3D MODELING AND PRODUCTION SCHEDULING OF KHEWRA SALT MINES

In this study, AutoCAD based 3D Modelling of production scheduling, visualization of mining, and geological features in Khewra Salt Mines are showing. Unmanned Aerial Vehicle (UAV), photogrammetry and GIS Softwares are used to generate 3D surface modelling of Khewra Salt Mining Area. Khewra Salt Mines is the oldest and largest mine of sub-continent in the Salt Range with huge salt reserves from industrial quality to piece grade. Being a state-of-the-art mine consisting of 17 levels, 70 chambers with hundreds of tunnels, a layman pattern of development and manual mining procedure is followed with handy-made planes and maps. Hundreds of levels and crosssection maps were unified to a single 3D Model, presenting all mining features like tunnels, chambers, levels, inclines, and geological deposition of different salt seams with their thickness and qualities, overburden, and surface feature. The quantity of salt excavated since the beginning of mining is calculated for corroboration, and the remaining amounts of different qualities of salt are determined from the model. 3D topographic Modelling can also be used for area, volume calculations, and planning of remedial actions for rainwater inundations inside the mine.


INTRODUCTION
Similarly, red marl with a ferruginous content and thick layers of salt (approx. 650 m) comprises the Billianwala Salt Member [3]. The leased area covers 2789.29 acres of land [4]. Salt [5]. In specific horizons, it is crystalline.
Estimated reserves of salt range from 82 -600 million tons [6]. Khewra salt mines produce approximately 400,000 tonnes of salt per annum [7] through the room and pillar mining method, mining only half of the salt and leaving the remaining half to support tunnel and chamber roofs. The main tunnel extends about 730 meters (2550 ft.) into the mountains from the tunnel mouth [8]. The accumulative length of tunnels is about 40 km covering 144 sq. km, with a total depth of 748 feet [4]. Asrarullah in his Report measured salt reserves by considering each salt seam separately in each chamber [10]. Table 2  The 3D digitalization of resources using different software makes it easy of understanding the underground geological and mining features [12]. The surface modeling generation through different techniques like UAV and GIS [13] are being used for optimized production scheduling [14]. Similarly, rehabilitation and reopening of abandoned underground mines can be done using a 3D digital mine inventory model [15].

OBJECTIVES
The objective of the research study is to digitalize the resources through AutoCAD software, develop geological Model from existing maps and generate 3D object file of Khewra Salt Mining area using Unmanned Aerial Vehicle (UAV), photogrammetry and GIS Software for production scheduling as per market demands.

COLLECTION OF DATA
Maps of levels, the cross-section of chambers, and inclines were collected from the site to gather required features like the height of chambers and working, tunnels, seams, deposition and dipping, level, and surfaces drawn on it are shown in figure 3. Tunnels of Khewra Salt Mines are driven in the West-East direction while chambers are driven in the North-South direction. All these features are shown by their center line in the chambers of the respective cross-section. The extension of chambers in the North-South direction has been divided into blocks of 100 meter having 0 meters Northing in the extreme South of the Mines that increases gradually towards the north.

DIGITIZATION OF 2D MAPS AND CONVERSION INTO 3D
Cross-sections (E-A and 1-65) scanned and then imported in AutoCAD for digitization. Datum lines at an RL of 274.39m, Northing blocks of 100m, Tunnels in all pillars, excavations in the chambers, seams layers, inclines, and surface line were digitized as shown in figure 4. All 2D maps were converted into 3D in SE Coordinates by the following steps and shown in figure 5.
i. Datum lines, level lines, and Northing blocks lines remained unchanged in 3D.
ii. In the first 42 chambers (E-A and 1-37), the excavations and openings were Extruded/lofted on both sides of the centerline to 5.334m to a total width of 10.668m.
iii. Seams lines of the first 42 chambers (E-A and 1-37) were also extruded/lofted to 5.334m on both sides of the centerline.
iv. Inclines tunnels were lofted obliquely to a horizontal distance of 5.334m on both sides of the centerline of the incline in every chamber.
v. Surface lines of the first 42 chambers were also lofted in the same way.
vi. In the remaining 28 (38-65) chambers of 15.24m, the centerline of chambers, tunnels, seams, and surfaces were extruded to 7.62m on both sides of the centerline to a total of 15.24m.
vii. Inclines tunnels in the remaining chambers were also lofted obliquely to a horizontal distance of 7.62m on both sides of the centerline in each chamber.               iv. 3D Surface/topographic Modelling can be used for maintenance and monitoring of changes in surface topography. v. 3D topographic Modelling can also be used for area, volume calculations, and planning of remedial actions for rainwater inundations inside the mine. vi. Different salt seams thickness, quality, and dipping are visualized for development and future mining.