Instrumented geotechnical monitoring of a natural cave in a near mine operation e Towards a sustainable approach to mining and preservation of speleological heritage Iuri Viana Brandi a , Marcelo Roberto Barbosa a, * , Rafael Guimar ~ aes de Paula a , Ramon Nunes Araújo a , Rafael Sim ~ oes Vieira de Moura b , Hernani Mota de Lima c a Vale S.A, Av. Doutor Marco Paulo S. Jardim, 3580, Mina  Aguas Claras, Nova Lima, MG, CEP: 34.006-270, Brazil b UFSJ - Department of Thermal and Fluid Sciences, Praça Frei Orlando, 170, S~ ao Jo~ ao Del Rei, MG, CEP: 36307-352, Brazil c UFOP - Department of Mining Engineering, Campus Morro do Cruzeiro, Pilar, Ouro Preto, MG, CEP: 35400-000, Brazil article info Article history: Received 6 July 2018 Received in revised form 11 August 2019 Accepted 13 August 2019 Available online 14 August 2019 Handling editor: Mingzhou Jin Keywords: Speleology Geotechnical instrumentation monitoring Natural cave Sustainable mining Iron ore Caraj as abstract The iron ore mining in Brazil is currently restricted due to federal laws for natural caves protection. Four classes of cave relevance are formally designated based primarily on geological and biospeleological criteria. According to the law, Maximum Relevance caves must be protected, together with a 250 m buffer zone. This protection zone, on the other hand, blocks substantial iron ore reserves that impacts mining projects feasibility and postpones or discontinues several ones. This 250 m buffer zone has a preliminary status and can be increased or reduced according to the results of specific long-term studies that ensure caves’ physical integrity, as well as the maintenance of its ecological balance. Considering the need to preserve the natural caves and to conduct a sustainable mining operation, this paper presents the geotechnical monitoring methodology used to anticipate instabilities in the cave, as well as to optimize the study time, considering an approach through remote instrumentation. A pilot project with opera- tions within the 250 m protected zone of a natural cave was conducted at the iron ore mine N4EN, in Caraj as, Brazil. Strain and convergence measurements were conducted on the weaknesses points/zones within the caves, identified during geostructural-geotechnical mapping. The data collected were continuously transmitted via web in real time to a database server; automatically treated and turned into updated reports and control charts available on the Internet from an expert software. The results demonstrated the applicability of remote geotechnical techniques for monitoring the structural stability of caves near mining operations, even when subjected to seismic waves, generated by regular blasting. This approach has contributed to the sustainability of the operations that reached a distance of 75 m from the studied cave that remained stable and with its speleological balance and functionality. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction Iron ore production in Brazil is part of an important contribution to keep the country's positive trade balance in the mining industry, that represents around 4.2% of the Gross Domestic Product (IBRAM, 2019). Despite its importance, mining industry faces an even more stringent environmental restriction represented by the current policies for natural caves. Iron caves were not considered until recently in the Brazilian speleological scenario. but first descriptions date from 1842, by Noel Aime Pissis (Pil o and Auler, 2005). In the 1980's, Brazilian speleological groups initiated the in- ventory of iron cave in Caraj as, northern Brazil, describing the first archaeological site in ferruginous caves (Moreira and Paiva, 1988). The Caraj as formation is a banded iron-formation (BIF), which contains a large number of iron caves (>1000), one of the most cave dense areas in Brazil (Parker et al., 2013). In 1990 a Federal Decree, in Brazil, established that all caves should be preserved together with their immediate surroundings (250 m distance as a buffer zone) (Brasil, 1990). In 2008, another Federal Decree established criteria to different classifications for natural underground caves, in four relevance levels according to its * Corresponding author. E-mail address: marcelo.roberto.barbosa@vale.com (M.R. Barbosa). Contents lists available at ScienceDirect Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro https://doi.org/10.1016/j.jclepro.2019.118040 0959-6526/© 2019 Elsevier Ltd. All rights reserved. Journal of Cleaner Production 239 (2019) 118040