The most important and pertinent part of each paper submitted to the Theme IV is herewith summarized and commented within a broad framework, as an attempt to present systematically the subject. This Report includes a short introduction on the problems related to displacements of surface and underground workings, and a general discussion on the factors affecting the prediction of displacements (as investigations on the rock mass and intact rock, determination of its properties residual stresses, calculation of stress and deformation possibilities, monitoring, and construction methods). The existing methods to forecast displacements resulting from surface excavation and ground subsidence due to underground works are also discussed.
Les aspects vitaux et les plus importants de chaque travail presente à ce Theme IV sont resumes et commentes dans une structure plus generale qui essaye de presenter le sujet d'une façon systematique. Ce rapport comprend un petit commentaire sur les problêmes de deplacements dans les ouvrages de superfice et souterrains. I I contient aussi une discussion generale sur les facteurs qui interviennent dans la prevision des deplacements (cet à dire, 1'etude des roches et des massifs rocheuex, la determination de leurs proprietes, les contraintes naturelles, le calcul des deplacements, d'auscultation et les methodes de construction). Sont aussi montrees les methodes existentes, pour le calcul des deplacements resultants des travaux de superficie, et des tassements superficiels provoques par les ouvrages souterains.
Die sachdienlichen und wichligsten Teile aller Abhandlungen, aufgefuhert zu Thema IV, sind nachfolgend zusammengefasst und umfassend komentiert als Versuch das Subjekt systematisch darzustellen. Die nachfolgende Berichtserstattung schliesst eine kurze Auffuehrung der Probleme bezueglich der Boden-Oberflaechenverschiebungen ein, die hervorgerufen werden koennen von kuerstlichen Erdverschiebungen oder Untergrundarbeiten. Aussserdem werden Faktoren diskutiert, die Voraussagen von Oberflaechenverschiebungen beeinflussen z.B. Fels-Massive und intakter (fehlerfreier) Fels, Bestimmung der Charakteristiken und Eigenschaftern, der natuerlichen Eigenspannungen, Berechnung der Spannungen und Verformungen, Dauerbeobachtungen, Arbeitsmethoden. Bekannte Methoden zur Voraussage von Oberflaechenverchiebungen werden in der Abhandlung aufgefuehrt.
Our civilization today has enormous demands for energy, raw materials extraction, process and transformation industries, transportation, water resources, sewerage, storage, etc., requiring progressively larger and more numerous workings in rock. The necessary step for these work ins is the excavation both at surface and underground. surficial excavation are generally required to gain more space or to reach certain burried objective as an ore deposit, or a certain level or position as for a highway, powerhouse, or foundation of structures. Underground excavation is required for objectives such as access, crossing and transporting through, ore extraction, and building-up - of space for installations, or storage. The shortage of surficial space in certain areas, and for energy savings reason sometimes, also forces a more intensive use of underground space for installations and living space. Present day economy demands high benefit cost ratios for those projects, which are usually achieved by scale economy. To fulfill this condition and demands, larger capacity plants, mines, or installations are being built, requiring mechanization, for better production rates, less support or treatment, etc. This trend leads to larger cavities, as the case of some underground coal mines and storage cavities. Bergman and Bjurstrom include as interesting introduction to their paper stating the requirements of modern workings in Sweden. As a result of excavations, in situ stresses are developed, resulting in deformations within the rock mass, and displacements of the surface of the working (slope or cut surface, tunnel or mine walls). The propagation of these movements may cause displacements of other parts of the ground. causing slope displacements or subsidence. The deformations may be exessive for the rock or rock mass, case in which It fails or closes the opening resulting in slope failures, and cave-ins or sagging and closure of underground openings. The cave-in or closure of underground mines is very commonly allowed or provoked, for economical reasons; however, this movement propagated to the surface results in subsidence. Most of man-made underground workings and related problems have already been similary observed in nature, although time and construction conditions under which they occur may have very large differences. Presently many man-made excavations produce cavities of dimensions too big and in different geological setting when compared to natural ones as, for instance, the complete extraction of coal layers. Formation of voids and cavities may cause the cave-In of the roof with consequent foundation of sink-holes or surface subsidence. Loss of strength, additional loads and erosion may also lead to slope deformation and stability problems. Natural agents that may lead to subsidence are briefly reviewed as follow.
(a) Phenomena caused by presence of water: solubilization of some rocks as limestones, dolomites, anhidrite, gypsite; chlorides are also soluble but due to their plastic properties they creep filling the void (unless their cap rock is too competent to deform, when it spans the opening).
