An experimental method for measuring tunnel face stability in soft and hard composite formations

Abstract

The present invention relates to an experimental device and method for measuring the stability of a tunnel face in a soft-hard composite stratum, wherein a transparent observation plate (2) and a model frame (1) with a groove form a model box; the model frame (1) is provided with a semi-tunnel-shaped opening that cooperates with a semi-tunnel-shaped door (3); and a pull-out groove (4) can be inserted into the model box through the semi-tunnel-shaped opening. During the experiment, the prepared soft and hard soil samples are added to the model box; the semi-tunnel-shaped door is opened to excavate a soil groove; the pull-out groove (4) is inserted into the soil groove through the semi-tunnel-shaped door (3), and the soil face repose angle is recorded after the soil body stabilizes; this process is repeated until the soft and hard soil samples of the hard soil layer at different positions on the tunnel face are traversed, and the position of the harder soil layer on the tunnel face when the stratum is most stable is determined based on the obtained minimum tunnel face repose angle. The present invention can well simulate the tunnel excavation process under soft and hard composite stratum conditions and can determine the stability of the tunnel face under known and determined stratum conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel engineering, in particular to an experimental method and device for measuring the stability of a tunnel face in a soft-hard composite stratum, belonging to a model experiment. Background Art

[0002] Rapid urban development is driving the development of underground space. However, geological conditions are complex and often not fully reflected in geological exploration. Failure to fully consider these conditions can lead to significant construction difficulties, slowing progress and increasing construction difficulty. Tunnel location design often considers many factors. Setting aside other factors, selecting favorable geological conditions can reduce construction difficulty and accelerate the pace of construction. Therefore, geological conditions are crucial in the route selection process.

[0003] Tunnel excavation causes three-dimensional disturbances to the surrounding rock, and the displacement and deformation of the tunnel face are also very important. With the continuous improvement of the mechanization level of domestic tunnel engineering, people are gradually tending to change the face excavation method from multi-step partial excavation to full-section excavation, which puts higher requirements on the stability of the face.

[0004] There are relatively soft soil layers and hard soil layers in the underground soil layer. The most common ones are soft on top and hard on the bottom. At this time, the position of the tunnel face is mostly controlled by other factors such as the line, station, and existing buildings and structures. When the geological conditions exist that there are soft soil layers interspersed with harder soil layers, the harder soil layers can enhance the stability of the tunnel face. The position of the tunnel face where the harder soil layer is located is the most stable. This position is worth discussing and needs to be verified through experiments. Summary of the Invention

[0005] The purpose of the present invention is to address the technical problems existing in the prior art and provide an experimental method and device for measuring the stability of the tunnel face in soft and hard composite strata. The method and device can well simulate the tunnel excavation process under soft and hard composite strata conditions, determine the stability of the tunnel face under known and certain stratum conditions, and provide an experimental basis for design and construction personnel to select a suitable location for arranging the tunnel face.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The present invention provides an experimental device for measuring the stability of a tunnel face in a soft-hard composite formation, which comprises:

[0008] Model frame, transparent observation panel, semi-tunnel door and drawer slot;

[0009] The model frame includes a bottom plate, a first side plate, a second side plate and a rear plate respectively fixed to three sides of the bottom plate and vertically connected; the bottom plate, the first side plate and the second side plate are respectively provided with corresponding grooves at their front ends;

[0010] The two sides of the transparent observation panel are respectively embedded in the grooves of the first side panel and the second side panel, and the bottom is embedded in the prefabricated groove of the bottom panel to form a model box;

[0011] The first side plate and / or the second side plate of the model frame are provided with a semi-tunnel-shaped opening close to the groove portion, which matches the semi-tunnel-shaped door; the semi-tunnel-shaped door can be inserted into the model box through the semi-tunnel-shaped opening;

[0012] The drawing groove is a semi-tunnel-shaped arc structure, and the drawing groove can be inserted into the model box through the semi-tunnel-shaped opening.

[0013] More preferably, the transparent viewing plate is marked with grid lines of fixed intervals.

[0014] More preferably, the drawing groove includes a semi-tunnel-shaped arc-shaped inner body and a semi-tunnel-shaped arc-shaped outer body nested together.

[0015] More preferably, the drawing groove includes a semi-tunnel-shaped arc-shaped outer body.

[0016] The present invention also provides an experimental method for measuring the stability of a tunnel face in a soft-hard composite formation, which comprises:

[0017] Step S101: insert the transparent observation plate into the groove of the model frame and fix it, close the semi-tunnel door to form the model box;

[0018] Step S102: Add the configured soft and hard soil samples into the model box according to the position requirements of the hard soil layer at the tunnel face; compact and level each layer of soft and hard soil sample after adding it;

[0019] Step S103: After the last portion of soil is compacted and leveled, the soil is left to stand to allow the internal stress of the soil to balance automatically;

[0020] Step S104: Open the semi-tunnel-shaped door and excavate inward along the semi-tunnel-shaped opening to form a first portion of the soil trough; insert the pull-out trough through the semi-tunnel-shaped door and extend the pull-out trough inward along the soil trough, with the extension length recorded as a first length;

[0021] Step S105: As the soil in the model box flows in parallel, part of the flowing soil is discharged from the drawing trough, and the deformation of the soil in the model box and the time are observed from the transparent observation plate. After the deformation stabilizes, the repose angle of the soil in the model box is recorded.

[0022] Step S106: Whether the preset excavation length has been reached. If not, step S107 is executed, i.e., excavation is continued inward to form a second part of the soil groove; the pulling groove is continued to be extended inward along the soil groove; then the process returns to step S105; if yes, step S108 is executed;

[0023] Step S108, determining whether the hard and soft soil samples at different positions of the hard soil layer have been traversed, if not, executing step S109; if traversed, executing step S110;

[0024] Step S109, clearing the model box, selecting the soft and hard soil samples to be configured at the next position of the hard soil layer on the tunnel face, and then returning to step S101;

[0025] Step S110 , selecting a minimum tunnel face repose angle from the recorded tunnel face repose angles, and determining the position of the harder soil layer at the tunnel face when the stratum is most stable based on the minimum tunnel face repose angle.

[0026] More preferably, the experimental method further comprises:

[0027] A variety of soft and hard soil samples are configured according to the position of the hard soil layer on the tunnel face.

[0028] More preferably, the process of extending the pulling groove inwardly along the soil groove in step S104 or step S106 includes:

[0029] The outer body of the semi-tunnel-shaped arc structure in the drawing groove is extended into the soil groove, so that the outer body of the semi-tunnel-shaped arc structure forms a primary supporting structure for the soil in the entire model box.

[0030] More preferably, the process of extending the pulling groove inwardly along the soil groove in step S104 or step S106 includes:

[0031] After the semi-tunnel-shaped arc-shaped outer body of the pull-out trough is extended to a first length, the semi-tunnel-shaped arc-shaped inner body of the pull-out trough is tightly attached to the semi-tunnel-shaped arc-shaped outer body and extended to a set length, which shall not exceed the first length; so that the semi-tunnel-shaped arc-shaped inner body and the semi-tunnel-shaped arc-shaped outer body of the pull-out trough form a secondary lining structure for the soil in the entire model box.

[0032] It can be seen from the above technical solutions of the present invention that the present invention has the following technical effects compared with the prior art:

[0033] The present invention uses an experimental device for measuring the stability of the tunnel face in soft and hard composite strata to effectively simulate the tunnel excavation process in soft and hard composite strata. By adjusting the soil layer thickness, it can simulate most interlayer strata. The present invention has a simple structure and is easy to operate.

[0034] The present invention simulates the position of the tunnel face through an experimental method for measuring the stability of the tunnel face in a soft-hard composite formation, and can determine the stability of the tunnel face under known and determined formation conditions. This provides an experimental basis for design and construction personnel, and allows them to select a suitable position for arranging the tunnel face, thereby reducing the occurrence of engineering difficulties from a design perspective. In actual construction, the tunnel face stability can be improved, a self-stabilizing structure can be formed as much as possible, and tunnel face displacement can be reduced. This can improve the safety level, reduce the use of support measures, reduce construction costs, and greatly improve project quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is an exploded view of the experimental device structure of the present invention.

[0036] Figure 2 This is a schematic structural diagram of the experimental device of the present invention in its initial state before use;

[0037] Figure 3-1 A three-dimensional structural diagram of a semi-tunnel door in the experimental device of the present invention;

[0038] Figure 3-2 A top view of a semi-tunnel door in the experimental device of the present invention;

[0039] Figure 4-1 A three-dimensional structural diagram of the drawing slot in the experimental device of the present invention;

[0040] Figure 4-2 Schematic diagram of the cross-sectional structure of the drawing slot in the experimental device of the present invention;

[0041] Figure 5 This is a flow chart of the experimental method for measuring the stability of a tunnel face in a soft-hard composite formation according to the present invention;

[0042] Figure 6 This is a state diagram of the use process of the simulated primary support structure of the experimental device of the present invention, and the soft and hard soil layer samples that are not within the protection scope of the present invention are omitted in the figure;

[0043] Figure 7 This is a state diagram of the use process of the simulated primary support and secondary lining structure of the experimental device of the present invention. The figure omits soft and hard soil layer samples that are not within the protection scope of the present invention.

[0044] Reference numerals:

[0045] Model frame 1, transparent observation panel 2, semi-tunnel door 3, and drawer slot 4. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the technical solutions of the present application, the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0047] The terms "up", "down", "left", "right", "front", and "back" in this application are based on the positional relationships shown in the accompanying drawings. The corresponding positional relationships may vary depending on the drawings, and should not be construed as limiting the scope of protection.

[0048] In the present invention, the terms "installed," "connected," "connected," "connected," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, integral connection, mechanical connection, electrical connection, or mutual communication. They may be directly connected or indirectly connected through an intermediate medium. They may refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances. Example 1

[0049] The present invention provides an experimental device for measuring the stability of the tunnel face in a soft and hard composite formation. Figure 1 and Figure 2 As shown, it includes: a model frame 1, a transparent observation panel 2, a semi-tunnel door 3 and a drawer slot 4.

[0050] The model frame 1 includes a bottom plate, a first side plate, a second side plate, and a rear plate that are fixed to and vertically connected to the three sides of the bottom plate. The bottom plate, the first side plate, and the second side plate are each prefabricated with corresponding grooves at their respective front ends.

[0051] The transparent viewing panel 2 can be inserted along the grooves of the first and second side panels of the model frame 1, with its bottom embedded in the groove of the bottom panel; thus, the transparent viewing panel 2 and the model frame 1 together form the model box. For easy observation, the transparent viewing panel 2 is marked with grid lines with fixed spacing.

[0052] The first side plate and / or the second side plate of the model frame 1 are provided with a semi-tunnel-shaped opening close to the groove portion, so that the semi-tunnel-shaped door 3 can be inserted into the semi-tunnel-shaped opening. The structure of the semi-tunnel-shaped door 3 is as follows Figure 3-1 to Figure 3-2As shown, the semi-tunnel-shaped door 3 has a slot that can be snapped onto the first and second side panels extending from the semi-tunnel-shaped opening. When adding soft or hard soil samples for the experiment to the model box, the semi-tunnel-shaped door 3 is pressed against the semi-tunnel-shaped opening to return it to its original position. The semi-tunnel-shaped opening is now closed, and the soft or hard soil samples can now be added to the model box. When tunnel excavation simulation is required, the semi-tunnel-shaped door 3 is removed from the semi-tunnel-shaped opening and moved away, opening the semi-tunnel-shaped opening. The semi-tunnel-shaped door 3, as an independent component, can be fixedly connected to the model frame 1 in a variety of ways, such as being hinged to the model frame 1 and capable of opening outward. The semi-tunnel-shaped door 3 can also be an independent component that is not fixedly connected to the model frame 1 and can be freely removed from the semi-tunnel-shaped opening. When adding samples, the semi-tunnel-shaped door 3 forms part of the model box.

[0053] The drawing slot 4 is an independent device that can be inserted into the model box through the semi-tunnel-shaped opening in the open state to simulate the primary support or the secondary lining of the tunnel. Figure 4-1 and Figure 4-2 As shown, the drawer trough 4 is a semi-tunnel-shaped arc structure, with a notch formed within the arc of the semi-tunnel-shaped arc structure. The drawer trough 4 comprises a semi-tunnel-shaped arc structure inner body and a semi-tunnel-shaped arc structure outer body. The semi-tunnel-shaped arc structure inner body fits snugly within the semi-tunnel-shaped arc structure outer body, and the two can be separated from each other. The semi-tunnel-shaped arc structure outer body can simulate the primary support structure of a tunnel; when the semi-tunnel-shaped arc structure inner body and the semi-tunnel-shaped arc structure outer body are nested together, they can simulate the secondary lining structure of a tunnel. The material used for the drawer trough 4 can be selected based on the model experiment parameters.

[0054] Example 2

[0055] The second embodiment of the present invention provides an experimental method for measuring the stability of the tunnel face of a soft and hard composite stratum, which is suitable for measuring the stability of a soil-sand composite stratum. Before implementing the present invention, the corresponding soft and hard soil samples are configured according to the position requirements of the hard soil layer on the tunnel face. Then, the following is performed: Figure 5 The process shown includes the following steps:

[0056] Step S101: insert the transparent observation plate 2 into the groove of the model frame 1 and fix it, close the semi-tunnel door 3, and form the following: Figure 2 The model cabinet in the shown state.

[0057] Step S102: Add the configured soft and hard soil samples in sequence according to the position requirements of the hard soil layer on the tunnel face, and compact and level each layer of soil after adding it.

[0058] The thickness of each layer is determined according to the requirements of the experimental plan.

[0059] Step S103: After the last portion of soil is compacted and leveled, the soil is left to stand to allow the internal stress of the soft and hard soil samples to automatically balance.

[0060] The resting time is determined according to the experimental plan. The resting time of soft and hard soil samples in the model box is usually 1-2 days.

[0061] Step S104, open the semi-tunnel door 3, excavate the soil inside the model box along the semi-tunnel opening to form a first part of the soil groove, and insert the pulling groove 4 from the semi-tunnel door 3 and extend it into the soil groove for a first length.

[0062] In step S104, when it is necessary to simulate the primary support structure, it is only necessary to extend the outer body of the semi-tunnel-shaped arc structure in the drawing groove 4 into the soil groove formed by the excavation of the soil in the model box by a first length. At this time, the drawing groove 4 is extended into the state as shown in FIG. Figure 6 As shown, in this case, the outer body of the semi-tunnel-shaped arc structure serves as the primary support structure to support the soil in the entire model box.

[0063] In step S104, when it is necessary to simulate the secondary lining structure, the semi-tunnel-shaped arc structure outer body of the drawing groove 4 needs to be extended to the first length, and then the semi-tunnel-shaped arc structure inner body of the drawing groove 4 is extended from the semi-tunnel-shaped door 3 to the set length close to the semi-tunnel-shaped arc structure outer body. The set length shall not exceed the first length. At this time, the drawing groove 4 is extended as follows Figure 7 As shown, in this case, the semi-tunnel-shaped arc structure inner body and the semi-tunnel-shaped arc structure outer body of the drawing trough 4 serve as a secondary lining structure to support the soil in the entire model box.

[0064] In step S105, as the soil in the model box deforms and flows, the flowing soil is discharged from the notch of the pull-out groove 4. The deformation of the tunnel face and the time are observed from the transparent observation plate 2. After the deformation stabilizes, the repose angle of the tunnel face of the soft and hard soil samples in the model box is recorded.

[0065] After the soil of the soft and hard soil samples in the model box stops flowing, the deformation of the tunnel face is considered stable. At this time, the angle between the inclined surface of the soft and hard soil samples and the horizontal plane corresponding to this time is recorded. This angle is the repose angle of the tunnel face.

[0066] The larger the repose angle of the tunnel face, the lower the stability of the soft and hard soil samples in the model box, and the smaller the repose angle of the tunnel face, the higher the stability of the soft and hard soil samples in the model box.

[0067] Step S106, determines whether the preset simulated excavation length has been reached. If not, execute step S107, that is, continue to excavate along the semi-tunnel-shaped opening into the soil inside the model box to form a second part of the soil trough, and push the pulling groove 4 to continue to extend along the soil trough, and then return to step S105; if yes, execute step S108.

[0068] In step S106, the pull-out groove 4 can still be used as a primary support, or as a secondary lining structure to support the soil in the mold box. The specific situation is the same as step S104 and will not be described in detail here.

[0069] Step S108, determining whether the hard and soft soil samples at different positions of the hard soil layer have been traversed, if not, executing step S109; if traversed, executing step S110;

[0070] Step S109, clearing the model box, selecting a soft and hard soil sample with a hard soil layer below the tunnel face, and then returning to step S101 to repeat the experiment according to the experimental plan;

[0071] Step S110 , selecting a minimum tunnel face repose angle from the recorded tunnel face repose angles, and determining the position of the harder soil layer on the tunnel face when the soft and hard soil samples are most stable based on the minimum tunnel face repose angle.

[0072] It can be seen from the above embodiments that the present invention has the following technical advantages:

[0073] Through this method, the present invention can identify the location of the harder soil layer at the tunnel face when the ground is most stable, in composite stratum conditions when a harder soil layer is sandwiched between two soft soil layers. In actual engineering, when geological conditions have been explored and designers are conducting line selection design, they can use the above method to simulate and select a suitable location for the tunnel face. This shows that the present invention can not only reduce engineering difficulties from a design perspective, but also improve tunnel face stability in actual construction, form a self-stabilizing structure, reduce tunnel face displacement, improve safety standards, reduce the use of support measures, reduce construction costs, and greatly improve project quality.

[0074] Although the present invention has been disclosed above with reference to preferred embodiments, the embodiments do not limit the present invention. Any equivalent changes or modifications made without departing from the spirit and scope of the present invention also fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the content defined by the claims of this application.

Claims

1. An experimental method for measuring the stability of a tunnel face in a soft-hard composite formation, characterized by: The experimental method is implemented based on an experimental device for measuring the stability of a tunnel face in a soft-hard composite formation; The experimental device comprises: a model frame (1), a transparent observation panel (2), a semi-tunnel-shaped door (3) and a drawer slot (4); the model frame (1) comprises a bottom plate, a first side plate, a second side plate and a rear plate respectively fixed to three sides of the bottom plate and vertically connected; the bottom plate, the first side plate and the second side plate are respectively provided with corresponding grooves at their respective front ends; the two sides of the transparent observation panel (2) are respectively embedded in the grooves of the first side plate and the second side plate, and the bottom is embedded in the prefabricated groove of the bottom plate to form a model box; the first side plate and / or the second side plate of the model frame (1) are provided with a semi-tunnel-shaped opening that matches the semi-tunnel-shaped door (3) in close contact with the groove portion; the semi-tunnel-shaped door (3) can be inserted into the model box from the semi-tunnel-shaped opening; the drawer slot (4) is a semi-tunnel-shaped arc structure, and the drawer slot (4) can be inserted into the model box through the semi-tunnel-shaped opening; The experimental method includes: Step S101, inserting the transparent observation plate (2) into the groove of the model frame (1) and fixing it, closing the semi-tunnel-shaped door (3), and forming the model box; Step S102: Add the configured soft and hard soil samples into the model box according to the position requirements of the hard soil layer at the tunnel face; compact and level each layer of soft and hard soil sample after adding it; Step S103: After the last portion of soil is compacted and leveled, the soil is left to stand to allow the internal stress of the soil to balance automatically; Step S104, opening the semi-tunnel-shaped door (3), excavating inwardly along the semi-tunnel-shaped opening to form a first portion of the soil trough; inserting the drawing trough (4) through the semi-tunnel-shaped door (3), extending the drawing trough (4) inwardly along the soil trough, and recording the extending length as the first length; Step S105, as the soil in the model box flows in parallel, part of the flowing soil is discharged from the drawing trough (4), and the deformation of the tunnel face of the soil in the model box and the time are observed from the transparent observation plate (2), and the repose angle of the tunnel face of the soil in the model box is recorded after the deformation stabilizes; Step S106, whether the preset excavation length is reached, if not, then execute step S107, i.e. continue to excavate inwards to form the second part of the soil groove; continue to extend the pulling groove (4) inwards along the soil groove; then return to step S105; if yes, then execute step S108; Step S108, determining whether the hard and soft soil samples at different positions of the hard soil layer have been traversed, if not, executing step S109; if traversed, executing step S110; Step S109, clearing the model box, selecting the soft and hard soil samples to be configured at the next position of the hard soil layer on the tunnel face, and then returning to step S101; Step S110 , selecting a minimum tunnel face repose angle from the recorded tunnel face repose angles, and determining the position of the harder soil layer at the tunnel face when the stratum is most stable based on the minimum tunnel face repose angle.

2. The experimental method for measuring the stability of a tunnel face in a soft-hard composite formation according to claim 1 is characterized in that: The experimental method also includes: A variety of soft and hard soil samples are configured according to the position of the hard soil layer on the tunnel face.

3. The experimental method for measuring the stability of a tunnel face in a soft-hard composite formation according to claim 1 is characterized in that: The process of extending the pulling groove (4) inwardly along the soil groove in step S104 or step S106 includes: The outer body of the semi-tunnel-shaped arc structure in the drawing groove (4) is extended into the soil groove, so that the outer body of the semi-tunnel-shaped arc structure forms a primary support structure for the soil in the entire model box.

4. The experimental method for measuring the stability of a tunnel face in a soft-hard composite formation according to claim 1 is characterized in that: The process of extending the pulling groove (4) inwardly along the soil groove in step S104 or step S106 includes: After the semi-tunnel-shaped arc-shaped outer body of the drawing groove (4) is extended to a first length, the semi-tunnel-shaped arc-shaped inner body of the drawing groove (4) is tightly attached to the semi-tunnel-shaped arc-shaped outer body and extended to a set length, the set length not exceeding the first length; so that the semi-tunnel-shaped arc-shaped inner body and the semi-tunnel-shaped arc-shaped outer body of the drawing groove (4) form a secondary lining structure for the soil in the entire model box.

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