Primary support displacement evaluation system in highway tunnel safety step range

Abstract

The invention relates to the technical field of tunnel engineering, and discloses a primary support displacement grading evaluation system in a highway tunnel safety step range, which comprises an image information acquisition unit, an image information analysis unit and an output unit, the image information acquisition unit comprises a cloth lens, a camera and a light source; the image information analysis unit comprises an image information converter and a displacement data grading evaluation processor. The system for evaluating the initial support displacement in the highway tunnel safety step range is based on a machine vision technology, and under the condition that construction organization is not affected, a tunnel measuring point displacement-time curve with densely arranged measuring points in a continuous time period is obtained; the method comprises the following steps: obtaining a hole circumference displacement-time function according to regression analysis of continuous hole circumference displacement data of a tunnel, further obtaining a displacement rate change trend function and a displacement rate function, and reasonably evaluating the displacement state of a safe step section by combining the regression functions.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel engineering, and in particular to a system for evaluating initial support displacement within a safe step distance range of a highway tunnel. Background Art

[0002] As mountain tunnels continue to emerge, their geological conditions are more complex and changeable; during the construction of mountain tunnels, the safe step range, that is, the section between the secondary lining and the face with only initial support, is an important interval that affects engineering safety and construction efficiency. According to the requirements, the safe step length is stipulated to be no more than 90m for Grade IV surrounding rock and no more than 70m for Grade V and above surrounding rock. However, in the actual construction process, affected by factors such as the surrounding rock engineering characteristics, surrounding rock occurrence, hydrogeological conditions, and construction technology and methods, if the safe step length is fixed according to the surrounding rock grade and is not further adjusted dynamically in combination with the results of monitoring and measurement, it is contrary to the dynamic design and construction concept of the current mainstream construction method "New Austrian Tunneling Method".

[0003] In addition, according to the requirements, the tunnel monitoring and measurement should be carried out 1-2 times / day within 15 days after the completion of the support construction. Too high a monitoring frequency will affect the construction organization and increase the human resource cost. At the same time, the monitoring frequency of 1-2 times / day cannot timely and completely reflect the changing trend of the initial support displacement. When the surrounding rock conditions change, the engineering parameters such as the support scheme and the safe step distance cannot be adjusted in time, and the displacement data in a continuous time cannot be obtained to analyze the displacement data, predict the displacement development, and then take corresponding engineering measures.

[0004] To sum up, how to obtain displacement monitoring data within the safe step range in a timely manner with little impact on construction, and make a reasonable graded evaluation of the surrounding rock and support displacement status based on the displacement data, is the key to improving construction efficiency, proposing reasonable engineering measures, and ensuring project safety. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a system for evaluating the initial support displacement within the safe step distance range of a highway tunnel.

[0006] The technical solution adopted by the present invention is:

[0007] A system for evaluating the displacement of an initial support within a safe step distance range of a highway tunnel, the system comprising an image information acquisition unit, an image information analysis unit and an output unit;

[0008] The image information acquisition unit includes a lens and a camera arranged at the front end of the secondary lining trolley, and a number of displacement monitoring targets and in-hole light sources arranged on the primary support along the longitudinal section; the image information analysis unit includes an image information converter and a displacement data grading evaluation processor, the image information converter is connected to the camera and the displacement data grading evaluation processor for data transmission, and the displacement data grading evaluation processor is connected to the output unit for data transmission.

[0009] Furthermore, the lens and camera installed at the front end of the second lining trolley keep their relative position to the tunnel axis unchanged, serving as the reference point for deformation monitoring in the tunnel; displacement targets are arranged at a certain longitudinal spacing according to the actual situation on site; the light source in the tunnel provides the camera with light for acquiring images.

[0010] Furthermore, the image information acquisition unit acquires the image information in the hole within the safe step range;

[0011] The image information converter of the image information analysis unit converts the image information collected by the lens into displacement data, forms a displacement-time curve of each measuring point in a continuous time, and transmits the displacement-time curve to the displacement data classification evaluation processor;

[0012] The displacement data classification evaluation processor of the image information analysis unit performs regression analysis based on the displacement-time curve to obtain a classification evaluation of the support displacement state;

[0013] The analysis result output unit outputs the graded evaluation results of the support displacement state, so that engineering and technical personnel can select corresponding engineering measures according to these results.

[0014] Furthermore, the image information analysis unit obtains the following process for graded evaluation of the support displacement state:

[0015] Firstly, a regression analysis is performed based on the displacement-time curve to obtain the displacement-time regression function;

[0016] Displacement-time regression function:

[0017] U=f(t)

[0018] In the formula, U represents displacement, unit: m; f(t) is the function form of displacement with respect to time, obtained through regression analysis, describing the displacement changing with time; t is time, unit: s;

[0019] Then, the displacement rate change trend function and displacement rate function are further obtained according to the regression function:

[0020] Displacement rate change trend function:

[0021]

[0022] In the formula, v' represents the rate of change of displacement velocity, that is, the change of velocity over time, unit: m / s 2 ; It represents the second-order derivative of the displacement function, reflecting the change of the displacement rate; Indicates the increment of time;

[0023] Then, the displacement rate change trend function and displacement rate function are further obtained according to the regression function:

[0024] Displacement rate change trend function:

[0025]

[0026] In the formula, v' represents the rate of change of displacement velocity, that is, the change of velocity over time, unit: m / s 2 ; It represents the second-order derivative of the displacement function, reflecting the change of the displacement rate; Indicates the increment of time;

[0027] Finally, the support displacement status is graded and evaluated based on the displacement rate change trend function and the displacement rate function.

[0028] A method for evaluating the initial support displacement within a safe step distance range of a highway tunnel, based on the above-mentioned initial support displacement evaluation system within a safe step distance range of a highway tunnel, comprises the following steps:

[0029] Step 1: The image information acquisition unit obtains the image information inside the cave within the safe step range;

[0030] Step 2: The image information converter of the image information analysis unit converts the image information collected by the lens into displacement data, forms a displacement-time curve of each measuring point in a continuous time, and transmits the displacement-time curve to the displacement data classification evaluation processor;

[0031] Step 3: The displacement data classification evaluation processor of the image information analysis unit performs regression analysis based on the displacement-time curve to obtain a displacement-time regression function U=f(t); and further obtains a displacement rate change trend function based on the regression function. And the displacement rate function: Based on the displacement rate change trend function and the displacement rate function, the support displacement state is graded and evaluated;

[0032] Step 4: The analysis result output unit outputs the graded evaluation results of the support displacement status so that engineering technicians can select corresponding engineering measures based on these results.

[0033] Furthermore, the support displacement status is graded and evaluated in step 3, and the engineering technicians select corresponding engineering measures according to these results in step 4, as follows:

[0034] First, determine the displacement trend around the hole. When the displacement rate trend is increasing or unchanged, that is: The surrounding rock assessment is: the surrounding rock is unstable; the response measures are: specific engineering measures should be taken according to the actual engineering conditions;

[0035] When the displacement rate of the surrounding rock changes in a decreasing trend, that is: Further judgment is made based on the current initial support displacement rate:

[0036] If the displacement rate is greater than 1mm / d, that is: The surrounding rock assessment is: the surrounding rock tends to be stable, but the deformation rate is fast, which is easy to cause the primary support to be damaged; the response measures are: strengthening measures should be adopted to strengthen the support and limit the deformation of the surrounding rock;

[0037] If the surrounding rock velocity is between 0.2 mm / d and 1 mm / d, that is: The surrounding rock assessment is: the surrounding rock tends to be stable, but the deformation rate is fast, and the primary support has the risk of damage; the countermeasures are: based on the fitted displacement-time function f(t), the cumulative displacement at the time node before the secondary lining is constructed can be predicted, and corresponding treatment measures can be adopted according to the final displacement to be achieved;

[0038] When the displacement rate is less than 0.2 mm / d, that is: The surrounding rock assessment is: stable; the response measures are: no treatment is required.

[0039] The beneficial effects of the present invention are:

[0040] The initial support displacement evaluation system within the safe step range of the highway tunnel adopts machine vision technology to observe the initial support deformation, ensuring the timeliness and integrity of the monitoring data without affecting the construction organization; the initial support displacement evaluation system within the safe step range of the highway tunnel adopts displacement-time curve regression analysis to obtain displacement-time function, displacement rate function, displacement rate change trend function, and combines the three levels of indicators of displacement rate deformation trend, displacement rate, and displacement value to form a comprehensive hierarchical evaluation method for the initial support displacement status. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the initial support displacement evaluation system within the safe step distance range of the highway tunnel of the present invention;

[0042] Figure 2 It is a camera installation position diagram of the image information acquisition unit of the present invention;

[0043] Figure 3 It is a measured curve and a regression function curve diagram of Application Example 1 of the present invention;

[0044] Figure 4 It is the measured curve and regression function curve diagram of application example 2 of the present invention;

[0045] Figure 5 It is the measured curve and regression function curve diagram of application example 3 of the present invention;

[0046] Figure 6 It is the measured curve and regression function curve diagram of application example 2 of the present invention;

[0047] In the figure: 1- camera, 2- secondary lining trolley, 3- initial support, 4- secondary lining. DETAILED DESCRIPTION

[0048] The following will be combined with the accompanying drawings of the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Example 1

[0050] This embodiment provides a system for evaluating the displacement of an initial support within a safe step distance range of a highway tunnel. The system for evaluating the displacement of an initial support within a safe step distance range of a highway tunnel includes an image information acquisition unit, an image information analysis unit, and an output unit; Figure 1 As shown, the specific structure and function of each unit are as follows:

[0051] Image information acquisition unit:

[0052] The image information acquisition unit is used to obtain the image information inside the cave within the safe step distance. Figure 2 As shown, the image information acquisition unit includes a lens and a camera arranged at the front end of the secondary lining trolley, as well as a number of displacement monitoring targets and in-tunnel light sources arranged on the primary support along the longitudinal section; the left side of the figure is the primary support, and the right side is the secondary lining.

[0053] Among them, the lens and camera placed at the front end of the secondary lining trolley, whose relative position to the tunnel axis remains unchanged, serve as the reference point for deformation monitoring in the tunnel. Displacement targets are arranged at a certain longitudinal spacing according to the actual situation on site. The light source in the tunnel provides the camera with light for acquiring images.

[0054] Image information analysis unit:

[0055] The image information analysis unit includes an image information converter and a displacement data hierarchical evaluation processor; wherein the image information converter is connected with the camera and the displacement data hierarchical evaluation processor for data transmission.

[0056] The image information converter converts the image information collected by the lens into displacement data, forms a displacement-time curve of each measuring point in a continuous time, and transmits the displacement-time curve to the displacement data grading evaluation processor.

[0057] The displacement data classification evaluation processor first performs regression analysis based on the displacement-time curve to obtain a displacement-time regression function;

[0058] Displacement-time regression function:

[0059] U=f(t)

[0060] Where U is displacement, unit: m; f(t) is the function form of displacement with respect to time, obtained through regression analysis, which describes the displacement changing with time; t is time, unit: s.

[0061] Then, the displacement rate function and displacement rate change trend function are further obtained according to the regression function:

[0062] Displacement rate function:

[0063]

[0064] In the formula, v represents the displacement rate, that is, the displacement change per unit time, unit: m / s; Represents the change in displacement function over time, i.e., increment; Represents an increment in time.

[0065] Displacement rate change trend function:

[0066]

[0067] In the formula, v' represents the rate of change of displacement velocity, that is, the change of velocity over time, unit: m / s 2 ; It represents the second-order derivative of the displacement function, reflecting the change of the displacement rate; Indicates an increment of time.

[0068] Finally, the support displacement status is graded and evaluated based on the displacement rate change trend function and the displacement rate function.

[0069] Analysis result output unit:

[0070] The analysis result output unit is used to output the graded evaluation results of the support displacement status so that engineering technicians can choose corresponding engineering measures based on these results.

[0071] Example 2

[0072] Based on the initial support displacement evaluation system within the safe step distance range of a highway tunnel proposed in Example 1, this embodiment also proposes an initial support displacement evaluation method within the safe step distance range of a highway tunnel, comprising the following steps:

[0073] Step 1: The image information acquisition unit obtains the image information inside the cave within the safe step range;

[0074] Step 2: The image information converter of the image information analysis unit converts the image information collected by the lens into displacement data, forms a displacement-time curve of each measuring point in a continuous time, and transmits the displacement-time curve to the displacement data classification evaluation processor;

[0075] Step 3: The displacement data classification evaluation processor of the image information analysis unit performs regression analysis based on the displacement-time curve to obtain a displacement-time regression function U=f(t); and further obtains a displacement rate change trend function based on the regression function. And the displacement rate function: Based on the displacement rate change trend function and the displacement rate function, the support displacement state is graded and evaluated;

[0076] Step 4: The analysis result output unit outputs the graded evaluation results of the support displacement status so that engineering technicians can select corresponding engineering measures based on these results.

[0077] Furthermore, in step 3, the support displacement state is graded and evaluated, and in step 4, the engineering technicians select corresponding engineering measures based on these results, as shown in the following table:

[0078]

[0079]

[0080] First, determine the displacement trend around the hole. When the displacement rate trend is increasing or unchanged, that is: The surrounding rock assessment is: the surrounding rock is unstable; the response measures are: stop excavation at the face, determine the cause of the surrounding rock instability, and take corresponding treatment measures.

[0081] When the displacement rate of the surrounding rock changes in a decreasing trend, that is: Further judgment is made based on the current initial support displacement rate:

[0082] If the displacement rate is greater than 1mm / d, that is: The surrounding rock assessment is: the surrounding rock tends to be stable, but the deformation rate is fast, which can easily lead to the destruction of the initial support; the response measures are: strengthening measures should be adopted to strengthen the support and limit the deformation of the surrounding rock.

[0083] If the surrounding rock velocity is between 0.2 mm / d and 1 mm / d, that is: The surrounding rock assessment is: the surrounding rock tends to be stable, but the deformation rate is fast, and the primary support is at risk of damage; the countermeasures are: based on the fitted displacement-time function f(t), the cumulative displacement at the time node before the secondary lining is constructed can be predicted, and corresponding treatment measures can be adopted according to the final displacement to be achieved.

[0084] When the displacement rate is less than 0.2 mm / d, that is: The surrounding rock assessment is: stable; the response measures are: no treatment is required.

[0085] Compare the existing safety control regulations for displacement around the cave:

[0086] The existing safety control regulations for displacement around the cave are as follows:

[0087] 1) Provisions for displacement values

[0088] Displacement Countermeasures <![CDATA[U<1 / 3U0]]> No treatment <![CDATA[1 / 3U0≤U<2 / 3U0]]> Strengthen support <![CDATA[U≥2 / 3U0]]> Taking special measures

[0089] 2) Provisions for the initial displacement rate

[0090] Displacement rate around the hole (mm / d) Countermeasures V<0.2 No treatment 0.2≤V<1 Strengthen observation and make preparations for reinforcement V≥1 Strengthen initial support

[0091] 3) Provisions on the trend of the initial displacement rate

[0092] Displacement rate change trend Countermeasures Increase (surrounding rock is extremely unstable) Stop excavation and adopt emergency measures Unchanged (surrounding rock is unstable) Strengthen support Reduce (Surrounding rock stability) No treatment

[0093] The existing safety control regulations for tunnel perimeter displacement have made corresponding provisions for the three levels of surrounding rock displacement status, namely, displacement value, displacement rate, and displacement rate change trend. However, the regulations at each level are independent of each other, and the three-level indicators of displacement value, rate, and rate change trend are not combined to form a comprehensive evaluation of the surrounding rock displacement status.

[0094] The method for evaluating the displacement of the initial support within the safe step range of the highway tunnel proposed in this embodiment adopts machine vision technology to observe the deformation of the initial support, which ensures the timeliness and integrity of the monitoring data without affecting the construction organization; displacement-time curve regression analysis is adopted to obtain the displacement-time regression function, displacement rate change trend function, and displacement rate function, and the three-level indicators of displacement rate change trend function, displacement rate function and displacement value are combined to form a comprehensive hierarchical evaluation method for the displacement status of the initial support.

[0095] Further, in order to verify the effect of the initial support displacement evaluation method within the safe step distance range of the highway tunnel, this embodiment provides the following application examples:

[0096] Application Example 1:

[0097] In a two-way 4-lane separated highway tunnel, the distance between the secondary lining and the tunnel face in the IV-level surrounding rock section is controlled according to the 70m specified in the specification. A machine vision lens and camera for collecting the initial support displacement image are set at the front end of the secondary lining trolley. According to the image information of the arch target point 5m away from the tunnel face, it is converted into the corresponding displacement-time curve, and regression analysis is performed. The measured curve and the regression function curve are as follows: Figure 3 As shown;

[0098] The regression displacement-time function equation is as follows:

[0099] U=f(t)=-1.191×e -2.365t +0.0214×e 2.104t +0.702

[0100] According to the displacement-time function, the displacement rate function can be obtained by calculating its first and second derivatives. Function of displacement rate change

[0101] v=2.8167×e -2.365t +0.045×e 2.104t

[0102] v′=-6.6615×e -2.365t +0.095×e 2.104t

[0103] When t>0.951, v′>0, the displacement deformation rate gradually increases, and the surrounding rock is unstable. The primary support near the section where the target point is located should be temporarily reinforced immediately, and the lining type used on the face should be strengthened so that the surrounding rock is in a stable state after excavation and support.

[0104] Application Example 2:

[0105] In a two-way 4-lane separated highway tunnel, the distance between the secondary lining and the tunnel face in the IV-level surrounding rock section is controlled according to the 70m specified in the specification. A machine vision lens and camera for collecting the initial support displacement image are set at the front end of the secondary lining trolley. According to the image information of the arch target point 35m away from the tunnel face, it is converted into the corresponding displacement-time curve, and regression analysis is performed. The measured curve and the regression function curve are as follows Figure 4 As shown;

[0106] The regression displacement-time function equation is as follows:

[0107] U=f(t)=0.0007026×e 0.5267t -1.984×e -0.4615t +2.186 According to the displacement-time function, the displacement rate function can be obtained by taking its first and second derivatives. Function of displacement rate change

[0108] v=0.000370×e 0.5267t +0.9156×e -0.4615t

[0109] v′=0.000195×e 0.5267t -0.4226×e -0.4615t

[0110] When t<6.1705d, v′<0, and v<1mm / d. When t>6.1705, v′>0, that is, in the initial period of time, the surrounding rock tends to be stable, but the unfavorable structural surface inside the surrounding rock is further developed, and the stability of the surrounding rock changes. The support near this target point should be reinforced, the construction rate of the second lining should be accelerated, the second lining should be constructed in time, the deformation of the primary support should be limited, the safety of the project should be ensured, and the surrounding rock occurrence should be paid attention to during the excavation of the face, and engineering measures to deal with the unfavorable structural surface should be adopted.

[0111] Application Example 3:

[0112] In a two-way 4-lane separated highway tunnel, the distance between the secondary lining and the tunnel face in the IV-level surrounding rock section is controlled according to the 70m specified in the specification. A machine vision lens and camera for collecting the initial support displacement image are set at the front end of the secondary lining trolley. According to the image information of the arch target point 9m away from the tunnel face, it is converted into the corresponding displacement-time curve, and regression analysis is performed. The measured curve and the regression function curve are as follows: Figure 5 As shown;

[0113] The regression displacement-time function equation is as follows:

[0114] U=f(t)=4.441×e 0.08449t -4.448×e -0.3765t

[0115] According to the displacement-time function, the displacement rate function can be obtained by calculating its first and second derivatives. Function of displacement rate change

[0116] v=0.3752×e 0.08449t +1.6747×e -0.3765t

[0117] v′=0.0317×e 0.08449t -0.6305×e -0.3765t

[0118] When v′<0, but v>1mm / d, the surrounding rock tends to be stable, but the deformation rate of the surrounding rock is fast, which can easily lead to large displacement of shotcrete and damage to the primary support. The primary support of this section should be strengthened and the lining should be constructed as soon as possible to avoid damage to the primary support.

[0119] Application Example 4:

[0120] In a two-way 4-lane separated highway tunnel, the distance between the secondary lining and the tunnel face in the IV-level surrounding rock section is controlled according to the 70m specified in the specification. A machine vision lens and camera for collecting the initial support displacement image are set at the front end of the secondary lining trolley. According to the image information of the arch target point 50m away from the tunnel face, it is converted into the corresponding displacement-time curve, and regression analysis is performed. The measured curve and the regression function curve are as follows: Figure 6 As shown;

[0121] The regression displacement-time function equation is as follows:

[0122] U = f(t) = 26.98 × e 0.009703t -26.99×e -0.02587t

[0123] According to the displacement-time function, the displacement rate function can be obtained by calculating its first and second derivatives. Function of displacement rate change

[0124] v=0.26179×e 0.009703t +0.69823×e -0.07545t

[0125] v′=2.5401×10 -3 ×e 0.009703t -0.05268×e -0.07545t

[0126] v′<0, and 0.2mm / d≤v<1mm / d. The construction rate of the tunnel with Class IV surrounding rock is about 2.5m / d. It takes about 28 days from the construction of the primary support to the pouring of the secondary lining. According to the prediction and calculation of the regression function, the displacement before the pouring of the secondary lining is U=f(28)=22.3221mm. The displacement of the primary support is large, which is easy to cause the damage of the primary support. The method of reducing the distance between the secondary lining and the tunnel face can be adopted to reduce the displacement time of the primary support, so as to achieve the purpose of reducing the deformation of the primary support and avoiding its excessive displacement.

[0127] Through the above application examples, it is verified that in actual tunnel engineering, the initial support displacement evaluation method within the safe step range of the highway tunnel adopts displacement-time curve regression analysis to obtain displacement-time regression function, displacement rate change trend function, and displacement rate function, and combines the three-level indicators of displacement rate change trend function, displacement rate function and displacement value to make a reasonable graded evaluation of the surrounding rock and support displacement status, effectively improve construction efficiency, give reasonable engineering measures, and ensure project safety.

[0128] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A grading evaluation system for primary support displacement within the safe step range of a highway tunnel, characterized by: The initial support displacement evaluation system within the safe step distance range of a highway tunnel includes an image information acquisition unit, an image information analysis unit and an output unit; The image information acquisition unit includes a lens and a camera arranged at the front end of the secondary lining trolley, and a number of displacement monitoring targets and in-hole light sources arranged on the primary support along the longitudinal section; the image information analysis unit includes an image information converter and a displacement data grading evaluation processor, the image information converter is connected to the camera and the displacement data grading evaluation processor for data transmission, and the displacement data grading evaluation processor is connected to the output unit for data transmission.

2. The initial support displacement evaluation system within the safe step distance range of a highway tunnel according to claim 1 is characterized in that: The lens and camera placed at the front end of the secondary lining trolley keep their relative position to the tunnel axis unchanged and serve as the reference point for deformation monitoring in the tunnel; displacement targets are arranged at a certain longitudinal spacing according to the actual situation on site; the light source in the tunnel provides the camera with light for acquiring images.

3. The initial support displacement evaluation system within the safe step distance range of a highway tunnel according to claim 1 is characterized in that: The image information acquisition unit acquires the image information in the hole within the safe step range; The image information converter of the image information analysis unit converts the image information collected by the lens into displacement data, forms a displacement-time curve of each measuring point in a continuous time, and transmits the displacement-time curve to the displacement data classification evaluation processor; The displacement data classification evaluation processor of the image information analysis unit performs regression analysis based on the displacement-time curve to obtain a classification evaluation of the support displacement state; The analysis result output unit outputs the graded evaluation results of the support displacement state, so that engineering and technical personnel can select corresponding engineering measures according to these results.

4. The initial support displacement evaluation system within the safe step distance range of a highway tunnel according to claim 3 is characterized in that: The image information analysis unit obtains the following process for graded evaluation of the support displacement state: Firstly, a regression analysis is performed based on the displacement-time curve to obtain the displacement-time regression function; Displacement-time regression function: U=f(t) In the formula, U represents displacement, unit: m; f(t) is the function form of displacement with respect to time, obtained through regression analysis, describing the displacement changing with time; t is time, unit: s; Then, the displacement rate change trend function and displacement rate function are further obtained according to the regression function: Displacement rate change trend function: In the formula, v' represents the rate of change of displacement velocity, that is, the change of velocity over time, unit: m / s 2 ; It represents the second-order derivative of the displacement function, reflecting the change of the displacement rate; Indicates the increment of time; Then, the displacement rate change trend function and displacement rate function are further obtained according to the regression function: Displacement rate change trend function: In the formula, v' represents the rate of change of displacement velocity, that is, the change of velocity over time, unit: m / s 2 ; It represents the second-order derivative of the displacement function, reflecting the change of the displacement rate; Indicates the increment of time; Finally, the support displacement status is graded and evaluated based on the displacement rate change trend function and the displacement rate function.

5. A method for evaluating the initial support displacement within the safe step distance range of a highway tunnel, the method for evaluating the initial support displacement within the safe step distance range of a highway tunnel is based on the initial support displacement evaluation system within the safe step distance range of a highway tunnel according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: The image information acquisition unit obtains the image information inside the cave within the safe step range; Step 2: The image information converter of the image information analysis unit converts the image information collected by the lens into displacement data, forms a displacement-time curve of each measuring point in a continuous time, and transmits the displacement-time curve to the displacement data classification evaluation processor; Step 3: The displacement data classification evaluation processor of the image information analysis unit performs regression analysis based on the displacement-time curve to obtain a displacement-time regression function U=f(t); and further obtains a displacement rate function based on the regression function: And the displacement rate change trend function Based on the displacement rate change trend function and the displacement rate function, the support displacement state is graded and evaluated; Step 4: The analysis result output unit outputs the graded evaluation results of the support displacement status so that engineering technicians can select corresponding engineering measures based on these results.

6. The method for evaluating the initial support displacement within the safe step distance range of a highway tunnel according to claim 5, characterized in that: The graded evaluation of the support displacement status in step 3 and the selection of corresponding engineering measures by the engineering technicians based on these results in step 4 are as follows: First, determine the displacement trend around the hole. When the displacement rate trend is increasing or unchanged, that is: The surrounding rock assessment is: the surrounding rock is unstable; the response measures are: specific engineering measures should be taken according to the actual engineering conditions; When the displacement rate of the surrounding rock changes in a decreasing trend, that is: Further judgment is made based on the current initial support displacement rate: If the displacement rate is greater than 1mm / d, that is: The surrounding rock assessment is: the surrounding rock tends to be stable, but the deformation rate is fast, which is easy to cause the primary support to be damaged; the response measures are: strengthening measures should be adopted to strengthen the support and limit the deformation of the surrounding rock; If the surrounding rock velocity is between 0.2 mm / d and 1 mm / d, that is: The surrounding rock assessment is: the surrounding rock tends to be stable, but the deformation rate is fast, and the primary support has the risk of damage; the countermeasures are: based on the fitted displacement-time function f(t), the cumulative displacement at the time node before the secondary lining is constructed can be predicted, and corresponding treatment measures can be adopted according to the final displacement to be achieved; When the displacement rate is less than 0.2 mm / d, that is: The surrounding rock assessment is: stable; the response measures are: no treatment is required.

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