## 3 Design and Fabrication of Diversion Function Pipe Segment Model Test Box
### Design of the Diversion Function Pipe Model Test Box  
Pore water pressure and earth pressure around the guide function pipe segments are the key indicators for evaluating the restoration of groundwater flow function. The stress state of the guide function pipe segments under different water pressures is crucial for the operation and durability of the pipe segment. However, field monitoring faces challenges, such as multiple interference factors, high costs, and great difficulties, making it extremely difficult to achieve effective monitoring. Building a scaled model test box that simulates the working condition of the guide function pipe segment (referred to as the \"test box\") is an effective solution to this problem. The test box is constructed from 10 mm thick tempered glass using the lamination method, with dimensions of 1280 mm \(\times\) 480 mm \(\times\) 1000 mm, as shown in Figure 4. The joints between the tempered glass pieces are bonded with special adhesive to ensure the box has good sealing performance. The model box is filled with sieved, medium-grained sand to simulate the permeable pebble layer. In Figure 4, the water injection and pressure hole (1) is located on the upper middle position of the left sidewall of the test box, with a diameter of 20 mm, mainly used for  
Figure 4: A schematic diagram of the model test box. Figure 3: Schematic diagram of groundwater flow through diversion function pipe segments. injecting water and increasing pressure. The upper and lower glass partitions (2) are used to simulate the impervious layers. The iron rings (3) simulate the pipe segments of the tunnel, plastic soft tubes 4 simulate the diversion pipe, arranged in a ring shape within the iron ring, simulating a 20 mm diameter hole reserved on the pipe segments. The collection pipe (5) and drainage pipe (6) pass through the reserved holes, distributed on both sides of the glass partition, connected to the diversion pipe with three-way connections, and the diversion pipe is equipped with upper and lower switches (7) to control the flow rate of the diversion flow. The blowoff hole (8) is located at the lower middle position of the right sidewall of the test box, with a diameter of 20 mm. The switch (9) is installed at the blowoff hole, controlling the flow speed of the water from the blowoff hole, and the drainage hole (10) is located on the front sidewall of the test box, one on each side, symmetrically distributed, with a diameter of 20 mm, mainly used for draining water during the experiment. The model box with layered sand filling, the earth pressure cell, and the pore water pressure gauges are buried symmetrically at the side of the pipe section at distances of 0.3 m, 0.5 m, and 0.7 m from the bottom of the model box, respectively, with one earth pressure cell (11) and one pore water pressure gauges (12) buried on both sides at the same height around the model box, and strain gauges are attached at eight test points on the inner side of the pipe section along its longitudinal center, every 45\({}^{\circ}\) apart, including above, below, left, right, left-up, right-up, left-down, and right-down, with strain gauges attached circumferentially inside the pipe section to measure the radial deformation of the pipe. At the beginning of the experiment, water is continuously injected into the model box through the water injection hole. The incoming water on one side of the intake flows into the diversion pipe through the collection pipe, and then into the dispersal pipe on the other side, and finally into the sand layer through the dispersal pipe. Meanwhile, the switch to the relief hole is opened, allowing water to flow out of the relief hole. Under stable water injection conditions, the water level on the left side of the model box remains unchanged. The switch of the diversion pipe and the relief hole work together to adjust the flow rates of the diversion pipe and the relief hole.