CN115221727B - Numerical simulation model parameter determination method of rock mass based on water content - Google Patents
Numerical simulation model parameter determination method of rock mass based on water content Download PDFInfo
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Abstract
The invention discloses a method for determining parameters of a numerical simulation model of a rock mass based on water content, which comprises the following steps: generating an joint fracture simulation model; acquiring a change relation of parameters along with the water content; calibrating parameters of the rock mass; and obtaining rock mechanical parameters under different water contents. According to the method, on the basis of determining the change rule of rock mechanical characteristics along with the water content by combining an indoor rock mechanical experiment, rock mechanical parameters under the condition of specific water content are obtained by adopting a parameter calibration method, and a change relation of the rock mechanical parameters is further determined based on the mapping relation of the rock mechanical parameters and the rock mechanical parameters, so that calculation of parameters is realized by a rock numerical simulation model under the condition of different water contents, deformation data of a tunnel can be obtained efficiently and accurately, and guidance is provided for numerical simulation analysis of tunnel construction safety.
Description
Technical Field
The invention relates to the technical field of tunnel construction, in particular to a method for determining parameters of a numerical simulation model of a rock mass based on water content.
Background
The water content of the rock mass at different mileage of the tunnel is greatly changed under the influence of complex geological conditions, for example, surface precipitation, underground water and the like can permeate along cracks in a fault fracture zone. The water content of the rock mass around the fracture zone gradually decreases due to the increase of the distance from the fracture zone. For soft rock, the mechanical properties are significantly affected by the water content, e.g., rock with higher water content tends to have lower strength. The change of the water content can also cause the change of the elastic modulus, the cohesion and the internal friction angle of the rock.
During construction of underground works such as tunnels, safety has been a focus of attention of practitioners in the relevant fields. When the rock around the tunnel is soft rock, the tunnel excavation construction is easy to generate large deformation problems under the condition of high water content, such as primary support fracture, concrete stripping, secondary lining fracture and the like, and serious challenges are brought to construction safety. The existing engineering experience simultaneously shows that the tunnel excavation can not have large deformation problem under the condition of low water content for the rock mass of the same type. This means that the water content of the rock mass has an extremely significant effect on the deformation of the tunnel.
When the rock mass around the tunnel is soft and the water content of the rock mass possibly changes greatly, for example, the tunnel needs to pass through a fault fracture zone, in order to cope with the possible large deformation risk, risk countermeasures are usually formulated in advance, and thus construction safety analysis needs to be carried out in advance. With the development of computer technology, numerical simulation is becoming one of the important means for analyzing the tunnel construction safety. Whether the method adopts a finite element method, a finite difference method, a discrete element method, a block discrete element method and the like or not, the accuracy of the analysis result of the established numerical simulation model is closely related to the input rock mechanical parameters, joint surface parameters and the like. Of these parameters, the accuracy of the rock mass mechanical parameters is particularly important, mainly the elastic modulus, cohesion and internal friction angle.
The indoor experiment is an important means for determining the mechanical characteristics of the rock, and basic mechanical parameters such as the elastic modulus, the cohesive force, the internal friction angle and the like of the rock can be obtained through the method. The rock mass is a composite of rock and structural surfaces. The structural surface is a weak interface of the rock mass, and the shearing strength, the tensile strength and the like of the structural surface are lower than those of the rock. The mechanical parameters of the rock mass are significantly lower than those of the rock under the influence of the structural plane. Based on the current experimental conditions, experiments for determining basic mechanical parameters such as the elastic modulus, the cohesive force, the internal friction angle and the like of the rock mass still cannot be effectively carried out, so that the determination method of the mechanical parameters of the rock mass has larger subjectivity, is unfavorable for simulation analysis of tunnel construction safety, cannot effectively carry out tunnel deformation analysis under the condition of different water contents, and brings great inconvenience to tunnel deformation prediction.
Disclosure of Invention
The invention provides a rock mass numerical simulation model parameter determination method based on water content, which is characterized in that on the basis of determining the change rule of rock mechanical characteristics along with the water content by combining an indoor rock mechanical experiment, rock mass mechanical parameters under the condition of specific water content are obtained by adopting a parameter calibration method, and the change relation of the rock mass mechanical parameters is further determined based on the mapping relation of the rock mass mechanical parameters and the rock mass mechanical parameters, so that calculation of parameters of a rock mass numerical simulation model under the condition of different water content is obtained, deformation data of a tunnel can be obtained efficiently and accurately, and guidance is provided for numerical simulation analysis of tunnel construction safety. The specific technical scheme of the method is as follows:
a method for determining parameters of a numerical simulation model of a rock mass based on water content comprises the following steps:
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 saturated 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;
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.
Preferably, 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.
Preferably, in the obtaining of the relation of the variation of the parameter 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 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 internal friction angle of the corresponding rock as a function of the water content.
Preferably, in calibrating the parameters of the 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.
Preferably, 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.
Preferably, 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.
Preferably, the change of the elastic modulus, the cohesive force and the internal friction angle in the rock mass along with the water content in rock mass mechanical parameters under different water contents is obtained as follows:
the modulus of elasticity varies with the water content as follows:
E rm ＝E rm0 e -Aw ；
wherein: e (E) rm The elastic modulus of the rock mass under the condition of a certain water content, E 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 the 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 the dry state.
Preferably, the error range between the deformation data of the tunnel which is allowed to be calculated and the deformation data monitored on site in parameter calibration is not more than 5%.
Drawings
FIG. 1 is a flow chart of a method for determining parameters of a numerical simulation model in embodiment 1 of the present invention;
FIG. 2 is a schematic diagram of Morlet circle under different working conditions in embodiment 1 of the present invention;
FIG. 3 is a schematic view of the primary-supported cell in example 1 of the present invention;
fig. 4 is a schematic diagram of tunnel deformation calculated in example 1 of the present invention.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to the drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making clear and unambiguous the scope of the present invention.
Examples:
a method for determining parameters of a numerical simulation model of a rock mass based on water content specifically comprises the following steps as shown in figure 1:
step one, obtaining a change relation of parameters along with the water content (namely obtaining the change of rock mechanical parameters along with the water content based on an indoor test), which specifically comprises the following steps: determining parameters of the rock in different saturated 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. The details are as follows:
the elastic modulus of the rock under different water content states is determined by carrying out stress-strain tests of the rock, and the test method is as follows: firstly, obtaining the strength of rock through uniaxial loading, then taking another same rock sample to carry out loading and unloading test, loading to 70% of the strength of the rock, unloading, and thus circulating for 3-5 times to obtain a stress-strain curve of the rock during loading and unloading, and then taking the elastic modulus during the last unloading as the elastic modulus of the rock, wherein the calculation formula is as follows:
wherein: Δσ and Δε are the stress and strain change amounts during the last unloading, respectively.
Assuming that the strength of the rock under the condition of a certain water content is 30MPa, the stress-strain parameters of the rock are obtained by successive loading are shown in the table 1:
table 1 rock stress-strain parameter statistics
And carrying out triaxial test on a batch of rocks under the condition of specific water content, respectively measuring rock strength when confining pressure is 2, 4, 6 and 8 (MPa), drawing Moire circles in a shear stress-normal stress coordinate system by combining with uniaxial compression test strength, and obtaining a shear strength change curve of the rocks under the state of the water content by fitting, thereby obtaining cohesive force and internal friction angle of the rocks.
The triaxial strength of the rock assuming a certain water content is given in table 2 below:
TABLE 2 triaxial Strength statistics of rock at certain moisture content
| Working conditions of | 1 | 2 | 3 | 4 | 5 |
| Confining pressure/MPa | 0 | 2 | 4 | 6 | 8 |
| strength/MPa | 30 | 33.3 | 36.9 | 40.6 | 43.9 |
The Morse circles under different conditions may be further plotted as shown in FIG. 2. In fig. 2: the left-most abscissa of the semicircle is the confining pressure, and the right-most point abscissa is the intensity. A straight line may be approximated such that the straight line is tangent to the semicircles. The slope of the straight line is the internal friction angleThe intersection point with the vertical axis is the cohesive force c, so that the cohesive force and the internal friction angle under the condition of the water content can be obtained.
Finally, software such as origin or Excel is adopted, and regression analysis method is adopted to fit and obtain the change relation of the mechanical parameters of the rock along with the water content 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 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 internal friction angle of the corresponding rock as a function of the water content.
Step two, generating a joint fracture simulation model, which specifically comprises the following steps:
step 2.1, counting the joint fracture characteristics of the tunnel face based on deep Labv3+, specifically: 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; here, preference is given to: and 5-10 pictures are shot on the tunnel face, so that the image analysis result can more truly reflect the joint crack distribution characteristics of the current tunnel face, in addition, 5-10 tunnel faces under the same stratum condition are shot, and the average value of the joint crack distribution characteristics of the tunnel face is taken as the joint crack characteristic modeling basis of the numerical simulation model.
Step 2.2, generating an joint fracture simulation model based on a Monte-Carlo method, wherein the joint fracture simulation model specifically comprises the following steps: generating an joint fracture simulation model which is matched with joint fracture characteristics of a tunnel face by adopting a Monte-Carlo method, introducing the joint fracture simulation model into 3DEC block discrete meta-software, further partitioning the introduced model by adopting a subdivision method and the like, thereby presetting a tunnel excavation range to facilitate simulation analysis of tunnel excavation, dividing the established model into a plurality of grids, simulating an actual rock mass by giving the grids a mechanical parameter experience value of the rock mass, further restraining the bottom surface and the side surface of the model, applying a gravity field to simulate a stratum stress state before tunnel excavation, and then performing simulation calculation of tunnel excavation to obtain a simulation result of tunnel deformation.
The creation idea of the numerical simulation model is as follows: firstly, generating a cuboid, partitioning the cuboid in a partitioning mode, wherein a part of partitioned areas are used for simulating tunnel excavation, and the rest areas are used for simulating rock mass around the tunnel. After the subdivision, the cuboid is subdivided again, and the subdivided cuboid is obtained.
At this time, the rectangular parallelepiped includes two parts of a split surface and a split block. And performing grid division on the split cuboid to divide the split block into a plurality of smaller unit bodies. At this time, the initially created rectangular parallelepiped is composed of two parts, namely, a split surface and a unit body. The split surface is endowed with mechanical parameters of joint cracks, and the unit body is endowed with mechanical parameters of rock mass, so that the aim of simulating an actual rock mass is fulfilled. The bottom surface and the side surface of the cuboid are further restrained, and a gravity acceleration is applied to all the unit bodies to simulate the gravity influence in the actual environment. At this time, the rock mass creation work is completed, and the generated model can be regarded as a numerical simulation model. Further spreading out the calculation, the unbalance force of all the unit bodies can be calculated once every 3DEC, when the unbalance force is small to a certain degree, such as 1e-5, the balance can be considered to be reached, and at the moment, the ground stress can be considered to be balanced, namely the stress state of the cuboid is the same as the stratum stress state in the actual environment.
It should be noted that at this time, the rectangular parallelepiped cell body has been deformed. When tunnel excavation analysis is carried out, zero-returning operation is needed to be carried out on deformation and other contents, and the situation that stratum is not displaced and has a certain stress state before tunnel excavation is indicated. When the tunnel is excavated and simulated, the aim of simulating the tunnel excavation is achieved by deleting the unit bodies in the tunnel range. In addition, another part of the unit body simulating the primary support is applied at the tunnel contour by a similar method, and mechanical parameters of the primary support are given to the unit body, so that the primary support during actual construction is simulated. And continuing to calculate, and considering that the tunnel is in a stable condition when the unbalanced force is small enough. At this time, the unit body simulating the primary support is deformed, and the deformation is a simulation value of tunnel deformation. Fig. 3 is an established cuboid, wherein: the horseshoe-shaped black area is the split tunnel area, and the black lines which look like disorder are generated joint cracks. FIG. 4 shows the calculated tunnel deformation, as shown in FIG. 4 (the black arrow in the lower right corner area indicates the split plane formed by splitting the cube, the black oval frame indicates the block formed by splitting), and it can be seen that there are a plurality of small triangles, which are the unit bodies formed; which is tetrahedral in three dimensions; the black lines are endowed with mechanical parameters of joint cracks, and the unit bodies are endowed with mechanical parameters of rock mass, so that the purpose of simulating an actual rock mass is achieved.
Calibrating parameters of the rock mass (namely calibrating the parameters of the rock mass based on a numerical simulation model considering joint cracks and deformation data monitored on site), specifically: and combining deformation data monitored on site, and determining rock mechanical parameters in a certain water content state by adopting a parameter calibration method, wherein the rock mechanical parameters are as follows:
the deformation data of the tunnel comprising vault subsidence and horizontal convergence (the width of the outline in the tunnel) are tracked and measured by adopting a total station, and the method specifically comprises the following steps: firstly, determining the value of a rock mass mechanical parameter based on experience, then inputting the mechanical parameter into the model established in the second step for calculation to obtain a simulation result of tunnel deformation, and then judging, wherein the method specifically comprises the following steps: if the simulation result is larger than the result measured based on the total station, increasing rock mechanical parameters, and calculating again to reduce the tunnel deformation value obtained by calculation; if the simulation result is smaller than the result measured by the total station, the mechanical parameters of the rock mass are reduced, and calculation is performed again, so that the tunnel deformation obtained by calculation is increased. And (3) adjusting the mechanical parameters of the rock mass input in the three-dimensional simulation model to enable the tunnel deformation data obtained through calculation to be continuously approximate to the measurement value, and if the deformation obtained by inputting a certain parameter of the rock mass is obviously larger than the measurement result, adjusting the input parameter of the rock mass and recalculating. 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.
The preferred embodiment is:
the moisture content state of the rock includes dry (i.e., 0%), 20%, 40%, 60%, 80%, and 100%, the percentages being the moisture content in the rock.
The deformation of the tunnel exhibits a linear increase with decreasing 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.
In the present embodiment, preferably, B 1 、B 2 The value range of (C) is 1 e-4-1 e-3 1 The value of C is within the range of-10 to-100 2 The value range of (2) is within the range of-0.1 to-2.
When the deviation is within the acceptable range, for example, 5%, the input model parameters can be considered to be reliable, at the moment, the input rock mechanical parameters can be considered to be the mechanical parameters of the rock mass near the tunnel deformation monitoring position, at the moment, the water content corresponding to the rock mechanical parameters can be obtained by sampling near the tunnel monitoring point for indoor water content test, as shown in table 3:
table 3 deformation monitoring data statistics table
Step four, obtaining rock mechanical parameters under different water contents (based on the mapping relation of the rock mechanical parameters and the rock mechanical parameters, obtaining the rock mechanical parameters under different water contents), wherein the rock mechanical parameters under different water contents are as follows: 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. The preferred embodiment is:
the change of the elastic modulus, the cohesive force and the internal friction angle along with the water content in the rock mass mechanical parameters is as follows:
the modulus of elasticity varies with the water content as follows:
E rm ＝E rm0 e -Aw ；
wherein: e (E) rm The elastic modulus of the rock mass under the condition of a certain water content, E 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 the 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 the dry state.
The specific application cases of the scheme of the invention are as follows:
case 1: the Zhang Jihuai railway Xinhua mountain tunnel needs to pass through a fault breaking belt, and rock cracks in the breaking belt develop, so that a good seepage passage can be provided for groundwater seepage. And under the condition of no rainfall, the water content of the rock mass around the tunnel is lower. In the case of rainfall, surface water will flow along the breaker belt, so that it gradually seeps to the vicinity of the tunnel, resulting in an increase in the water content of the rock mass around the tunnel. In natural conditions, the seepage of water in the rock mass is slow, so that there is a large difference in the water content of the rock mass at different positions of the tunnel near the zone of the fracture. For example, the water content at the position of the breaker belt is 100%, the water content at 10m from the breaker belt is 80%, and the water content at 50m from the breaker belt is 50%. When the region far away from the fault fracture zone (such as 100m from the fracture zone) is excavated, the tunnel deformation is within an allowable range, and the water content of the rock mass is about 10%. However, if no additional reinforcing measures are taken during the process of crossing the fault fracture zone, the deformation of the tunnel may exceed the allowable value, and even the supporting system is cracked and damaged, so that the problems of construction period delay, construction cost increase and the like are caused. If a large number of reinforcing measures are blindly adopted, the problems of material waste, increased engineering cost and the like are caused. Therefore, construction safety under the condition of different water contents of the rock mass needs to be analyzed, and a certain theoretical basis is provided for reinforcement measures.
However, under the condition of different water contents, how to determine the mechanical parameters of the rock mass cannot be known, and the mechanical parameters of the rock under the condition of different water contents can only be obtained through the indoor rock mechanical experiment. Based on the invention, an indoor rock mechanical experiment can be firstly carried out to obtain that the rock elastic modulus is 36.30GPa and 8.50GPa respectively under the dry state and the 100% water content, so as to obtain the elastic modulus reduction coefficient A=1.45, namely the change relation of the rock elastic modulus along with the water content is as follows:
E＝36.3e -1.45w 。
based on the invention, the change relation of the elastic modulus of the rock mass along with the water content is as follows:
E rm ＝E rm0 e -1.45w 。
in the above, E rm0 Is unknown but can be determined by parameter calibration.
Further calibrating rock mechanical parameters based on field measured data to obtain the elastic modulus of the rock with the water content of 10% of about 1.04GPa, namely 1.04=E rm0 e -1.45×0.1 Can obtain E rm0 =1.2gpa, to obtain a rate of change of elastic modulus of rock mass with water content, as shown in the following formula:
E rm ＝1.2e -1.45w 。
thus, the change of the elastic modulus of the rock mass along with the water content can be obtained. The change relation of the rock mass cohesion and the internal friction angle along with the water content can be obtained by adopting a similar method, and finally the mechanical parameters of the rock mass under the condition of different water contents can be determined. Substituting the parameters into the established three-dimensional simulation model, and calculating tunnel deformation under the condition of different water contents. The summary is shown in Table 4:
TABLE 4 mechanical parameters of rock mass and calculation of tunnel deformation using the method of the invention with different water contents
And according to the vault subsidence and the horizontal convergence value obtained through calculation, additional strengthening measures to be adopted under the condition of different water contents of the rock mass can be further determined.
If the rock mass parameter determining method provided by the invention is not adopted, the mechanical parameters of the rock mass under the condition of different water contents and the rock mass deformation obtained by calculation can be taken as shown in the table 5:
TABLE 5 rock mechanical parameters and calculation of tunnel deformation at different water contents
It can be seen that the evaluation by other methods results in less deformation of the rock mass as calculated. If certain reinforcing measures are not adopted based on the method, accidents such as initial support cracking and damage can occur during tunnel construction.
Case 2:
the surrounding rock mass of the Li yang Jiao Weiqin tunnel is crushed under the influence of the fault crushing belt. Under the condition of large rainfall, rainwater can permeate to the periphery of the tunnel. Under natural conditions, the joint cracks of the rock mass are unevenly distributed, so that the water content of the rock mass in different areas is different to a certain extent. In order to ensure construction safety, the tunnel deformation expansion analysis is required to be performed under the condition of different water contents.
Based on the invention, firstly, rock mechanics experiments are carried out, and the change relation of the rock cohesive force along with the water content is obtained as follows:
c r ＝-450w+1750；
further calibrating rock mechanical parameters based on field measured data to obtain the cohesive force and the internal friction angle of the rock under the condition of 30% water content as 395kPa and 26 degrees respectively, thereby obtaining the change rate of the cohesive force and the internal friction angle of the rock along with the water content, wherein the change rate is shown in the following formula:
c rm ＝-450w+530；
based on the above, the change condition of the cohesive force and the internal friction angle of the rock mass along with the water content can be obtained. The change relation of the elastic modulus of the rock mass along with the water content can be obtained by adopting a similar method. Substituting the parameters into the established numerical model, and calculating tunnel deformation under the condition of different water contents. The rock mechanical parameters and tunnel deformation under the condition of different water contents are summarized as shown in table 6:
TABLE 6 mechanical parameters of rock mass and calculation of tunnel deformation using the method of the present invention with different water contents
If the rock mass parameter determining method provided by the invention is not adopted, the mechanical parameters of the rock mass under the condition of different water contents can be taken, and the rock mass deformation is calculated as shown in Table 7:
TABLE 7 rock mechanical parameters and calculation of tunnel deformation under different moisture contents
It can be seen that the evaluation by other methods results in a larger deformation of the rock mass as calculated. If a stronger reinforcing measure is adopted based on the method, the consumption of steel bars, concrete and the like can be greatly increased, so that the construction cost is increased.
The foregoing description is only illustrative of the present invention and is not intended to limit the scope of the invention, and all equivalent structures or equivalent processes or direct or indirect application in other related technical fields are included in the scope 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%.
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