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Biocementation is being used to seal cracks in stone and concrete for retrofitting and consolidation works, as alternative to conventional solutions such as using polymeric mortar. As when such traditional techniques are used, joint thickness and roughness play an important role on sealing efficiency and this must be investigated when using biocement. The efficiency of biocementation to seal joints in stone samples considering simultaneously their width and roughness is discussed in this paper. Joints with 0.4, 0.7 and 1 mm width, having smooth and rough surfaces, were artificially created on basalt stone disks. The joints were treated by biocementation until become sealed, i.e., until fluid stop flowing through the joint. Adhesion achieved with the treatment was evaluated by tensile strength measurements in Brazilian splitting tests, in which the samples were split by the sealed joint. The joint surfaces separated after the splitting test were analysed by digital analysis of photographs and stereomicroscope images to check the presence and homogeneity of the precipitated biocement. The tensile strength was larger for the artificial joints with larger width and rough surfaces (maximum values found are 3.94 and 5.67 MPa for the smooth and rough surfaces, respectively). The values found were half the values measured for the intact rock (8 MPa), but still in the order of magnitude of Mega Pascal, therefore indicating strong adhesion between the stone and biocement. Biocementation treatment therefore appears to be adequate for sealing stone joints with different widths within the range investigated and variable roughness.

The stability and productivity concerning a modification on the traditional room and pillar for a new selective technique at the Portuguese Panasqueira Mine have been described. The traditional room-and-pillar stoping uses 5.0-m wide rooms with 3.0 m ×3.0 m pillars, while the selective room-and-pillar mining technique consists in stoping with rooms of 4.0 m wide and pillars of 4 m ×4 m with a subsequent selective cutting of the quartz veins at the mid pillar of approximately 0.5 m high, to obtain a pillar section with an area of 3.0 m × 3.0 m. The stability and productivity analyses indicate that the selective technique obtains smaller average pillar safety factor, more rock mass displacement, more extraction and selectivity ratios, and ore grade improvement, compared with the traditional technique. These results show that the selective technique is also more convenient. This proposed selective room-and-pillar mining technique is applicable to any sub-horizontal narrow quartz veins with wolfram, gold, etc. such as the famous La Rinconada gold mine in the Peruvian Andes.

For marble underground excavation it is important to develop a collection of procedures, rules and models in order to collect information to build a database, making it usable and available to all users so that they can make decisions. The information must be based on technical and economic criteria, during the lifetime of the excavation and after the close down of the mining activities. The importance of geotechnical characterization in the economical evaluation of underground mining of dimension stone is so emphasized. A sensitivity analysis of the economic indicators with the variation of the geotechnical and ornamental parameters is performed. The results of an economic feasibility study of an underground exploitation of marble at Pardais, Vila Vicosa, are presented.