| About 11% of the land area in the world is covered by ice.These ice layers contain about 75% of the resources of freshwater on the earth as well as abundant information,including energy storage,hydrological cycle,atmospheric and oceanic circulation,climatic change,crustal theology and elevation of sea level.While Antarctic glaciers account for 90% of the earth's ice,some subtle changes of Antarctic glaciers will have a profound impact on the global environment.The ice connected with the continental shelf is ice shelf,which extends to the ocean,mainly distributed in the edge of the glacier.With their respectively speciality of global cold sources and expanse,the polar and the ocean are playing a very important role in the global climate system.In order to elucidate the mechanism of climatic change scientifically,the observation of the polar and the ocean is very important.Ice shelf as the link between the ocean and the ice sheet is obviously the key of research.The study of interaction among the ice sheet,ice shelf and ocean has became a hot issue in research of the global change.The ice core,known as the heart of the Antarctic,contains the secret of climatic change about the earth and is the most effective method to study the problem of glacial climate.How to obtain ice cores quickly and efficiently on the ice shelf is an important scientific problem.This paper firstly introduced the development of ice-core drilling and all kinds of technologies in ice-core drilling.According to the characteristics of ice shelf,we finally determined hot-water ice-coring drill as the main research method for ice shelves.Learned from the foreign drilling experience and combined with the characteristics of the hot-water drill,a new kind of hot-water coring drill is designed with explicit parameters and processed.The drill includes reamer and a 3m long core barrel.The outer diameterand inner diameter of core barrel is respectively 130 mm and 96 mm,with 36 nozzles distributed on the end of drill.According to the formula of energy conservation,the effect of water flow and water temperature on the ROP(rate of penetration)is analyzed,and a corresponding theoretical model is established.Thus the relationship between ROP and flow rate and temperature is determined: for the same water flow,the higher the temperature is,the faster the ROP;for the same water temperature,the higher water flow is,the faster the ROP.And then the water temperature reached the bottom of the hole under the actual Antarctic field conditions was calculated,based on that,the temperature factor of testing is determined from 50?to 70?.Then based on the theoretical study of calculation,a special experimental system for hot-water ice-core drilling is designed in the ice drilling facility from polar research center of Jilin University and can monitor different kinds of parameters include ROP,water temperature,water flow,load,drilling depth and so on.The later experimental results study on the drill showed that for the same water flow,the ROP is obviously increased with the increase of water temperature and the maximum speed is 27.8m/h;For ice-core drilling,the hot water of 70? is too high melting the core,but at 50?,obtained the quality of ice cores obtained are generally better with a maximum diameter of 59 mm.The comparison about the results showed that they have the similar variation trend.The minimum error is 6%,the maximum error is only 12%,which proved theoretical model is still meaningful and can be used as a reference in the actual field. |
PDF Full Text Request