Water inrush is one of the most frequent and catastrophic hazards in tunnel engineering. and poses serious threats to the safety of engineering and personnel. This paper presents a case study of a water inrush and ground collapse in the Qingdao Metro Line 4. which caused a cave-in with the diameter and depth of about 30 m and 6 m. https://www.freeebookfinder.com/product-category/spool-gun/