*3.2. Model Validation*

To verify the accuracy and reliability of the finite element numerical model, the stress monitoring data and displacement monitoring data of the key roof nodes during the construction process were determined [26]. Stress monitoring distributions of roof grid beams was conducted at 16 different places with strain gauges installed on both the upper and lower surfaces of the beam spans, as shown in Figure 3a; while deformation monitoring was conducted in nine places with the measuring points set in the middle of the grid beams, as shown in Figure 3c.

**Figure 3.** Schematic diagram of the monitoring points of roof grid beams. (**a**) Schematic diagram for stress monitoring points; (**b**) stress diagram of grid beams; (**c**) schematic diagram of displacement monitoring points; (**d**) vertical displacement of roof.

A comparison of the results between the measured data and the model calculation of grid beam stress and node vertical displacement are, respectively, displayed in Figure 3b,d, from which we can see that the overall difference between the two data sets is small. Among them, No. 16 beam is the one with the biggest stress error, which is 16.1 MPa between the actual measurement and theoretical calculation, and No. 5 beam has the biggest displacement error, which is 10.1 mm. Given the good agreemen<sup>t</sup> between the simulation and experiment results in each construction stage with acceptable errors, the numerical model was used as the simulation analysis model.
