CN115221727A - Method for determining parameters of numerical simulation model of rock mass based on water content - Google Patents
Method for determining parameters of numerical simulation model 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 a joint fracture simulation model; obtaining a relational expression of the parameters changing along with the water content; calibrating the parameters of the rock mass; and obtaining rock mass 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, the rock mechanical parameters under the condition of specific water content are obtained by adopting a parameter calibration method, and the change relational expression of the rock mechanical parameters is further determined on the basis of the mapping relation of the rock mechanical parameters and the rock mechanical parameters, so that the rock numerical simulation model under the conditions of different water content is obtained to realize parameter calculation, the deformation data of the tunnel can be efficiently and highly accurately obtained, 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
Under the influence of complex geological conditions, the water content of rock masses at different mileage positions of the tunnel is greatly changed, for example, surface precipitation, underground water and the like can seep in a fault fracture zone along cracks. The water content of rock mass around the fault fracture zone is gradually reduced due to the increase of the distance from the fault fracture zone. For soft rock, the mechanical properties are significantly affected by moisture content, e.g., rock with higher moisture content tends to have lower strength. The change of the water content can also cause the change of the elastic modulus, the cohesive force and the internal friction angle of the rock.
During the construction of underground engineering such as tunnels and the like, safety is always the focus of attention of practitioners in the relevant fields. When the rocks around the tunnel are soft rocks, the tunnel excavation construction is easy to have large deformation under the condition of high water content, such as primary support fracture, concrete peeling, serious secondary lining cracking and the like, and serious challenges are brought to the construction safety. The existing engineering experience shows that for the same type of rock mass, under the condition of lower water content, the problem of large deformation cannot occur in tunnel excavation. This indicates that the moisture content of the rock mass has an extremely significant influence on the deformation of the tunnel.
The rock mass around the tunnel is soft rock mass, and when its moisture content probably has great change, if the tunnel need pass through the broken area of fault, in order to deal with the big deformation risk that probably takes place, need formulate the risk counter measure in advance usually, this just needs to carry out construction safety analysis in advance. With the development of computer technology, numerical simulation is becoming one of the important means for analyzing the safety of tunnel construction. No matter which one of the finite element method, the finite difference method, the discrete element method, the block discrete element method and the like is adopted, the accuracy of the analysis result of the established numerical simulation model is closely related to the input rock mechanical parameters, the joint plane parameters and the like. Among these parameters, the accuracy of the rock mechanics 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 indoor experiment. Rock mass is a complex of rock and structural surfaces. The structural surface is a soft joint surface of a rock body, and the shear strength, the tensile strength and the like of the structural surface are lower than those of the rock body. Under the influence of the structural plane, the mechanical parameters of the rock mass are significantly lower than those of the rock. Based on the current experimental conditions, the experiments for determining the basic mechanical parameters such as the elastic modulus, cohesive force and internal friction angle of the rock mass still cannot be effectively carried out, so that the determination method of the rock mass mechanical parameters has high subjectivity, is not beneficial to the 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 the prediction of tunnel deformation.
Disclosure of Invention
The invention provides a method for determining parameters of a rock mass numerical simulation model 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, a parameter calibration method is adopted to obtain rock mechanical parameters under the condition of specific water content, and further, a change relational expression of the rock mechanical parameters is determined based on the mapping relation of the rock mechanical parameters and the rock mechanical parameters, so that the rock mass numerical simulation model under different water content conditions is obtained to realize parameter calculation, the deformation data of a tunnel can be efficiently and highly accurately obtained, 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 crack simulation model specifically comprises the following steps: taking a picture of the tunnel face, analyzing the picture by adopting a DeepLabv3+ algorithm, and extracting the characteristics of the joint cracks, wherein the characteristics comprise length, number and spacing; a joint crack simulation model matched with the characteristics of the joint crack is regenerated by adopting a Monte-Carlo method;
the acquisition of the parameter variation relation along with the water content specifically comprises the following steps: determining parameters of the rock in different saturation states by adopting an indoor experimental mode, and obtaining a change relational expression of each parameter along with the water content through fitting treatment; parameters include modulus of elasticity, cohesion and internal friction angle;
the method comprises the following steps of calibrating parameters of a rock body, specifically: determining rock mechanical parameters under a certain water content state by adopting a parameter calibration method in combination with deformation data monitored on site;
rock mass mechanical parameters under different water contents are obtained, and the method specifically comprises the following steps: and substituting the obtained rock mass mechanical parameters into a relational expression of the change of the parameters along with the water content to obtain the rock mass mechanical parameters under different water contents.
Preferably, in the generation of the joint fracture simulation model:
photographing the tunnel face, specifically photographing 5-10 sheets; 5-10 working faces under the same stratum condition are photographed, and the average value of the distribution characteristics of the joint fractures of the tunnel working faces is taken as the modeling basis of the joint fracture simulation model.
Preferably, in the obtaining of the relational expression 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 changes of the elastic modulus, cohesive force and internal friction angle in the rock along with the water content are as follows:
the elastic modulus varies with the water content as follows:
E＝E 0 e -Aw ；
wherein: e is the modulus of elasticity of the rock at a certain water content, E 0 The elastic modulus of the rock in a dry state, w is the water content, and A is the elastic modulus reduction coefficient;
the cohesive force changes linearly with the change of the water content as follows:
c＝k 1 w+c 0 ；
wherein: c is cohesive force of 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 cohesive force of the corresponding rock along with the change of the water content;
the internal friction angle changes linearly with the change of the water content as follows:
wherein:
is the internal friction angle of the rock under 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 changing with the water content.
Preferably, the parameters of the rock mass are calibrated by:
tracking and measuring deformation data of the tunnel by using a total station, wherein the deformation data comprises vault settlement and the inner contour width of the tunnel;
the judgment standard for successful parameter calibration is as follows: based on the input rock mass mechanical parameters, the deformation data of the tunnel obtained by the calculation of the numerical simulation model in the parameter calibration method is matched with the deformation data monitored on site.
Preferably, in the parameter calibration process: if the calculated deformation data of the tunnel 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 decreasing internal friction angle and cohesion, as follows:
D＝B 1 c+d 0 ，
wherein: d is the tunnel deformation, B 1 、B 2 Is constant, c and
respectively representing cohesion and internal friction angle, d 0 The tunnel deformation is the cohesive force or when the internal friction angle is 0;
the deformation of the tunnel increases as an inversely proportional function with decreasing elastic modulus as follows:
wherein: d is the deformation of the tunnel, C 1 、C 2 Is constant and x is the modulus of elasticity.
Preferably, the changes of the elastic modulus, the cohesive force and the internal friction angle in the rock body along with the water content in the rock body mechanical parameters under different water contents are obtained as follows:
the elastic modulus varies with the water content as follows:
E rm ＝E rm0 e -Aw ；
wherein: e rm Modulus of elasticity of rock mass at a certain water content, E rm0 For drying rock massModulus of elasticity in the state.
The cohesive force changes linearly with the change of the water content as follows:
c rm ＝k 1 w+c rm0 ；
wherein: c. C rm Is the cohesive force of the rock mass under a certain water content state, c rm0 Is the cohesion of the rock mass in a dry state.
The internal friction angle changes linearly with the change of the water content as follows:
wherein:
is the internal friction angle of the rock mass under a certain water content state,
is the internal friction angle of the rock mass in a dry state.
Preferably, the error range of the calculated deformation data of the tunnel and the deformation data monitored on site is allowed to be not more than 5% in parameter calibration.
Drawings
Fig. 1 is a schematic flow chart of a method for determining parameters of a numerical simulation model according to embodiment 1 of the present invention;
FIG. 2 is a schematic view of a Mohr circle under different operating conditions in example 1 of the present invention;
FIG. 3 is a schematic view of a preliminary bracing unit cell in example 1 of the present invention;
fig. 4 is a schematic diagram of tunnel deformation calculated in embodiment 1 of the present invention.
Detailed Description
The embodiments of the present invention will be described in detail with reference to the accompanying drawings so that the advantages and features of the invention can be more easily understood by those skilled in the art, and the scope of the invention will be clearly and clearly defined.
Example (b):
a method for determining parameters of a numerical simulation model of a rock mass based on water content is shown in figure 1, and specifically comprises the following steps:
step one, obtaining a relation of the change of the parameter along with the water content (namely, obtaining the change of the rock mechanical parameter along with the water content based on an indoor test), and specifically comprising the following steps: determining parameters of the rock in different saturation states by adopting an indoor experimental mode, and obtaining a change relational expression 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 on the rock, and the test method comprises the following steps: firstly obtaining the strength of the rock through uniaxial loading, then taking another same rock sample to carry out loading and unloading tests, loading the rock until 70% of the strength of the rock, then unloading the rock, repeating the steps for 3-5 times to obtain a stress-strain curve of the rock during loading and unloading, then taking the elastic modulus during the last unloading as the elastic modulus of the rock, and calculating the formula as follows:
wherein: Δ σ and Δ ε are the changes in stress and strain, respectively, during the last unload.
Assuming that the strength of the rock under a certain water content is 30MPa, the stress-strain parameters of the rock obtained by successive loading are shown in Table 1:
TABLE 1 statistical table of rock stress-strain parameters
And taking another batch of rock to carry out a triaxial test under the condition of specific water content, respectively measuring the rock strength when the confining pressure is 2, 4, 6 and 8 (MPa), drawing a Mohr circle in a shear stress-normal stress coordinate system by combining the strength of the uniaxial compression test, and obtaining a shear strength change curve of the rock under the water content state through fitting so as to obtain the cohesive force and the internal friction angle of the rock.
The triaxial strength of the rock assuming a certain water cut is given in table 2 below:
TABLE 2 triaxial Strength statistical Table of rock under certain moisture content
| Working conditions | 1 | 2 | 3 | 4 | 5 |
| Confining pressure/ |
0 | 2 | 4 | 6 | 8 |
| strength/ |
30 | 33.3 | 36.9 | 40.6 | 43.9 |
The morse circles for different operating conditions may be further plotted as shown in fig. 2. In FIG. 2: the left-most abscissa of the semicircle is confining pressure, and the right-most abscissa of the point is intensity. A straight line can be drawn approximately such that the straight line is tangent to the semi-circles. The slope of the line is the internal friction angle
The intersection point of the water content and 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, adopting origin software or Excel software and the like, and adopting a regression analysis method to fit to obtain the relation of the change of the mechanical parameters of the rock along with the water content as follows:
the elastic modulus varies with the water content as follows:
E＝E 0 e -Aw ；
wherein: e is the elastic modulus of the rock at a certain water content, E 0 The elastic modulus of the rock in a dry state, w is the water content, and A is the reduction coefficient of the elastic modulus;
the cohesive force changes in a linear relationship with the change of the water content as follows:
c＝k 1 w+c 0 ；
wherein: c is cohesive force of 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 cohesive force of the corresponding rock along with the change of the water content;
the internal friction angle changes linearly with the change of the water content as follows:
wherein:
is the internal friction angle of the rock under 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 changing with the water content.
Step two, generating a joint fracture simulation model, which specifically comprises the following steps:
step 2.1, counting the characteristics of the joint crack of the palm surface based on DeepLabv3+, which specifically comprises the following steps: taking a picture of the tunnel face, analyzing the picture by adopting a DeepLabv3+ algorithm, and extracting the characteristics of the joint cracks, wherein the characteristics comprise length, number and spacing; preference is given here to: and (3) photographing the tunnel face, wherein 5-10 images are photographed, so that the image analysis result can reflect the joint fracture distribution characteristics of the current tunnel face more truly, 5-10 tunnel faces under the same stratum condition are photographed, and the average value of the joint fracture distribution characteristics of the tunnel faces is taken as the joint fracture characteristic modeling basis of the numerical simulation model.
Step 2.2, generating a joint fracture simulation model based on a Monte-Carlo method, which specifically comprises the following steps: a joint fissure simulation model matched with the joint fissure characteristics of a tunnel face is generated by a Monte-Carlo method and is led into 3DEC block discrete element software, the led model is further partitioned by adopting methods such as subdivision and the like, so that the tunnel excavation range is predetermined to facilitate simulation analysis of tunnel excavation, the established model is divided into a plurality of grids, an actual rock mass is simulated by endowing the grids with mechanical parameter empirical values of the rock mass, the bottom face and the side face of the model are further constrained, a gravity field is applied to simulate the formation stress state before tunnel excavation, and then simulation calculation of tunnel excavation is performed, so that a simulation result of tunnel deformation is obtained.
The numerical simulation model is created according to the following thought: firstly, a cuboid is generated, partitioning is carried out on the cuboid by adopting a partitioning mode, a part of partitioned areas are used for simulating tunnel excavation, and the rest of partitioned areas are used for simulating rock mass around a tunnel. After the division, the rectangular parallelepiped is divided again to obtain a divided rectangular parallelepiped.
In this case, the rectangular parallelepiped includes two portions of a split surface and a split block. And carrying out grid division on the split cuboid to divide the split block into a plurality of smaller unit bodies. At this time, the rectangular parallelepiped originally created is composed of two parts, i.e., the split plane and the cell body. And giving the mechanical parameters of the joint fracture to the splitting surface and giving the mechanical parameters of the rock mass to the unit body, thereby achieving the purpose of simulating the actual rock mass. The bottom surface and the side surface of the cuboid are further restrained, a gravity acceleration is applied to all the unit bodies, and the gravity influence under the actual environment is simulated. At this time, the rock body creation work is completed, and the generated model can be regarded as a numerical simulation model. Further performing calculation, calculating the unbalanced force of all the unit bodies once every time 3DEC is calculated, and when the unbalanced force is small to a certain degree, such as 1e-5, considering that the unbalanced force is balanced, and at the moment, considering that the ground stress is balanced, namely the stress state of the cuboid is the same as the stress state of the stratum in the actual environment.
It should be noted that, at this time, the rectangular parallelepiped unit body has been deformed. When the tunnel excavation analysis is carried out, the contents such as deformation and the like need to be subjected to zero resetting operation, and the condition that the stratum has no displacement and a certain stress state before the tunnel excavation is indicated is obtained. During tunnel excavation simulation, the aim of simulating tunnel excavation is achieved by deleting the unit bodies in the tunnel range. In addition, in a similar way, another part of the unit body simulating the preliminary bracing is applied to the contour of the tunnel, and mechanical parameters of the preliminary bracing are given to the unit body simulating the preliminary bracing during actual construction. The calculation is continued, and when the unbalance force is small enough, the tunnel is considered to be in a stable condition. At this time, the cells simulating the preliminary bracing may be deformed, which is a simulation value of the tunnel deformation. Fig. 3 shows the established cuboid, wherein: the horseshoe-shaped black area is a cut-out tunnel area, and the black lines which look disordered are generated joint cracks. Fig. 4 shows the calculated tunnel deformation, as shown in fig. 4 (the black arrow in the lower right corner region indicates the splitting surface formed by splitting the cube, and the black oval frame is the block formed by splitting), it can be seen that there are many small triangles, and the small triangles are the formed unit bodies; it is tetrahedral in three dimensions; the black lines are endowed with the mechanical parameters of the joint fractures, and the unit bodies are endowed with the mechanical parameters of the rock mass, so that the aim of simulating the actual rock mass is fulfilled.
Step three, calibrating the parameters of the rock mass (namely calibrating the rock mass parameters based on the numerical simulation model considering the joint fracture and the deformation data monitored on site), specifically: and determining rock mechanical parameters under a certain water content state by adopting a parameter calibration method in combination with deformation data monitored on site, wherein the method comprises the following steps:
the method comprises the following steps of adopting a total station to track and measure deformation data of a tunnel containing vault settlement and horizontal convergence (inner contour width of the tunnel), and specifically comprises the following steps: firstly, determining the value of the 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 specific steps are as follows: if the simulation result is larger than the result measured by the total station, increasing rock mass mechanical parameters, and calculating again to reduce the calculated tunnel deformation value; and if the simulation result is smaller than the measurement result of the total station, reducing the mechanical parameters of the rock mass, and calculating again to increase the calculated tunnel deformation. And adjusting the rock mass mechanical parameters input in the three-dimensional simulation model to enable the calculated tunnel deformation data to approach to the measurement value continuously, and if the deformation obtained by inputting a certain parameter of the rock mass is obviously greater than the measurement result, increasing the input parameter of the rock mass and recalculating. The judgment standard for successful parameter calibration is as follows: based on the input rock mass mechanical parameters, the deformation data of the tunnel obtained by the calculation of the numerical simulation model in the parameter calibration method is matched with the deformation data monitored on site.
The present embodiment is preferred:
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 shows a linear increase with decreasing internal friction angle and cohesion, as follows:
D＝B 1 c+d 0 ，
wherein: d is the tunnel deformation, B 1 、B 2 Is constant, c and
respectively representing cohesion and internal friction angle, d 0 The tunnel deformation is the cohesive force or when the internal friction angle is 0;
the deformation of the tunnel increases as an inversely proportional function with decreasing elastic modulus as follows:
wherein: d is the deformation of the tunnel, C 1 、C 2 Is constant and x is the modulus of elasticity.
Preferred in this example, B 1 、B 2 The value range of (A) is in the range of 1e-4 to 1e-3, C 1 The value range of (A) is in the range of-10 to-100, C 2 The value range of (a) is in 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, the input rock mechanical parameters can be considered to be the mechanical parameters of the rock near the tunnel deformation monitoring position, and the moisture content corresponding to the rock mechanical parameters can be obtained by sampling near the tunnel monitoring point and performing indoor moisture content testing, as shown in table 3:
TABLE 3 statistical table of deformation monitoring data
Step four, rock mass mechanical parameters under different water contents are obtained (based on the mapping relation between the rock mechanical parameters and the rock mass mechanical parameters, the rock mass mechanical parameters under different water contents are obtained), and the method comprises the following steps: and substituting the obtained rock mass mechanical parameters into a relational expression of the parameters changing along with the water content to obtain the rock mass mechanical parameters under different water contents. The present embodiment is preferable:
the changes of the elastic modulus, the cohesive force and the internal friction angle in rock mass mechanics parameters along with the water content are as follows:
the elastic modulus varies with the water content as follows:
E rm ＝E rm0 e -Aw ；
wherein: e rm Modulus of elasticity of rock mass at a certain water content, E rm0 The modulus of elasticity of the rock mass in a dry state.
The cohesive force changes linearly with the change of the water content as follows:
c rm ＝k 1 w+c rm0 ；
wherein: c. C rm Is the cohesive force of the rock mass under a certain water content state, c rm0 Is the cohesion of the rock mass in a dry state.
The internal friction angle changes linearly with the change of the water content as follows:
wherein:
is the internal friction angle of the rock mass under a certain water content state,
is the internal friction angle of the rock mass in a dry state.
The specific application case of the scheme of the invention is as follows:
case 1: zhang Jihuai railway Xinhuashan tunnel needs to pass through a fault fracture zone, and rock mass fractures in the fracture zone develop, so that a good seepage channel can be provided for underground water seepage. Under the condition of no rainfall, the moisture content of rock mass around the tunnel is lower. Under the rainfall condition, surface water flows along the broken zone, so that the surface water gradually seeps to the vicinity of the tunnel, and the water content of rock mass around the tunnel is increased. Under natural conditions, the seepage of water in the rock mass is slow, so that the water content of the rock mass at different positions of the tunnel close to the broken belt area is greatly different. For example, the water content at the position of the crushing zone is 100%, the water content at the position 10m from the crushing zone is 80%, and the water content at the position 50m from the crushing zone is 50%. When the excavation is carried out in a region far away from the fault fracture zone (such as 100m away from the fracture zone), the tunnel deformation is within an allowable range, and the water content of the rock mass is about 10%. However, during the fault fracture zone crossing, if extra reinforcement measures are not taken, the deformation of the tunnel may exceed the allowable value, even the support system is cracked and damaged, and the problems of construction period delay, cost increase and the like are caused. If a large amount of reinforcement measures are taken blindly, the problems of material waste, engineering cost increase and the like can be caused. Therefore, the construction safety of the rock under different water content needs to be analyzed, and a certain theoretical basis is provided for the proposal of reinforcement measures.
However, under the conditions of different water contents, how to determine the mechanical parameters of the rock mass cannot be known, and the indoor rock mechanical experiment can only obtain the mechanical parameters of the rock under the conditions of different water contents. Based on the invention, a rock mechanical experiment in a room can be developed to obtain that the elastic modulus of the rock is 36.30GPa and 8.50GPa respectively under a dry state and 100% water content, so that the reduction coefficient of the elastic modulus A =1.45 is obtained, namely the change relation of the elastic modulus of the rock 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 formula, 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 mass of about 1.04GPa under the condition of 10% water content, namely 1.04= E rm0 e -1.45×0.1 Obtaining E rm0 =1.2GPa, thereby obtaining the elastic modulus of the rock massThe rate of change with water content is shown by the following formula:
E rm ＝1.2e -1.45w 。
so that the change of the elastic modulus of the rock mass along with the water content can be obtained. The variation relation between the cohesive force of the rock mass 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 conditions of different water contents can be determined. And substituting the parameters into the established three-dimensional simulation model, and calculating to obtain the tunnel deformation under the conditions of different water contents. The summary is shown in Table 4:
table 4 rock mass mechanical parameters and calculated tunnel deformation under different water contents by adopting the method of the invention
And according to the vault settlement and horizontal convergence value obtained by calculation, additional reinforcement measures to be taken under the conditions of different water contents of the rock mass can be further determined.
If the rock mass parameter determination method provided by the invention is not adopted, the mechanical parameters of the rock mass under the conditions of different water contents can be taken, and the rock mass deformation obtained by calculation is shown in table 5:
TABLE 5 rock mechanical parameters and calculation of Tunnel deformation under different water content conditions
It can be seen that other methods of evaluation result in less calculated deformation of the rock mass. If a certain reinforcing measure is not adopted based on the method, accidents such as cracking and damage of the primary support can occur during the tunnel construction.
Case 2:
influenced by a fault fracture zone, the Liyang Jiao Weiqin tunnel surrounding rock mass is relatively broken. Under the condition of large rainfall, the rainwater can seep to the periphery of the tunnel. Under natural conditions, the rock mass joint cracks are not uniformly distributed, so that the water content of the rock mass in different areas has certain difference. In order to ensure the construction safety, the tunnel deformation is required to be analyzed under the conditions of different water contents.
Based on the invention, firstly, a rock mechanics experiment is carried out, and the change relation of rock cohesion along with the water content is obtained as follows:
c r ＝-450w+1750；
further calibrating rock mass mechanical parameters based on field measured data to obtain the cohesive force and the internal friction angle of the rock mass as 395kPa and 26 degrees respectively under the condition of 30% water content, thereby obtaining the change rate of the cohesive force and the internal friction angle of the rock mass along with the water content, which is shown in the following formula:
c rm ＝-450w+530；
based on the above formula, the change conditions 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. And substituting the parameters into the established numerical model, and calculating to obtain the tunnel deformation under the conditions of different water contents. The rock mechanical parameters and tunnel deformation under different water contents are summarized as shown in table 6:
table 6 rock mass mechanical parameters and calculation of tunnel deformation under different water contents by adopting the method of the invention
If the rock mass parameter determination method provided by the invention is not adopted, the mechanical parameters of the rock mass under different water contents can be taken and the rock mass deformation can be obtained by calculation as shown in the following table 7:
TABLE 7 rock mass mechanics parameters and calculation of tunnel deformation under different water contents
It can be seen that other methods of evaluation result in a large calculated deformation of the rock mass. If a stronger reinforcing measure is adopted based on the method, the consumption of reinforcing steel bars, concrete and the like can be greatly increased, so that the construction cost is increased.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (8)
1. A method for determining parameters of a numerical simulation model of a rock mass based on water content is characterized by comprising the following steps:
the generation of the joint crack simulation model specifically comprises the following steps: taking a picture of the tunnel face, analyzing the picture by adopting a DeepLabv3+ algorithm, and extracting the characteristics of the joint cracks, wherein the characteristics comprise length, number and spacing; a joint crack simulation model matched with the characteristics of the joint crack is regenerated by adopting a Monte-Carlo method;
the acquisition of the parameter variation relation 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 relational expression of each parameter along with the water content through fitting treatment; parameters include modulus of elasticity, cohesion and internal friction angle;
the method comprises the following steps of calibrating parameters of a rock mass, specifically: determining rock mass mechanical parameters under a certain water content state by adopting a parameter calibration method in combination with deformation data monitored on site;
rock mass mechanical parameters under different water contents are obtained, and the method specifically comprises the following steps: and substituting the obtained rock mass mechanical parameters into a relational expression of the change of the parameters along with the water content to obtain the rock mass mechanical parameters under different water contents.
2. The method for determining numerical simulation model parameters according to claim 1, wherein in the generation of the joint fracture simulation model:
photographing the tunnel face, specifically photographing 5-10 sheets; 5-10 working faces under the same stratum condition are photographed, and the average value of the distribution characteristics of the joint fractures of the tunnel working faces is taken as the modeling basis of the joint fracture simulation model.
3. The method for determining parameters of a numerical simulation model according to claim 2, wherein in the obtaining of the relationship of the parameters with the change of the water content:
the water content state of the rock comprises dry, 20%, 40%, 60%, 80% and 100%;
the changes of the elastic modulus, cohesive force and internal friction angle in the rock along with the water content are as follows:
the elastic modulus varies with the water content as follows:
E＝E 0 e -Aw ；
wherein: e is the modulus of elasticity of the rock at a certain water content, E 0 The elastic modulus of the rock in a dry state, w is the water content, and A is the elastic modulus reduction coefficient;
the cohesive force changes linearly with the change of the water content as follows:
c＝k 1 w+c 0 ；
wherein: c is cohesive force of 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 cohesive force of the corresponding rock along with the change of the water content;
the internal friction angle changes linearly with the change of the water content as follows:
wherein:
is the internal friction angle of the rock under 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 changing with the water content.
4. The numerical simulation model parameter determination method according to claim 3, wherein in calibrating the parameters of the rock mass:
tracking and measuring deformation data of the tunnel by using a total station, wherein the deformation data comprises vault settlement and the inner contour width of the tunnel;
the judgment standard for successful parameter calibration is as follows: based on the input rock mass mechanical parameters, the deformation data of the tunnel obtained by the calculation of the numerical simulation model in the parameter calibration method is matched with the deformation data monitored on site.
5. The method for determining numerical simulation model parameters according to claim 4, wherein in the parameter calibration process: if the calculated deformation data of the tunnel 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.
6. The method of determining numerical simulation model parameters of claim 5, wherein 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 the deformation of the tunnel, B 1 、B 2 Is constant, c and
respectively representing cohesion and internal friction angle, d 0 The tunnel deformation is the cohesive force or when the internal friction angle is 0;
the deformation of the tunnel increases as an inversely proportional function with decreasing elastic modulus as follows:
wherein: d is the deformation of the tunnel, C 1 、C 2 Is constant and x is the modulus of elasticity.
7. The method for determining the parameters of the numerical simulation model according to claim 3, wherein the changes of the elastic modulus, the cohesive force and the internal friction angle in the rock body along with the water content in the rock mechanical parameters under different water contents are obtained as follows:
the elastic modulus varies with the water content as follows:
E rm ＝E rm0 e -Aw ；
wherein: e rm Modulus of elasticity of rock mass at a certain water content, E rm0 The modulus of elasticity of the rock mass in a dry state;
the cohesive force changes linearly with the change of the water content as follows:
c rm ＝k 1 w+c rm0 ；
wherein: c. C rm Is the cohesive force of the rock mass under a certain water content state, c rm0 Is the cohesion of the rock mass in a dry state;
the internal friction angle changes linearly with the change of the water content as follows:
wherein:
is the internal friction angle of the rock mass under a certain water content state,
is the internal friction angle of the rock mass in a dry state.
8. The method for determining the parameters of the numerical simulation model according to claim 4, wherein the error range of the deformation data of the tunnel allowed to be calculated in the parameter calibration and the deformation data monitored in the field is not more than 5%.
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