A test method for active and passive instability failure of excavation face

Abstract

The invention discloses a method for testing active and passive instability damage of excavation face, comprising: pasting wallpaper on the inner side of a model box, and setting scale lines on the wallpaper; filling soil in layers in the model box, and setting an observation section perpendicular to the propulsion direction of a shield machine, and arranging a stratum displacement meter, an earth pressure box, and a surface displacement meter around the observation section; drilling and excavating soil in the model box by a shield machine to respectively perform active instability damage test of tunnel excavation face and passive instability damage test of tunnel excavation face, and recording data of the surface displacement meter, stratum displacement meter, and earth pressure box; excavating tunnels with different burial depths for testing, so as to study the progressive deformation law of strata during active and passive instability of tunnel excavation face. The advantages of the invention are: through the active instability damage test of tunnel excavation face and the passive instability damage test of tunnel excavation face, the progressive deformation law of strata during active and passive instability of excavation face can be studied.

Description

Technical Field

[0001] The invention relates to the technical field of underground engineering, in particular to an active and passive instability failure test method for an excavation face. Background Art

[0002] At present, domestic subway construction is booming, and most of them are constructed using the shield method. When using the shield method in sand and gravel formations, over-excavation often occurs due to disturbance, scattering, and collapse of the face, resulting in cavities and ground collapse, which has a serious impact on upper roads, pipelines, and buildings. This is mainly because sand and gravel is a typical mechanically unstable formation with large pores between particles and no cohesion; in the absence of water, the sand and gravel formation transmits force point to point between particles, and the formation reacts sensitively; when the cutterhead rotates and cuts, the formation can easily destroy the original relatively stable or balanced state and collapse, causing greater surrounding rock disturbance, causing the excavation surface and the tunnel wall to lose constraints and become unstable.

[0003] Stability control of the shield tunnel excavation face is extremely important. However, many experiments do not consider the realization process of active and passive instability failure of the excavation face, and the monitoring scheme is not detailed.

[0004] Therefore, a test method for active and passive instability failure of excavation face is needed to study the progressive deformation law of strata during active and passive instability of excavation face. Summary of the invention

[0005] The purpose of the present invention is to provide an active and passive instability failure test method for an excavation face in light of the deficiencies of the above-mentioned prior art. Firstly, the similarity ratio is calculated based on the engineering background and the size of the model test platform, and then the relative density and density of the soil used in the model test are obtained. A series of model tests are carried out on shield tunnels in sand and gravel strata with different burial depths, and the progressive deformation law of the strata during the active and passive instability of the excavation face is analyzed. The rubber clamping structure is used to simulate the transmission of the soil squeezing effect of the soil layer to a distance, thereby avoiding the phenomenon of squeezing and compacting the soil layer at the inner wall of the plate body, and simulating the process in which the conduction of the soil layer gradually weakens during the squeezing process.

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

[0007] A method for testing active and passive instability failure of an excavation face, characterized in that the method comprises:

[0008] (S1) installing a model box, pasting wallpaper on the inner side of the model box, and setting scale lines on the wallpaper;

[0009] (S2) using the scale lines on the wallpaper to fill the model box in layers, setting an observation section perpendicular to the propulsion direction of the shield machine, and arranging a stratum displacement meter, an earth pressure box and a surface displacement meter around the observation section;

[0010] Wherein, the stratum displacement meter and the earth pressure box are arranged inside the soil body, and the surface displacement meter is arranged on the surface of the soil body;

[0011] (S3) a shield machine is arranged at the rear end plate of the model box, and soil is excavated in the model box by the shield machine to respectively perform an active instability failure test of the tunnel excavation face and a passive instability failure test of the tunnel excavation face, and record data of the surface displacement meter, the stratum displacement meter and the earth pressure box;

[0012] When the cutter head of the shield machine reaches the observation section, the active instability process of the tunnel excavation face is simulated; when the cutter head of the shield machine excavates to a certain distance from the observation section, the passive instability process of the tunnel excavation face is simulated;

[0013] The active instability simulation method is: control the shield machine to stop excavating forward, that is, set the excavation speed to 0 mm / min, the cutter head speed of the shield machine to 0.2 r / min, and the spiral excavator speed of the shield machine to 1.0 r / min;

[0014] The passive instability simulation method is as follows: when the cutter head of the shield machine is excavated to a distance of 50 mm from the observation section, the passive instability process of the tunnel excavation face is simulated, the cutter head and the spiral excavator of the shield machine are controlled to be shut down, and the jacking speed of the shield machine is set to 2 mm / min;

[0015] (S4) Excavating tunnels with different burial depths for testing, repeating the above steps S1 to S3, so as to study the progressive deformation law of the stratum during the active and passive instability of the tunnel excavation face.

[0016] In the process of layered filling, the soil mass required for each layer of filling is calculated by the relative density of the soil, and then the soil is weighed and filled into the model box, compacted with a rammer and checked with a laser level; after the filling reaches a predetermined height, the specific burial positions of the stratum displacement meter and the soil pressure box are determined by the laser level.

[0017] In the active instability failure test and the passive instability failure test of the tunnel excavation face, the stratum displacement meters are respectively arranged above the shield machine excavation area, above the boundary of the shield machine excavation area, and above one side of the shield machine excavation area; the surface displacement meters are respectively arranged above the shield machine excavation area, above the boundary of the shield machine excavation area, and above the other side of the shield machine excavation area; the earth pressure boxes are respectively arranged above the shield machine excavation area, on both sides of the shield machine excavation area, and above both sides of the shield machine excavation area.

[0018] The surface displacement meter is connected to a static strain collector and the static strain collector is used to collect and record all surface displacement and deformation data.

[0019] The stratum displacement meter is connected with the grating ruler displacement monitoring system.

[0020] The model box is a cubic box with an open top, including a bottom plate, a front plate, a rear plate, side plates on both sides and two corner connecting plates; wherein:

[0021] The two ends of the front end plate are connected to the side plates through the corner connecting plates respectively; the corner connecting plates are in a right angle shape; the ends of the corner connecting plates, the ends of the side plates and the ends of the front end plate are all connected by a rubber clamping structure;

[0022] A rubber clamping structure is also used between the two end portions of the rear end plate and the two side plates.

[0023] The rubber clamping structure comprises a rubber wall plate and a through-axis linear screw mechanism, wherein bosses are respectively provided at both ends of the rubber wall plate, and slots are respectively provided at the ends of the corner connecting plate, the ends of the side plate, the ends of the front end plate, and the ends of the rear end plate, wherein the bosses and the slots are adapted to each other in size and shape, and the clamping is achieved by clamping the bosses at both ends of the rubber wall plate into the slots at the ends of the plate body to be connected; the through-axis linear screw mechanism is pre-embedded in the ends of the side plate, the ends of the front end plate, and the ends of the rear end plate, and a through hole is provided at the center of the rubber wall plate for the screw in the through-axis linear screw mechanism to pass through, and the rubber wall plate is finely adjusted to be compressed or stretched by driving the screw forward or backward;

[0024] For the rubber clamping structure located between the side plate and the corner connecting plate, the through-axis linear screw mechanism is pre-buried in the side plate and the front end of the screw of the through-axis linear screw mechanism is fixedly connected to the end of the corner connecting plate.

[0025] For the rubber clamping structure located between the front end plate and the corner connecting plate, the through-axis linear screw mechanism is pre-buried in the front end plate and the front end of the screw of the through-axis linear screw mechanism is fixedly connected to the end of the corner connecting plate;

[0026] For the rubber clamping structure located between the rear end plate and the side plate, the through-shaft linear screw mechanism is pre-buried in the rear end plate and the front end of the screw of the through-shaft linear screw mechanism is fixedly connected to the end of the side plate.

[0027] In step S3, the shield machine is arranged on a support pedestal and driven to move forward and backward by a ball screw mechanism.

[0028] In step S3, during the process of the shield machine drilling into the soil in the model box, based on the soil squeezing effect generated by the shield machine in the longitudinal direction and on both sides during excavation, each of the through-axis linear screw mechanisms is controlled to support forward so that the front end plate is displaced in the longitudinal direction and the side plates on both sides are displaced outward, and the rubber wall panels follow and extend.

[0029] The required displacement data of the front end plate and the side plate are calculated respectively based on the displacement data of the formation displacement meter.

[0030] The advantages of the present invention are:

[0031] (1) Through active and passive instability tests on tunnel excavation faces, the progressive deformation law of the strata during active and passive instability of the excavation faces is studied;

[0032] (2) By setting a rubber clamping structure that can generate longitudinal and lateral displacements on the model box, that is, a rubber wall panel that can adapt to stretching or compression and a through-axis linear screw mechanism that can drive deformation, the actual soil environment can be better simulated to avoid the soil layer terminating displacement transmission at the side panels and the front end panel in the narrow model box, causing the soil layer to be compacted at the wall panel position. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a plan view of the model box and the shield machine test mechanism in the present invention;

[0034] Figure 2 It is a split schematic diagram of the rubber wall panel, the corner connecting plate and the side plate in the present invention;

[0035] Figure 3 For the present invention Figure 1 An enlarged schematic diagram of the local A in FIG.

[0036] Figure 4It is a schematic diagram of the screw in the through-shaft linear screw mechanism of the present invention pushing the corner connecting plate to extend the rubber wall plate;

[0037] Figure 5 is the buried depth ratio in the active instability failure test of the present invention C / D =2.0: Layout of the surface displacement meter in the top view of the model box;

[0038] Figure 6 is the buried depth ratio in the active instability failure test of the present invention C / D =2.0: Arrangement of the formation displacement meter and the surface displacement meter in the side view of the model box;

[0039] Figure 7 is the buried depth ratio in the active instability failure test of the present invention C / D =2.0 Arrangement diagram of the formation displacement meter and the surface displacement meter under the main view of the model box;

[0040] Figure 8 is the buried depth ratio in the active instability failure test of the present invention C / D =1.0: Layout of the surface displacement meter in the top view of the model box;

[0041] Fig. 9 is the buried depth ratio in the active instability failure test of the present invention C / D =1.0: Arrangement of the formation displacement meter and the surface displacement meter in the side view of the model box;

[0042] Fig.10 is the buried depth ratio in the active instability failure test of the present invention C / D =1.0: Arrangement of the formation displacement meter and the surface displacement meter under the main view of the model box;

[0043] Fig.11 is the buried depth ratio in the active instability failure test of the present invention C / D =0.5: Layout of the surface displacement meter in the top view of the model box;

[0044] Fig.12 is the buried depth ratio in the active instability failure test of the present invention C / D =0.5: Arrangement of the formation displacement meter and the surface displacement meter in the side view of the model box;

[0045] Fig.13 is the buried depth ratio in the active instability failure test of the present invention C / D =0.5, the layout of the formation displacement meter and the surface displacement meter under the main view of the model box;

[0046] Fig.14 is the buried depth ratio in the active instability failure test of the present invention C / D =2.0: Layout of the earth pressure box in the top view of the model box;

[0047] Fig.15 is the buried depth ratio in the active instability failure test of the present invention C / D =2.0: Layout of the earth pressure box in the side view of the model box;

[0048] Fig.16 is the buried depth ratio in the active instability failure test of the present invention C / D =2.0: Layout of the earth pressure box in the main view of the model box;

[0049] Fig.17 is the buried depth ratio in the active instability failure test of the present invention C / D =1.0: Layout of the earth pressure box in the top view of the model box;

[0050] Fig.18 is the buried depth ratio in the active instability failure test of the present invention C / D =1.0: Layout of the earth pressure box in the side view of the model box;

[0051] Fig.19 is the buried depth ratio in the active instability failure test of the present invention C / D =1.0 is the layout of the earth pressure box in the main view of the model box;

[0052] Fig. 20 is the buried depth ratio in the passive instability failure test of the present invention C / D =1.5: Layout of the surface displacement meter in the top view of the model box;

[0053] Fig.21 is the buried depth ratio in the passive instability failure test of the present invention C / D =1.5: Arrangement of the formation displacement meter and the surface displacement meter in the side view of the model box;

[0054] Fig. 22 is the buried depth ratio in the passive instability failure test of the present invention C / D =1.5, the layout of the formation displacement meter and the surface displacement meter under the main view of the model box;

[0055] Fig.23 is the buried depth ratio in the passive instability failure test of the present invention C / D =1.0: Layout of the surface displacement meter in the top view of the model box;

[0056] Fig.24 is the buried depth ratio in the passive instability failure test of the present invention C / D =1.0: Arrangement of the formation displacement meter and the surface displacement meter in the side view of the model box;

[0057] Fig.25 is the buried depth ratio in the passive instability failure test of the present invention C / D=1.0: Arrangement of the formation displacement meter and the surface displacement meter under the main view of the model box;

[0058] Fig.26 is the buried depth ratio in the passive instability failure test of the present invention C / D =0.5: Layout of the surface displacement meter in the top view of the model box;

[0059] Fig. 27 is the buried depth ratio in the passive instability failure test of the present invention C / D =0.5: Arrangement of the formation displacement meter and the surface displacement meter in the side view of the model box;

[0060] Fig.28 is the buried depth ratio in the passive instability failure test of the present invention C / D =0.5, the layout of the formation displacement meter and the surface displacement meter under the main view of the model box;

[0061] Fig.29 is the buried depth ratio in the passive instability failure test of the present invention C / D =1.5: Layout of the earth pressure box in the top view of the model box;

[0062] Fig.30 is the buried depth ratio in the passive instability failure test of the present invention C / D =1.5: Layout of the earth pressure box in the side view of the model box;

[0063] Fig.31 is the buried depth ratio in the passive instability failure test of the present invention C / D =1.5: Layout of the earth pressure box in the main view of the model box;

[0064] Fig.32 is the buried depth ratio in the passive instability failure test of the present invention C / D =1.0: Layout of the earth pressure box in the top view of the model box;

[0065] Fig.33 is the buried depth ratio in the passive instability failure test of the present invention C / D =1.0: Layout of the earth pressure box in the side view of the model box;

[0066] Fig.34 is the buried depth ratio in the passive instability failure test of the present invention C / D =1.0 is the layout of the earth pressure box in the main view of the model box;

[0067] Fig.35 is the buried depth ratio in the passive instability failure test of the present invention C / D =0.5: Layout of the earth pressure box in the top view of the model box;

[0068] Fig.36 is the buried depth ratio in the passive instability failure test of the present invention C / D =0.5: Layout of the earth pressure box in the side view of the model box;

[0069] Fig.37 is the buried depth ratio in the passive instability failure test of the present invention C / D =0.5: Layout of the earth pressure box in the main view of the model box. DETAILED DESCRIPTION

[0070] The features of the present invention and other related features are further described in detail below through embodiments in conjunction with the accompanying drawings to facilitate understanding by those skilled in the art:

[0071] like Figure 1-37 As shown, the reference numerals in the figure are: shield machine test mechanism 1, shield machine 11, ball screw mechanism 12, support pedestal 13; model box 2, side plate 21, front end plate 22, rear end plate 23, corner connecting plate 24, rubber wall plate 25, through-axis linear screw mechanism 26, through hole 27.

[0072] Example: Figure 1-37 As shown, this embodiment relates to a method for testing active and passive instability failure of an excavation face, which mainly includes:

[0073] (S1) Figure 1-4 As shown, smooth wallpaper is pasted on the inner side of the model box 2 to reduce the friction between the soil and the inside of the box, and scale lines are set on the wallpaper to ensure more accurate control of the soil sample density during the filling process.

[0074] The length, width and height of the model box 2 are 2000 mm×2000 mm×1500 mm respectively. The model box 2 is a cubic box with an open top, including a bottom plate, a front plate 22, a rear plate 23, side plates 21 on both sides and two corner connecting plates 24. The bottom plate is laid flat on the ground, the two ends of the front plate 22 are connected to the side plates 21 on both sides through the corner connecting plates 24, and the two ends of the rear plate 23 are connected to the side plates 21 on both sides, together forming the circumferential vertical panel of the model box 2.

[0075] The corner connecting plate 24 is in a right-angle shape, and one end of the corner connecting plate 24 is clamped to the end of the side plate 21 via a rubber clamping structure, and the other end of the corner connecting plate 24 is clamped to the end of the front end plate 22 via a rubber clamping structure; in addition, the two ends of the rear end plate 23 are also clamped to the ends of the side plates 21 on both sides via a rubber clamping structure.

[0076] like Figure 2 , 34, each rubber clamping structure adopts the same structure. In this embodiment, the rubber clamping structure between the corner connecting plate 24 and the side plate 21 is used as an example for explanation. The rubber clamping structure includes a rubber wall plate 25 and a through-axis linear screw mechanism 26. The two ends of the rubber wall plate 25 are respectively provided with bosses and the middle position has the same thickness as the side plate 21. The ends of the corner connecting plate 24 and the ends of the side plate 21 are respectively provided with card grooves. The shapes and sizes of the bosses and the card grooves correspond to each other. When assembling, by The bosses of 25 are correspondingly assembled in the slots of the two end plates to form a snap-fit ​​relationship; the through-axis linear screw mechanism 26 is pre-buried and fixed in the front end cavity of the side plate 21, and a through hole 27 is provided in the center of the rubber wall plate 25 for the screw in the through-axis linear screw mechanism 26 to pass through. The front end of the screw in the through-axis linear screw mechanism 26 is fixedly connected to the end surface of the corner connecting plate 24 (but the screw can be rotated), and the rubber section in the middle of the rubber wall plate 25 is finely adjusted to be compressed or stretched by driving the screw forward or backward. Specifically, by driving the through-axis linear screw mechanism 26 in the two sets of rubber snap-fit ​​structures here, the longitudinal displacement of the front end plate 22 can be achieved.

[0077] like Figure 1-4 As shown, for the rubber clamping structure located between the front end plate 22 and the corner connecting plate 24, a through-axis linear screw mechanism 26 is pre-buried in the front end plate 22 and the front end of the screw of the through-axis linear screw mechanism 26 is fixedly connected to the end of the corner connecting plate 24 and can rotate relatively.

[0078] For the rubber clamping structure between the rear end plate 23 and the side plate 21 , the through-axis linear screw mechanism 26 is embedded in the rear end plate 23 and the front end of the screw of the through-axis linear screw mechanism 26 is fixedly connected to the rear end of the side plate 21 and can rotate relatively.

[0079] Specifically, when the through-shaft linear screw mechanisms 26 in the front end plate 22 and the rear end plate 23 are driven simultaneously, lateral displacement of the side plates 21 on both sides can be achieved.

[0080] (S2) Using the scale lines on the wallpaper, fill the model box 2 in layers, and set an observation section perpendicular to the advancing direction of the shield machine 11. In this embodiment, the observation section is set at 1 / 2 of the entire advancing length in the model box 2, and a stratum displacement meter, an earth pressure box, and a surface displacement meter are arranged around the observation section.

[0081] Among them, the formation displacement meter and earth pressure box are arranged inside the soil, the surface displacement meter is arranged on the surface of the soil, and the observation section is the cross section at the 1 / 2 length position of the model box.

[0082] The unit height during the filling process is set to 10 cm. After calculating the mass of soil required for each layer of filling, the soil is weighed and filled into the model box 2, and compacted with a rammer and checked with a laser level. After the filling reaches the predetermined height, the specific buried position of the stratum displacement meter and the earth pressure box is determined by the laser level. The minimum dry density and maximum dry density of the test soil sample are obtained through geotechnical tests. First, the minimum density obtained by filling the model box 2 with a 10 cm soil sample is tested, and then the maximum density obtained is tested in the same way. Finally, the minimum and maximum operable density is determined. During the test, the corresponding soil filling density is calculated based on the relative density, and then the mass of the required soil is calculated according to 10 cm. In addition, the layered filling of the soil is achieved by filling the soil in blocks. After the filling and the arrangement of the stratum displacement meter and the earth pressure box are completed, the flatness is checked again, and the surface displacement meter positioning frame is set. After the surface displacement meter and the formation displacement meter are installed, the surface displacement meter is connected to the static strain collector, the formation displacement meter is connected to the grating ruler displacement monitoring system, and the static strain collector and the grating ruler displacement monitoring system are connected to the computer. In this embodiment, the surface displacement meter adopts a top rod displacement meter, and the static strain collector adopts a DH3818Y static strain collector, which is used to collect and record all surface displacement and deformation data, and its collection frequency is 1-200Hz. The formation displacement meter is composed of a serrated steel plate, a steel strand and a plexiglass capillary, and the unit of the collected data of the grating ruler displacement monitoring system is μm.

[0083] The ground displacement meters are arranged above the excavation area of ​​the shield machine 11, above the boundary of the excavation area of ​​the shield machine 11, and above one side of the excavation area of ​​the shield machine 11. The surface displacement meters are arranged above the excavation area of ​​the shield machine 11, above the boundary of the excavation area of ​​the shield machine 11, and above the other side of the excavation area of ​​the shield machine 11. The earth pressure cells are arranged above the excavation area of ​​the shield machine 11, on both sides of the excavation area of ​​the shield machine 11, and above both sides of the excavation area of ​​the shield machine 11 to ensure the accuracy of data collection. The earth pressure cells are used to measure x , y , z Earth pressure in three directions, y Direction is the excavation direction of the shield machine. x Direction perpendicular to y The horizontal direction of the direction, z is perpendicular to y The vertical direction of the direction.

[0084] (S3) A shield machine test mechanism 1 is arranged on the outer wall of the model box 2. The shield machine test mechanism 1 includes a shield machine 11, a ball screw mechanism 12 and a support pedestal 13. The shield machine 11 is arranged on the support pedestal 13, and the tail of the shield machine 11 is connected to the ball screw mechanism 12 and driven to move forward and backward. The shield machine 11 is used to drill and dig soil in the model box 2 to perform active instability failure tests and passive instability failure tests on the tunnel excavation face, and record data of the surface displacement meter, the stratum displacement meter and the earth pressure box.

[0085] Among them, when the shield machine cutter head reaches the observation section (500 mm), the active instability process of the tunnel excavation face is simulated. At this time, the shield machine no longer advances forward, that is, the excavation speed is set to 0 mm / min. The cutter head speed is set to 0.2 r / min, and the spiral excavator speed is set to 1.0 r / min. In addition, the instability time of the excavation face at C / D=0.5 and C / D=1.0 is 36 minutes. In order to more intuitively observe the instability of the excavation face when C / D=2.0, the excavation time is set to 41 minutes. Among them, C / D is the burial depth ratio of the shield machine in the model box.

[0086] When the shield machine cutterhead excavated to 50 mm from the observation section, the passive instability process of the tunnel excavation face was simulated. At this time, the shield machine cutterhead and spiral excavator were shut down, and the shield machine jacking speed was set to 2 mm / min.

[0087] It should be noted that:

[0088] In the process of controlling the shield machine 11 to simulate tunnel excavation in the soil layer of the model box 2, it is inevitable that a soil squeezing effect will be produced on the longitudinal front end and both sides of the shield machine 11, that is, the position close to the shield machine 11 is affected by the soil squeezing and the displacement is the largest. As the distance increases, the soil is affected by the soil squeezing less and the displacement will also be weakened. However, since the size of the model box 2 is generally small, the soil is usually blocked at the inner wall surface of the plate body of the model box 2 by the soil squeezing, resulting in the accumulation of soil layer compression at the inner wall surface, which makes it impossible to truly simulate the displacement and compression of the soil layer during the excavation process of the shield machine 11. In order to solve this problem, it is necessary to provide a stable supporting force to the rubber clamping structure between the plates of the model box 2 so that the rubber wall plate 25 thereon can be slowly extended to simulate the force transmission and displacement transmission of the excavated layer, and the extension of the rubber wall plate 25 will still keep the inner wall surface of the model box 2 smooth.

[0089] Specifically, each through-axis linear screw mechanism 26 is controlled to support forward so that the front end plate 22 is displaced longitudinally and the side plates 21 on both sides are displaced outwardly, and the rubber wall plate 25 is slowly extended accordingly. The specific extension size of the rubber wall plate 25 can be determined based on experience or test parameters, and the extension value of the rubber wall plate 25 is controlled to be 1-10 mm during the entire excavation process of the shield machine 11.

[0090] In this embodiment, based on the displacement data of the stratum displacement meter, the law that the stratum displacement decreases with the increase of the distance is sorted out, and then the values ​​of the lateral displacement compensation required for the side plates 21 on both sides are derived according to the distance between the side plates 21 and the shield machine 11, that is, the required extension values ​​of the rubber wall plates 25 at both ends of the rear plate 23, and the required extension values ​​of the rubber wall plates 25 at both ends of the front plate 22. According to the advancement distance of the shield machine 11 in the model box 2, the through-axis linear screw mechanism 26 at both ends of the rear plate 23 is first controlled to slowly support and extend the rubber wall plates 25 at both ends of the rear plate 23. When the shield machine 11 is advanced in the model box 2 to the front plate 22, the through-axis linear screw mechanism 26 at both ends of the front plate 22 is further controlled to slowly support and extend the rubber wall plates 25 at both ends of the front plate 22.

[0091] In addition, the required longitudinal movement compensation value of the front end plate 22 , ie, the required extension value of the rubber wall plate 25 at the front ends of the side plates 21 on both sides, is derived according to the distance between the front end plate 22 and the front end of the shield machine 11 .

[0092] (S4) Excavating tunnels with different burial depths for testing, repeating the above steps S1 to S3, so as to study the progressive deformation law of the stratum during the active and passive instability of the tunnel excavation face.

[0093] Among them, the formation displacement meter, surface displacement meter and earth pressure cell in the active instability failure test at different burial depths can be found in Figure 5-19 As shown in Figure 2, the formation displacement meter, surface displacement meter and earth pressure cell in the passive instability failure test at different burial depths can be found in Figure 20-37 shown.

[0094] The beneficial technical effects of this embodiment are:

[0095] Through active and passive instability tests on tunnel excavation faces, the progressive deformation law of the strata during active and passive instability of the excavation faces is studied.

[0096] By arranging a rubber clamping structure that can generate longitudinal and lateral displacements on the model box, that is, a rubber wall panel that can adapt to stretching or compression and a through-axis linear screw mechanism that can drive deformation, the actual soil layer environment can be better simulated, avoiding the soil layer in a narrow model box from terminating displacement conduction at the side panels and the front end panel, causing the soil layer to be compacted at the wall panel position.

[0097] Although the above embodiments have described in detail the concepts and embodiments of the present invention with reference to the accompanying drawings, ordinary technicians in this field can recognize that various improvements and changes can still be made to the present invention without departing from the scope of the claims, so they are not described one by one here.

Claims

1. A method for testing active and passive instability of excavation faces, characterized in that The method comprises: (S1) installing a model box, pasting wallpaper on the inner side of the model box, and setting scale lines on the wallpaper; (S2) using the scale lines on the wallpaper to fill the model box in layers, setting an observation section perpendicular to the propulsion direction of the shield machine, and arranging a stratum displacement meter, an earth pressure box and a surface displacement meter around the observation section; Wherein, the stratum displacement meter and the earth pressure box are arranged inside the soil body, and the surface displacement meter is arranged on the surface of the soil body; (S3) a shield machine is arranged at the rear end plate of the model box, and soil is excavated in the model box by the shield machine to respectively perform an active instability failure test of the tunnel excavation face and a passive instability failure test of the tunnel excavation face, and record data of the surface displacement meter, the stratum displacement meter and the earth pressure box; When the cutter head of the shield machine reaches the observation section, the active instability process of the tunnel excavation face is simulated; when the cutter head of the shield machine excavates to a certain distance from the observation section, the passive instability process of the tunnel excavation face is simulated; The active instability simulation method is: control the shield machine to stop excavating forward, that is, set the excavation speed to 0 mm / min, the cutter head speed of the shield machine to 0.2 r / min, and the spiral excavator speed of the shield machine to 1.0 r / min; The passive instability simulation method is as follows: when the cutter head of the shield machine is excavated to a distance of 50 mm from the observation section, the passive instability process of the tunnel excavation face is simulated, the cutter head and the spiral excavator of the shield machine are controlled to be shut down, and the jacking speed of the shield machine is set to 2 mm / min; (S4) Excavating tunnels with different burial depths for testing, repeating the above steps S1 to S3, so as to study the progressive deformation law of the stratum during the active and passive instability of the tunnel excavation face.

2. A method for testing active and passive instability of excavation surface according to claim 1, characterized in that In the process of layered filling, the soil mass required for each layer of filling is calculated by the relative density of the soil, and then the soil is weighed and filled into the model box, compacted with a rammer and checked with a laser level; after the filling reaches a predetermined height, the specific burial positions of the stratum displacement meter and the soil pressure box are determined by the laser level.

3. A method for testing active and passive instability of excavation surface according to claim 1, characterized in that In the active instability failure test and the passive instability failure test of the tunnel excavation face, the stratum displacement meters are respectively arranged above the shield machine excavation area, above the boundary of the shield machine excavation area, and above one side of the shield machine excavation area; the surface displacement meters are respectively arranged above the shield machine excavation area, above the boundary of the shield machine excavation area, and above the other side of the shield machine excavation area; the earth pressure boxes are respectively arranged above the shield machine excavation area, on both sides of the shield machine excavation area, and above both sides of the shield machine excavation area.

4. A method for testing active and passive instability of excavation surface according to claim 1, characterized in that The surface displacement meter is connected to a static strain collector and the static strain collector is used to collect and record all surface displacement and deformation data.

5. A method for testing active and passive instability of excavation surface according to claim 1, characterized in that The stratum displacement meter is connected with the grating ruler displacement monitoring system.

6. A method for testing active and passive instability of excavation surface according to claim 1, characterized in that The model box is a cubic box with an open top, including a bottom plate, a front plate, a rear plate, side plates on both sides and two corner connecting plates; wherein: The two ends of the front end plate are connected to the side plates through the corner connecting plates respectively; the corner connecting plates are in a right angle shape; the ends of the corner connecting plates, the ends of the side plates and the ends of the front end plate are all connected by a rubber clamping structure; A rubber clamping structure is also used between the two end portions of the rear end plate and the two side plates.

7. A method for testing active and passive instability of excavation face according to claim 6, characterized in that The rubber clamping structure comprises a rubber wall plate and a through-axis linear screw mechanism, wherein bosses are respectively provided at both ends of the rubber wall plate, and slots are respectively provided at the ends of the corner connecting plate, the ends of the side plate, the ends of the front end plate, and the ends of the rear end plate, wherein the bosses and the slots are adapted to each other in size and shape, and the clamping is achieved by clamping the bosses at both ends of the rubber wall plate into the slots at the ends of the plate body to be connected; the through-axis linear screw mechanism is pre-embedded in the ends of the side plate, the ends of the front end plate, and the ends of the rear end plate, and a through hole is provided at the center of the rubber wall plate for the screw in the through-axis linear screw mechanism to pass through, and the rubber wall plate is finely adjusted to be compressed or stretched by driving the screw forward or backward; For the rubber clamping structure located between the side plate and the corner connecting plate, the through-axis linear screw mechanism is pre-buried in the side plate and the front end of the screw of the through-axis linear screw mechanism is fixedly connected to the end of the corner connecting plate. For the rubber clamping structure located between the front end plate and the corner connecting plate, the through-axis linear screw mechanism is pre-buried in the front end plate and the front end of the screw of the through-axis linear screw mechanism is fixedly connected to the end of the corner connecting plate; For the rubber clamping structure located between the rear end plate and the side plate, the through-shaft linear screw mechanism is pre-buried in the rear end plate and the front end of the screw of the through-shaft linear screw mechanism is fixedly connected to the end of the side plate.

8. A method for testing active and passive instability of excavation face according to claim 7, characterized in that In step S3, the shield machine is arranged on a support pedestal and driven to move forward and backward by a ball screw mechanism.

9. A method for testing active and passive instability of excavation face according to claim 8, characterized in that In step S3, during the process of the shield machine drilling into the soil in the model box, based on the soil squeezing effect generated by the shield machine in the longitudinal direction and on both sides during excavation, each of the through-axis linear screw mechanisms is controlled to support forward so that the front end plate is displaced in the longitudinal direction and the side plates on both sides are displaced outward, and the rubber wall panels follow and extend.

10. A method for testing active and passive instability of excavation surface according to claim 8, characterized in that The required displacement data of the front end plate and the side plate are calculated respectively based on the displacement data of the formation displacement meter.

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