Strata and Surface Influence Range of Deep Coal Mining for Mine Land Reuse

The rational assessment and determination of strata and surface influence range of underground coal mining is straightly associated to the safe production of the wellbore, the reuse of mine land and the regional development. With the depth of coal mining in the world increasing, if the boundary curve of strata and surface movement continues to be considered as a straight line, there will be a great deviation from the real situation, which will seriously waste the land resources of mining area. To solve this issue, the numerical simulation methods were employed to investigate the stratum and surface movement boundary curves of deep caving and backfilling mining in this paper. The findings indicated that: 1) The strata and surface movement boundary of deep caving and backfilling mining were all curves, and they were in accordance with the exponential function, but the influence range of strata and surface movement of deep different mining methods were different; 2) The backfilling rate of deep backfilling mining had an influence on movement boundary of strata and surface. With the backfilling rate decreasing, the influence range of strata and surface movement boundary were increased. 3) The research results were applied to a case in order to confirm the new methods for determining the influence range of strata and surface movement of deep mining. Example application shows that the safe production of the wellbore not only can be guaranteed, but also the reuse area of the mine field can be enhanced.

METHOD TO PREDICT LONG TIME SPAN OF SCOUR AROUND OFFSHORE WIND TURBINE FOUNDATIONS

A new method to predict scour development around offshore structures has been developed. The method has been tested on a monopile. The method consists of table of scour rates, which is used to predict the scour development around the structure at different stages of the scour hole. The scour rate tables have been made based on full 3D numerical simulations of the flow and sediment transport for fixed configurations of the scour hole. When changing the governing parameters which are causing the scour development around the structure, the erosion rate or backfilling rate can be calculated from the mass balance of the sediment. This leads to the scour rates tables that are used to analyses the development of the scour hole under different current conditions. The method has been tested against experimental scour data and showed very promising results.