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Mining Technology and Mine Management

Analysis on Rock Breakage Characteristic and Its Influence Factors of Conical Pick Under Uniaxial Confining Stress

  • Yu TANG ,
  • Shaofeng WANG
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  • School of Resources and Safety Engineering,Central South University,Changsha 410083,Hunan,China

Received date: 2020-12-29

  Revised date: 2021-04-06

  Online published: 2021-12-17

Highlights

With the gradual depletion of shallow resources,deep mining is an inevitable trend. However,the traditional drilling and blasting method has been difficult to meet the requirements of continuous,large-scale,safe,efficient and green resource exploitation in deep mining. Non-explosive mechanized mining based on cutting tool rock breaking will be one of the main alternative methods for deep mining. The cuttability of deep hard rock is the key factor to determine the non-explosive mechanical rock breaking. Therefore,we carried out the rock breaking experiment by conical pick and studied the rock cuttability under different confining pressures and rock properties. The experiment was performed on the TRW-3000 true triaxial electro-hydraulic servo test system designed and manufactured by Central South University. The system can simulate the stress conditions under uniaxial,biaxial and triaxial confining stress conditions. The maximum static load applied in XY and Z directions is 2 000 kN,2 000 kN and 3 000 kN respectively. The rock samples utilized in this experiment are granite,marble,red sandstone and phosphate rock,all of which are cubic rock samples with the size of 100 mm×100 mm×100 mm. In order to simulate the stress on the pillar to be mined,uniaxial confining pressure was applied to the rock sample on the Y-axis. The range of confining pressure of granite and marble is 0~120 MPa,that of red sandstone is 0~90 MPa,and that of phosphate rock is 0~100 MPa. Then,the rock breakage load is applied to rock specimen by conical pick through Z-axis,so as to cut the rock sample vertically. In the whole experiment process,the system recorded the load change on rock in the loading process automatically. According to the curve change,the peak indentation force and corresponding penetration depth of the pick were obtained,and the cutting work required for rock breaking could be obtained. Then,the specific energy of rock breaking could be calculated according to the cutting work and the volume of the spalling rock block. In addition,according to the ISRM standards,the uniaxial compressive strength and tensile strength of four types of rocks were obtained by uniaxial compression test and Brazilian splitting test. Then,the brittleness index of rock was obtained. The uniaxial compressive strength,brittleness index,peak indentation force and specific energy were normalized. Through regression analysis,the regression models of the relationships among the peak indentation force,rock strength characteristics and confining stress conditions,as well as the relationships among specific energy,rock strength characteristics and confining stress conditions were obtained. Finally,the entropy weight method was used to evaluate the influence weights of rock strength characteristics and confining stress conditions on the peak indentation force and specific energy. Through the above experimental study,regression analysis,and the weight determination,the necessary theoretical basis can be provided for the feasibility evaluation of non-explosive mechanized mining and the design of rock breaking parameter in deep mine. This study has important guiding significance for the realization of non-explosive mechanized mining in deep hard rock.

Cite this article

Yu TANG , Shaofeng WANG . Analysis on Rock Breakage Characteristic and Its Influence Factors of Conical Pick Under Uniaxial Confining Stress[J]. Gold Science and Technology, 2021 , 29(5) : 669 -679 . DOI: 10.11872/j.issn.1005-2518.2021.05.009

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秘鲁财政部长:国家需要矿业投资

据BNAmericas网站报道,秘鲁经济和财政部长佩德罗·弗兰克(Pedro Franke)日前在参加评级机构穆迪公司举办的网络会议上表示,政府将保持目前经济政策的稳定,不过他强调需要实施税收改革以缩小社会差距。弗兰克强调,政府高层将充分尊重私人财产和储蓄、合同、法律安全。

当被问及政府公共政策“缺少连续性”,以及总理米尔塔·瓦斯奎兹(Mirtha Vasquez)宣布关闭阿亚库乔大区南部的四座矿山所引发的争议时,这位部长表示,“秘鲁需要矿业投资”,但他强调,这必须在“爱护环境和尊重社区”的前提下。在这方面,弗兰克承认该国需要“大变革”以及“采矿与环境关系的结构性转型”,这需要政府与公众之间应加强信任,采掘业应该为地方或大区经济发展创造机会,而不能仅仅使少数人受益。

另外,弗兰克强调,不但要维持而且要扩大多方参与的圆桌会议,将公众与私企召集在一起共同讨论问题,协调解决问题的最佳方案,以提高生产率和竞争力。另一方面,他重申,卡斯蒂略总统提出的税收改革措施需要落实,以解决一些领域存在的严重不平等问题,比如教育、卫生和饮用水。弗兰克说,“税制改革当然会触及一些方面的利益,但社会差距太大,需要解决这些问题”。

这项税改的目的是增加税收收入,秘鲁税收占该国GDP的20%,低于拉丁美洲的27%,只有经合组织国家(OECD)的40%。弗兰克解释说,除了增加尚未确定的税率外,税改的另一目的是希望通过打击逃税扩大征收基数,逃税行为造成的税收损失占秘鲁GDP的8%,是该国在卫生领域投资的3倍,是公共教育预算支出的2倍,是社会保护项目支出的10倍。这位部长补充说,财政改革的目的是为了应对紧急卫生情况导致的公共支出显著增加,并实现政府设定的明年财政赤字缩减目标,2022年预计为GDP的3.7%。

http://www.goldsci.ac.cn/article/2021/1005-2518/1005-2518-2021-29-5-669.shtml

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