Method for evaluating the structural morphology of engineering rock masses

Abstract

The present invention discloses a method for assessing the structural morphology of engineering rock masses. The method involves percussing a hole in the engineering rock mass, recording and storing the drilling parameters in real time during the drilling process. After the hole is formed, a high-definition camera is used to image the entire hole along the depth of the hole. The drilling parameters are filtered. The principal component analysis method is used to reduce the dimension of the drilling parameters to determine two principal components and calculation parameters. The rock mass state in the hole is classified into several types based on the in-hole imaging photos. The principal component density map of each type of rock mass is plotted based on the calculation parameters to determine the first principal component. The probability density curve of the first principal component of each type of rock mass is plotted to divide the first principal component intervals of various types of rock mass. The first principal component value is calculated based on the drilling parameters to determine the rock mass state type. The present invention helps technicians use drilling measurement parameters to quickly and accurately assess the structural morphology of engineering rock masses, providing a decision-making basis for tunnel support, excavation, and mine planning and design.

Description

Technical Field

[0001] The present invention relates to the field of tunnel and ore body excavation, and more particularly to a method for evaluating the structural morphology of an engineering rock mass. Background Art

[0002] Tunnel excavation and support, mine planning and design are usually based on rock mass properties, including the strength and structural properties of the rock mass. In order to reduce costs, traditional core drilling holes are widely spaced, and rock mass division is usually interpolated, resulting in overly rough characterization of the rock mass and ignoring the understanding of small-scale rock mass structural properties. This will significantly affect the results of the operation and may increase production costs and reduce excavation and mining efficiency; if rock masses with poor conditions are ignored, safety will ultimately be reduced. In addition, geophysical logging can be performed in core holes and production blast holes to provide a variety of field geological information, such as fractures, holes, fracture zones, etc. However, specific geophysical logging (such as FMI logging) is very expensive and has unexpected problems such as sticking and blocking in horizontal holes, and cannot be used in most field or conventional production practices.

[0003] Numerous studies have shown that rock characteristics significantly influence drilling response. Techniques that measure drilling parameters to monitor drill rig performance offer a high-resolution assessment of rock mass changes. Measurement while drilling (MWD) records borehole data at specific intervals, providing information on drilling operation parameters. This technology provides high-resolution data with minimal disruption to production, making MWD a complementary tool for rock mass characterization.

[0004] However, despite the inherent advantages of this technology, the extensive drilling data generated by advance drilling and blasting drilling in tunnel and mining projects is complicated by the difficulties in processing and interpreting this data, making its application as a decision-making tool in daily construction. Therefore, there is an urgent need to develop new methods that can utilize these large amounts of measurement-while-drilling parameters, distinguish the true from the false, and filter out information that truly reflects changes in rock mass properties. This information can then be used to quickly and cost-effectively assess rock mass structural morphology, providing a basis for decision-making in tunnel support, excavation, and mine planning and design. Summary of the Invention

[0005] The purpose of this invention is to provide a method for evaluating the structural morphology of engineering rock masses, which can help technicians use the measurement parameters while drilling to quickly and accurately evaluate the structural morphology of engineering rock masses, and provide a decision-making basis for tunnel support, excavation and mine planning and design.

[0006] The technical solution adopted by the present invention to solve this technical problem is: a method for evaluating the structural morphology of an engineering rock mass, comprising the following steps:

[0007] Step 1: Impact drilling is performed on the engineering rock mass, and the drilling parameters are recorded and stored in real time during the drilling process. After the hole is completed, a high-definition camera is used to image the entire hole along the depth of the hole.

[0008] Step 2: Filter the while-drilling parameters; use the principal component analysis method to reduce the dimension of the while-drilling parameters, determine the two principal components and calculate the parameters;

[0009] Step 3: Based on the in-hole imaging photos, the rock mass state in the hole is divided into several types; based on the calculation parameters, the principal component density map of each type of rock mass is drawn to determine the first principal component;

[0010] Step 4: Draw the probability density curve of the first principal component of each type of rock mass and divide the first principal component intervals of various types of rock mass;

[0011] Step 5: Calculate the value of the first principal component based on the drilling parameters and determine the rock mass state type.

[0012] Preferably, in step one, water pressure flushing is used while impacting the hole to prevent dust pollution and cool the drill bit; no less than 5 drilling parameters are collected, including at least drilling depth, drilling rate, drilling pressure, torque and rotation speed, and the drilling parameters are collected every 2 cm of drilling. If there are water pressure parameters, they can also be included.

[0013] Preferably, in step one, the borehole is cleaned before imaging the borehole to facilitate identification of the structural morphology inside the borehole; a high-definition camera is pushed into the hole through the drill rod, and the hole depth corresponding to the hole wall is recorded and photographed through a cable with a length mark.

[0014] Preferably, the diameter of the high-definition camera and the drill rod are both 2 cm or more smaller than the hole diameter to prevent the drill rod and the camera from getting stuck in the borehole; in order to match the drilling depth, the minimum scale of the cable is 1 cm.

[0015] Preferably, the filtering of the drilling parameters in step 2 is specifically as follows: based on the complete data set, the drilling rate, bit pressure, torque and rotational speed are analyzed within the 95% confidence interval, and the remaining 5% of the data is filtered out.

[0016] Preferably, the principal component analysis method in step 2 is specifically as follows: 1) the importance of drilling parameters is ranked in the order of drilling rate > drilling pressure > torque > drilling speed change rate > normalized drilling pressure > torque change rate > rotational speed, and all parameters are included in the principal component analysis; 2) when the cumulative contribution rate of the first two principal components is calculated to be less than 80%, the parameters with the lower ranking are removed in turn and the principal component analysis is performed again; 3) until the cumulative contribution rate of the first two principal components reaches 80% or above, the final calculation parameters are determined, and the cumulative contribution rate is 80% or above, indicating that the two principal components can reflect 80% or more of the information and functions of all parameters, and the cumulative contribution rate requirement is relatively high.

[0017] Preferably, in step three, the hole wall rock mass state is divided into four categories based on the hole imaging photos, namely intact rock mass, broken rock mass, collapsed area and hole, and the category division is relatively comprehensive.

[0018] Preferably, the distribution range of the density maps of the four intrapore structural morphologies is reflected on the two principal component coordinates. The smaller the overlapping range of the two principal component coordinates corresponding to the four density maps and the more obvious the staggering, the easier it is to distinguish the four intrapore structural morphologies. In this case, the principal component that is easy to distinguish is selected as the first principal component.

[0019] A principal component density map is drawn for each type of rock mass to determine the first principal component, and the steps specifically include: 1) finding the depth ranges corresponding to the four types of intra-hole structural morphologies in the borehole based on the borehole imaging records; 2) finding the corresponding drilling parameters and the calculation parameters based on the depth ranges; 3) using the principal component analysis method to draw a principal component density map; and 4) determining the first principal component based on the overlap and stagger of the distribution map.

[0020] Preferably, in step 4, four probability density curves are drawn, and the first principal component coordinate value corresponding to the intersection point is the dividing point, so that a total of four dividing points and five intervals are obtained, corresponding to five types of intrapore structural morphologies.

[0021] Preferably, for a new borehole, the calculated value of the first principal component is obtained by using the filtered calculation parameters, and then the interval corresponding to step four is found to determine the structural morphology category in the hole, thereby realizing the identification of the structural morphology of the engineering rock mass using the measurement parameters while drilling.

[0022] The present invention provides at least the following beneficial effects: The method for assessing the structural morphology of engineering rock masses overcomes the shortcomings of traditional coring methods, such as the high workload, extensive rock mass characterization, high multi-solution geophysical logging, and high cost. It enables rapid and accurate assessment of the structural morphology of small-scale, in-situ rock masses, such as tunnel excavation faces and mine blasting bodies.

[0023] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a process of engineering rock mass structural morphology assessment method;

[0025] Figure 2 is the curve of the variation of the drilling parameters along the depth;

[0026] Figure 3 It is the type of rock mass structure in the hole;

[0027] Figure 4 is the probability density of the first principal component;

[0028] Figure 5 It is the classification of rock mass structure morphology based on measurement while drilling parameters; DETAILED DESCRIPTION

[0029] The present invention is described in detail and completely below with reference to the accompanying drawings. Those skilled in the art will be able to implement the present invention based on this description. Before describing the present invention with reference to the accompanying drawings, it should be noted that the technical solutions and technical features provided in various parts of the present invention, including those described below, may be combined with each other unless they conflict.

[0030] In addition, the embodiments of the present invention described below are generally only part of the embodiments of the present invention, rather than all of the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making any creative efforts should fall within the scope of protection of the present invention.

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific implementation process is as follows:

[0032] Example 1

[0033] like Figure 1 The figure shows a flow chart of the engineering rock mass structure morphology assessment process of the present invention, and the specific steps include:

[0034] Step 1: Impact drilling of engineering rock mass, and collection of drilling parameters, including drilling depth, drilling speed, drilling pressure, torque and speed (such as Figure 2 shown).

[0035] Step 2: Use Matlab software to implement principal component analysis. The specific steps are as follows:

[0036] 1) Arrange the drilling parameters into a matrix X with depths as rows and drilling parameters as columns;

[0037] 2) Calculate the sample correlation matrix R by R = corrcoef(X);

[0038] 3) Calculate the principal component pc, the eigenvalue latent, and the principal component contribution explained of R by [pc, latent, explained] = pcacov(R);

[0039] 4) Calculate the cumulative contribution rate and determine the calculation parameters;

[0040] The calculation shows that the cumulative contribution of the two principal components is 84.7%, and the calculation parameters are drilling rate, bit weight, torque, drilling rate change rate and normalized bit weight.

[0041] Step 3: The in-hole imaging results are divided into four types of rock mass structures: intact rock mass, broken rock mass, collapsed area and holes (such as Figure 3 shown).

[0042] Step 4: Draw the main component probability density curves of the four structural forms of rock masses (such as Figure 4 As shown in Figure 3, 5 intervals are obtained, and the rock mass structures corresponding to the 5 intervals are complete rock mass, broken rock mass, collapsed area, small holes and large holes.

[0043] Step 5: Based on the drilling parameters of the new borehole, the drilling rate, drilling pressure, torque, drilling speed change rate and normalized drilling pressure are used as calculation parameters to draw the first principal component-drilling depth curve. The borehole is mainly divided into three structural forms; the collapse area obtained by the model evaluation is compared with the measured collapse starting point, and the results are very close (such as Figure 5 ), which verifies the accuracy of this method.

[0044] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for evaluating the structural morphology of an engineering rock mass, characterized in that: The following steps are involved: Step 1: Impact drilling is performed on the engineering rock mass, and the drilling parameters are recorded and stored in real time during the drilling process. After the hole is completed, a high-definition camera is used to image the entire hole along the depth of the hole. Step 2: Filter the while-drilling parameters; use the principal component analysis method to reduce the dimension of the while-drilling parameters, determine the two principal components and calculate the parameters; The principal component analysis method is as follows: 1) All parameters are included in the principal component analysis in the order of drilling rate > drilling weight > torque > drilling speed change rate > normalized drilling weight > torque change rate > rotational speed; 2) When the cumulative contribution rate of the first two principal components is less than 80%, the parameters with the lower ranking are removed in turn and the principal component analysis is repeated; 3) The final calculation parameters are determined until the cumulative contribution rate of the first two principal components reaches 80% or above; Step 3: Based on the in-hole imaging photos, the rock mass state of the hole wall is divided into 4 categories, namely intact rock mass, broken rock mass, collapsed area and hole; based on the calculation parameters, the principal component density map of each type of rock mass is drawn respectively to determine the first principal component, specifically including: 1) According to the borehole imaging records, the corresponding depth ranges of the four types of in-hole structural forms in the borehole are found respectively; 2) According to the depth range, the corresponding drilling parameters and the calculation parameters are found; 3) The principal component density map is drawn using the principal component analysis method; 4) The first principal component is determined based on the overlap and stagger of the distribution map; Step 4: Draw 4 probability density curves, and the coordinate value of the first principal component corresponding to the intersection point is the dividing point. A total of 4 dividing points and 5 intervals are obtained, corresponding to 5 types of in-hole structural forms; Step 5: Calculate the value of the first principal component based on the drilling parameters and determine the rock mass state type.

2. The engineering rock mass structure morphology assessment method according to claim 1, characterized in that: The collected drilling parameters shall be no less than 5, including at least drilling depth, drilling rate, bit pressure, torque and rotation speed.

3. The engineering rock mass structure morphology assessment method according to claim 1, characterized in that: The high-definition camera is pushed into the hole through the drill pipe, and the hole depth corresponding to the hole wall is recorded and photographed through a cable with length markings.

4. The engineering rock mass structure morphology assessment method according to claim 3, characterized in that: The diameters of the high-definition camera and drill rod are both 2 cm or more smaller than the hole diameter, and the minimum scale of the cable length mark is 1 cm.

5. The engineering rock mass structure morphology assessment method according to claim 2, wherein: The filtering of the drilling parameters in step 2 is specifically as follows: based on the complete data set, the data of drilling rate, bit pressure, torque and rotational speed are retained within the 95% confidence interval for analysis, and the remaining 5% of the data are filtered out.

6. The engineering rock mass structure morphology assessment method according to claim 1, wherein: In step 5, for a new borehole, steps 1 to 3 are used to obtain the calculated value of the first principal component, which is then divided into the corresponding interval according to step 4 to determine the hole wall structure morphology category, thereby realizing the identification of the engineering rock mass structure morphology using the while drilling measurement parameters.

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