Patent ID: 12258862

In the figures: base1, upper crossbeam2, standing column3, bottom plate4, front side plate5, rear side plate6, left side plate7, right side plate8, top plate9, tunnel excavation port10, horizontal loading cylinder11, vertical loading cylinder12, inner guide rail13, outer guide rail14, mobile lifting wheel15, horizontal pushing hydraulic cylinder16, ordinary moving wheel17, triangular gantry18, limiter19, moving base20, hydraulic telescopic cylinder21, and tunnel mold22.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The technical solution in the embodiments of the present invention is clearly and completely described below. In view of the embodiments of the present invention, all other embodiments obtained by those having ordinary skill in the art without creative work shall fall within the scope of the protection of the present invention.

Referring toFIGS.1-3, the present invention provides the following technical solution. An experimental system for surrounding rock crack evolution and water inrush disaster change in a tunnel excavation of a near-covered karst cave includes the base1, the upper crossbeam2, the standing columns3, an experimental cabin, guide rails, a tunnel excavation device and an experimental control system.

The standing columns3are symmetrically arranged on the base1, one end of each of the standing columns3is inserted in the base1, and the other end of each of the standing columns3penetrates the upper crossbeam2to form a reaction frame.

The experimental cabin includes a bottom plate4, a front side plate5, a rear side plate6, a left side plate7, a right side plate8and a top plate9. The bottom plate4of the experimental cabin is placed directly on the base1. The front side plate5and the rear side plate6are symmetrically arranged on symmetrical sides of the base1, respectively. The left side plate7and the right side plate8are symmetrically arranged on the other symmetrical sides of the base1, respectively. A tunnel excavation port10is symmetrically arranged at the middle position of the front side plate5and the rear side plate6, and the shape of the tunnel excavation port10may be set according to the actual shape of a tunnel. The left side plate7and the right side plate8are symmetrically provided with equidistant installation grooves for installing the horizontal loading cylinder11. The horizontal loading pressure head is installed on the loading cylinder, and the horizontal loading pressure head directly provides a horizontal load for a physical model in the experimental cabin. The top plate9is centered symmetrically and equidistantly, and is connected to a vertical loading pressure head of the vertical loading cylinder12. The vertical loading pressure head directly provides a vertical load for the physical model in the experimental cabin. The vertical loading cylinder12is installed on the upper crossbeam2. In the process of performing horizontal and vertical loading on the physical model at the same time, in order to avoid that the horizontal loading pressure head and the vertical loading pressure head squeeze each other, the left and right sizes of the vertical loading pressure head are smaller than the left and right sizes of the experimental cabin. However, in order to improve the overall tightness of the experimental cabin, a closed baffle is installed above the inside of the left side plate7and the right side plate8, and is fixed on the left side plate7and the right side plate8by bolts.

The guide rails include a set of inner guide rails and a set of outer guide rails. The inner guide rails13are configured to move the whole the experimental cabin, and the outer guide rails14are configured for the separate movement of the front side plate5of the experimental cabin. The set of inner guide rails is symmetrically fixed on two sides of the base1, and the set of outer guide rails is symmetrically fixed on two sides of the base1. Mobile lifting wheels15are respectively arranged on the inner guide rails13, and the mobile lifting wheels15are symmetrically fixed on the bottom plate4of the experimental cabin. When the whole experimental cabin is required to be moved, the lifting hydraulic cylinders above the mobile lifting wheels15are started to lift the whole experimental cabin by 3 to 5 mm away from the base1. At this time, the experimental cabin is completely supported by the mobile lifting wheels15, the horizontal pushing hydraulic cylinder16is started, and the whole experimental cabin is horizontally moved by relying on the telescopic action of the horizontal pushing hydraulic cylinder16. Ordinary moving wheels17are arranged on the outer guide rail14, and the ordinary moving wheels17are symmetrically fixed at the bottom of the triangular gantry18. The triangular gantries18are fixed on the left and right sides of the front side plate5by bolts. After the experiment of the physical model is completed, without damaging the physical model, the front side plate5may be driven by the ordinary moving wheels17to be separated from the experimental cabin, such that the front side of the physical model is observed directly. In order to prevent the pressure head from failing to be centered in the vertical loading process due to the back and forth movement of the experimental cabin, preferably, the limiter19is arranged on the base1for positioning the experimental cabin.

The tunnel excavation device includes the moving base20, the hydraulic telescopic cylinder21and the tunnel mold22. Universal wheels are symmetrically arranged at the bottom of the moving base201to facilitate the free adjustment of the position of the tunnel excavation device. The hydraulic telescopic cylinder21is horizontally fixed above the moving base20, and is connected to the tunnel mold22through a connector. The shape of the tunnel mold22is consistent with the shape of the tunnel excavation port10, but the size of the tunnel mold22is slightly smaller than the size of the tunnel excavation port10. The tunnel mold22is configured to enter and leave freely under the traction of the hydraulic telescopic cylinder21. The interior of the tunnel mold22is hollow, and the camera is configured to enter the tunnel excavation space from the outside of the experimental cabin to collect real-time images of the whole process of the tunnel excavation.

The experimental control system includes a servo system and a control center. The servo loading system includes a load and displacement dual control servo system and a water pressure and water flow dual control servo system. The load and displacement dual control servo system is configured to realize the dual control of load and displacement. The horizontal loading cylinder12and the horizontal loading cylinder11are controlled by the load and displacement dual control servo system to respectively provide the vertical load and the horizontal load for the physical model in the experimental cabin, so as to meet the requirements of different simulation environments. The water pressure and water flow dual control servo system is configured to realize the dual control of water pressure and water flow, which can not only provide stable water flow supply to a cave in the physical model, but also maintain the constant water pressure in the cave in the physical model. In the whole process, the control center is configured to realize automatic control of the servo system, and real-time monitoring and collection of the displacement, the load, the water pressure and the water flow. A data collection frequency can be set according to the actual needs. In addition, according to the requirements of the experiment, monitoring elements, such as a pore water pressure sensor, an earth pressure sensor and a displacement sensor, are added in the physical model.

The process of the experiment:

According to the comprehensive bar chart of strata and the physical and mechanical test results of each stratum, the lithology, thickness and physical and mechanical parameters of each stratum are obtained. According to a geometric similarity ratio and a stress similarity ratio, a geometric size and a spatial position of a tunnel and a covered karst cave in the model, a geometric size of each stratum, and a proportion of a similar material are determined. The similar material is a mixture of various hydrophobic materials. The lifting hydraulic cylinders above the mobile lifting wheels15are started to lift the whole experimental cabin by 3 to 5 mm away from the base1. The horizontal pushing hydraulic cylinder16is started to horizontally move the whole experimental cabin out of the reaction frame. Then, the lifting hydraulic cylinders are stopped to allow the experimental cabin to fall back to the guide rails, such that the weight of the experimental cabin and the physical model is borne by the guide rails, so as to improve the safety of the guide rails in the process of laying the model.

In the experimental cabin, the similar material is adopted to lay the model of the strata. The shape, size and position of the tunnel mold22and a covered karst cave mold are designed based on the geometric size and the spatial position of the tunnel and the covered karst cave, and the tunnel mold22and the covered karst cave mold are placed in the model in the process of laying the model. The manufacturing process of the covered karst cave mold is as follows: according to the shape and size of the covered karst cave, the covered karst cave is copied by a 3D printer, and the copied covered karst cave mold is in the form of a thin-walled cavity, and the cavity of the mold is fully filled with water. The mold is placed in a low-temperature cabinet to allow water to be condensed into ice, and the ice obtained after the mold is removed presents the same shape and size as the covered karst cave. According to the spatial position of the covered karst cave, the ice is placed in the model in the process of laying the model, and at the same time, an external pressure-bearing water pipe is connected to the water pressure and water flow dual control servo system, and is configured to adjust the water pressure and the water flow in the covered karst cave. The ice in the shape of the covered karst cave forms an effective support to the surrounding rock mass to avoid collapse in the process of laying the model. In order to prevent the ice from melting, preferably, the temperature should be lower than 0° C. in the process of laying the model. The lifting hydraulic cylinders above the mobile lifting wheels15are started to lift the whole experimental cabin by 3 to 5 mm away from the guide rails after the laying of the model is completed. The horizontal pushing hydraulic cylinder16is started to horizontally move the whole experimental cabin back to the inside of the reaction frame. Then, the lifting hydraulic cylinders are stopped to allow the experimental cabin to fall back to the base1. The load and displacement dual control servo system is started to apply predetermined vertical and horizontal loads to the physical model to simulate an original stress environment of the strata. In order to reduce the damage to the physical model caused by load loading, preferably, the vertical load and the horizontal load are applied by hierarchical loading.

The water pressure and water flow dual control servo system is stared to provide and maintain a predetermined water pressure to the covered karst cave, and then adjusting an ambient temperature of the experimental cabin to above 0° C. to facilitate the melting of the ice in the covered karst cave. After the ice completely melts, the covered karst cave consistent with the actual shape and fully filled with a certain pressure water is formed. At this time, the pressurized water body in the covered karst cave forms an effective support to the surrounding rock mass. The hydraulic telescopic cylinder21on the tunnel excavation device is started to drag the tunnel mold22out of the physical model according to a predetermined speed, so as to simulate the step-by-step excavation of the tunnel. At the same time, the camera, which is configured to enter, leave and rotate freely through the inside of the tunnel mold22, enters the tunnel excavation space from the outside of the experimental cabin to collect real-time images of the whole process of the tunnel excavation. As the tunnel face approaches the covered karst cave, under the superposition of the stress of the surrounding rock mass and the water pressure in the covered karst cave to a waterproof rock mass, generating new cracks, expanding original cracks, and allowing confined water in the covered karst caves to quickly enter the tunnel along crack channels to cause the water inrush disaster.

When the excavation of the tunnel is completed, the water pressure and water flow dual control servo system is controlled to stop the water supply, the load and displacement dual control servo system is controlled to reset the horizontal loading cylinder12and the horizontal loading cylinder11, the front side plate5of the experimental cabin is detached from the experimental cabin, and the horizontal push hydraulic cylinder16is started to separate the front side plate5from the whole experimental cabin. In this way, the deformation and damage of the front side of the physical model can be directly observed, and alternatively, the physical model is subjected to cross-sectional cutting and observed according to the requirements of the experiment.

Although embodiments of the present invention have been shown and described, for those having ordinary skill in the art, it should be understood that a variety of changes, modifications, replacements and variants may be made to these embodiments without departing from the principle and spirit of the present invention, and the scope of the present invention is limited by the attached claims and their equivalents.