A monitoring device and method for measuring the external water pressure of the lining of a deeply buried tunnel

Abstract

The present invention belongs to the field of lining water pressure measurement, and provides a monitoring device and method for measuring the external water pressure of a deep-buried tunnel lining. The device includes a drill hole and a piezometer. The drill hole is drilled horizontally in the middle of the side wall of the deep-buried tunnel and extends beyond the weakly disturbed area of groundwater. The piezometers are buried along the inner part of the drill hole, and the outside of each piezometer is wrapped and compacted with medium-coarse sand. By inputting the piezometer data at different positions of the deep-buried tunnel into the far-field water head models corresponding to different positions and calculating them respectively, the present invention realizes the distributed monitoring of groundwater at different positions of the deep-buried tunnel, solves the problem of incomplete monitoring of the spatio-temporal law of groundwater affected by tunnel excavation, is beneficial to providing a scientific basis for the design and calculation of the lining structure of the deep-buried tunnel, and provides an important guarantee for the long-term safe operation of the engineering structure of the deep-buried tunnel.

Description

Technical Field

[0001] The present invention relates to the field of lining water pressure measurement, and particularly to a monitoring device and method for measuring the external water pressure of a deep-buried tunnel lining. Background Art

[0002] In the construction of some mountain tunnels, the tunnel has a large burial depth, passes through a water-rich area, and has a high water head. For example, the Yuanliangshan Tunnel and the Jinping Traffic Tunnel. How to safely and reliably carry out tunnel design, construction and operation without affecting the ecological environment is a key issue, and one of the key problems is how to determine the magnitude of the water pressure on the lining.

[0003] Currently, in the calculation of tunnel lining water loads, the railway and transportation departments have not formulated unified specifications. Most still refer to the design specifications and empirical methods of hydraulic tunnels, and the discussions on water loads are also scattered in the monographs and professional magazines of various departments and disciplines. The lining water load in a hydraulic tunnel generally includes two parts: internal water pressure and external water pressure, and the acting object of both is the lining. The external water pressure is relative to the internal water pressure in a pressurized tunnel, while railway and highway tunnels generally do not have internal water pressure and are usually simply referred to as "water pressure". Therefore, the lining water load and the external water pressure refer to the same concept.

[0004] Currently, the following 4 common methods are available for the calculation and treatment of the external water pressure of a tunnel lining:

[0005] (1) In mountain tunnels constructed by the shallow-buried mining method, when the "drainage-based" condition is adopted for groundwater treatment, the railway tunnel design specification does not consider the lining to bear water pressure; however, studies have shown that when a permeable cushion layer is set behind the lining to drain groundwater, the lining still has to bear a certain amount of water pressure. When groundwater drainage is not allowed in urban subway tunnels or full-block waterproofing is adopted, the water pressure on the lining is the hydrostatic pressure at that location (i.e., the static water head at that location);

[0006] (2) For mountain tunnels with a relatively high water head, in order to protect the groundwater resources and environment around the tunnel and under the condition that the "drainage-based" method cannot be adopted and the principle of "blocking-based and limited discharge" is adopted, new problems are posed to the tunnel engineering community in the calculation of tunnel water pressure. Insufficient attention has been paid to the water pressure on the previous tunnel lining, so there is a lack of research data in this regard, and it can be said that there are no standardized and recognized methods and rules to follow. In water conservancy and hydropower projects, more research has been carried out on water pressure earlier and corresponding design specifications have been formulated. Therefore, when railway tunnels encounter high water pressure, the method of calculating water pressure in hydraulic tunnels is mostly used for reference, that is, the external water pressure reduction coefficient method.

[0007] (3) Since there are many differences in the setting of the tunnel waterproof and drainage system between railway and highway tunnel projects and those in water conservancy and hydropower projects, it is obvious that there are deficiencies in simply using the reduction coefficient method. Therefore, with the construction of railway tunnels in high water table and water-rich areas in recent years, research work in this area has begun. The research methods adopted are also different, but generally, starting from the reduction coefficient method, gradually assuming homogeneous surrounding rock and analyzing the seepage field of the tunnel surrounding rock according to Darcy's law of seepage to determine the external water pressure on the lining.

[0008] (4) The magnitude of the water pressure on the tunnel lining is related to the medium of the tunnel surrounding rock (fractured, homogeneous), the permeability of the surrounding rock, the water head of the groundwater, and also related to the stress state in the tunnel surrounding rock. This is the problem of the coupling effect between the seepage field and the surrounding rock stress field. Theoretically, considering the coupling effect is a more accurate and reasonable method. The research results of the coupling effect between the seepage field and the surrounding rock stress field are mainly for dam foundation projects and are mostly used for the research of water inflow. However, there is very little research on the water pressure acting on the lining in view of the drainage and structural characteristics of tunnel projects. Therefore, more model tests and on-site tests are required for research in this area.

[0009] There are few domestic regulatory guiding documents on the reduction coefficient of external water pressure, and the values of external water pressure and reduction coefficient abroad are also extremely inconsistent. Generally, there are the following three situations: (1) The reduction coefficient method. According to statistics of different projects, the value of βe is about between 0.15 and 0.9. Australia, the United States, and Japan sometimes use this method. (2) The full water head method (βe = 1), which is commonly used in the United States and France. (3) The possible maximum water head value. In the United States, Canada, Brazil and other countries, the static water head borne by the tunnel lining is often calculated to the ground surface. For different lining structure types (sealing type, combined drainage and blocking type), the concept of external water pressure reduction and the value taken are different.

[0010] To sum up, the existing monitoring methods for measuring the external water pressure of deep-buried tunnel linings all have the problem of incomplete monitoring of the spatio-temporal law of groundwater affected by tunnel excavation. Therefore, designing a new monitoring method for measuring the external water pressure of deep-buried tunnel linings is of great significance for the structural design of deep-buried tunnels and ensuring the long-term safe operation of tunnels. Summary of the Invention

[0011] In order to solve the technical problem of incomplete monitoring of the spatio-temporal law of groundwater affected by tunnel excavation, the present invention provides a monitoring device and method for measuring the external water pressure of deep-buried tunnel linings, realizing distributed monitoring of the groundwater level at different positions of deep-buried tunnels, which is beneficial to providing a scientific basis for the design and calculation of deep-buried tunnel lining structures and providing an important guarantee for the long-term safe operation of deep-buried tunnel engineering structures.

[0012] In a first aspect, the present invention provides a monitoring device for measuring the external water pressure of the lining of a deep-buried tunnel, comprising a borehole and a piezometer;

[0013] The borehole is drilled horizontally in the middle of the side wall of the deep-buried tunnel and extends beyond the weakly disturbed area of groundwater;

[0014] The piezometers are distributed and buried along the inner part of the borehole, and the outside of each piezometer is wrapped and compacted with medium-coarse sand.

[0015] Preferably, the drilling depth of the borehole extends at least 10 m beyond the groundwater disturbance area.

[0016] Preferably, the diameter of the borehole is not less than 50 mm.

[0017] Preferably, there is a filling material filled between every two adjacent piezometers in the borehole.

[0018] Preferably, the filling material includes expanded clay balls or cement slurry.

[0019] Preferably, the interval distance of the piezometers distributed and buried in the borehole is 8 - 10 cm.

[0020] Preferably, the length of the piezometer is greater than 30 cm.

[0021] In a second aspect, the present invention further provides a monitoring method for measuring the external water pressure of the lining of a deep-buried tunnel, which is applied to the above-mentioned monitoring device for measuring the external water pressure of the lining of a deep-buried tunnel, and comprises the following steps:

[0022] Obtain piezometer readings, wherein the piezometer readings include piezometer values, corresponding piezometer burial position information, and corresponding time information, and the piezometer burial positions include strongly disturbed areas and weakly disturbed areas;

[0023] Cluster the piezometer readings according to the piezometer burial position information;

[0024] Input the piezometer readings of the strongly disturbed area after clustering into the corresponding first far-field water head model, and input the piezometer readings of the weakly disturbed area after clustering into the corresponding second far-field water head model to obtain the far-field water heads at different times;

[0025] Conduct stepwise regression statistical analysis on the far-field water heads at different times to obtain the optimal far-field water head.

[0026] Preferably, before obtaining the piezometer readings, the method further comprises:

[0027] Judge whether the piezometer readings for three consecutive times do not exceed 1% of the average value. If so, obtain the piezometer readings, wherein the interval between two adjacent piezometer readings is 24 h.

[0028] Preferably, the first far - field water head model is:

[0029] H0 = C3lnR0 + C4,

[0030] wherein, H0 is the far - field water head, and R0 is the far - field water head radius. r ini is the tunnel excavation radius, γ is the unit weight of water, k r is the permeability coefficient of the surrounding rock in the non - disturbed area, k s is the permeability coefficient of the surrounding rock in the loosening zone, r i is the outer radius of the secondary lining, the outer diameter of the primary lining or the outer diameter of the grouting layer, P i is the external water pressure on the lining, the external water pressure on the shotcrete layer or the external water pressure on the grouting layer, i is 1, 2 or 3, r s is the radius of the loosening zone;

[0031] The second far - field water head model is:

[0032] H0 = C5lnR0 + C6,

[0033] wherein,

[0034] By inputting the piezometer data at different positions of the deep - buried tunnel into the far - field water head models corresponding to different positions and calculating them respectively, the present invention realizes the distributed monitoring of groundwater at different positions of the deep - buried tunnel, solves the problem of incomplete monitoring of the spatio - temporal law of groundwater affected by tunnel excavation, is conducive to providing a scientific basis for the design and calculation of the lining structure of the deep - buried tunnel, and provides an important guarantee for the long - term safe operation of the engineering structure of the deep - buried tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 1. Figure 1 is a schematic structural diagram of a monitoring device for measuring the external water pressure on the lining of a deep - buried tunnel provided by an embodiment of the present invention;

[0036] 2. Figure 2 is a schematic flow diagram of a monitoring method for measuring the external water pressure on the lining of a deep - buried tunnel provided by an embodiment of the present invention;

[0037] 3. Figure 3 is a schematic diagram of a groundwater seepage field calculation model provided by an embodiment of the present invention;

[0038] 4. Figure 4 is a schematic diagram of the water head distribution in the surrounding rock before and after the excavation of a deep - buried tunnel provided by an embodiment of the present invention.

[0039] BEST MODE FOR CARRYING OUT THE INVENTION

[0040] To enable those skilled in the art to more clearly understand a monitoring device and method for measuring the external water pressure of a deep-buried tunnel lining provided by the present invention, the following will provide a detailed description thereof in conjunction with the accompanying drawings.

[0041] As Figure 1 shown, an embodiment of the present invention provides a monitoring device for measuring the external water pressure of a deep-buried tunnel lining, including a borehole 2 and a piezometer 4;

[0042] The borehole 2 is drilled horizontally in the middle of the side wall of the deep-buried tunnel 1 and extends beyond the weak groundwater disturbance area 6;

[0043] The piezometers 4 are distributed and buried along the inside of the borehole 2, and the outside of each piezometer 4 is wrapped and compacted with medium-coarse sand 5.

[0044] It should be noted that for the monitoring device for measuring the external water pressure of a deep-buried tunnel lining provided by the embodiment of the present invention, the specific construction method may be:

[0045] 1. After the excavation of the deep-buried tunnel 1, drill horizontally in the middle of the side wall of the deep-buried tunnel, and the depth extends beyond the weak groundwater disturbance area 6.

[0046] Preferably, the diameter of the borehole is not less than 50 mm.

[0047] Preferably, the depth of the borehole extends at least 10 m beyond the groundwater disturbance area.

[0048] 2. Immerse several piezometers 4 for more than 24 h, and then wrap and compact each piezometer 4 with saturated medium-coarse sand 5 respectively. Distribute and bury the several piezometers 4 that have been wrapped and compacted with medium-coarse sand 5 inside the borehole 2, and distribute them at different positions in the strong groundwater disturbance area 3, weak disturbance area 6, and non-disturbance area.

[0049] The installation sequence of the piezometers 4 is: starting from the bottom of the borehole 2 and ending at the side wall of the deep-buried tunnel 1.

[0050] 3. After each piezometer 4 is buried inside the borehole 2, backfill with a backfill material 7 at the corresponding position of the piezometer 4.

[0051] Only after the backfill material has initially set can the next position be entered to continue burying the next piezometer.

[0052] Preferably, the length of the backfill is greater than 20 cm.

[0053] Preferably, the burial interval distance between two adjacent piezometers 4 is 8 - 10 cm.

[0054] Preferably, the length of each piezometer 4 is greater than 30 cm.

[0055] Preferably, the backfill material 7 includes expansive soil balls or cement slurries for partitioning outside the position of the piezometer 4 wrapped by medium-coarse sand 5.

[0056] As Figure 2 shown, an embodiment of the present invention provides a monitoring method for measuring the external water pressure of a deep-buried tunnel lining, including the following steps:

[0057] S1: Obtain the piezometer readings, where the piezometer readings include the piezometer value, the corresponding piezometer installation position information, and the corresponding time information, and the piezometer installation positions include a strong disturbance area and a weak disturbance area;

[0058] S2: Cluster the piezometer readings according to the piezometer installation position information;

[0059] S3: Input the piezometer readings of the clustered strong disturbance area into the corresponding first far-field water head model, and input the piezometer readings of the clustered weak disturbance area into the corresponding second far-field water head model to obtain the far-field water heads at different times;

[0060] S4: Perform stepwise regression statistical analysis on the far-field water heads at different times to obtain the far-field water head with the optimal solution.

[0061] Preferably, before obtaining the piezometer readings, it further includes: when reading the piezometer readings at each position of this hole, after ensuring that the three consecutive readings at an interval of 24 hours do not exceed 1% of the average value, select the initial value.

[0062] It should be noted that each piezometer reading data includes the piezometer value measured by the piezometer at its corresponding position, and the time tag corresponding to this piezometer value. Each piezometer at the corresponding position can obtain multiple reading data. First, perform time series analysis on all the obtained piezometer readings to obtain the time history curves of the piezometers at each position, then perform correlation analysis on the piezometers at two positions pairwise, and then cluster according to the piezometer installation position information.

[0063] Partition the positions of the piezometers according to the water level, that is, including a disturbance area and a non-disturbance area, where the disturbance area is further divided into a strong disturbance area and a weak disturbance area. The strong disturbance area is located in the inner surrounding rock mass, and the weak disturbance area is located in the outer surrounding rock mass.

[0064] Therefore, after clustering is completed, input the piezometer readings at the positions corresponding to each partition into the first far-field water head model and the second far-field water head model corresponding to the strong disturbance area and the weak disturbance area respectively to obtain a series of far-field water heads at different times.

[0065] Preferably, the specific implementation manners of the first far-field water head model and the second far-field water head model may be:

[0066] As Figure 3 and4 As shown in the figure, the composite lining system mainly consists of four parts: the consolidated grouting circle, the primary support, the secondary support, and the waterproof and drainage system. Assuming that the confining pressure is an isotropic, homogeneous, and continuous medium, the tunnel is circular, the groundwater head at the center axis point of the tunnel is H1, the water flow is a steady flow, and its motion law follows Darcy's law. r0 is the inner diameter of the tunnel, r1 is the outer radius of the secondary lining, r2 is the outer diameter of the primary lining, r3 is the outer diameter of the grouting layer, and r4 is the outer radius of the stable seepage field formed after the tunnel excavation. The water heads at the corresponding positions are h0, h1, h2, h3, and H1 respectively. The permeability coefficient of the secondary lining is k1, the permeability coefficient of the primary lining is k2, the permeability coefficient of the grouting layer is k3, and the permeability coefficient of the surrounding rock layer is k4.

[0067] The water flow field in the rock mass is approximately perpendicular to the tunnel axis, the water head potential function is symmetric about the tunnel axis, the seepage satisfies the continuity equation, the surrounding rock can be equivalent to a uniformly permeable rock mass, the tunnel axis is the z-axis, and the seepage satisfies the continuity equation (i.e., Laplace's equation):

[0068]

[0069] That is

[0070]

[0071] The water flow is perpendicular to the z-axis Therefore, at the same time, since the water head field function H is symmetric about the tunnel axis z, then So equation (2) can be simplified to:

[0072]

[0073] That is

[0074]

[0075]

[0076] The flow rates of different cross-sections are equal. According to Darcy's law, the water inflow per meter of the tunnel is:

[0077]

[0078] Then

[0079]

[0080] Substitute equation (7) into equation (5) to get

[0081]

[0082] Separate variables to get

[0083]

[0084] The boundary conditions are as follows:

[0085]

[0086] Integrating Equation (9), we get

[0087]

[0088] From the boundary condition (10), we can obtain

[0089]

[0090] Since Q 4-3 = Q 3-2 = Q 2-1 = Q 1-0 = Q0, then

[0091]

[0092]

[0093] Therefore, the water head H1 of the surrounding rock is expressed as:

[0094]

[0095] The external water pressures are respectively

[0096]

[0097] Then when there is no internal water pressure in the secondary lining, the water heads of the lining and the grouting body are:

[0098]

[0099] The external water pressures are respectively:

[0100]

[0101] In the formula: P1 is the external water pressure of the lining, in Pa; P2 is the external water pressure of the shotcrete layer, in Pa; P3 is the external water pressure of the grouting layer, in Pa; γ W is the unit weight of groundwater, 10 kN / m 3 .

[0102] H0 and r4 are respectively the initial pressure water head and the initial pressure water head radius at the tunnel axis position. When H0 is in the unit of water head height, its value is equal to r4.

[0103] If the horizontal plane at the top of the deep-buried tunnel is used as the reference plane, the groundwater head at point B with a radius of r can be expressed as:

[0104]

[0105] In the formula: r ini is the tunnel excavation radius, R0 is the far-field water head radius, that is, the influence radius of the groundwater change caused by the tunnel excavation, H0 is the far-field water head, p is the pressure water head in the surrounding rock at a radius of r, γ is the unit weight of water, r ini ≤ r ≤ R0.

[0106] Considering the influence of the surrounding rock excavation on the disturbance of the surrounding rock, a disturbed area is generated in the tunnel surrounding rock, and the permeability of the disturbed area has changed. Then, Equation (20) changes into the following two equations.

[0107] For the groundwater pressure water head in the disturbed area, it is expressed as:

[0108]

[0109] For the groundwater pressure water head outside the disturbed area, it is expressed as:

[0110]

[0111] In the above two equations, the radius of the loosening zone is r s , the permeability coefficient of the surrounding rock in the undisturbed area is k r , and the permeability coefficient of the surrounding rock in the loosening zone is k s .

[0112] If the piezometer is buried in the surrounding rock mass in the disturbed area, that is, the strong disturbance area, then substituting the measured pressure water head data into Equation (21) gives:

[0113]

[0114] Through transformation, the first far-field water head model can be obtained:

[0115] H0 = C3lnR0 + C4

[0116] Among them,

[0117] If the piezometer is buried in the surrounding rock mass outside the disturbed area, that is, the weak disturbance area, then substituting the measured pressure water head data into Equation (22) gives the second far-field water head model:

[0118] H0 = C5lnR0 + C6

[0119] Among them,

[0120] A series of far - field water heads at different times are calculated according to the above - mentioned first far - field water head model and the second far - field water head model, and then the obtained series of far - field water heads at different times are subjected to step - wise regression statistical analysis to obtain the far - field water head of the optimal solution, that is, the external water pressure on the lining of the deep - buried tunnel.

[0121] In summary, in the embodiments of the present invention, by inputting the piezometer data at different positions of the deep - buried tunnel into the far - field water head models corresponding to different positions and calculating them respectively, the distributed monitoring of groundwater at different positions of the deep - buried tunnel is realized, solving the problem of incomplete monitoring of the spatio - temporal law of groundwater affected by tunnel excavation, which is beneficial to providing a scientific basis for the design and calculation of the lining structure of the deep - buried tunnel and providing an important guarantee for the long - term safe operation of the engineering structure of the deep - buried tunnel.

[0122] The embodiments of the present invention have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A monitoring method for measuring the external water pressure of the lining of a deeply buried tunnel, characterized in that, It includes the following steps: Obtain the piezometer readings, where the piezometer readings include the piezometer value, the corresponding piezometer installation location information, and the corresponding time information, and the piezometer installation location includes a strong disturbance area and a weak disturbance area; Cluster the piezometer readings according to the piezometer installation location information; Input the piezometer readings of the strongly disturbed areas after clustering into the corresponding first far-field water head model, and input the piezometer readings of the weakly disturbed areas after clustering into the corresponding second far-field water head model to obtain the far-field water heads at different times; wherein, the first far-field water head model is: H0 = C3lnR0 + C4, where H0 is the far-field water head, R0 is the far-field water head radius, r ini is the tunnel excavation radius, γ is the unit weight of water, k r is the permeability coefficient of the surrounding rock in the undisturbed area, k s is the permeability coefficient of the surrounding rock in the loosening zone, r i is the outer radius of the secondary lining, the outer diameter of the primary lining or the outer diameter of the grouting layer, P i is the external water pressure on the lining, the external water pressure on the shotcrete layer or the external water pressure on the grouting layer, i is 1, 2 or 3, r s is the radius of the loosening zone; the second far-field water head model is: H0 = C5lnR0 + C6, where, Perform stepwise regression statistical analysis on the far-field water heads at different times to obtain the far-field water head with the optimal solution.

2. The monitoring method for measuring the external water pressure on the lining of a deeply buried tunnel according to claim 1, characterized in that, Before obtaining the piezometer readings, the method further includes: Judge whether the piezometer readings for three consecutive times do not exceed 1% of the average value. If so, obtain the piezometer readings, where the interval between two adjacent piezometer readings is 24 h.

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