Abstract：wall cracks appear on the house No.6 near the deep pit foundation of open-cut tunnel. With the characteristics of the cracks and construction design，safety monitoring in the area is conducted，which include house cracks，house settlement，displacements of deep soil，horizontal displacements of piles，blasting vibration，etc.. According to the numerical simulation and the monitoring results with rapid cracking in three stages，the causes of cracking are analysed，which exclude the factors such as uneven settlement，temperature difference，slope instability，anchor tension，etc.. The results show that dynamic load is the main factor which causes the rapid expansion cracks；and the mechanical properties of the wall are weakened by punch pile construction as well as cracks induced by blasting，and the original cracks will expand continuously if the vibration velocity of the wall is greater than 1.0 cm/s in several days. It is also shown that the temperature difference of environment has effect on expansion width of crack. Based on the above results，strict control measures for vibration velocity are adopted in blasting operation near the house No.7，making the original crack in house No.7 expand much slower than those in the house No.6 before being deal with，so that the cracks in the house No.7 are well controlled during the construction period，and the safety of the house is ensured.
