The stability of longwall face and performance of longwall shields are the major ground control concerns in mining thick coal seams,and require a study of interactions between shield and strata.Physical modeling tests are frequently used for understanding the shield-strata interactions but the realistic hydraulic operations of longwall shields were widely ignored in the previous studies.This paper reproduces the behaviors of the longwall face and shield in response to roof loading through a physical modeling study with a consideration of the basic operating principles of the shield leg cylinder.A clear understanding of the extension and retraction of leg cylinder with relationship to mining height is provided in this research,as well as a detailed analysis of the important characteristics of longwall shields including shield capacity,setting force,vertical stiffness and yielding behavior.The results show that: (1) The vertical stiffness of longwall shields has a positive correlation with the shield capacity,and it decreases with the extension of hydraulic liquid inside the leg cylinder;(2) Higher capacity (stiffness) shields may develop more load on the shield in response to roof convergence,but remain some reserve capacity to prevent the shield from highly stressed or damage;(3) Yielding of a modern shield represents a 10% drop in the yielding pressure,and produces 5~10 mm of reduction in shield height and 100~250 tons of loss in support loading;and (4) Physical modeling study of shield-strata interaction with a consideration of leg hydraulic operation indicates a step function of roof deflection during shield yielding events.Face and roof displace in a slow rate during the initial shield loading stage but increase rapidly during the yielding events.