This paper describes the treatment of tunneling problems at Kurtkulagi irrigation tunnel, particularly focusing on the Kurtkulagi tunnel which is 1255 m in length and 3.50 m in diameter, is an important of the Yumurtalik Plain Irrigation Project. The tunnel was excavated using conventional dull and blast, but during the tunneling problems occurred. Within a 70 m long section of the tunnel, cave-in occurred at two locations both along the fault zone in tunnel alignment. Slope stability problems were experienced too at inlet and outlet section of the tunnel. A sinkhole was formed at the surface as a result of the cave-in. There are an Allocthonous Cretaceous complex sequence and Miocene sandstone-claystone units, which have a faulty contact in the tunnel alignment area. The complex sequence consists of mainly weathered andesite, spilitic agglomerate, radiolarite, serpentinite and limestone blocks. The claystone to sandstone is thin-medium bedded and has medium-weak rock substance properties. The fault zone with an approximate width of 150 m and consisting of extremely weak crushed rocks crosses the tunnel alignment at midsection. Some treatment methods were applied to remedy this collapse. Cut and cover method was applied for the first 955 m of the tunnel inlet due to the shallow overburden and very weak rock properties. However, cave-ins delayed the tunnel construction for 1 year and increased the cost by 9%. (C) 2003 Elsevier Science Ltd. All rights reserved.