CN115221727B - A method for determining parameters of numerical simulation model of rock mass based on water content - Google Patents

Abstract

The invention discloses a method for determining parameters of a numerical simulation model of rock mass based on moisture content, which includes: generation of joint and fissure simulation models; acquisition of relationship expressions of parameters changing with moisture content; calibration of parameters of rock mass; acquisition of different water contents Rock mass mechanical parameters under the rate. The method of the present invention combines indoor rock mechanics experiments to determine the changing rules of rock mechanical characteristics with water content, adopts parameter calibration methods to obtain rock mass mechanical parameters under specific water content conditions, and further calculates rock mass mechanical parameters based on rock mechanical parameters and rock mass mechanical parameters. The mapping relationship determines the changing relationship of the mechanical parameters of the rock mass, thereby obtaining the numerical simulation model of the rock mass under different water contents to calculate the parameters. It can obtain the deformation data of the tunnel with high efficiency and high precision, providing numerical simulation analysis for the safety of tunnel construction. guide.

Description

A method for determining parameters of numerical simulation model of rock mass based on water content

Technical field

The invention relates to the technical field of tunnel construction, and in particular to a method for determining parameters of a numerical simulation model of rock mass based on moisture content.

Background technique

Affected by complex geological conditions, the moisture content of the rock mass at different mileage of the tunnel changes greatly. For example, surface precipitation, groundwater, etc. will seep along the cracks in the fault fracture zone. For the rock mass surrounding the fault fracture zone, its moisture content will gradually decrease as the distance from the fault fracture zone increases. For soft rocks, their mechanical properties are significantly affected by moisture content. For example, rocks with higher moisture content tend to have lower strength. Changes in moisture content will also cause changes in the rock's elastic modulus, cohesion, and internal friction angle.

During the construction of tunnels and other underground projects, safety has always been the focus of practitioners in related fields. When the rock around the tunnel is soft rock, tunnel excavation construction under high moisture content is prone to large deformation problems, such as initial support fractures, concrete spalling, severe secondary lining cracking, etc., which pose serious challenges to construction safety. . Existing engineering experience also shows that for the same type of rock mass, when the water content is low, large deformation problems will not occur during tunnel excavation. This shows that the moisture content of the rock mass has an extremely significant impact on the tunnel deformation.

When the rock mass around the tunnel is soft rock mass and its moisture content may change greatly, if the tunnel needs to pass through a fault fracture zone, in order to deal with the risk of large deformation that may occur, risk response measures usually need to be formulated in advance, which requires prior Conduct construction safety analysis. With the development of computer technology, numerical simulation has gradually become one of the important means to analyze the safety of tunnel construction. No matter which of the many methods such as finite element method, finite difference, discrete element method, and block discrete element method is used, the accuracy of the analysis results of the established numerical simulation model is consistent with the input rock mass mechanical parameters and joint planes. parameters are closely related. Among these parameters, the accuracy of rock mass mechanical parameters is particularly important, mainly elastic modulus, cohesion, and internal friction angle.

Indoor experiments are an important means to determine the mechanical characteristics of rocks, through which basic mechanical parameters such as elastic modulus, cohesion and internal friction angle of rocks can be obtained. Rock mass is a complex composed of rocks and many structural surfaces. The structural surface is the weak interface of rock mass, and its shear and tensile strength are lower than that of rock. Affected by structural planes, the mechanical parameters of rock mass will be significantly lower than those of rock. Based on the current experimental conditions, experiments to determine basic mechanical parameters such as rock mass elastic modulus, cohesion and internal friction angle still cannot be effectively carried out, resulting in a large subjectivity in the method of determining rock mass mechanical parameters, which is not conducive to tunnels. Simulation analysis of construction safety cannot effectively carry out tunnel deformation analysis under different water contents, which brings great inconvenience to tunnel deformation prediction.

Contents of the invention

The present invention provides a method for determining parameters of a numerical simulation model of rock mass based on moisture content. This method uses a parameter calibration method to obtain specific moisture content conditions based on combining indoor rock mechanics experiments to determine the changing rules of rock mechanical characteristics with moisture content. The rock mass mechanical parameters under the conditions are further determined based on the mapping relationship between the rock mechanical parameters and the rock mass mechanical parameters, so as to obtain the calculation of parameters of the rock mass numerical simulation model under different water contents, which can efficiently And the deformation data of the tunnel can be obtained with high precision, providing guidance for numerical simulation analysis of tunnel construction safety. The specific technical solution of this method is as follows:

A method for determining parameters of a numerical simulation model of rock mass based on water content, including the following steps:

The generation of the joint crack simulation model specifically includes: taking photos of the tunnel face, using the DeepLabv3+ algorithm to analyze the photos, and extracting the characteristics of the joint cracks, which include length, number, and spacing; using the Monte-Carlo method to regenerate and A joint crack simulation model consistent with the characteristics of joint cracks;

Obtaining the relationship expression of parameters changing with water content specifically includes: using indoor experiments to determine the parameters of rocks under different saturation states, and obtaining the relationship expression of each parameter changing with water content through fitting processing; parameters include elastic modulus, Cohesion and internal friction angle;

Calibrate the parameters of the rock mass, specifically: combined with the deformation data monitored on site, use the parameter calibration method to determine the mechanical parameters of the rock mass under a certain moisture content state;

Obtain the rock mass mechanical parameters under different water contents, specifically: substitute the obtained rock mass mechanical parameters into the relationship between parameters changing with water content to obtain the rock mass mechanical parameters under different water contents.

Preferably, the joint and crack simulation model is being generated:

Take photos of the tunnel face, specifically 5-10 photos; take photos of 5-10 tunnel faces under the same stratigraphic conditions, and take the average value of the joint and crack distribution characteristics of the tunnel face as the joint and crack simulation model Modeling basis.

Preferably, the relationship between parameters changing with moisture content is obtained:

Moisture content states of rock include dry, 20%, 40%, 60%, 80% and 100%;

The elastic modulus, cohesion and internal friction angle in rocks change with water content as follows:

The elastic modulus changes with moisture content as follows:

E＝E ₀ e ^-Aw ;

Among them: E is the elastic modulus of rock under a certain moisture content, E ₀ is the elastic modulus of rock in a dry state, w is the moisture content, and A is the elastic modulus reduction coefficient;

The cohesion changes linearly with changes in moisture content as follows:

c=k ₁ w+c ₀ ;

Among them: c is the cohesion of rock in a certain moisture content state, c ₀ is the cohesion of rock in dry state, k ₁ is the corresponding coefficient of rock cohesion changing with moisture content;

The internal friction angle changes linearly with the change of moisture content as follows:

in: is the internal friction angle of rock under a certain moisture content,/> is the internal friction angle of the rock in the dry state, and k ₂ is the corresponding coefficient of the internal friction angle of the rock that changes with the moisture content.

Preferably, the parameters of the rock mass are being calibrated:

A total station is used to track and measure the deformation data of the tunnel, which includes the vault settlement and the inner contour width of the tunnel;

The criterion for successful parameter calibration is: based on the input rock mass mechanical parameters, the deformation data of the tunnel calculated through the numerical simulation model in the parameter calibration method is consistent with the deformation data monitored on site.

Preferably, during the parameter calibration process: if the calculated deformation data of the tunnel is greater than the deformation data monitored on site, increase the mechanical parameters of the rock mass and recalibrate; if the calculated deformation data of the tunnel is less than the deformation monitored on site, If the data is obtained, the mechanical parameters of the rock mass will be reduced and recalibrated.

Preferably, the deformation of the tunnel increases linearly as the internal friction angle and cohesion decrease, as shown in the following formula:

D=B ₁ c+d ₀ ,

Among them: D is the tunnel deformation, B ₁ and B ₂ are constants, c and represent the cohesion force and internal friction angle respectively, and d ₀ is the tunnel deformation when the cohesion force or internal friction angle is 0;

The deformation of the tunnel increases as an inversely proportional function as the elastic modulus decreases, as follows:

Among them: D is the tunnel deformation, C ₁ and C ₂ are constants, and x is the elastic modulus.

Preferably, the elastic modulus, cohesion and internal friction angle of the rock mass in the mechanical parameters of the rock mass under different water contents are obtained as follows:

The elastic modulus changes with moisture content as follows:

E _rm =E _rm0 e ^-Aw ;

Among them: E _rm is the elastic modulus of rock mass under a certain moisture content, and E _rm0 is the elastic modulus of rock mass in dry state.

The cohesion changes linearly with changes in moisture content as follows:

c _rm = k ₁ w + c _rm0 ;

Among them: c _rm is the cohesion of rock mass in a certain moisture content state, and cr _rm0 is the cohesion of rock mass in dry state.

The internal friction angle changes linearly with the change of moisture content as follows:

in: is the internal friction angle of the rock mass under a certain moisture content,/> is the internal friction angle of the rock mass in the dry state.

Preferably, the parameter calibration allows the error range between the calculated tunnel deformation data and the field-monitored deformation data to be no more than 5%.

Description of drawings

Figure 1 is a schematic flow chart of a method for determining parameters of a numerical simulation model in Embodiment 1 of the present invention;

Figure 2 is a schematic diagram of Mohr's circle under different working conditions in Embodiment 1 of the present invention;

Figure 3 is a schematic diagram of the initial support unit in Embodiment 1 of the present invention;

Figure 4 is a schematic diagram of tunnel deformation calculated in Embodiment 1 of the present invention.

Detailed ways

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, and the protection scope of the present invention can be more clearly defined.

Example:

A method for determining the parameters of a numerical simulation model of rock mass based on moisture content. The specific process is shown in Figure 1, which specifically includes the following steps:

Step 1. Obtain the relationship between parameters and water content (that is, obtain rock mechanical parameters as water content changes based on indoor experiments). Specifically, it includes: using indoor experiments to determine the parameters of rocks in different saturated states, and processing them through fitting. The relationship between each parameter changing with moisture content is obtained; the parameters include elastic modulus, cohesion and internal friction angle. Details are as follows:

By carrying out stress-strain testing of rock, its elastic modulus under different moisture content conditions is determined. The testing method is as follows: first, the strength of the rock is obtained through uniaxial loading, and then another identical rock sample is taken to carry out a loading and unloading test. After reaching 70% of the rock strength, unload, repeat this cycle 3-5 times, and obtain the stress-strain curve of the rock during loading and unloading. Then take the elastic modulus of the last unloading as the elastic modulus of the rock. The calculation formula is as follows:

Among them: Δσ and Δε are the stress and strain changes during the last unloading period respectively.

Assuming that the strength of rock at a certain moisture content is 30MPa, the rock stress-strain parameters obtained by successive loading are shown in Table 1:

Table 1 Statistical table of rock stress-strain parameters

Another batch of rocks were selected to conduct triaxial tests under specific water content conditions. The rock strengths were measured when the confining pressure was 2, 4, 6, and 8 (MPa). Combined with the uniaxial compression experimental strength, the shear stress-normal Mohr's circle is drawn in the stress coordinate system, and the shear strength change curve of the rock under this moisture content state is obtained through fitting, thereby obtaining the cohesion force and internal friction angle of the rock.

Assume that the triaxial strength of rock under a certain moisture content is obtained as shown in Table 2:

Table 2 Statistical table of triaxial strength of rocks under a certain moisture content

Working conditions 1 2 3 4 5 Confining pressure/MPa 0 2 4 6 8 Strength/MPa 30 33.3 36.9 40.6 43.9

Mohr's circles under different working conditions can be further drawn as shown in Figure 2. In Figure 2: the leftmost abscissa of the semicircle is the confining pressure, and the abscissa of the rightmost point is the intensity. A straight line can be drawn approximately such that it is tangent to these semicircles. Then the slope of the straight line is the internal friction angle The intersection point with the vertical axis is the cohesion c, from which the cohesion and internal friction angle at this moisture content can be obtained.

Finally, using software such as origin or Excel, the regression analysis method is used to fit the relationship between the changes in these mechanical parameters of the rock with the water content as follows:

The elastic modulus changes with moisture content as follows:

E＝E ₀ e ^-Aw ;

Among them: E is the elastic modulus of rock under a certain moisture content, E ₀ is the elastic modulus of rock in a dry state, w is the moisture content, and A is the elastic modulus reduction coefficient;

The cohesion changes linearly with changes in moisture content as follows:

c=k ₁ w+c ₀ ;

Among them: c is the cohesion of rock in a certain moisture content state, c ₀ is the cohesion of rock in dry state, k ₁ is the corresponding coefficient of rock cohesion changing with moisture content;

The internal friction angle changes linearly with the change of moisture content as follows:

in: is the internal friction angle of rock under a certain moisture content,/> is the internal friction angle of the rock in the dry state, and k ₂ is the corresponding coefficient of the internal friction angle of the rock that changes with the moisture content.

Step 2: Generation of joint crack simulation model, including:

Step 2.1. Based on DeepLabv3+, make statistics on the joint crack characteristics of the tunnel face. Specifically, take photos of the tunnel tunnel face, use the DeepLabv3+ algorithm to analyze the photos, and extract the characteristics of the joint cracks, which include length, number, and spacing; Preferred here: 5-10 photos should be taken of the tunnel face, so that the image analysis results can more truly reflect the joint and crack distribution characteristics of the current tunnel face. In addition, 5-10 photos should be taken under the same stratigraphic conditions. Take pictures of each tunnel face, and take the average value of the joint and crack distribution characteristics of the tunnel face as the basis for modeling the joint and crack characteristics of the numerical simulation model.

Step 2.2. Generate a joint crack simulation model based on the Monte-Carlo method. Specifically, use the Monte-Carlo method to generate a joint crack simulation model consistent with the joint crack characteristics of the tunnel face, and import it into the 3DEC block discrete element software. Use methods such as segmentation to partition the imported model to predetermine the tunnel excavation range to facilitate the simulation analysis of tunnel excavation. Then divide the established model into several grids, and assign the mechanical parameters of the rock mass to the grids. Empirical values are used to simulate the actual rock mass, and the bottom and sides of the model are further constrained, and a gravity field is applied to simulate the stratigraphic stress state before tunnel excavation, and then the simulation calculation of tunnel excavation is performed to obtain the simulation results of tunnel deformation.

The idea of creating a numerical simulation model is as follows: first generate a cuboid, use a subdivision method to partition the cuboid, part of the subdivided area is used to simulate tunnel excavation, and the remaining area is used to simulate the rock mass around the tunnel. After segmentation, the cuboid is segmented again to obtain the segmented cuboid.

At this time, the cuboid consists of two parts: the split surface and the split block. The divided cuboid is meshed to divide the divided block into several smaller units. At this point, the initially created cuboid consists of two parts, namely the splitting surface and the unit body. The split plane is given the mechanical parameters of joints and fissures, and the unit body is given the mechanical parameters of the rock mass, thereby achieving the purpose of simulating the actual rock mass. The bottom and sides of the cuboid are further constrained, and a gravity acceleration is applied to all unit bodies to simulate the influence of gravity in the actual environment. At this point, the rock mass creation work is completed, and the generated model can be considered a numerical simulation model. To further expand the calculation, each calculation of 3DEC will calculate the unbalanced force of all units. When the unbalanced force is small to a certain extent, such as 1e-5, it can be considered that equilibrium has been reached. At this time, the ground stress can be considered to have been reached. Equilibrium means that the current stress state of the cuboid is the same as the formation stress state in the actual environment.

It should be noted that at this time, the unit body of the cuboid has been deformed. When performing tunnel excavation analysis, it is necessary to reset the deformation and other contents to zero, which means that the ground layer has no displacement and a certain stress state before tunnel excavation. When simulating tunnel excavation, the purpose of simulating tunnel excavation is achieved by deleting the units within the tunnel range. In addition, a similar method is used to apply another part of the unit body to simulate the initial support at the tunnel contour, and give it the mechanical parameters of the initial support to simulate the initial support during the actual construction. Continuing with the calculation, when the unbalanced force is small enough, the tunnel can be considered to be in a stable condition. At this time, the unit body simulating the initial support will deform, and this deformation is the simulated value of the tunnel deformation. Figure 3 shows the established cuboid, in which the horseshoe-shaped black area is the divided tunnel area, and the seemingly messy black lines are the generated joint cracks. Figure 4 shows the calculated tunnel deformation, as shown in Figure 4 (the black arrow in the lower right corner points to the splitting surface formed by splitting the cube, and the black oval frame is the block formed by splitting) , it can be seen that it has many small triangles, which are the formed unit bodies; it is a tetrahedron in the three-dimensional space; the black lines in the black pass are given the mechanical parameters of joints and cracks, and these unit bodies are given the rock Mechanical parameters of the body to achieve the purpose of simulating the actual rock mass.

Step 3: Calibrate the parameters of the rock mass (that is, calibrate the parameters of the rock mass based on a numerical simulation model that considers joints and cracks and the deformation data monitored on site). Specifically, it is determined by using the parameter calibration method based on the deformation data monitored on site. The mechanical parameters of rock mass under a certain moisture content state are as follows:

Use a total station to track and measure the deformation data of the tunnel including vault settlement and horizontal convergence (tunnel inner contour width). Specifically: first determine the values of the rock mass mechanical parameters based on experience, and then input the mechanical parameters into step 2. Calculate in the established model to obtain the simulation results of tunnel deformation, and then make a judgment. Specifically: if the simulation results are greater than the results based on total station measurement, increase the rock mass mechanical parameters and perform calculations again, which will make The calculated tunnel deformation value decreases; if the simulation result is smaller than the total station measurement result, then reduce the mechanical parameters of the rock mass and perform the calculation again, which will increase the calculated tunnel deformation. By adjusting the rock mass mechanical parameters input in the three-dimensional simulation model, the calculated tunnel deformation data will continue to approach the measured value. If the deformation obtained by inputting a certain parameter of the rock mass is significantly greater than the measured result, increase the rock mass input. Parameters, recalculate. The criterion for successful parameter calibration is: based on the input rock mass mechanical parameters, the deformation data of the tunnel calculated through the numerical simulation model in the parameter calibration method is consistent with the deformation data monitored on site.

Preferred in this embodiment:

The moisture content status of the rock includes dry (i.e. 0%), 20%, 40%, 60%, 80% and 100%, and the percentage is the moisture content in the rock.

The deformation of the tunnel increases linearly with the decrease of the internal friction angle and cohesion, as shown in the following formula:

D=B ₁ c+d ₀ ,

Among them: D is the tunnel deformation, B ₁ and B ₂ are constants, c and represent the cohesion force and internal friction angle respectively, and d ₀ is the tunnel deformation when the cohesion force or internal friction angle is 0;

The deformation of the tunnel increases as an inversely proportional function as the elastic modulus decreases, as follows:

Among them: D is the tunnel deformation, C ₁ and C ₂ are constants, and x is the elastic modulus.

Preferably in this embodiment, the value range of B ₁ and B ₂ is in the range of 1e-4 to 1e-3, the value range of C ₁ is in the range of -10 to -100, and the value range of C ₂ is in the range of - Within the range of 0.1~-2.

When the deviation is within the acceptable range, such as 5%, the input model parameters can be considered reliable. At this time, the input rock mass mechanical parameters can be considered as the mechanical parameters of the rock mass near the tunnel deformation monitoring position. At this time, the rock mass mechanical parameters are The moisture content corresponding to the body mechanics parameters can be obtained by sampling indoor moisture content near the tunnel monitoring point, as shown in Table 3:

Table 3 Deformation monitoring data statistics table

Step 4: Obtain the rock mass mechanical parameters under different water contents (based on the mapping relationship between the rock mechanical parameters and the rock mass mechanical parameters, obtain the rock mass mechanical parameters under different water contents). The following is: Substitute the obtained rock mass mechanical parameters into The rock mass mechanical parameters under different water contents are obtained from the relationship between parameters changing with water content. Preferred in this embodiment:

The elastic modulus, cohesion and internal friction angle among the rock mass mechanical parameters change with the water content as follows:

The elastic modulus changes with moisture content as follows:

E _rm =E _rm0 e ^-Aw ;

Among them: E _rm is the elastic modulus of rock mass under a certain moisture content, and E _rm0 is the elastic modulus of rock mass in dry state.

The cohesion changes linearly with changes in moisture content as follows:

c _rm = k ₁ w + c _rm0 ;

Among them: c _rm is the cohesion of rock mass in a certain moisture content state, and cr _rm0 is the cohesion of rock mass in dry state.

The internal friction angle changes linearly with the change of moisture content as follows:

in: is the internal friction angle of the rock mass under a certain moisture content,/> is the internal friction angle of the rock mass in the dry state.

Specific application cases of the solution of the present invention:

Case 1: The Xinhuashan Tunnel of the Zhangjihuai Railway needs to pass through a fault fracture zone. The rock mass cracks in the fracture zone are developed, which can provide a good seepage channel for groundwater seepage. In the absence of rainfall, the moisture content of the rock mass around the tunnel is low. During rainfall, surface water will flow along the fracture zone and gradually seep to the vicinity of the tunnel, causing the moisture content of the rock mass around the tunnel to increase. Under natural conditions, the seepage of water in the rock mass is slow, resulting in large differences in the moisture content of the rock mass at different locations near the fracture zone of the tunnel. For example, the moisture content at the location of the crushing zone is 100%, the moisture content at a location 10m away from the crushing zone is 80%, and the moisture content at a location 50m away from the crushing zone is 50%. When excavating in an area far away from the fault fracture zone (such as 100m away from the fracture zone), the tunnel deformation is within the allowable range, and the moisture content of the rock mass at this time is about 10%. However, if additional reinforcement measures are not taken during the process of crossing the fault fracture zone, the deformation of the tunnel may exceed the allowable value, and even cause cracks and damage to the support system, resulting in delays in the construction period, increased costs, and other problems. If a large number of reinforcement measures are taken blindly, it will lead to problems such as material waste and increased project costs. To this end, it is necessary to analyze the construction safety under different moisture contents of the rock mass, thereby providing a certain theoretical basis for proposing reinforcement measures.

However, it is unknown how to determine the mechanical parameters of rock mass under different water contents. Indoor rock mechanics experiments can only obtain the mechanical parameters of rocks under different water contents. Based on the present invention, indoor rock mechanics experiments can be carried out first to obtain that the rock elastic modulus in the dry state and 100% moisture content are 36.30GPa and 8.50GPa respectively, thereby obtaining the elastic modulus reduction coefficient A = 1.45, that is, the rock elastic modulus The relationship between the amount and moisture content is as follows:

E=36.3e ^-1.45w .

Based on the present invention, it can be seen that the relationship between the elastic modulus of rock mass and the change of water content is as follows:

E _rm =E _rm0 e ^-1.45w .

In the above formula, E _rm0 is unknown, but it can be determined through parameter calibration.

The mechanical parameters of the rock mass were further calibrated based on the field measured data, and the elastic modulus of the rock mass at 10% moisture content was obtained to be approximately 1.04GPa, that is, 1.04=E _rm0 e ^-1.45×0.1 , and it can be obtained that E _rm0 =1.2GPa, Thus, the rate of change of the elastic modulus of the rock mass with the water content is obtained, as shown in the following formula:

E _rm =1.2e ^-1.45w .

Thus, the change of rock mass elastic modulus with water content can be obtained. The relationship between rock mass cohesion and internal friction angle with water content can be obtained using a similar method, and finally the mechanical parameters of the rock mass under different water contents can be determined. By substituting these parameters into the established three-dimensional simulation model, the tunnel deformation under different moisture contents can be calculated. The summary is shown in Table 4:

Table 4: Rock mass mechanical parameters and calculated tunnel deformation under different water contents using the method of the present invention

Based on the calculated vault settlement and horizontal convergence values, additional reinforcement measures that should be taken under different water contents of the rock mass can be further determined.

If the rock mass parameter determination method proposed by this invention is not used, the mechanical parameters of the rock mass under different water contents may be taken and the calculated rock mass deformation is shown in Table 5:

Table 5 Rock mass mechanical parameters and calculated tunnel deformation under different water contents

It can be seen that using other methods to evaluate will result in smaller calculated rock mass deformations. If certain reinforcement measures are not taken based on this method, accidents such as initial support cracking and damage may occur during tunnel construction.

Case 2:

Affected by the fault fracture zone, the rock mass around the Liyang Jiaoweiqin Tunnel is relatively fractured. In the case of heavy rainfall, rainwater will seep to the periphery of the tunnel. Under natural conditions, the joints and fissures of the rock mass are unevenly distributed, resulting in certain differences in the moisture content of the rock mass in different areas. In order to ensure construction safety, it is necessary to analyze the tunnel deformation under different moisture contents.

Based on the present invention, rock mechanics experiments are first carried out, and the relationship between rock cohesion and moisture content is obtained as follows:

c _r =-450w+1750;

The mechanical parameters of the rock mass were further calibrated based on on-site measured data, and it was found that the cohesion and internal friction angle of the rock mass were 395kPa and 26° respectively under the condition of 30% water content, thus obtaining the cohesion and internal friction angle of the rock mass with varying degrees. The rate of change of moisture content is as shown in the following formula:

_crm =-450w+530;

Based on the above formula, the changes of rock mass cohesion and internal friction angle with water content can be obtained. Using a similar method, the relationship between the elastic modulus of the rock mass and the water content can be obtained. Substituting these parameters into the established numerical model, the tunnel deformation under different moisture contents can be calculated. A summary of the rock mass mechanical parameters and tunnel deformation under different water contents is shown in Table 6:

Table 6: Rock mass mechanical parameters and calculated tunnel deformation under different water contents using the method of the present invention

If the rock mass parameter determination method proposed by this invention is not used, the mechanical parameters of the rock mass under different water contents and the calculated rock mass deformation may be obtained as shown in Table 7:

Table 7 Rock mass mechanical parameters and calculated tunnel deformation under different water contents

It can be seen that using other evaluation methods will lead to larger calculated rock mass deformations. If strong reinforcement measures are taken based on this method, the amount of steel bars, concrete, etc. may increase significantly, resulting in an increase in project costs.

The above are only examples of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the description and drawings of the present invention, or directly or indirectly applied to other related technologies fields are equally included in the scope of patent protection of the present invention.

Claims (6)

1. The method for determining the parameters of the numerical simulation model of the rock mass based on the water content is characterized by comprising the following steps of:

the generation of the joint fracture simulation model specifically comprises the following steps: photographing a tunnel face, analyzing the photograph by adopting a deep Labv3+ algorithm, and extracting the characteristics of joint cracks, wherein the characteristics comprise length, quantity and interval; regenerating an joint fracture simulation model which is matched with the characteristics of the joint fracture by adopting a Monte-Carlo method;

the obtaining of the variation relation of the parameters along with the water content specifically comprises the following steps: determining parameters of the rock in different water content states by adopting an indoor experimental mode, and obtaining a change relation of each parameter along with the water content through fitting treatment; parameters include modulus of elasticity, cohesion and internal friction angle;

in the acquisition of the relation of the change of the parameters along with the water content:

the water content state of the rock comprises dry, 20%, 40%, 60%, 80% and 100%;

the change of the elasticity modulus, the cohesion and the internal friction angle in the rock along with the water content is as follows:

the modulus of elasticity varies with the water content as follows:

E＝E ₀ e ^-Aw ；

wherein: e is the elastic modulus of the rock under the condition of a certain water content, E ₀ The elastic modulus of the rock in a dry state is represented by w, the water content is represented by w, and the modulus of elasticity is represented by A;

the cohesion changes in a linear relationship with the change in water content as follows:

c＝k ₁ w+c ₀ ；

wherein: c is the cohesive force of the rock under a certain water content state, c ₀ Is the cohesion of the rock in the dry state, k ₁ Is the coefficient of the corresponding cohesive force of the rock along with the change of the water content;

the internal friction angle varies in a linear relationship with the change in water content as follows:

wherein:is the internal friction angle of rock in a certain water content state,/->Is the internal friction angle, k, of the rock in the dry state ₂ Is the coefficient of the change of the internal friction angle of the corresponding rock along with the water content;

the change of the elastic modulus, the cohesion and the internal friction angle in the rock mass along with the water content is as follows:

the modulus of elasticity varies with the water content as follows:

E _rm ＝E _rm0 e ^-Aw ；

wherein: e (E) _rm Modulus of elasticity, E, of rock mass at a certain water content _rm0 Is the elastic modulus of the rock mass in a dry state;

the cohesion changes in a linear relationship with the change in water content as follows:

c _rm ＝k ₁ w+c _rm0 ；

wherein: c _rm Is the cohesive force of rock mass under a certain water content state, c _rm0 Is the cohesive force of the rock mass in a dry state;

the internal friction angle varies in a linear relationship with the change in water content as follows:

wherein:is the internal friction angle of rock mass under a certain water content state, +.>Is the internal friction angle of the rock mass in a dry state;

calculating the value of the rock elastic modulus under the dry state and the water content of 100% based on the rock elastic modulus obtained by the indoor rock mechanical experiment to obtain an elastic modulus reduction coefficient A;

determination of E by parameter calibration _rm0 ；

The change relation of the rock mass cohesive force and the internal friction angle along with the water content is obtained by adopting a similar method;

calibrating parameters of a rock mass, specifically: combining deformation data monitored on site, and determining rock mechanical parameters in a certain water content state by adopting a parameter calibration method;

rock mechanical parameters under different water contents are obtained, and the rock mechanical parameters concretely are: substituting the obtained rock mechanical parameters into a relation equation of the parameters changing with the water content to obtain the rock mechanical parameters under different water contents.

2. The method for determining parameters of a numerical simulation model according to claim 1, wherein in the generation of the joint fracture simulation model:

photographing the tunnel face, and particularly photographing 5-10 sheets; and 5-10 tunnel faces under the same stratum condition are photographed, and an average value of joint fracture distribution characteristics of the tunnel faces is taken as a modeling basis of the joint fracture simulation model.

3. The method for determining parameters of a numerical simulation model according to claim 1, wherein in the calibration of parameters of a rock mass:

tracking and measuring deformation data of the tunnel by adopting a total station, wherein the deformation data comprise vault settlement and inner contour width of the tunnel;

the criterion of successful parameter calibration is as follows: based on the input rock mechanical parameters, the deformation data of the tunnel calculated by the numerical simulation model in the parameter calibration method is identical with the deformation data monitored on site.

4. A method for determining parameters of a numerical simulation model according to claim 3, wherein in the parameter calibration process: if the deformation data of the tunnel obtained through calculation is larger than the deformation data monitored on site, increasing the mechanical parameters of the rock mass for recalibration; and if the calculated deformation data of the tunnel is smaller than the deformation data monitored on site, reducing the mechanical parameters of the rock mass and recalibrating.

5. The method for determining parameters of a numerical simulation model according to claim 4, wherein the deformation of the tunnel exhibits a linear increase with a decrease in internal friction angle and cohesion, as follows:

D＝B ₁ c+d ₀ ，

wherein: d is tunnel deformation, B ₁ 、B ₂ Is constant, c andrespectively represent cohesion and internal friction angle, d ₀ Tunnel deformation at 0 for cohesion or internal friction angle;

the deformation of the tunnel increases as an inversely proportional function with the decrease in elastic modulus as follows:

wherein: d is tunnel deformation, C ₁ 、C ₂ Is constant, x is elastic modulus.

6. A method according to claim 3, wherein the error range between the deformation data of the tunnel which is allowed to be calculated in parameter calibration and the deformation data monitored in the field is not more than 5%.