Characterization method of urban shallow underground paleochannel based on drilling and sedimentation analysis

Abstract

The method for characterizing shallow underground ancient river channels in cities based on drilling and sedimentation analysis specifically includes the following steps: (i) preliminary analysis and speculation of the possible distribution patterns and areas of shallow underground ancient river channels in cities; (ii) isochronous high-precision stratigraphic comparison of the entire area of ​​shallow underground ancient river channels in cities; (iii) comprehensive interpretation of the sedimentary patterns and scales of ancient river channels in typical areas and major construction areas through dense geological drilling, and clarifying the quantitative model of a single river channel; (iv) clarifying the accurate distribution and characteristics of urban underground ancient river channels; (v) targeted stratification of the development depth of urban underground space to guide the development of underground space. The present invention can make full use of the engineering geological survey drilling data at various stages of urban construction and planning to specifically characterize urban underground ancient river channels. At the same time, on this basis, it can propose planning suggestions for different functional types based on the distribution of ancient river channels, which can effectively guide the planning and utilization of underground space.

Description

Technical Field

[0001] The present invention relates to the field of urban shallow underground space planning and analysis, and in particular to a method for characterizing urban shallow underground ancient river channels based on drilling and sedimentation analysis. Background Art

[0002] Human civilization and urban development are often closely related to rivers. The ancient river channels that were inherited during the geological history period are buried underground in the city. Due to its own vertical and longitudinal evolution characteristics, the distribution of poor underground rock and soil in the city is relatively complex. The characteristics of the river channel itself cause the distribution of poor underground rock and soil in the city to be relatively complex. However, given the prominent contradictions in engineering geological issues such as the sensitivity and fragility of the ancient river channel distribution area in the process of underground space development, and the increasingly important role of the ancient river channel in controlling groundwater distribution as a natural permeable channel, it is urgent to understand its spatial distribution characteristics and engineering characteristics. On the other hand, with the continuous advancement of urbanization, society has not only achieved rapid economic development, but also profound changes have taken place in towns and urban land use, and urban hardening has been fully rolled out. The continuous reduction of outcrops and the fragmentation of survey data have become huge difficulties faced by urban geological surveys in old and new urban areas, and traditional working methods have shown certain limitations.

[0003] Miall, an American fluvial expert, proposed the concept of sedimentary architecture in 1985, which mainly refers to the geometric shape, size, direction and mutual configuration relationship of the internal components of the sedimentary geological body. The quantitative description of various sedimentary architecture units through the idea of ​​hierarchical analysis can effectively represent the heterogeneity of underground geological bodies, evaluate the connectivity of sand units of different levels, and guide the analysis of underground fluid flow, achieving good application results.

[0004] Therefore, the sedimentary architecture method provides a new approach for urban geological surveys in old and newly built urban areas. Summary of the invention

[0005] The purpose of the present invention is to provide a method for characterizing urban shallow underground ancient river channels based on drilling and sedimentation analysis. The present invention can make full use of the engineering geological survey drilling data in various stages of urban construction and planning to specifically characterize urban underground ancient river channels, and provide a reference for the study of urban underground space with developed underground ancient river channels. At the same time, on this basis, planning suggestions for different functional types can be put forward according to the distribution of ancient river channels, which can effectively guide the planning and utilization of underground space.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] The method for characterizing urban shallow underground paleo-river channels based on drilling and sedimentation analysis specifically includes the following steps:

[0008] (I) With reference to the inherited modern sediments on the surface, based on the current river channel pattern and distribution characteristics and hydrodynamic conditions, a preliminary analysis is made to infer the possible distribution pattern and area of ​​the shallow underground ancient river channel in the city;

[0009] (ii) Conduct isochronous high-precision stratigraphic comparison of the entire shallow underground ancient river channel in the city;

[0010] (iii) Based on the drilling work and shallow geophysical data in step (i) and previous regional sedimentary facies research, using sedimentary architecture theory and methods, select typical areas and major construction areas, densely arrange geological boreholes according to the predicted possible paleo-river channel scale, conduct a comprehensive sedimentary interpretation of the paleo-river channel style and scale in typical areas and major construction areas through dense geological drilling, and clarify the quantitative model of a single river channel;

[0011] (iv) Clarify the exact distribution and characteristics of ancient underground river channels in cities;

[0012] (V) Based on the accurate distribution and characteristics of ancient underground river channels in cities and the stages of development of vertical ancient river channels, the development depth of urban underground space is stratified in a targeted manner, and the geotechnical characteristics of the developed and undeveloped locations of ancient river channels are analyzed. Based on their engineering mechanics characteristics, suggestions and avoidance suggestions for engineering development are put forward to guide the development of underground space.

[0013] The specific content of step (ii) is as follows: Stratigraphic correlation is the basis for the detailed depiction of ancient river channels. In order to ensure the detailed correlation of river facies strata, the stratigraphic correlation method and principle of "marker layer control, cycle correlation, hierarchical constraint, and three-dimensional closure" are adopted:

[0014] (1) Marking layer control

[0015] Marker layers refer to strata with wide distribution, special lithology, stable thickness and isochronous characteristics within a certain range. Marker layers are used to control and constrain strata.

[0016] (2) Cycle comparison

[0017] Cycle correlation is to compare strata according to the lithology and geophysical characteristics of the strata based on the base level cycle division, and according to the sedimentary cycle, rather than simply comparing lithology and grain size.

[0018] (3) Hierarchical constraints

[0019] Under the control of the marker layer, the sedimentary cycle characteristics of each sub-level stratum of a single-stage paleo-valley-single-stage paleo-channel are used to compare the strata step by step. "Grading constraints" means establishing a stratigraphic framework according to different levels, and comparing the strata step by step from high to low levels.

[0020] (4) Three-dimensional closure

[0021] Three-dimensional closure is to close the skeleton profile of the whole area in three-dimensional space to avoid the problem of different layers and different river channels being linked during stratigraphic correlation, so as to establish a truly isochronous stratigraphic framework. The specific methods include: ① Bridge-type correlation, establishing several intersecting correlation profiles in both the direction of the provenance and the direction of the provenance; ② Triangulation network correlation, connecting the boreholes that are not on the profile with the boreholes on the profile and the boreholes between the profiles into a triangulation network for systematic correlation and closure.

[0022] The specific contents of step (iii) are as follows:

[0023] (1) Clarify the accuracy of the dissection: The accuracy of the dissection is controlled by the complexity of the underground and the actual demand for the development and utilization of underground space, including two levels: single-period ancient river valley and single-period ancient river channel:

[0024] Single-period ancient river valley refers specifically to the complex of multiple-period ancient river channels. At present, the degree of urban geological underground dissection is mostly concentrated on this scale. Although the research on its distribution characteristics can basically meet the needs of the urban planning stage, when it comes to a specific area or project development, its characterization degree is far from meeting the requirements for understanding the distribution of underground rock and soil bodies;

[0025] A single-stage ancient river channel is a sedimentary river system within a certain period of time within the same ancient river valley. In the development of regional underground space, it is mainly for medium- and long-term underground tracks and motor vehicle lanes. The gravel developed in the ancient river channel is likely to have an adverse effect on shield excavation, and the work accuracy is concentrated at the level of a single-stage river channel;

[0026] (2) Select a typical representative area and arrange dense drilling to conduct underground river channel dissection. Summarize the identification marks of ancient river channel boundaries, the superposition pattern of river channel units and the quantitative scale suitable for the study area. Under the guidance of the sedimentary model, follow the idea of ​​"vertical periodization, direction finding and demarcation, and horizontal section interaction" to dissect the ancient river channel in the whole area, summarize the single-period ancient river channel and its distribution characteristics, and obtain its distribution pattern and quantitative scale to guide the dissection of ancient river channels in neighboring areas or similar sedimentary environments.

[0027] The specific steps of "vertical staging, direction finding and demarcation, and horizontal section interaction" in step (iii) are:

[0028] Ⅰ. Vertical stage division, using landmark layers within stratigraphic units to divide anatomical areas;

[0029] II. Direction finding and demarcation: Identify the boundary of a single river channel through river channel identification marks, including the following identification features:

[0030] ① The appearance of river mud

[0031] Interchannel mud is mud deposited in the low-lying areas of two single diverging channels, and the interior of the same channel is continuous sand deposits. Therefore, the appearance of interchannel mud means the existence of a boundary between single channels and is an accurate and reliable identification mark for identifying a single channel.

[0032] ② The emergence of elevation difference of river bottom

[0033] The river channel deposits are "flat on top and convex on the bottom", and the river channels formed in different periods often have elevation differences. Therefore, after being leveled with the marker layer, when there is an elevation difference on the bottom of the sand bodies of two adjacent drilled holes, it can be used as a lateral identification mark to judge the deposition of different river channels. However, due to the error of stratigraphic comparison, this identification mark cannot be used alone, and needs to be combined with a variety of identification marks for comprehensive analysis;

[0034] ③ Differences in river scale

[0035] Due to the combined influence of provenance supply conditions, initial hydrodynamic conditions, and sedimentary paleo-geomorphology, the thickness and width of sediments in different river channels, as well as the grain size of sediments, are significantly different. The boundaries of these differences can be distinguished along the direction of the provenance, thus different river channels can be divided.

[0036] III. Flat-section interaction

[0037] In the process of sedimentary configuration dissection, we cannot rely solely on single river channel identification, but need to combine it with planar sedimentary microstructures. Under the guidance of sedimentary patterns, the plane and section interact and combine boundaries.

[0038] The specific content of step (iv) is as follows: through the main section to carry out controlled drilling work, combined with the analogy of drilling holes to reveal the strata in major engineering areas, the relevant parameters and sedimentary patterns are extended to the whole basin, the distribution range, material composition, and sensitive geological elements of the ancient river channels in the area are clarified, and repeated comparisons are made vertically and horizontally from point to line, from line to surface, and from surface to volume until the three-dimensional closure of urban areas with similar sedimentary characteristics is achieved.

[0039] Compared with the prior art, the present invention has outstanding substantive features and remarkable progress. Specifically, the present invention can make full use of the engineering geological survey drilling data in various stages of urban construction and planning to specifically depict urban underground ancient river channels, and provide reference for the study of urban underground space with developed underground ancient river channels. At the same time, on this basis, planning suggestions for different functional types can be put forward according to the distribution of ancient river channels, which can effectively guide the planning and utilization of underground space. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a technical route frame diagram of the present invention. DETAILED DESCRIPTION

[0041] The embodiments of the present invention are further described below with reference to the accompanying drawings.

[0042] like Figure 1 As shown in the figure, the method for characterizing the shallow underground paleo-river channel in an urban area based on drilling and sedimentation analysis specifically includes the following steps:

[0043] (I) With reference to the inherited modern sediments on the surface, based on the current river channel pattern and distribution characteristics and hydrodynamic conditions, a preliminary analysis is made to infer the possible distribution pattern and area of ​​the shallow underground ancient river channel in the city;

[0044] (ii) Conduct isochronous high-precision stratigraphic comparison of the entire shallow underground ancient river channel in the city;

[0045] (iii) Based on the drilling work and shallow geophysical data in step (i) and previous regional sedimentary facies research, using sedimentary architecture theory and methods, select typical areas and major construction areas, densely arrange geological boreholes according to the predicted possible paleo-river channel scale, conduct a comprehensive sedimentary interpretation of the paleo-river channel style and scale in typical areas and major construction areas through dense geological drilling, and clarify the quantitative model of a single river channel;

[0046] (iv) Clarify the exact distribution and characteristics of ancient underground river channels in cities;

[0047] (V) Based on the accurate distribution and characteristics of ancient underground river channels in cities and the stages of development of vertical ancient river channels, the development depth of urban underground space is stratified in a targeted manner, and the geotechnical characteristics of the developed and undeveloped locations of ancient river channels are analyzed. Based on their engineering mechanics characteristics, suggestions and avoidance suggestions for engineering development are put forward to guide the development of underground space.

[0048] The specific content of step (ii) is as follows: Stratigraphic correlation is the basis for the detailed depiction of ancient river channels. In order to ensure the detailed correlation of river facies strata, the stratigraphic correlation method and principle of "marker layer control, cycle correlation, hierarchical constraint, and three-dimensional closure" are adopted:

[0049] (1) Marking layer control

[0050] Marker layers refer to strata with wide distribution, special lithology, stable thickness and isochronous characteristics within a certain range. Marker layers are used to control and constrain strata.

[0051] (2) Cycle comparison

[0052] Cycle correlation is to compare strata according to the lithology and geophysical characteristics of the strata based on the base level cycle division, and according to the sedimentary cycle, rather than simply comparing lithology and grain size.

[0053] (3) Hierarchical constraints

[0054] Under the control of the marker layer, the sedimentary cycle characteristics of each sub-level stratum of a single-stage paleo-valley-single-stage paleo-channel are used to compare the strata step by step. "Grading constraints" means establishing a stratigraphic framework according to different levels, and comparing the strata step by step from high to low levels.

[0055] (4) Three-dimensional closure

[0056] Three-dimensional closure is to close the skeleton profile of the whole area in three-dimensional space to avoid the problem of different layers and different river channels being linked during stratigraphic correlation, so as to establish a truly isochronous stratigraphic framework. The specific methods include: ① Bridge-type correlation, establishing several intersecting correlation profiles in both the direction of the provenance and the direction of the provenance; ② Triangulation network correlation, connecting the boreholes that are not on the profile with the boreholes on the profile and the boreholes between the profiles into a triangulation network for systematic correlation and closure.

[0057] The specific contents of step (iii) are as follows:

[0058] (1) Clarify the accuracy of the dissection: The accuracy of the dissection is controlled by the complexity of the underground and the actual demand for the development and utilization of underground space, including two levels: single-period ancient river valley and single-period ancient river channel:

[0059] Single-period ancient river valley refers specifically to the complex of multiple-period ancient river channels. At present, the degree of urban geological underground dissection is mostly concentrated on this scale. Although the research on its distribution characteristics can basically meet the needs of the urban planning stage, when it comes to a specific area or project development, its characterization degree is far from meeting the requirements for understanding the distribution of underground rock and soil bodies;

[0060] A single-stage ancient river channel is a sedimentary river system within a certain period of time within the same ancient river valley. In the development of regional underground space, it is mainly for medium- and long-term underground tracks and motor vehicle lanes. The gravel developed in the ancient river channel is likely to have an adverse effect on shield excavation, and the work accuracy is concentrated at the level of a single-stage river channel;

[0061] (2) Select a typical representative area and arrange dense drilling to conduct underground river channel dissection. Summarize the identification marks of ancient river channel boundaries, the superposition pattern of river channel units and the quantitative scale suitable for the study area. Under the guidance of the sedimentary model, follow the idea of ​​"vertical periodization, direction finding and demarcation, and horizontal section interaction" to dissect the ancient river channel in the whole area, summarize the single-period ancient river channel and its distribution characteristics, and obtain its distribution pattern and quantitative scale to guide the dissection of ancient river channels in neighboring areas or similar sedimentary environments.

[0062] The specific steps of "vertical staging, direction finding and demarcation, and horizontal section interaction" in step (iii) are:

[0063] Ⅰ. Vertical stage division, using landmark layers within stratigraphic units to divide anatomical areas;

[0064] II. Direction finding and demarcation: Identify the boundary of a single river channel through river channel identification marks, including the following identification features:

[0065] ① The appearance of river mud

[0066] Interchannel mud is mud deposited in the low-lying areas of two single diverging channels, and the interior of the same channel is continuous sand deposits. Therefore, the appearance of interchannel mud means the existence of a boundary between single channels and is an accurate and reliable identification mark for identifying a single channel.

[0067] ② The emergence of elevation difference of river bottom

[0068] The river channel deposits are "flat on top and convex on the bottom", and the river channels formed in different periods often have elevation differences. Therefore, after being leveled with the marker layer, when there is an elevation difference on the bottom of the sand bodies of two adjacent drilled holes, it can be used as a lateral identification mark to judge the deposition of different river channels. However, due to the error of stratigraphic comparison, this identification mark cannot be used alone, and needs to be combined with a variety of identification marks for comprehensive analysis;

[0069] ③ Differences in river scale

[0070] Due to the combined influence of provenance supply conditions, initial hydrodynamic conditions, and sedimentary paleo-geomorphology, the thickness and width of sediments in different river channels, as well as the grain size of sediments, are significantly different. The boundaries of these differences can be distinguished along the direction of the provenance, thus different river channels can be divided.

[0071] III. Flat-section interaction

[0072] In the process of sinkhole configuration dissection, we cannot rely solely on single river channel identification, but need to combine it with planar sedimentary microstructures. Under the guidance of sedimentary patterns, the plane and section interact and combine boundaries.

[0073] The specific content of step (iv) is as follows: through the main section to carry out controlled drilling work, combined with the analogy of drilling holes to reveal the strata in major engineering areas, the relevant parameters and sedimentary patterns are extended to the whole basin, the distribution range, material composition, and sensitive geological elements of the ancient river channels in the area are clarified, and repeated comparisons are made vertically and horizontally from point to line, from line to surface, and from surface to volume until the three-dimensional closure of urban areas with similar sedimentary characteristics is achieved.

[0074] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for characterizing urban shallow underground paleo-river channels based on drilling and sedimentation analysis, characterized by: The specific steps include: (I) With reference to the inherited modern sediments on the surface, based on the current river channel pattern and distribution characteristics and hydrodynamic conditions, a preliminary analysis is made to infer the possible distribution pattern and area of ​​the shallow underground ancient river channel in the city; (ii) Conduct isochronous high-precision stratigraphic comparison of the entire shallow underground ancient river channel in the city; (III) Based on the drilling work and shallow geophysical data in step (I) and previous regional sedimentary studies, using sedimentary architecture theory and methods, select typical areas and major construction areas, densely arrange geological boreholes according to the predicted possible paleo-river channel scale, conduct a comprehensive sedimentary interpretation of the paleo-river channel style and scale in typical areas and major construction areas through dense geological drilling, and clarify the quantitative model of a single river channel; (iv) Clarify the exact distribution and characteristics of ancient underground river channels in cities; (V) Based on the accurate distribution and characteristics of ancient underground river channels in cities and the stages of development of vertical ancient river channels, the development depth of urban underground space is stratified in a targeted manner, and the geotechnical characteristics of the developed and undeveloped locations of ancient river channels are analyzed. Based on their engineering mechanics characteristics, suggestions and avoidance suggestions for engineering development are put forward to guide the development of underground space.

2. The method for characterizing an urban shallow underground ancient river channel based on drilling and sedimentation analysis according to claim 1 is characterized in that: The specific content of step (ii) is as follows: Stratigraphic correlation is the basis for the detailed depiction of ancient river channels. In order to ensure the detailed correlation of river facies strata, the stratigraphic correlation method and principle of "marker layer control, cycle correlation, hierarchical constraint, and three-dimensional closure" are adopted: (1) Marking layer control Marker layers refer to strata with wide distribution, special lithology, stable thickness and isochronous characteristics within a certain range. Marker layers are used to control and constrain strata. (2) Cycle comparison Cycle correlation is to compare strata according to the lithology and geophysical characteristics of the strata based on the base level cycle division, and according to the sedimentary cycle, rather than simply comparing lithology and grain size. (3) Hierarchical constraints Under the control of the marker layer, the sedimentary cycle characteristics of each sub-level stratum of the single-stage paleo-valley-single-stage paleo-channel are used to compare the strata step by step. "Grading constraint" means to establish a stratigraphic framework according to different levels, and to compare the strata step by step from high level to low level. (4) Three-dimensional closure Three-dimensional closure is to close the skeleton profile of the whole area in three-dimensional space to avoid the problem of different layers and different river channels being linked during stratigraphic correlation, so as to establish a truly isochronous stratigraphic framework. The specific methods include: ① Bridge-type correlation, establishing several intersecting correlation profiles in both the direction of the provenance and the direction of the provenance; ② Triangulation network correlation, connecting the boreholes that are not on the profile with the boreholes on the profile and the boreholes between the profiles into a triangulation network for systematic correlation and closure.

3. The method for characterizing an urban shallow underground ancient river channel based on drilling and sedimentation analysis according to claim 1 is characterized in that: The specific contents of step (iii) are as follows: (1) Clarify the accuracy of the dissection: The accuracy of the dissection is controlled by the complexity of the underground and the actual demand for the development and utilization of underground space, including two levels: single-period ancient river valley and single-period ancient river channel: Single-period ancient river valley refers specifically to the complex of multiple-period ancient river channels. At present, the degree of urban geological underground dissection is mostly concentrated on this scale. Although the research on its distribution characteristics can basically meet the needs of the urban planning stage, when it comes to a specific area or project development, its characterization degree is far from meeting the requirements for understanding the distribution of underground rock and soil bodies; A single-stage ancient river channel is a sedimentary river system within a certain period of time within the same ancient river valley. In the development of regional underground space, it is mainly for medium- and long-term underground tracks and motor vehicle lanes. The gravel developed in the ancient river channel is likely to have an adverse effect on shield excavation, and the work accuracy is concentrated at the level of a single-stage river channel; (2) Select typical representative areas and arrange dense drilling to conduct underground river channel dissection. Summarize the identification marks of paleochannel boundaries, the superposition pattern and quantitative scale of channel units suitable for the study area. Under the guidance of the sedimentary model, follow the idea of ​​"vertical periodization, direction finding and demarcation, and horizontal section interaction" to dissect the paleochannel of the entire area, summarize the single-period paleochannel and its distribution characteristics, and obtain its distribution pattern and quantitative scale to guide the dissection of paleochannels in neighboring areas or similar sedimentary environments.

4. The method for characterizing an urban shallow underground ancient river channel based on drilling and sedimentation analysis according to claim 3 is characterized in that: The specific steps of "vertical staging, direction finding and demarcation, and horizontal section interaction" in step (iii) are: Ⅰ. Vertical staging: the anatomical areas are divided by using landmark layers within the stratigraphic units; II. Direction finding and demarcation: Identify the boundary of a single river channel through river channel identification marks, including the following identification features: ① The appearance of river mud Interchannel mud is mud deposited in the low-lying areas of two single diverging channels, and the interior of the same channel is continuous sand deposits. Therefore, the appearance of interchannel mud means the existence of a boundary between single channels and is an accurate and reliable identification mark for identifying a single channel. ② The emergence of elevation difference of river bottom The river channel deposits are "flat on top and convex on the bottom". The river channels formed in different periods often have elevation differences. Therefore, after being leveled with the marker layer, when there is an elevation difference on the bottom of the sand bodies of two adjacent drilled wells, it can be used as a lateral identification mark to judge the deposition of different river channels. However, due to the error of stratigraphic comparison, this identification mark cannot be used alone and needs to be combined with multiple identification marks for comprehensive analysis. ③ Differences in river scale Due to the combined influence of provenance supply conditions, initial hydrodynamic conditions, and sedimentary paleo-geomorphology, the thickness and width of sediments in different river channels, as well as the grain size of sediments, are significantly different. The boundaries of these differences can be distinguished along the direction of the provenance, thus different river channels can be divided. III. Flat-section interaction In the process of sedimentary configuration dissection, we cannot rely solely on single river channel identification, but need to combine it with planar sedimentary microstructures. Under the guidance of sedimentary patterns, the plane and section interact and combine boundaries.

5. The method for characterizing an urban shallow underground ancient river channel based on drilling and sedimentation analysis according to claim 1 is characterized in that: The specific content of step (iv) is as follows: through the main section to carry out controlled drilling work, combined with the analogy of drilling holes to reveal the strata in major engineering areas, the relevant parameters and sedimentary patterns are extended to the whole basin, the distribution range, material composition, and sensitive geological elements of the ancient river channels in the area are clarified, and repeated comparisons are made vertically and horizontally from point to line, from line to surface, and from surface to volume until the three-dimensional closure of urban areas with similar sedimentary characteristics is achieved.

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