CN116992545A - Large deformation grading method for ultra-high ground stress ultra-large buried depth soft rock tunnel - Google Patents

Abstract

The application discloses a large deformation grading method for an ultra-high ground stress ultra-large buried depth soft rock tunnel, which relates to the field of soft rock tunnels and comprises the following steps: firstly, obtaining large deformation grading parameters; the large deformation classification parameters include: surrounding rock strength, surrounding rock strength stress ratio and deformation rate; then classifying the large deformation of the ultra-high ground stress ultra-large buried deep soft rock tunnel based on a preset judging standard by combining the obtained large deformation classification parameters; the grading scheme provided by the application is simple and reasonable, the grading parameter is convenient and reliable to take value, and the design requirement of the on-site tunnel construction dynamic support structure can be met.

Description

Large deformation classification method for ultra-high ground stress and ultra-deep buried soft rock tunnels

Technical field

The invention relates to the field of soft rock tunnels, and specifically to a large deformation classification method for soft rock tunnels with ultra-high ground stress and ultra-large burial depth.

Background technique

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

The problem of large deformation of surrounding rock caused by the construction of ultra-high ground stress and ultra-large deep tunnels is a major scientific problem faced by underground engineering construction. It is different from the general large deformation of tunnels in that it has a higher deformation rate, larger deformation amount, and longer deformation duration. , the resulting deformation of the surrounding rock is more serious, and the damage form of the supporting structure is more complex. The risk of collapse of the surrounding rock and supporting structure of the tunnel is high, which will cause serious personal safety threats and economic losses to the operators and the normal construction of the tunnel. .

At present, scholars have carried out relevant technical research on the problem of large deformation in tunnels and classification methods, but so far there has not been a unified and applicable large deformation classification scheme. The reason is that the existing tunnel large deformation classification methods are too cumbersome and rarely take into account the special geological environment of ultra-large deep-buried high-stress tunnels; the classification methods are mostly in the survey and design stage and are difficult to apply to the tunnel construction stage. The currently proposed large deformation classification scheme involves as many as six classification parameters, the values of which are difficult to determine; some of them are mainly used in the survey and design stage; while the currently proposed uneven large deformation classification method uses the overall deformation of the tunnel as the core classification Parameters and classification parameters are too simple and their universality needs to be improved. Therefore, in view of the shortcomings of current classification methods, it is particularly important to propose a fast and effective large deformation classification method to better guide on-site tunnel construction.

Contents of the invention

The purpose of this invention is to solve the problem that the current support structure design of ultra-high ground stress and ultra-large deep buried tunnel is difficult to meet the dynamic construction process, and there are problems such as mismatch and incoordination between tunnel deformation and supporting structure, resulting in inability to deform the surrounding rock of the tunnel. To effectively control phenomena such as severe damage to supporting structures and other phenomena, a large deformation classification method for ultra-high ground stress and ultra-large burial depth soft rock tunnels is provided. The deformation grade of the tunnel is demarcated based on the strength-stress ratio of the tunnel's surrounding rock, the strength of the surrounding rock, and the deformation rate. , in order to take reasonable deformation control measures in advance, so as to better serve tunnel construction and achieve safe and efficient tunnel construction, thereby solving the above problems.

The technical solution of the present invention is as follows:

Large deformation classification method for ultra-high ground stress and ultra-deep buried soft rock tunnels, including:

Step S1: Obtain large deformation classification parameters; the large deformation classification parameters include: surrounding rock strength, surrounding rock strength-stress ratio, and deformation rate;

Step S2: Based on the preset evaluation criteria and combined with the obtained large deformation classification parameters, classify the large deformation of the ultra-high ground stress and ultra-deep buried soft rock tunnel.

Further, the method for obtaining the surrounding rock strength is as follows:

Step A: Carry out on-site tunnel surrounding rock sampling to obtain surrounding rock samples, and then carry out point load and uniaxial compression tests to determine the strength of the surrounding rock samples. Based on a large number of test results, the point load strength and uniaxial compressive strength are established. The fitting relationship between the two;

Step B: Measure the point load strength of the on-site tunnel surrounding rock, and quickly obtain the uniaxial compressive strength of the on-site tunnel surrounding rock based on the fitting relationship;

Step C: Based on the uniaxial compressive strength of the on-site tunnel surrounding rock and combined with the Hoek-Brown strength criterion, the surrounding rock strength of the on-site tunnel surrounding rock is obtained.

Further, step A includes:

Based on the point load strength and uniaxial compressive strength test data of a large number of surrounding rock samples, different fitting relationship curves are established, and the best matching relationship between the two is determined based on the level of fitting correlation.

Further, the different fitting relationship curves include:

Linear and logarithmic relationships;

Wherein, the linear relationship formula is: σ _c =aI _S(50) +b;

The logarithmic relational expression is: σ _c =aln(I _S(50) )+b;

In the formula: σ _c is the uniaxial compressive strength, I _{S (50)} is the point load strength, a and b are constants.

Further, step C includes:

σ _cmass =σ _c1 S ^a

In the formula: σ _cmass is the strength of the surrounding rock, σ _c1 is the uniaxial compressive strength of the surrounding rock of the on-site tunnel, and S and a are the empirical parameters of rock mass mechanics.

Further, the rock mass mechanics empirical parameter S is calculated by the following formula:

The rock mass mechanics empirical parameter a is calculated by the following formula:

In the formula: GSI is the geological strength index, and D is a parameter indicating the degree of disturbance of the excavated rock mass.

Further, the method for obtaining the surrounding rock strength stress ratio is as follows:

Step 1: Establish a three-dimensional finite element model with complex terrain features;

Step 2: Combined with the measured geostress data with limited geological survey data, use the multiple linear regression analysis method to conduct regression and inversion analysis of the stress field of the tunnel line, determine the distribution characteristics and size of the initial stress field of the tunnel line, and determine the principal stress of each mileage section. Thus the maximum principal stress is obtained;

Step 3: Based on the maximum principal stress and surrounding rock strength, calculate the surrounding rock strength-stress ratio.

Further, the third step includes:

α＝ _σcmass / _σmax

In the formula: α is the strength stress ratio of surrounding rock, and σ _max is the maximum principal stress.

Further, the method for obtaining the deformation rate is as follows:

Calculation is performed based on the single-day convergence deformation corresponding to the monitored section.

Further, the evaluation criteria are as follows:

When the strength of the surrounding rock is greater than 8MPa, the strength-stress ratio of the surrounding rock is greater than 0.5, and the deformation rate is less than 1cm·d ^-1 , the large deformation grade of the ultra-high ground stress and ultra-deep buried soft rock tunnel is judged to be none;

When the surrounding rock strength is between 6 and 8 MPa, the surrounding rock strength-stress ratio is between 0.25 and 0.5, and the deformation rate is between 1 and 3 cm·d ^-1 , the large deformation level of ultra-high ground stress and ultra-deep buried soft rock tunnels can be determined. to be slight;

When the surrounding rock strength is between 4 and 6 MPa, the surrounding rock strength-stress ratio is between 0.15 and 0.25, and the deformation rate is between 3 and 6 cm·d ^-1 , the large deformation grade of ultra-high ground stress and ultra-deep buried soft rock tunnels can be determined. is medium;

When the surrounding rock strength is between 2 and 4MPa, the surrounding rock strength-stress ratio is between 0.05 and 0.15, and the deformation rate is between 6 and 10cm·d ^-1 , the large deformation grade of ultra-high ground stress and ultra-deep buried soft rock tunnels can be determined. to be serious;

When the strength of the surrounding rock is less than 2MPa, the strength-to-stress ratio of the surrounding rock is less than 0.05, and the deformation rate is greater than 10cm·d ^-1 , the large deformation level of the ultra-high ground stress and ultra-deep buried soft rock tunnel is judged to be extremely serious.

Compared with the existing technology, the beneficial effects of the present invention are:

The large deformation classification method for ultra-high ground stress and ultra-deep buried soft rock tunnels includes: first obtaining large deformation classification parameters; the large deformation classification parameters include: surrounding rock strength, surrounding rock strength-stress ratio, and deformation rate; and then based on the preset The evaluation standard combines the obtained large deformation classification parameters to classify the large deformation of soft rock tunnels with ultra-high ground stress and large burial depths; it delineates the tunnel deformation grade based on the strength-stress ratio of the tunnel's surrounding rock, the strength of the surrounding rock, and the deformation rate. In order to take reasonable deformation control measures in advance, so as to better serve tunnel construction and achieve safe and efficient tunnel construction, the grading scheme is simple and reasonable, the grading parameter values are convenient and reliable, and can meet the dynamic support structure design requirements of on-site tunnel construction.

Description of the drawings

Figure 1 is a schematic diagram of the large deformation classification method for ultra-high ground stress and ultra-large burial depth soft rock tunnels;

Figure 2 is a schematic diagram of the method for obtaining the strength of surrounding rock;

Figure 3 is a schematic diagram of the method for obtaining the maximum principal stress of the tunnel line.

Detailed ways

It should be noted that relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or operations are mutually exclusive. any such actual relationship or sequence exists between them. Furthermore, the terms "comprises," "comprises," or any other variations thereof are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also those not expressly listed other elements, or elements inherent to the process, method, article or equipment. Without further limitation, an element defined by the statement "comprises a..." does not exclude the presence of additional identical elements in a process, method, article, or apparatus that includes the stated element.

The features and performance of the present invention will be described in further detail below with reference to examples.

Embodiment 1

Please refer to Figure 1, the large deformation classification method for soft rock tunnels with ultra-high geostress and ultra-deep burial depth, which specifically includes the following steps:

Step S1: Obtain large deformation classification parameters; the large deformation classification parameters include: surrounding rock strength, surrounding rock strength-stress ratio, and deformation rate;

Step S2: Based on the preset evaluation criteria and combined with the obtained large deformation classification parameters, classify the large deformation of the ultra-high ground stress and ultra-deep buried soft rock tunnel.

In this embodiment, specifically, the method for obtaining the surrounding rock strength is as follows:

Step A: Carry out on-site tunnel surrounding rock sampling to obtain surrounding rock samples, and then carry out point load and uniaxial compression tests to determine the strength of the surrounding rock samples. Based on a large number of test results, the point load strength and uniaxial compressive strength are established. The fitting relationship between the two makes it convenient to later calculate the corresponding uniaxial compressive strength based on the point load intensity;

Step B: Measure the point load strength of the on-site tunnel surrounding rock, and quickly obtain the uniaxial compressive strength of the on-site tunnel surrounding rock based on the fitting relationship;

Step C: Based on the uniaxial compressive strength of the on-site tunnel surrounding rock and combined with the Hoek-Brown strength criterion, the surrounding rock strength of the on-site tunnel surrounding rock is obtained; that is, based on the uniaxial compressive strength of each tunnel rock sample, comprehensive consideration is given to revealing the surrounding rock strength. Influenced by joints, cracks, size effects and other aspects, the conventional rock mechanical parameters are modified and converted into rock mass mechanical parameters, and then the surrounding rock strength is obtained. The solution process is shown in Figure 2.

In this embodiment, specifically, step A includes:

Based on the point load strength and uniaxial compressive strength test data of a large number of surrounding rock samples, different fitting relationship curves are established, and the best matching relationship between the two is determined based on the level of fitting correlation.

In this embodiment, specifically, the different fitting relationship curves include:

Linear and logarithmic relationships;

Wherein, the linear relationship formula is: σ _c =aI _S(50) +b;

The logarithmic relational expression is: σ _c =aln(I _S(50) )+b;

In the formula: σ _c is the uniaxial compressive strength, I _{S (50)} is the point load strength, a and b are constants.

In this embodiment, specifically, step C includes:

σ _cmass =σ _c1 S ^a

In the formula: σ _cmass is the strength of the surrounding rock, σ _c1 is the uniaxial compressive strength of the surrounding rock of the on-site tunnel, and S and a are the empirical parameters of rock mass mechanics.

In this embodiment, specifically, the rock mass mechanics empirical parameter S is calculated by the following formula:

The rock mass mechanics empirical parameter a is calculated by the following formula:

In the formula: GSI is the geological strength index, and D is a parameter indicating the degree of disturbance of the excavated rock mass.

In this embodiment, further, the derivation process of the calculation formula for the surrounding rock strength is given, as follows:

In the formula: σ ₁ and σ ₃ are the maximum principal stress and minimum principal stress when the rock mass is damaged, m _b , S and a are the empirical parameters of rock mass mechanics; in the process of rock mass excavation, controlled blasting and Mechanical excavation, so D=0. The rock strength test adopts uniaxial compressive strength test, so σ ₃ =0. Therefore, the calculation formula of surrounding rock strength is as follows:

σ _cmass =σ ₁ =σ _c1 S ^a

In this embodiment, specifically, as shown in Figure 3, the method for obtaining the surrounding rock strength stress ratio is as follows:

Step 1: Establish a three-dimensional finite element model with complex terrain features;

Step 2: Combined with the measured geostress data with limited geological survey data, use multiple linear regression analysis methods (least squares method or ridge regression method) to conduct regression and inversion analysis of the stress field of the tunnel line to determine the initial stress field distribution characteristics of the tunnel line and size, determine the principal stress of each mileage section, so as to obtain the maximum principal stress;

Step 3: Based on the maximum principal stress and surrounding rock strength, calculate the surrounding rock strength-stress ratio.

In this embodiment, specifically, step three includes:

α＝ _σcmass / _σmax

In the formula: α is the strength stress ratio of surrounding rock, and σ _max is the maximum principal stress.

In this embodiment, specifically, the method for obtaining the deformation rate is as follows:

The deformation rate (that is, the deformation rate of the surrounding rock) can not only measure the severity of tunnel deformation, but also is an important parameter that characterizes the release speed of the deformation performance of the surrounding rock during excavation. Its value can be calculated based on the single-day convergence deformation corresponding to the monitoring section.

In this embodiment, specifically, the evaluation criteria are as follows:

When the strength of the surrounding rock is greater than 8MPa, the strength-stress ratio of the surrounding rock is greater than 0.5, and the deformation rate is less than 1cm·d ^-1 , the large deformation grade of the ultra-high ground stress and ultra-deep buried soft rock tunnel is judged to be none;

When the surrounding rock strength is between 6 and 8 MPa, the surrounding rock strength-stress ratio is between 0.25 and 0.5, and the deformation rate is between 1 and 3 cm·d ^-1 , the large deformation level of ultra-high ground stress and ultra-deep buried soft rock tunnels can be determined. to be slight;

When the surrounding rock strength is between 4 and 6 MPa, the surrounding rock strength-stress ratio is between 0.15 and 0.25, and the deformation rate is between 3 and 6 cm·d ^-1 , the large deformation grade of ultra-high ground stress and ultra-deep buried soft rock tunnels can be determined. is medium;

When the surrounding rock strength is between 2 and 4MPa, the surrounding rock strength-stress ratio is between 0.05 and 0.15, and the deformation rate is between 6 and 10cm·d ^-1 , the large deformation grade of ultra-high ground stress and ultra-deep buried soft rock tunnels can be determined. to be serious;

When the strength of the surrounding rock is less than 2MPa, the strength-to-stress ratio of the surrounding rock is less than 0.05, and the deformation rate is greater than 10cm·d ^-1 , the large deformation level of the ultra-high ground stress and ultra-deep buried soft rock tunnel is judged to be extremely serious.

That is, the evaluation criteria are shown in Table 1.

Table 1 Judgment Criteria

The above-described embodiments only express specific implementation modes of the present application, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of protection of the present application. It should be noted that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the technical solution of the present application, and these all fall within the protection scope of the present application.

This Background section is provided to generally present the context of the invention, the work of the inventors currently named, the work to the extent described in this Background section, and the description in this section that does not constitute prior art at the time of filing. aspects are neither expressly nor implicitly admitted to be prior art to the present invention.

Claims (10)

1. The large deformation grading method for the ultra-high ground stress ultra-large buried deep soft rock tunnel is characterized by comprising the following steps of:

step S1: obtaining large deformation grading parameters; the large deformation classification parameters include: surrounding rock strength, surrounding rock strength stress ratio and deformation rate;

step S2: and classifying the large deformation of the ultra-high ground stress ultra-large buried deep soft rock tunnel based on a preset judgment standard by combining the obtained large deformation classification parameters.

2. The grading method for large deformation of the ultra-high ground stress ultra-large buried soft rock tunnel according to claim 1, wherein the surrounding rock strength obtaining method is as follows:

step A: performing on-site tunnel surrounding rock sampling to obtain a surrounding rock sample, then respectively carrying out point load and uniaxial compression test to determine the strength of the surrounding rock sample, and establishing a fitting relation between the point load strength and the uniaxial compression strength according to a large number of test results;

and (B) step (B): measuring the point load strength of the surrounding rock of the field tunnel, and rapidly obtaining the uniaxial compressive strength of the surrounding rock of the field tunnel based on the fitting relation;

step C: and obtaining the surrounding rock strength of the surrounding rock of the field tunnel based on the uniaxial compressive strength of the surrounding rock of the field tunnel and combining the Hoek-Brown strength criterion.

3. The method for grading the large deformation of the ultra-high ground stress ultra-large buried soft rock tunnel according to claim 2, wherein the step a comprises:

and establishing different fitting relation curves according to the point load strength and the uniaxial compressive strength test data of a large number of surrounding rock samples, and determining the best matching relation of the two fitting relation curves according to the fitting correlation.

4. A method of grading large deformations of ultra-high ground stress ultra-large buried soft rock tunnel according to claim 3, characterized in that said different fitted relationship curves comprise:

linear and logarithmic relationships;

wherein the linear relationship is: sigma (sigma) _c ＝aI _S(50) +b；

The logarithmic relation is: sigma (sigma) _c ＝aln(I _S(50) )+b；

Wherein: sigma (sigma) _c Is uniaxial compressive strength, I _S(50) For point load strength, a and b are constants.

5. The grading method for large deformation of ultra-high ground stress ultra-large buried soft rock tunnel according to claim 4, wherein the step C comprises:

σ _cmass ＝σ _c1 S ^a

wherein: sigma (sigma) _cmass For the strength of surrounding rock, sigma _c1 The uniaxial compressive strength of the surrounding rock of the field tunnel is shown, and S and a are experimental parameters of rock mass mechanics.

6. The grading method for large deformation of ultra-high ground stress ultra-large buried soft rock tunnel according to claim 5, wherein the empirical parameter S of rock mass mechanics is calculated by the following formula:

the rock mass mechanics empirical parameter a is calculated by the following formula:

wherein: GSI is a geological strength index, and D is a disturbance degree parameter for representing the excavated rock mass.

7. The grading method for large deformation of the ultra-high ground stress ultra-large buried soft rock tunnel according to claim 5, wherein the surrounding rock strength stress ratio obtaining method is as follows:

step one: establishing a three-dimensional finite element model with complex topography and landform characteristics;

step two: carrying out regression inversion analysis on the tunnel stress field by adopting a multiple linear regression analysis method in combination with the ground stress actual measurement data with limited ground survey data, determining the distribution characteristics and the size of the tunnel initial stress field, and determining the principal stress of each mileage section so as to obtain the maximum principal stress;

step three: and calculating the stress ratio of the surrounding rock strength based on the maximum main stress and the surrounding rock strength.

8. The method for grading the large deformation of the ultra-high ground stress ultra-large buried soft rock tunnel according to claim 7, wherein the third step comprises:

α＝σ _cmass /σ _max

wherein: alpha is the stress ratio of surrounding rock strength and sigma _max Is the maximum principal stress.

9. The grading method for large deformation of the ultra-high ground stress ultra-large buried soft rock tunnel according to claim 1, wherein the deformation rate obtaining method is as follows:

and calculating according to the single-day convergence deformation corresponding to the monitoring section.

10. The grading method for large deformation of the ultra-high ground stress ultra-large buried soft rock tunnel according to claim 1, wherein the evaluation criteria are as follows:

when the strength of the surrounding rock is more than 8MPa, the stress ratio of the strength of the surrounding rock is more than 0.5, and the deformation rate is less than 1cm & d ^-1 When the tunnel is in the high deformation level, the tunnel is in the high deformation level;

when the strength of the surrounding rock is between 6 and 8MPa, the stress ratio of the strength of the surrounding rock is between 0.25 and 0.5, and the deformation rate is between 1 and 3 cm.d ^-1 When the deformation grade is in between, the large deformation grade of the ultra-high ground stress ultra-large buried deep soft rock tunnel is judged to be slight;

when the strength of the surrounding rock is between 4 and 6MPa, the stress ratio of the strength of the surrounding rock is between 0.15 and 0.25, and the deformation rate is between 3 and 6 cm.d ^-1 When the deformation grade of the ultra-high ground stress ultra-large buried deep soft rock tunnel is medium;

when the strength of the surrounding rock is between 2 and 4MPa, the stress ratio of the strength of the surrounding rock is between 0.05 and 0.15, and the deformation rate is between 6 and 10 cm.d ^-1 When the time is in between, the judgment is overThe large deformation grade of the high-ground-stress ultra-large buried deep soft rock tunnel is serious;

when the strength of the surrounding rock is less than 2MPa, the stress ratio of the strength of the surrounding rock is less than 0.05, and the deformation rate is more than 10cm & d ^-1 And when the deformation grade of the ultra-high ground stress ultra-large buried deep soft rock tunnel is judged to be extremely serious.