A method for monitoring and early warning of riverbed scour risk in subway tunnel areas
By analyzing the evolution of the riverbed and identifying risk sources in the river section of the tunnel, and combining high-precision monitoring technology with risk level classification, the problem of monitoring and early warning of riverbed scouring and deformation in the tunnel area of major rivers has been solved, and effective early warning and management of tunnel safety has been achieved.
Patent Information
- Application Number
- CN202311173005.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-12
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2043-09-12
AI Technical Summary
The lack of existing technologies for monitoring and early warning methods for riverbed scouring and deformation in tunnels crossing major rivers means that tunnel operation and management units are unable to effectively address the safety threats posed by riverbed erosion to rail transit projects.
By analyzing the riverbed evolution of the river section under the tunnel, the main sources of scour risk were identified, a riverbed deformation monitoring plan was formulated, the location of the control section for riverbed deformation monitoring was determined, and a classification and early warning plan for riverbed scour risk levels was proposed. RTK and multibeam echo sounding systems were used for monitoring with an accuracy of no less than 1:500. The location of the control section was determined by combining the critical slope of the natural scour pit in the riverbed and the minimum thickness of the overburden layer at the top of the tunnel, and the risk was classified into four levels for early warning.
Effective monitoring and early warning methods for riverbed scour risks in river-crossing tunnel areas are provided to ensure safe tunnel operation. Through regular monitoring and early warning mechanisms, timely responses to changes in riverbed scour are made to ensure the stability and safety of the tunnel structure.
Smart Images
Figure CN117027952B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for monitoring and early warning of riverbed scour risks in subway tunnel areas, belonging to the field of water conservancy and hydropower engineering technology. Background Technology
[0002] The main structure of the river-crossing tunnel in the Hekou urban rail transit project is buried under the riverbed. Complex runoff, floods, tidal flows, local hydraulic phenomena of nearby river-related structures, and human activities often lead to changes in the riverbed due to scouring and deposition. This, in turn, alters the thickness of the overburden layer above the tunnel. If the riverbed continues to erode and the overburden layer thickness falls below the minimum safe overburden thickness, the tunnel structure's anti-buoyancy stability may fail to meet requirements, thus affecting the operational safety of the rail transit project. Therefore, it is crucial to pay attention to and prevent the hazards posed by riverbed erosion to the river-crossing tunnel, and monitoring and early warning of riverbed scouring risks in the tunnel area are essential.
[0003] Currently, riverbed monitoring in tunnels crossing major rivers mainly focuses on analyzing changes in riverbed erosion and deposition patterns and the thickness of the overburden at the top of the tunnels. There is no monitoring and early warning method for the risk of riverbed erosion and deformation in tunnel areas, which prevents tunnel operation and management units from effectively responding to early warnings based on the monitoring results of riverbeds in tunnel areas. Summary of the Invention
[0004] To address the shortcomings of existing technologies, this invention provides a method for monitoring and early warning of riverbed scour risks in subway tunnel areas, comprising the following steps:
[0005] (1) Conduct riverbed evolution analysis of the river section under the river crossing tunnel to determine the riverbed evolution trend and main sources of scour risk in the river crossing tunnel area;
[0006] (2) Develop a riverbed deformation monitoring plan for the river-crossing tunnel area;
[0007] (3) Determination of the location of the riverbed deformation monitoring and control section in the protection zone of the river-crossing tunnel;
[0008] (4) Propose a risk level classification and early warning scheme for riverbed scour and deformation in the tunnel area.
[0009] Preferably, step (1) specifically includes: collecting historical measured topographic data of the river section of the tunnel, overlaying the river topography of different years, analyzing the scouring and deposition characteristics of the riverbed plane and cross section of the tunnel, judging the evolution trend of the riverbed in the tunnel area, and analyzing the main causes of riverbed scouring for the scourged tunnel area, thereby determining the main risk sources that cause riverbed scouring.
[0010] Preferably, the main sources of riverbed scour risk in step (1) include: flood scour, tidal action, river dredging, and the impact of local hydraulic scour on river-related structures in the engineering section.
[0011] Preferably, step (2) specifically includes: based on the riverbed evolution trend and main scour risk sources in the river-crossing tunnel project area determined in step (1), formulating a riverbed deformation monitoring plan for the river-crossing tunnel area; the monitoring scope includes the upstream and downstream scour areas of the tunnel alignment that may affect the safety of the river-crossing tunnel, and the protection area of the river-crossing tunnel; monitoring is conducted twice a year, once before the flood season and once after the flood season; topographic monitoring is carried out using RTK and multibeam echo sounding system equipment; riverbed monitoring adopts an accuracy of not less than 1:500.
[0012] Preferably, the key monitoring contents in step (2) include the deformation of the cross-section of the tunnel and the change in the elevation of the deepest point of the cross-section, the deformation of the riverbed of the control section of the tunnel protection area and the change in the elevation of the deepest point of the cross-section, and the development trend of the upstream and downstream scour areas of the tunnel alignment that may affect the safety of the tunnel and the change in the elevation of the deepest point.
[0013] Preferably, step (3) specifically includes: the control section is located within the protection zone of the tunnel crossing the river. The control section should not be too far from the tunnel crossing the river. If it is too far away, it may not be able to accurately transmit the risks brought to the tunnel crossing the river by the terrain changes, thus losing the significance of monitoring. If it is too close, the safety margin will be insufficient, and the feedback of riverbed scour risk will be delayed, increasing the degree of risk. It is required that the riverbed scour deformation revealed by the control section can establish a certain relationship with the riverbed scour deformation of the tunnel alignment section. The riverbed scour deformation monitoring results of the control section can be used to judge the impact of the riverbed deformation in the upstream and downstream scour areas of the tunnel crossing alignment on the thickness of the safe overburden layer at the top of the tunnel crossing the river and make an early warning.
[0014] Preferably, in step (3), to reasonably determine the location of the control section, the critical slope ratio i0 of the natural scour pit in the riverbed and the minimum surplus thickness h of the overburden layer at the top of the tunnel are introduced; i0 is obtained by statistical analysis of the slope ratio of a large number of measured scour pits in the river in different years where the tunnel project is located, and i0 corresponds to the minimum slope ratio of the scour pit obtained by statistical analysis of a large number of measured scour pit data; h is the difference between the elevation Z1 of the deepest point of the riverbed at the top of the tunnel and the control elevation Z2 of the scour depth of the riverbed in the tunnel. If the thickness of the overburden layer at the top of the tunnel is to meet the safety requirements, h > 0 is required; the location of the control section is determined by i0 and h, and the horizontal projection distance L between the control section and the outer side of the outer edge of the tunnel structure is h / i0.
[0015] Preferably, step (4) specifically includes: introducing a risk monitoring and early warning value for riverbed scour and deformation in the tunnel area (denoted by △H, in meters), where △H is the difference between the deepest point of the control section described in step 3 and the control elevation of the scour depth of the tunnel; and classifying the riverbed scour risk in the tunnel area into four levels, as follows:
[0016] ① Blue alert, risk level IV, warning value 0≤△H<0.5h, at this time the scouring has little impact on the thickness of the overburden at the top of the tunnel;
[0017] ② Yellow alert, risk level III, warning value range 0>△H≥-0.5h. At this time, the scouring may have a significant impact on the thickness of the overburden at the top of the tunnel, which may reduce the maximum safety margin of the overburden thickness of the tunnel to 0.5h, posing a certain threat to the safety of the tunnel.
[0018] ③ Orange alert, risk level II, warning value range -0.5h>△H≥-h. At this time, scouring may reduce the safety margin of the overburden thickness of the river-crossing tunnel to 0m, posing a great threat to the safety of the river-crossing tunnel.
[0019] ④ Red alert, risk level I, warning value range △H < -h. At this time, scouring may lead to insufficient safety cover thickness at the top of the river-crossing tunnel, affecting the safety of the river-crossing tunnel.
[0020] Based on the monitoring of the protection zone of conventional river-crossing tunnels and the upstream and downstream scour areas of the tunnel alignment that may affect the safety of river-crossing tunnels, this invention proposes for the first time a monitoring control section for riverbed deformation in river-crossing tunnel areas and its determination method. It also proposes a method for classifying and warning of riverbed scour risk levels in river-crossing tunnel areas based on the riverbed monitoring results of the control section, which can provide technical basis for ensuring the safety and operation management of river-crossing tunnels. Attached Figure Description
[0021] Figure 1 This is a map showing the riverbed morphology of the Fuzhou Metro Line 1 crossing the Yangtze River in 2022.
[0022] Figure 2 A schematic diagram of the riverbed scour risk monitoring plan for the section of Fuzhou Metro Line 1 crossing the river.
[0023] Figure 3 This is a statistical result of the slope ratio of natural scour pits in the riverbeds of the Minjiang River (north and south). Detailed Implementation
[0024] The present invention will now be described in detail with reference to the accompanying drawings.
[0025] Example 1
[0026] like Figure 1 , 2 As shown in Figure 3, the monitoring and early warning of riverbed changes during the operation of the Minjiang North Port Tunnel of Fuzhou Rail Transit Line 1 is used as an example.
[0027] 1. Analysis of Riverbed Evolution and Major Scour Risk Sources in the River-Crossing Section of Fuzhou Metro Line 1. Measured data shows that the riverbed morphology in the Line 1 river-crossing tunnel area is complex, with branching channels, primarily the left branch. Both the left and right branches between the river-crossing tunnel and the Jiefang Bridge contain localized scour pits, with the left branch's scour pits being significantly larger than the right branch's. Furthermore, the left branch's scour pits are closer to the river-crossing tunnel (the deepest point is approximately 100m upstream of the tunnel), posing a significant threat to the tunnel. The riverbed morphology in 2022 is as follows: Figure 1 Comparative analysis of topographic data from 2011, 2017, and 2022 at the same mapping scale shows that the scour pit has expanded horizontally and deepened vertically in recent years, indicating a trend of further development (see Table 1). Riverbed evolution analysis indicates that the piers of the Jiefang Bridge and the riprap foundations beneath it significantly impound water, resulting in a large water level difference between the bridge and its surroundings. This leads to high flow velocity and a highly complex flow pattern beneath the bridge. Furthermore, the left bank embankment forms an angle at the Jiefang Bridge, creating a large angle with the water flow line, causing a significant deflection of the flow direction and the formation of eddies. Consequently, the riverbed in the section from the left branch of Zhongzhou Island, the Jiefang Bridge, to the Line 1 river-crossing tunnel is subjected to significant scour, threatening the safety of the Line 1 river-crossing tunnel. In other words, the threat of riverbed scour in the Line 1 river-crossing tunnel area mainly originates from the development of the scour pit in the left branch.
[0028] Table 1. Changes in scour pits between Fuzhou Metro Line 1 and Jiefang Bridge.
[0029]
[0030] 2. Develop a riverbed deformation monitoring and analysis plan for the river-crossing tunnel area. Based on the analysis results of riverbed evolution and major scour risk sources in the river-crossing tunnel project area in Step 1, develop a riverbed deformation monitoring plan for the river-crossing tunnel area. The monitoring scope includes the scour pit between the Jiefang Bridge and the river-crossing tunnel, as well as the protection area of the river-crossing tunnel (100m upstream and downstream of the outer edge of the tunnel structure). Monitoring will be conducted twice a year, once before the flood season and once after the flood season. RTK and multibeam echo sounding systems will be used for topographic monitoring. The mapping accuracy will be no less than 1:500. Key monitoring contents include the deformation of the river-crossing tunnel alignment section and the elevation change of the deepest point of the section, the riverbed deformation of the control section of the river-crossing tunnel protection area and the elevation change of the deepest point of the section, the horizontal scour and deposition changes of the riverbed in the river-crossing tunnel protection area, and the development trend of the scour pit in the left branch of Zhongzhou Island and the elevation change of its deepest point. The monitoring plan is as follows: Figure 2 As shown.
[0031] 3. Determination of the Control Section Location for Riverbed Deformation Monitoring in the River-Crossing Tunnel Protection Area. The location of this control section is determined by the critical slope i0 of the natural scour pit in the riverbed and the minimum excess thickness h of the overburden layer at the top of the tunnel. The horizontal projection distance L between the control section and the outer edge of the tunnel structure is L = h / i0. i0 is obtained through statistical analysis of a large number of measured scour pit slopes in multiple years in the river (section) where the river-crossing tunnel project is located. i0 corresponds to the minimum slope of the scour pit obtained through statistical analysis of a large number of measured scour pit data. According to the statistical results of 580 sets of scour pit slope data from multiple years in the Minjiang River downstream North and South Ports, the natural scour pit slopes in the Minjiang River North and South Ports account for approximately 53.1% of the total, approximately 24.14% for 0.2–0.25, approximately 8.97% for 0.25–0.3, approximately 6.90% for 0.3–0.33, and approximately 6.90% for greater than 0.33. (See...) Figure 3 Therefore, the slope of the scour pit should not exceed 0.1, meaning the minimum slope i0 of the scour pit in the river channel where Line 1 is located is determined to be 0.1. h is the difference between the elevation Z1 (the deepest point of the riverbed at the top of the tunnel) and the control elevation Z2 (the scour depth control elevation of the riverbed under the tunnel). Based on measured data, Z1 is -15.57m and Z2 is -18.57m, we can obtain: h = Z1 - Z2 = 3m; L = h / i0 = 30m, meaning the control section is located 30m upstream of the Line 1 river-crossing section.
[0032] 4. Determine the risk level classification and early warning plan for riverbed scour and deformation in the tunnel area.
[0033] A risk monitoring and early warning value for riverbed scour and deformation in the tunnel area is introduced (denoted by △H, in meters). △H is the difference between the deepest point of the control section described in step 3 and the control elevation of the scour depth of the tunnel. The risk of riverbed scour in the river-crossing tunnel area is divided into four levels, as follows: ① Blue warning, risk level IV, warning value 0 ≤ ΔH < 0.5h, at this time the scour has little impact on the thickness of the overburden at the top of the tunnel; ② Yellow warning, risk level III, warning value range 0 > ΔH ≥ -0.5h, at this time the scour may have a significant impact on the thickness of the overburden at the top of the tunnel, which may reduce the maximum safety margin of the overburden thickness to 0.5h, posing a certain threat to the safety of the tunnel; ③ Orange warning, risk level II, warning value range -0.5h > ΔH ≥ -h, at this time the scour may reduce the maximum safety margin of the overburden thickness to 0m, posing a significant threat to the safety of the tunnel; ④ Red warning, risk level I, warning value range ΔH < -h, at this time the scour may result in insufficient safety overburden thickness at the top of the tunnel, affecting the safety of the tunnel.
[0034] As shown in step 3, the minimum allowable thickness h of the top overburden layer of the Fuzhou Metro Line 1 tunnel is 3m. Therefore, the specific risk warning classification for riverbed scour deformation of Fuzhou Metro Line 1 is as follows: ① Blue warning, risk level IV, warning value 0 ≤ ΔH < 1.5. At this time, scour has little impact on the top overburden thickness of the tunnel. ② Yellow warning, risk level III, warning value range 0 > ΔH ≥ -1.5. At this time, scour may have a significant impact on the top overburden thickness of the tunnel, potentially reducing the maximum safety margin of the overburden thickness to 1.5m, posing a certain threat to the safety of the tunnel. ③ Orange warning, risk level II, warning value range -1.5 > ΔH ≥ -3. At this time, scour may reduce the maximum safety margin of the overburden thickness to 0m, posing a significant threat to the safety of the tunnel. ④ Red warning, risk level I, warning value range ΔH < -3. At this time, scour may result in insufficient safe overburden thickness at the top of the tunnel, affecting the safety of the tunnel.
[0035] According to the 2022 riverbed monitoring results, the deepest point of the control section is -17.5m, and the ΔH is 1.07. The warning value is 0≤ΔH<1.5, so the riverbed scour risk level in the No. 1 river tunnel area is determined to be Level IV.
[0036] The embodiments described above are merely preferred embodiments of the present invention, and are described in a relatively specific and detailed manner. However, the present invention is not limited to these embodiments. It should be noted that for those skilled in the art, any modifications made without departing from the spirit of the present invention fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.
Claims
1. A method for monitoring and early warning of riverbed scour risk in subway tunnel areas, characterized in that, Includes the following steps: (1) Conduct riverbed evolution analysis of the river section under the tunnel to determine the riverbed evolution trend and main sources of scour risk in the tunnel area; (2) Develop a riverbed deformation monitoring plan for the tunnel area; (3) Determining the location of the riverbed deformation monitoring control section in the protection zone of the tunnel, specifically including: the control section is located within the protection zone of the tunnel, and it is required that the riverbed scour deformation revealed by the control section can establish a certain relationship with the riverbed scour deformation of the tunnel alignment section. Based on the monitoring results of the riverbed scour deformation of the control section, the influence of the riverbed deformation in the upstream and downstream scour areas of the tunnel alignment on the thickness of the safe overburden layer at the top of the tunnel is assessed and an early warning is issued. To reasonably determine the location of the control section, the critical slope ratio i0 of the natural scour pit in the riverbed and the minimum allowable thickness h of the overburden layer at the top of the tunnel are introduced. i0 is obtained by statistical analysis of the slope ratio of scour pits in the river where the tunnel project is located in many different years. i0 corresponds to the minimum slope ratio of the scour pit obtained by statistical analysis of a large number of measured scour pit data. h is the difference between the elevation Z1 of the deepest point of the riverbed at the top of the tunnel and the control elevation Z2 of the scour depth of the riverbed in the tunnel. If the thickness of the overburden layer at the top of the tunnel is to meet the safety requirements, h > 0 is required. The location of the control section is determined by i0 and h together. The horizontal projection distance L between the control section and the outer edge of the tunnel structure is L = h / i0. (4) A risk level classification and early warning scheme for riverbed scour and deformation in the tunnel area is proposed, which includes: introducing a risk monitoring and early warning value for riverbed scour and deformation in the tunnel area, denoted by △H, in meters, where △H is the difference between the deepest point of the control section mentioned in step 3 and the control elevation of the scour depth of the tunnel; classifying the riverbed scour risk in the tunnel area into 4 levels, as follows: ① Blue alert, risk level IV, warning value 0≤△H<0.5h, at this time the scouring has little impact on the thickness of the overburden at the top of the tunnel; ② Yellow alert, risk level III, warning value range 0>△H≥-0.5h. At this time, the scouring may have a significant impact on the thickness of the overburden at the top of the tunnel, which may reduce the maximum safety margin of the overburden thickness of the tunnel to 0.5h, posing a certain threat to the safety of the tunnel. ③ Orange alert, risk level II, warning value range -0.5h>△H≥-h. At this time, scouring may reduce the safety margin of the overburden thickness of the river-crossing tunnel to 0m, posing a great threat to the safety of the river-crossing tunnel. ④ Red alert, risk level I, warning value range △H < -h. At this time, scouring may lead to insufficient safety cover thickness at the top of the river-crossing tunnel, affecting the safety of the river-crossing tunnel.
2. The method for monitoring and early warning of riverbed scour risk in a subway tunnel area according to claim 1, characterized in that, The specific steps (1) include: collecting historical measured topographic data of the river section of the tunnel, overlaying the river topography of different years, analyzing the scouring and sedimentation characteristics of the riverbed plane and cross section of the tunnel, judging the evolution trend of the riverbed in the tunnel area, and analyzing the main causes of riverbed scouring for the scourged tunnel area, thereby determining the main risk sources that cause riverbed scouring.
3. The method for monitoring and early warning of riverbed scour risk in a subway tunnel area according to claim 2, characterized in that, The main sources of riverbed scour risk in step (1) include: flood scour, tidal action, river dredging, and the impact of local hydraulic scour on river-related structures in the engineering section.
4. The method for monitoring and early warning of riverbed scour risk in a subway tunnel area according to claim 3, characterized in that, Step (2) specifically includes: based on the riverbed evolution trend and main scour risk sources in the river-crossing tunnel project area determined in step (1), formulating a riverbed deformation monitoring plan for the river-crossing tunnel area; the monitoring scope includes the upstream and downstream scour areas of the tunnel alignment that may affect the safety of the river-crossing tunnel, and the protection area of the river-crossing tunnel; monitoring is conducted twice a year, once before the flood season and once after the flood season; topographic monitoring is carried out using RTK and multibeam echo sounding system equipment; riverbed monitoring adopts an accuracy of not less than 1:
500.
5. The method for monitoring and early warning of riverbed scour risk in a subway tunnel area according to claim 4, characterized in that, The key monitoring contents in step (2) include the deformation of the cross-section of the tunnel and the change in the elevation of the deepest point of the cross-section, the deformation of the riverbed of the control section of the tunnel protection area and the change in the elevation of the deepest point of the cross-section, and the development trend of the upstream and downstream scour areas of the tunnel alignment that may affect the safety of the tunnel and the change in the elevation of the deepest point.