CN108241772A - Determination method of tunnel water inflow in fractured confined aquifer considering multiple factors - Google Patents

Abstract

The present invention provides Tunnel Gushing method for determination of amount in a kind of crack artesian aquifer for considering multiple factors, including：It determines soil layer division information and groundwater occurrence situation, obtains the physical and mechanical parameter of soil layer；It obtains length of tunnel, tunnel radius, tunnel center buried depth information, pumped well and its accordingly observes well information；Establish three-dimensional finite difference model, the osmotic coefficient k in soil layer x, y, z direction along inverting tunnel_x、k_y、k_zAnd water storage rate S_s；Determine governing equation and initial boundary conditions at any in tunnel；Determine dimensionless drawdown S_D(t_D)；Determine Tunnel Seepage Q (t) in the crack artesian aquifer of consideration multiple factors；Integrating tunnel water yield Q (t) is that the longitudinal axis establishes Descartes's rectangular coordinate system using time t as horizontal axis, water yield Q (t), makes Q (t) t relational graphs under different drawdown value S (t).The present invention is simple, applicable, convenient for promoting, has very big engineering application value.

Description

Determination method of tunnel water inflow in fractured confined aquifer considering multiple factors

technical field

The invention relates to a method in the technical field of underground construction engineering, in particular to a method for determining the water inflow of a tunnel in a fissure-bearing aquifer considering multiple factors.

Background technique

In recent years, shield tunnel construction has been widely used in urban subway construction. The common soil layers for tunnel construction are silt, sand, clay, shale, and granite. However, with the continuous expansion of urban subway construction, shield construction often encounters unfavorable geological soils, such as fault fracture zones, karst geology, weak zones, gas zones, etc. For soils such as fault fracture zones, due to the relatively well-developed fissures in the rock mass itself, when the groundwater is abundant, the fissure water in the rock mass is also abundant. Geological disasters such as water inrush and mud inrush, for example, the Yiwanbie Rock Trough Tunnel has a maximum water inflow of 1.55×10 ⁵ m ³ /d during fault construction; the expressway Wushaoling Tunnel in fault construction has the largest The water inflow is 7.991×10 ³ m ³ /d; Qingyunshan Tunnel is under fault construction, and the maximum water inflow on the fault is about 5.28×10 ⁴ m ³ /d. It can be seen that water inrush in tunnels has become a geological hazard problem that cannot be underestimated in fault construction.

At present, the commonly used methods for determining the water inflow of tunnels are aimed at unconfined aquifers, such as the method proposed in the article "Circular tunnel in asemi-infinite aquifer" published by EI Tani in "Tunnelling and Underground Space Technology" in 2003, and the method proposed by Park In the article "Analytical solution for steady-stategroundwater inflow into a drained circular tunnel in a semi-infinite aquifer: A revisit" published in "Tunnelling and Underground Space Technology" in 2008, the zero pore pressure around the tunnel was deduced by the conformal mapping method The method for determining the tunnel water inflow under the two boundary conditions of constant water head and constant water head, the applicable conditions are that the aquifer satisfies isotropy, equal thickness and homogeneity, and the seepage of groundwater conforms to Darcy's law. The above methods for determining water inflow in tunnels are limited to their applicable conditions, and cannot be used to determine tunnel water inflow in fractured confined aquifers because they cannot consider the anisotropy and inhomogeneity characteristics of the permeability of fractured rock mass media. Therefore, in view of the inadequacies of existing methods for determining water inflow, it is necessary to propose a method for determining water inflow in tunnels in fractured confined aquifers that considers multiple factors.

Contents of the invention

Aiming at the deficiencies in the prior art, a method for determining the water inflow of a tunnel in a fractured confined aquifer considering multiple factors is provided. The method takes into account the anisotropic characteristics of the fractured confined aquifer, breaking the existing tunnel In view of the limitations of the method for determining the water inflow, by establishing the relationship between the water inflow of the tunnel and the six factors of the permeability coefficient, water inflow time, water level drawdown, thickness of the fractured confined aquifer, tunnel length, and tunnel radius, the proposed fractured confined aquifer Method for determining water inflow in tunnels.

The present invention is achieved through the following technical solutions:

The present invention provides a method for determining water inflow in tunnels in fractured confined aquifers considering multiple factors, the method comprising the following steps:

The first step is to survey the tunnel construction site, determine the soil layer division information of the tunnel construction site and the distribution of groundwater, and conduct indoor geotechnical tests on the samples taken from the borehole to obtain the physical and mechanical parameters of the soil layer;

The second step is to check the tunnel design instructions to obtain the tunnel length, tunnel radius, and tunnel center buried depth information; through the field pumping test along the tunnel, obtain the pumping well and its corresponding observation well information;

The third step is to combine the information obtained in the first and second steps to establish a three-dimensional finite difference model to invert the permeability coefficient k _x , ky , k z and water storage rate S of the soil layer along the tunnel in the x, _y , and _z directions _s ;

The fourth step is to select a point (x ₀ , y ₀ , z ₀ ) in the tunnel, select the lengths dx, dy, and dz along the x, y, and z axes respectively, and assume that the confined aquifer of the tunnel fracture extends infinitely along the xy plane of the horizontal plane, The roof and bottom of the fractured confined aquifer are set as non-seepage boundaries, and the control equation and initial boundary conditions at (x ₀ , y ₀ , z ₀ ) in the tunnel are determined; the control equation satisfies the following formula:

In the formula: t is the time (d), h is the water level (m) of a certain point (x, y, z) in the tunnel at time t, Q(t) is the water level (m) of a certain point (x, y, z) in the tunnel at t The water inflow of the tunnel at any time;

The fifth step is to introduce the water level drawdown S(t) at time t, and convert S(t) and the variables t, x, y, and z in the control equation of the fourth step into dimensionless variables S _D (t), t _D , x _D , y _D , z _D , and then substitute the converted dimensionless variables into the control equation and initial boundary conditions in the fourth step to determine the dimensionless water level drawdown S _D (t _D );

The sixth step, according to the dimensionless water level drawdown S _D (t _D ) in the fifth step, determine the tunnel water inflow Q(t) in the fractured confined aquifer considering multiple factors;

The seventh step, combined with the water inflow Q(t) determined in the sixth step, establishes a Cartesian rectangular coordinate system with time t as the horizontal axis and water inflow Q(t) as the vertical axis, and draws down values of different water levels S( Q(t)-t relationship graph under t).

Preferably, in the first step, the determination of soil layer division information includes soil layer type and layer thickness, that is: percussive drilling is used to drill holes at intervals of 50m along the tunnel, and the depth of 50m below the surface is obtained with a thin-walled soil extractor. Soil mass within the scope, so as to obtain the soil layer type and layered thickness along the tunnel.

Preferably, in the first step, said determination of groundwater distribution includes aquifer type, thickness, and stable water level of aquifer; wherein:

The type and thickness of the aquifer are determined by the soil layer division information revealed by percussion drilling;

Drill wells to observe the stable water levels of different aquifers, and measure the stable water levels of the aquifers after isolating the measured aquifers from other aquifers by taking water-proof measures for the confined aquifers.

Preferably, in the first step, the indoor geotechnical test refers to: density test, indoor penetration test.

Preferably, in the first step, the physical and mechanical parameters of the soil layer refer to: natural weight and permeability coefficient.

More preferably, the permeability coefficient is divided into vertical z-direction permeability coefficient k _z ' and horizontal x-direction and y-direction permeability coefficient k _x ', _ky ', and k _x '= _ky '.

Preferably, in the second step, the pumping test refers to: drilling a well within the depth of the aquifer to be pumped, and the drilling depth is greater than the depth of the aquifer, using pumping equipment to pump water, and synchronously recording the pumping well during the pumping process and its corresponding observation well information.

Preferably, in the second step, the information of the pumping wells and their corresponding observation wells refers to: the pumping volume, pumping time, and water level drawdown values of the pumping wells, the water level drawdown values of the observation wells at different times, the pumping wells and The number and location relationship of the corresponding observation wells.

More preferably, the positional relationship between the pumping wells and their corresponding observation wells refers to: the horizontal distance and the vertical distance between the pumping wells, the horizontal distance between the pumping wells and their corresponding observation wells, the pumping wells and their corresponding observation wells The bottom burial depth of the well, the top burial depth and the bottom burial depth of the filter of the pumping well and its corresponding observation well.

Preferably, in the third step, the plane size of the three-dimensional finite difference model is determined according to the maximum influence radius R _max of the pumping well in the pumping test, and the three-dimensional finite difference model is gridded according to the soil layer division information obtained in the first step Divide, input the initial parameters, and set the initial water level and boundary conditions of the three-dimensional finite difference model, where: the initial water level is determined according to the stable water level of the aquifer obtained in the first step, and the boundary condition is set as the constant head boundary.

More preferably, the maximum influence radius R _max is the maximum value of the influence radius R of each pumping well in the pumping test.

More preferably, described R satisfies the following formula:

In the formula: _ri is the distance from the observation well to the pumping well (i=1, 2) (m), and _si is the maximum water level drawdown of the observation well (i=1, 2) (m).

More preferably, the plane size of the three-dimensional finite difference model is determined according to the maximum influence radius R _max of the pumping well in the pumping test, which means: determine the boundary pumping wells according to the relative positions of the pumping wells in the pumping test, that is, the uppermost and the lowermost , the leftmost and the rightmost, with the boundary pumping well as the center, respectively extending to the outermost by a distance greater than or equal to the maximum influence radius R _max , that is, to determine the plane size of the three-dimensional finite difference model.

More preferably, the initial parameters include: initial weight, initial x, y, z direction permeability coefficient and initial water storage rate; wherein: the natural weight determined in the first step is taken as the initial weight, and the first step is determined The permeability coefficients k _x ', _ky ', and k _z ' are used as the initial permeability coefficients in the x, y, and z directions respectively, and the initial water storage rate S _s ' is determined in accordance with the code "Code for Geological Survey of Water Conservancy and Hydropower Engineering" (GB50487-2008) .

Preferably, in the third step, the inversion refers to: input the pumping well and its corresponding observation well information obtained in the second step, run the three-dimensional finite difference model to calculate the water level drawdown value of the observation well, and calculate The water level drawdown value of the observation well is compared with the water level drawdown value of the observation well measured in the pumping test. If the error between the two is greater than 5%, the initial permeability coefficient in the x, y, and z directions and the initial water storage rate are adjusted according to experience. Re-run the three-dimensional finite difference model until the error between the two is less than 5%, so as to finally determine the permeability coefficient k _x , ky , k z and water storage rate S _s of the soil layer along the tunnel along the x, _y , and _z directions.

Preferably, in the fourth step, the initial boundary conditions satisfy the following formula:

h(x,y,z,t=0)=h ₀

h(x=±∞,y,z,t)=h(x,y=±∞,z,t)=h ₀

In the formula: h ₀ is the initial water level (m), and M is the thickness of the fractured confined aquifer (m).

Preferably, in the fifth step, the water level drawdown S(t) at the moment t satisfies the following formula:

S(t) = h ₀ -h.

Preferably, in the fifth step, the dimensionless variables S _D (t), t _D , x _D , y _D , and z _D respectively satisfy the following formulas:

In the formula: S _D (t), t _D , x _D , y _D , z _D are the dimensionless forms of S(t), t, x, y, z respectively, the purpose is to simplify the calculation and has no practical significance.

Preferably, in the fifth step, the dimensionless water level drawdown S _D (t _D ) satisfies the following formula:

where L is the length of the tunnel (m); τ is a time-related variable; z _wD and L _D are the dimensionless forms of z _w and L, and z _w is the vertical distance from the center of the tunnel to the floor of the fractured confined aquifer (m); erf(x) is a Gaussian error function; exp(x) is an exponential function; specifically satisfy the following formula:

In the formula: η is an integral variable, and its interval range is [0,x].

Preferably, in the sixth step, said Q(t) satisfies:

In the formula: Q(t) is the tunnel water inflow at a point (x, y, z) in the tunnel at time t; r is the radius of the tunnel (m); L is the length of the tunnel (m); S(t) is the time t M is the thickness of the fractured confined aquifer (m); k _x is the permeability coefficient of the soil layer along the tunnel in the x direction (m/d); k _y is the permeability coefficient of the soil layer along the tunnel in the y direction (m/d); k _z is the permeability coefficient in the z direction of the soil layer along the tunnel (m/d); S _s is the water storage rate of the soil layer along the tunnel (m ^-1 ); t is time (d).

Compared with the prior art, the present invention has the following beneficial effects:

The method of the present invention not only considers the anisotropic characteristics and time effects of the fractured confined aquifer, but also considers the relationship between the water inflow and the water level drop after the water gushes out of the tunnel. Under the change of different factors, the relationship of tunnel water inflow with time can be explored. The method of the invention is simple, applicable, easy to popularize and has great engineering application value.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is a diagram of the plane relationship between the tunnel and the fault fracture zone in a preferred embodiment of the present invention;

Fig. 2 is the relationship diagram of the observation well water level drawdown over time in a preferred embodiment of the present invention;

Fig. 3 is a three-dimensional finite difference model diagram of a preferred embodiment of the present invention;

Fig. 4 is a graph showing the variation of water inflow with time under different water level drawdowns in a preferred embodiment of the present invention;

Fig. 5 is a comparison chart of measured water inflow and calculated water inflow over time in a preferred embodiment of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

Taking a tunnel project crossing the fault fracture zone as an example to cause water gushing in the tunnel, the shield project is divided into the south line tunnel and the north line tunnel, with a total length of about 1676m. The excavation layer of the tunnel is weathered mixed granite and weathered siltstone under the action of dynamic metamorphism The resulting mylonite fault fracture zone. When the shield tunnel was excavated in the fracture zone of the mylonite fault, due to the large degree of fragmentation of the mylonite rock mass, the tunnel water gushing disaster occurred in the excavation of the south line tunnel. According to the on-site detection, the surrounding water level dropped to 10.13m after the tunnel water gushing .

A method for determining the water inflow of a tunnel in a fractured confined aquifer considering multiple factors, the specific implementation method is as follows:

The first step is to survey the tunnel construction site, determine its soil layer division information and groundwater distribution, and conduct indoor geotechnical tests on the samples taken from boreholes to obtain the physical and mechanical parameters of the soil layer.

Specifically: Percussive drilling method is used to drill holes every 50m along the tunnel to determine the soil layer information along the tunnel; after detection, there is a mylonite fault fracture zone, the mylonite fault fracture zone is 300m long in the south line tunnel, The length of the northern tunnels is 345m, and the width of the mylonite fault fracture zone is about 35m, and the shield layer is a strongly weathered layer. In addition, the mylonite fault fracture zone intersects the shield section at a small angle, but forms an included angle of 26° with the x-axis, as shown in Figure 1.

There are 6 layers of soil within the depth of 50m along the tunnel:

The first layer is plain fill, with a layer thickness of 2.15m, a natural weight of 19.56kN/m ³ , and a permeability coefficient k _x ', _ky ', and k _z ' of 1.31m/d;

The second layer is medium-coarse sand with a layer thickness of 3m, a natural gravity of 18.13kN/m ³ , and a permeability coefficient of k _x ', _ky ', and k _z ' of 3.35m/d;

The third layer is silty clay with a layer thickness of 3m, a natural weight of 18.63kN/m ³ , and a permeability coefficient k _x ', _ky ', k _z ' of 0.184m/d;

The fourth layer is composed of strongly weathered mixed granite, strongly weathered siltstone and strongly weathered mylonite. Strongly weathered mylonite is produced by strong weathered mixed granite and strongly weathered siltstone under dynamic metamorphism; among them: strongly weathered mixed The layer thickness of granite is 14.2m, the natural weight is 18.8kN/m ³ , and the permeability coefficients k _x ', _ky ', k _z ' are all 2m/d; the layer thickness of strongly weathered siltstone is 14.2m, and the natural weight is 19.6kN/m ³ , the permeability coefficient k _x ', _ky ', k _z ' are all 1.2m/d; the layer thickness of strongly weathered mylonite is 14.2m, the natural gravity is 24.5kN/m ³ , the permeability coefficient k _x ', k _y ', k _z ' are all 3.6m/d;

The fifth layer is composed of moderately weathered mixed granite, moderately weathered siltstone and moderately weathered mylonite. The moderately weathered mylonite is produced by the dynamic metamorphism of moderately weathered mixed granite and moderately weathered siltstone; among them: moderately weathered mixed The layer thickness of granite is 6.9m, the natural weight is 19.11kN/m ³ , and the permeability coefficients k _x ', _ky ', k _z ' are all 1.8m/d; the layer thickness of moderately weathered siltstone is 6.9m, and the natural weight is 24.5kN/m ³ , and the permeability coefficients k _x ', _ky ', ^and k _z ' are all 1.1m/d; the layer thickness of medium weathered mylonite is 6.9m, and the natural gravity is k _x ', k _y ', k _z ' are all 3.2m/d;

The sixth layer is composed of slightly weathered mixed granite, slightly weathered siltstone and slightly weathered mylonite. The slightly weathered mylonite is produced by the dynamic metamorphism of slightly weathered mixed granite and slightly weathered siltstone; among them: slightly weathered mixed The layer thickness of granite is 5.68m, the natural weight is 24.01kN/m ³ , and the permeability coefficients k _x ', _ky ', k _z ' are all 1.5m/d; the layer thickness of slightly weathered siltstone is 5.68m, and the natural weight is 25.48kN/m ³ , and the permeability coefficients k _x ', _ky ', and k _z ' are all 1.0m/d; the layer thickness of micro-weathered mylonite is ^5.68m , and the natural k _x ', _ky ', k _z ' are all 2.6m/d.

According to the soil exposed above, the aquifer can be divided into two types: pore phreatic and fractured confined aquifer, in which: the stable water level of the pore phreatic aquifer is 1.5m below the surface, and the stable water level of the fractured confined aquifer is below the surface 2m.

The second step is to check the tunnel design instructions to obtain the tunnel length, tunnel radius, and tunnel center buried depth information; through the field pumping test along the tunnel, obtain the pumping well and its corresponding observation well information.

In this embodiment: the total length of the shield tunnel is 1676m, the radius of the tunnel is 3m, and the buried depth of the center of the tunnel is about 13.58m below the surface; the field pumping test is carried out in the strong weathered layer of the mylonite fault fracture zone, wherein : The corresponding observation wells of pumping well M27-2 are M27-2-1 and M27-2-2, the corresponding observation wells of pumping well M24 are M24-1 and M24-2, and the corresponding observation wells of pumping well S07 are S07-1 , the horizontal distance between the observation well with "-1" at the end and its pumping well is 5m, the horizontal distance between the observation well with "-2" and its pumping well is 10m, and the level of pumping well M27-2 to pumping well M24 The distance is 44m and the vertical distance is 13m. The horizontal distance from M27-2 to S07 is 84m and the vertical distance is 3m. The bottom buried depth of pumping well M27-2 and its observation wells M27-2-1 and M27-2-2 is 20.8m, and the bottom buried depth of pumping well M24 and its observation wells M24-1 and M24-2 is 21m , the buried depth of the bottom of the pumping well S07 and its observation well S07-1 is 25m; for the pumping well M27-2 and its observation wells M27-2-1, M27-2-2: the buried depth of the top of the filter is 6.2m, The buried depth of the bottom of the filter is 20.8m; for the pumping well M24 and its observation wells M24-1 and M24-2: the buried depth of the top of the filter is 5m, and the buried depth of the bottom of the filter is 21m; for the pumping well S07 and its observation well S07 -1: The buried depth of the top of the filter is 9m, and the buried depth of the bottom of the filter is 25m.

There are three drawdowns in the pumping test, among which:

For the pumping well M27-2, the three water level drawdown values are 8.02m, 6.74m, 5.37m respectively, and the corresponding pumping volumes are 25.5m ³ /d, ^{20.7m 3} /d, 15.8m ³ /d respectively. The time is 1460min, 1400min, 1760min respectively;

For the pumping well M24, the three water level drawdowns are 5.63m, 4.55m, and 2.92m respectively, and the corresponding pumping volumes are 403.2m ³ /d, 245.28m ³ /d, and 84.72m ³ /d respectively, and the pumping time is respectively 1515min, 1435min, 1560min;

For the pumping well S07, the three water level drawdown values are 1.80m, 2.50m, 3.00m, the corresponding pumping volumes are 40.32m ³ /d, 76.9m ³ /d, ^{113.47m 3} /d respectively, and the pumping time is 1500min , 1490min, 1516min.

During the three drawdowns, the water level drawdown values of the observation well M27-2-1 were 1.9m, 1.58m, and 1.2m respectively, and the water level drawdown values of the observation well M27-2-2 were 0.55m and 0.42m respectively , 0.26m, the water level drawdown values of observation well M24-1 are 1.7m, 1.4m, 0.6m respectively, and the water level drawdown values of observation well M24-2 are 1.4m, 1.1m, 0.5m respectively; The variation of water level drawdown with time is shown in Fig. 2.

The third step is to combine the soil layer and pumping test information of the first and second steps to establish a three-dimensional finite difference model, and invert the permeability coefficients k _x , _ky , k _z and Water storage rate S _s .

The plane size of the three-dimensional finite difference model is determined according to the maximum influence radius _Rmax of the pumping wells in the pumping test, and _Rmax is the maximum value of the influence radius R of each pumping well in the pumping test; in the pumping test, the pumping wells M27-2, M24 The influence radius R satisfies the following formula:

Therefore, the maximum influence radius R _max of the pumping wells in the pumping test is 200m, and the boundary wells are the pumping wells M24 (topmost and leftmost), M27-2 (bottommost) and S07 (far right), according to the maximum influence radius R _max and the position of the boundary well, it is determined that the length of the 3D finite difference model along the horizontal direction is at least 528m, and the length along the vertical direction is at least 410m, then the plane size of the 3D finite difference model is taken as 600m ×600m (as shown in Figure 3);

Then divide the 3D finite difference model into grids according to the soil layer division information obtained in the first step, input the initial parameters, and set the initial water level and boundary conditions of the 3D finite difference model; run the program, the water level drawdown to be calculated and the measured water level drawdown When the relative error between values is less than 5% (as shown in Figure 2), the inversion coefficients k _x , ky , k _z and water storage rate S _s of the soil layers along the tunnel in x, _y , and z directions are obtained through inversion; of:

The k _x , _ky , k _z , S _s of the first layer of plain fill are 0.02m/d, 0.02m/d, 0.003m/d, 2.00E-06(m ^-1 ) respectively;

The k _x , _ky , k _z , and S _s of the coarse sand in the second layer are 3.50m/d, 3.50m/d, 1.00m/d, and 0.00025(m ^-1 ), respectively;

The k _x , _ky , k _z , and S _s of the third layer of silty clay are 0.25m/d, 0.25m/d, 0.1m/d, and 3.50E-06(m ^-1 ), respectively;

The k _x , _ky , k _z , S _s of the strongly weathered mixed granite of the fourth layer are 0.9m/d, 0.6m/d, 0.1m/d, 3.0E-06(m ^-1 ) respectively, and the strongly weathered siltstone k _x , _ky , k _z , and S _s are 0.5m/d, 0.08m/d, 0.05m/d, 1.5E-06(m ^-1 ) respectively, and k _x , k _y of strongly weathered mylonite , k _z , and S _s are 5.6m/d, 2.6m/d, 0.4m/d, and 6.0E-05(m ^-1 ), respectively.

The k _x , _ky , k _z , and S _s of the weathered mixed granite in the fifth layer are 0.6m/d, 0.3m/d, 0.2m/d, and 2.0E-06(m ^-1 ), respectively, and the weathered siltstone k _x , _ky , k _z , and S _s are 0.05m/d, 0.03m/d, 0.01m/d, and 7.5E-07(m ^-1 ) respectively, and k _x , k _y of moderately weathered mylonite , k _z , and S _s are 2.5m/d, 1.1m/d, 0.08m/d, and 4.00E-07(m ^-1 ), respectively.

The k _x , _ky , k _z , and S _s of the sixth layer of slightly weathered mixed granite are 0.1m/d, 0.08m/d, 0.04m/d, 2.0E-07(m ^-1 ), and the slightly weathered siltstone k _x , _ky , k _z , and S _s are 0.01m/d, 0.008m/d, 0.008m/d, and 1.00E-07(m ^-1 ) respectively, and k _x , k _y of slightly weathered mylonite , k _z , and S _s are 0.15m/d, 0.05m/d, 0.02m/d, and 3.0E-07(m ^-1 ), respectively.

The fourth step is to select a point (x ₀ , y ₀ , z ₀ ) in the tunnel, select the lengths dx, dy, and dz along the x, y, and z axes respectively, and assume that the confined aquifer of the tunnel fracture extends infinitely along the xy plane of the horizontal plane, The roof and bottom of the fractured confined aquifer are set as non-seepage boundaries, and the governing equations and initial boundary conditions at (x ₀ , y ₀ , z ₀ ) in the tunnel are determined.

The governing equation satisfies the following formula:

In the formula: t is the time (d); h is the water level (m) of a certain point (x, y, z) in the tunnel at time t; Q(t) is the water level (m) of a certain point (x, y, z) in the tunnel at t Time inflow of tunnel water.

The initial boundary conditions satisfy the following formula:

h(x,y,z,t=0)=h ₀ ＝8.19m

h(x=±∞,y,z,t)=h(x,y=±∞,z,t)=h ₀ ＝8.19m;

In the formula: h ₀ is the initial water level (m), and M is the thickness of the fractured confined aquifer (m).

The fifth step is to introduce the water level drawdown S(t) at time t, and convert S(t) and the variables t, x, y, and z in the control equation of the fourth step into dimensionless variables S _D (t), t _D , x _D , y _D , z _D , and then substitute the converted dimensionless variables into the control equation and initial boundary conditions in the fourth step to determine the dimensionless water level drawdown S _D (t _D ).

in:

The water level drawdown S(t) at time t satisfies the following formula:

S(t)=8.91-h;

The dimensionless variables respectively satisfy the following formulas:

z _wD = 0.49, L _D = 3.82;

The dimensionless water level drawdown S _D (t _D ) satisfies the following formula:

In the sixth step, according to the dimensionless water level drawdown S _D (t _D ) in the fifth step, determine the tunnel water inflow Q(t) in the fractured confined aquifer considering multiple factors.

Described Q (t) satisfies following formula:

but:

The seventh step, combined with the tunnel water inflow Q(t) in the fractured confined aquifer determined in the sixth step, taking time t as the horizontal axis and taking the tunnel water inflow Q(t) in the fractured confined aquifer as the vertical axis, Establish a Cartesian rectangular coordinate system, and make a Q(t)-t relationship diagram under different water level drawdown values S(t); as shown in Figure 4.

When the water level drawdown is 10.13m, the calculated tunnel water inflow value and the actual measured water inflow have a high degree of fitting, as shown in Figure 5.

A method for determining water inflow in tunnels in fractured confined aquifers in consideration of multiple factors described in the present invention, the method not only considers the anisotropic characteristics and time effects of fractured confined aquifers, but also considers the water inflow after tunnel water gushes The relationship between water level and water level drawdown, through the method of the present invention, not only can determine the water inflow of the tunnel, but also can explore the relationship of the water inflow of the tunnel with time under the change of different factors; the method of the present invention is simple, applicable, and convenient Promotion has great engineering application value.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (10)

1. a method for determining water inflow in tunnels in fractured confined aquifers considering multiple factors, is characterized in that, comprising the steps: The first step is to survey the tunnel construction site, determine the soil layer division information of the tunnel construction site and the distribution of groundwater, and conduct indoor geotechnical tests on the samples taken from the borehole to obtain the physical and mechanical parameters of the soil layer; The second step is to check the tunnel design instructions to obtain the tunnel length, tunnel radius, and tunnel center buried depth information; through the field pumping test along the tunnel, obtain the pumping well and its corresponding observation well information; The third step is to combine the information obtained in the first and second steps to establish a three-dimensional finite difference model to invert the permeability coefficient k _x , ky , k z and water storage rate S of the soil layer along the tunnel in the x, _y , and _z directions _s ; The fourth step is to select a point (x ₀ , y ₀ , z ₀ ) in the tunnel, select the lengths dx, dy, and dz along the x, y, and z axes respectively, and assume that the confined aquifer of the tunnel fracture extends infinitely along the xy plane of the horizontal plane, The roof and bottom of the fractured confined aquifer are set as non-seepage boundaries, and the control equation and initial boundary conditions at (x ₀ , y ₀ , z ₀ ) in the tunnel are determined; the control equation satisfies the following formula: In the formula: t is the time (d), h is the water level (m) of a certain point (x, y, z) in the tunnel at time t, Q(t) is the water level (m) of a certain point (x, y, z) in the tunnel at t The water inflow of the tunnel at any time; The fifth step is to introduce the water level drawdown S(t) at time t, and convert S(t) and the variables t, x, y, and z in the control equation of the fourth step into dimensionless variables S _D (t), t _D , x _D , y _D , z _D , and then substitute the converted dimensionless variables into the control equation and initial boundary conditions in the fourth step to determine the dimensionless water level drawdown S _D (t _D ); The sixth step, according to the dimensionless water level drawdown S _D (t _D ) in the fifth step, determine the tunnel water inflow Q(t) in the fractured confined aquifer considering multiple factors; The seventh step, combined with the water inflow Q(t) determined in the sixth step, establishes a Cartesian rectangular coordinate system with time t as the horizontal axis and water inflow Q(t) as the vertical axis, and draws down values of different water levels S( Q(t)-t relationship graph under t). 2. the method for determining water inflow in tunnels in a kind of fractured confined aquifer considering multiple factors according to claim 1, is characterized in that, in the first step, has following one or more characteristics: -The information on determining the division of soil layers includes the type of soil layer and the thickness of the layers, that is, percussive drilling is used to drill holes at intervals of 50m along the tunnel, and the soil within the depth range of 50m below the surface is obtained with a thin-walled soil extractor, thereby obtaining Soil layer type and layered thickness along the tunnel; -Determining the groundwater distribution includes aquifer type, thickness, and the stable water level of the aquifer, wherein: the aquifer type and thickness are determined by the soil layer division information exposed by percussion drilling; the stable water level of different aquifers is observed by drilling, for bearing Measure the stable water level of the aquifer after taking water-proof measures to isolate the measured aquifer from other aquifers; -The indoor geotechnical test refers to: density test, indoor penetration test; -The physical and mechanical parameters of the soil layer refer to: natural weight, permeability coefficient, wherein the permeability coefficient is divided into vertical z-direction permeability coefficient k _z ' and horizontal x-direction, y-direction permeability coefficient k _x ', k _y ' , and k _x '= _ky '. 3. the method for determining water inflow in tunnels in a kind of fractured confined aquifer considering multiple factors according to claim 1, is characterized in that, in the second step, has the following one or more characteristics: -The pumping test refers to: drilling a well within the depth of the aquifer to be pumped, and the drilling depth is greater than the depth of the aquifer, using pumping equipment to pump water, and synchronously recording the pumping well and its corresponding observation well information during the pumping process; -The pumping wells and their corresponding observation well information refer to: the pumping volume, pumping time, water level drawdown value of the pumping wells, the water level drawdown values of the observation wells at different times, the number of pumping wells and their corresponding observation wells and Positional relationship. 4. according to claim 3, a kind of method for determining water inflow in tunnels in fractured confined aquifers considering multiple factors, is characterized in that, the positional relationship of described pumping wells and corresponding observation wells thereof refers to: pumping wells Horizontal distance and vertical distance between water wells, horizontal distance between pumping wells and their corresponding observation wells, bottom embedding depths of pumping wells and their corresponding observation wells, top burial depth and bottom of filters of pumping wells and their corresponding observation wells Buried deep. 5. according to claim 1-4 any one described a kind of method for determining water inflow of tunnel in the fissure confined aquifer that considers multiple factors, it is characterized in that, in the 3rd step, described three-dimensional finite difference model plane The size is determined according to the maximum influence radius R _max of the pumping well in the pumping test, and the 3D finite difference model is meshed according to the soil layer division information obtained in the first step, and the initial parameters are input to set the initial water level and boundary of the 3D finite difference model conditions, where: the initial water level is determined according to the stable water level of the aquifer obtained in the first step, and the boundary condition is set as the constant head boundary. 6. the method for determining water inflow in a kind of fractured confined aquifer considering multiple factors according to claim 5, characterized in that, has one or more of the following characteristics: -The maximum influence radius R _max is the maximum value of the influence radius R of each pumping well in the pumping test; R satisfies the following formula: In the formula: _ri is the distance from the observation well to the pumping well, i=1, 2, (m); s _i is the maximum water level drawdown of the observation well, i=1, 2, (m); -The plane size of the three-dimensional finite difference model is determined according to the maximum influence radius R _max of the pumping well in the pumping test, which means: determine the boundary pumping well according to the relative position of the pumping well in the pumping test, that is, the top, the bottom, and the leftmost The side and the rightmost side, with the boundary pumping well as the center, respectively extend to the outermost side by a distance greater than or equal to the maximum influence radius R _max , that is, determine the plane size of the three-dimensional finite difference model; -The initial parameters include: initial gravity; initial x, y, z direction permeability coefficient and initial water storage rate; wherein: the natural gravity determined in the first step is used as the initial gravity, and the permeability coefficient determined in the first step is used as the initial gravity k _x ', _ky ', and k _z ' are the initial permeability coefficients in the x, y, and z directions, respectively, and the initial water storage rate S _s ' is determined in accordance with the code "Code for Geological Survey of Water Conservancy and Hydropower Engineering" (GB50487-2008). 7. the method for determining water inflow in tunnels in a kind of fractured confined aquifer considering multiple factors according to claim 1, is characterized in that, in the third step, described inversion refers to: input the second step The obtained pumping wells and their corresponding observation well information, run the three-dimensional finite difference model to calculate the water level drawdown value of the observation well, and compare the calculated water level drawdown value of the observation well with the measured water level drawdown value of the observation well in the pumping test , if the error of the two is greater than 5%, adjust the initial permeability coefficient and initial water storage rate in the x, y, and z directions according to experience, and re-run the three-dimensional finite difference model until the error of the two is less than 5%, so as to finally determine the soil along the tunnel. Permeability coefficients k _x , ky , k _z and water storage rate S _s of layers in x, _y , and z directions. 8. the method for determining water inflow in a kind of fractured confined aquifer considering multiple factors according to claim 1, is characterized in that, in the 4th step: described initial boundary condition satisfies the following formula: h(x,y,z,t=0)=h ₀ h(x=±∞,y,z,t)=h(x,y=±∞,z,t)=h ₀ In the formula: h ₀ is the initial water level (m), and M is the thickness of the fractured confined aquifer (m). 9. the method for determining water inflow in tunnels in a kind of fractured confined aquifer considering multiple factors according to claim 1, is characterized in that, in the 5th step, has following one or more characteristics: -The water level drawdown S(t) at the moment t satisfies the following formula: S(t)=h ₀ -h; -The dimensionless variables S _D (t), t _D , x _D , y _D , z _D respectively satisfy the following formulas: In the formula: S _D (t), t _D , x _D , y _D , z _D are dimensionless forms of S(t), t, x, y, z respectively; -The dimensionless water level drawdown S _D (t _D ) satisfies the following formula: where L is the length of the tunnel (m); τ is a time-related variable; z _wD and L _D are the dimensionless forms of z _w and L, and z _w is the vertical distance from the center of the tunnel to the floor of the fractured confined aquifer (m); erf(x) is a Gaussian error function; exp(x) is an exponential function; specifically satisfy the following formula: exp(x)=e ^x , In the formula: η is an integral variable, and its interval range is [0,x]. 10. the method for determining water inflow in a kind of fractured confined aquifer considering multiple factors according to claim 1, is characterized in that, in the 6th step, described Q (t) satisfies: In the formula: Q(t) is the tunnel water inflow at a point (x, y, z) in the tunnel at time t; r is the tunnel radius (m); L is the tunnel length (m); S(t) is the time t M is the thickness of the fractured confined aquifer (m); k _x is the permeability coefficient of the soil layer along the tunnel in the x direction (m/d); k _y is the permeability coefficient of the soil layer along the tunnel in the y direction (m/d); k _z is the permeability coefficient in the z direction of the soil layer along the tunnel (m/d); S _s is the water storage rate of the soil layer along the tunnel (m ^-1 ); t is time (d).