Subsidence Report Ukwa Mine INTRODUCTION:- Ukwa Mine is situated near Ukwa village of Baihar Tahsil of Balaghat District, Madhya Pradesh. and is about 45 Kms. North-East of Balaghat town. It is situated at 21° 58' North Latitude and 80° 28' East Longitude. Weather at this mine is tropical. Maximum temperature rises up to 40°C during April & May and lowers down up to 5° C during December & January. Monsoon sets during June to September with average rainfall of about 1600 mm. Mining was started at this mine in the Year 1904. Ukwa mine is having two leases namely a) 199.0673 Ha lease, b) 73.560 Ha. lease, The area of 73.567 ha is comprises of 3.986 ha forest land, that attracts the provision of Forest Act, 1980.

GEOLOGY: The manganese horizon is associated with mica schist of Munsar formation. The ore strikes almost east-west & dip with low angle due north west.

MINING: At the beginning, this mine was worked by opencast method, and extracted the ore out-cropped on the hilltop. Then the mine was converted into underground mine and worked by extending the inclines. At present this mine is worked by Flat Back Cut & Fill method of mining and voids created by extraction of ore are being filled by waste rock & sand.

First level (1950' L) and Second level (1850' L) are connected by underground incline at an interval ranging between 200' to 600' on strike direction. As the dip of ore body is 20°-30°, the mining activity is carried by cut & fill method with driving the sub levels between the two levels.

Owing to the nature & dip of the deposit, the mineral of main Ukwa lease (199.067 ha) extends beneath the area of 73.567 ha. Since the mineral is being worked by underground activities over decades in main lease area, these activities will also be extended for lower levels, beneath the area of 73.567 ha. Sinking of Vertical Shaft is under operation.

ANALYSIS:- The litho units of Ukwa fall with zone of low intensity deformation. Mineral body inclines with low angle. Except bedding and low intensity folds, no other structural features such as large folds, faults or shear zones are noticed in area. In absence of causative factors such as faults / shears, the tendency of dis-logging of the strata is ruled out. Mineral body is extracted with pre-mining support and the excavated area is filled with sand. The pre-mining support transfers the dead load from hang wall to foot wall, thus preventing the caving of host rock throughout the stoping operation. A large column of sand that develops, after the complete extraction of mineral from stope block, finally support the host rock and prevent from inward caving. As stated in introduction, the Mining operations at Ukwa commenced a century ago. Till date MOIL does not have any record of subsidence during or after mining operation at exhausted levels. The surface area is surveyed and monitored by Chief ranking persons from survey department. According to pages dated by survey department mine has no record of any subsidence.

CONCLUSION:- Low intensity deformation in area ruled out the presence of those structures which induce the strata movement. Hence the litho units are stable and offer better competency to Mining operations. Pre-mining support and thick column of sand prevent inward strata movement, recent time mine is free of subsidence history and MOIL do not apprehend any strata movement or subsidence in future also.