Study on Fracture and Stress Evolution Characteristics of Ultra-Thick Hard Sandstone Roof in the Fully Mechanized Mining Face with Large Mining Height: A Case Study of Xiaojihan Coal Mine in Western China

Table 2

Basic parameter table for physical similarity model.

Item	Parameters	Item	Parameters
Model type	2D pane	Excavation height	1.5 cm
Model length	2.5 m	Excavation distance	2.0 m
Model thickness	0.3 m	Model boundary	25 cm
Model height	127.3 cm	Excavation steps	50
Height of coal seam	1.5 cm	Single excavation distance	4 cm
Geometric similarity ratio	300 : 1	Excavation interval	0.5 h
Volume-weight ratio	1.667 : 1	Excavation time	25 h
Stress ratio	501 : 1	Upper load	0