weathering has always existed. The characteristics of the lower dam material are not significantly different from those of the upper dam material, which brings great challenges to the design of the dam structure.

Claims

1. A method for identifying interlayered weathering in metamorphic sandstone quarries, characterized in that: The identification method described above identifies interlayered weathering in metamorphic sandstone quarries and proposes mining and utilization methods through the following steps. S1. Use general exploration techniques for material yards to determine the lithology and spatial distribution of metamorphic sandstone material yards. S2. Based on S1, first conduct a regional geological genesis analysis, and then, based on the analysis conclusions, preliminarily determine whether there is interlayered weathering in the metamorphic sandstone quarry. S3. When it is initially determined that interlayered weathering exists in the metamorphic sandstone quarry, a saturated uniaxial compressive strength statistical analysis tool is introduced to conduct saturated uniaxial compressive strength tests on the samples and analyze the test statistical data. Based on the analysis results, a secondary determination is made as to whether interlayered weathering exists in the metamorphic sandstone quarry. S4. When it is determined again that interlayered weathering exists in the metamorphic sandstone quarry, a pre-compaction test process is introduced to conduct a pre-compaction test on the riprap material mined from the metamorphic sandstone quarry. Based on the pre-compaction test data, the interlayered weathering status of the metamorphic sandstone quarry is finally determined. S5. Based on the characteristics of metamorphic sandstone quarries with interlayered weathering, such as distinct bedding planes, easy cutting into smaller blocks by blasting, and poor gas-holding effect during blasting, the proposed mining method is to use vertical bedding drilling to obtain dam material with better gradation.

2. The method for identifying interlayered weathering in metamorphic sandstone quarries according to claim 1, characterized in that: Using the S4 step, it was confirmed that rockfill dams constructed from quarried metamorphic sandstone with interlayered weathering exhibit permeability anisotropy, with the vertical permeability coefficient being significantly lower than the horizontal permeability coefficient. When constructing such rockfill dams, regional planning should be carried out first, and horizontal drainage measures that are connected to the vertical drainage measures should be set up to ensure the seepage stability of the dam.

3. The method for identifying interlayered weathering in metamorphic sandstone quarries according to claim 1 or 2, characterized in that: Common exploration techniques for material yards include using surface mapping, drilling, tunneling, and geophysical exploration to explore metamorphic sandstone material yards. Drilling is arranged in a grid pattern, and adits and drilling are combined.

4. The method for identifying interlayered weathering in metamorphic sandstone quarries according to claim 1 or 2, characterized in that: Regional geological genesis analysis includes at least the following aspects: collecting data on the distribution characteristics and changes of strata or rock layers, rocks, and landforms from macroscopic to microscopic perspectives; collecting data on the geometric morphology of deformation structures and the evolution sequence of deformation and geological events; systematically collecting representative strata or rock layers, rocks, structures, river valleys and their terrace deposits along the main route, and systematically preparing, identifying and testing samples; and systematically collecting field measurement data and information on the macroscopic structure and geometric morphology of folds, faults and joints in the work area, and performing quantitative calculations and analysis by computer and phased matching.

5. The method for identifying interlayered weathering in metamorphic sandstone quarries according to claim 4, characterized in that: The preliminary judgment on whether there is interlayered weathering in metamorphic sandstone quarries based on the obtained regional geological genesis analysis data is carried out according to the following requirements: If there are metamorphic sandstone quarries formed by dynamic thermal flow metamorphism and / or thermal contact metamorphism in the surrounding area, and granitic igneous rocks are interbedded in the metamorphic sandstone, and the metamorphic sandstone rock mass is significantly compressed and deformed due to the intrusion of igneous rock mass and geological structure, and the rock strata have large variations in attitude, then it is preliminarily judged that there are general characteristics of interlayered weathering in metamorphic sandstone quarries.

6. The method for identifying interlayered weathering in metamorphic sandstone quarries according to claim 1, characterized in that: The statistical analysis of saturated uniaxial compressive strength was performed according to the following steps: First, core samples were prepared in three mutually perpendicular directions (X, Y, and Z), with at least five core samples in each direction. Saturated uniaxial compressive strength tests were then conducted on each core sample, and the average and range of the strength in each direction were calculated, denoted as X. 均 X 极 Y 均 Y 极 Z 均 Z 极 Find the coefficients X=X respectively. 极 / X 均 Y=Y 极 / Y 均 Z=Z 极 / Z 均 And calculate the statistical average T. 均 = (X 均 +Y 均 +Z 均 ) / 3,T 极 =max(X 均 Y 均 Z 均 )-min(X 均 Y 均 Z 均 ), calculate the statistical coefficient T=T 极 = / T 均 If the coefficients min(X, Y, Z) and T are all greater than 0.8, and most core samples are described as having well-developed or extremely well-developed fissures, with many fractures and interlayers, it indicates that the metamorphic sandstone field is uneven and has obvious anisotropy. Therefore, it is re-judged that there is interlayered weathering in the metamorphic sandstone field.

7. The method for identifying interlayered weathering in metamorphic sandstone quarries according to claim 1, characterized in that: The statistical analysis of saturated uniaxial compressive strength was carried out according to the following steps: rock blocks were collected from the cavern and numbered X1, X2, ..., X... n For each rock block, at least five core samples were prepared, and saturated uniaxial compressive strength tests were conducted. The average strength and range of each rock block were calculated and denoted as X. 1均 X 1极 X 2均 X 2极 ... X n均 X n极 Find the coefficients X1=X respectively. 1极 / X 1均 X2=X 2极 / X 2均 ... X n =X n极 / X n均 And calculate the statistical average T. 均 = (X 1均 +X 2均 +…+X n均 ) / n,T 极 =max(X 1均 X 2均 ... X n均 )-min(X 1均 X 2均 ... X n均 ), calculate the statistical coefficient T=T 极 = / T 均 If the coefficients min(X1, X2, ..., X...) n Both T and T are greater than 0.

8. Most core samples are described as having well-developed or extremely well-developed fissures, with many fractures and interlayers, indicating that the metamorphic sandstone field is uneven and has obvious anisotropy. Therefore, it is re-judged that there is interlayered weathering in the metamorphic sandstone field.

8. The method for identifying interlayered weathering in metamorphic sandstone quarries according to claim 6 or 7, characterized in that: The prepared core samples should ensure that the weathering degree and lithology of the samples are consistent, and avoid faults and influence zones; in addition, whether a layer of fine powder is produced when the geological hammer is used to strike the surface of fresh metamorphic sandstone in the tunnel during sample preparation can be used as evidence of interlayer weathering.

9. The method for identifying interlayered weathering in metamorphic sandstone quarries according to claim 8, characterized in that: The following three test criteria were obtained through pre-compaction tests, and based on these criteria, it was determined that interlayered weathering exists in the metamorphic sandstone quarry. Blasting tests were conducted according to the general blasting parameters for rockfill, and the gradation of the blasted rockfill was determined. If the content of particles smaller than 5mm was greater than 20%, it was used as test criterion 1. If, after paving and compaction, there is obvious concentration of fine powder on the surface, and after compaction, there is a concentrated and compacted fine powder layer with a thickness of 8-15 cm on the surface, this is used as test criterion 2. The compacted rockfill was excavated along the vertical direction. Visual inspection revealed obvious stratification. The particle size distribution of the finer surface layer and the coarser lower layer was analyzed separately, and seepage, compression, and triaxial tests were carried out. If the difference in the content of particles smaller than 5 mm between the finer and coarser layers was greater than 10%, the permeability coefficient difference was more than two orders of magnitude, and there were also significant differences in the deformation modulus and triaxial test mechanical parameters, these were used as test criterion 3.

10. The method for identifying interlayered weathering in metamorphic sandstone quarries according to claim 9, characterized in that: Conventional triaxial test studies should be conducted by scaling up the samples and carrying out the tests based on the characteristics of the S4 rockfill field compaction test. When conventional triaxial tests are insufficient to accurately reflect the true mechanical properties of interlayered weathered and metamorphic sandstone riprap, original gradation tests without scaling up are conducted to reveal its true mechanical characteristics. Parameters are then reasonably obtained to perform dam slope stability calculations and stress-strain calculations considering cumulative wetting and creep, which guide dam design and ensure dam safety.

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