2 Volumes Final Proceedings - Washington 1984.pdf - IARC Research

174OnmenK along with, in particular detail, all the geotechnical system. The methodological basis forelements of the original engineering-geological predicting changes in conditions affecting theconditions existing at the time when the design engineering geology is the comparative geologicalfor the operation of the gas field was first for- approach based on analysis of formations, faciesmulated. During the process of this examination it and paleogeographical and paleo-geomorphologicalis essential to obtain and analyze various of types conditions and on other methods of studying theinf0n”KiOn and, on the basis of an acceptable geological environment, and based on constant andscheme for extraction, and of acceptable recoverable widespread use of spatial and time analogs. Inreserves of gas and gas condensates, to carry out studying the elements of the engineering-geologythe necessary predictive calculations of the follow- conditions and the technology of the gas industrying parameters: 1) the drop in reservoir pressures a qualitative and quantitative evaluation is madeand dehydration of the strata being exploited; 2) of the parameters of both aspects with view a toextraction of mineral particles from the producing determining the limits of possible acceptable andstrata along with the gas, condensates and water; optimal changes in both. Special attention is paid3) compaction of the producing strata; 4) warping to studying the mobility and stability of linksof the overlying strata; 5) surface subsidence; betwe,en elements and to the identification of the6) raising of the groundwater table to due surface roles of individual factors affecting those elementssubsidence and development of the field; 7) accumu- The study proceeds by identifying the character andlation of surface drainage in depressions due to form of the functional relationship between thesurface subsidence; 8) changes in the temperature, obligatory structures of geotechnical functions.nature and properties of the surface sediments due At the same time studies also focus on the capacitto waterlogging and changes in other engineering- for resisting the altered engineering geology congeologicalprocesses; 9) changes in any otherditions and restoration of the equilibrium, upsetelements in the engineering-geology conditions due as a result of human activities. One of the tasksto the planned construction and to disruptive human of planning investigations is to establish theactivities in terms of the specific planned instal- symptoms for the changes occurring in the engineeringgeology conditions and any portents of criticallations for gas extraction and transport.The complexity of such forecasts is further paramerers in order to provide a monitoring servicincreased by the need to take into consideration to engineering geologists which will give accuratescientific and technical advances in the gasand reliable signals and diagnostic signs of theindustry which are not yet common property and have onset of any developing defects or failures innot been included in operational designs but have installations associated with gas extraction andalready proved their effectiveness in industrial distribution. All information on engineeringexperiments, and hence can and must be brought into geology conditions and on changes in those conoperationaluse during the designed lifetime of the ditions, correlated with potential planninggas field. In addition to those parameters derived decisions re development and construction of a gasby the process of traditional engineering explora- field, is examined from the point of view of systemstion, the attainment of such long-term, comprehen- and factor analysis during the process of compresivequantitative engineering geology forecasts hensive engineering geology predictions.demands the identification and evaluation of aThe algorithm of such predictions may be dividedwhole range of parameters concerning geological into seven steps, each of which may in turn beconditions: 1) the coefficient of linear tempera- divided into a number of stages. Comprehensiveture-related deformation of mineral and organic engineering geology predictions begin with thesoils and peat; 2) maximum sustained strength of following: 1) a scientific hypothesis as tothe frozen materials; 3) coefficients of thermal possible changes in engineering geology conditionsconductivity and apparent electrical resistivity of and the consequences associated with the implemenfrozenand thawed materials; 4) specific electrical tation of specific activities during the developmentconductivity and dielectrical penetrability of of gas resources in a specific area; 2) the creationfrozen and thawed materials; 5) thixotropic and of a working hypothesis, a plan for the operationrheological properties of thawed materials; 6 ) the the designed geotechnical system, and a sequence ofphase composition of H,O in the materials at various geological processes in association with implementemperatures;7) composition of organic materials, tation of potential design decisions.soluble salts and exchangeable cations in thawed The second step involves the process of studyingmaterials; 8) content of ferrous oxides, aluminum the structure and clarifying the limits of the geotechnicalsystem being forecast and the testing ofoxides, oxides and protoxides of iron, amorphousacids and carbonates in thawing sediments; 9)the working hypothesis as to how it functions. Thiscapillary vacuum, capillary moisture capacity, water stage ends with the translation of the hypothesesloss and the coefficient of filtration anisotropy into a conceptual, graphic information model of tin thawing and freezing materials; 10) flow linesin bog water, and other parameters.To provide comprehensive engineering geologypredictions using both traditional sources andthese additional sources of information it isessential to carry out comprehensive long-termgeological investigations at many levels, Thefocus, content, time frame and scale of theseinvestigations can be determined by using a flowchart of objectives, closely related to a geodynamicmodel of the functioning of a predictivesystem and the execution of a qualitative comprehensiveforecast.On the basis of such prediction, a program ofinvestigations, experiments and of practical andanalog modelling is implemented; a geodynamiccause-and-effect model of the functioning of thegeotechnical system with all the anticipatedvariants is built and a corresponding computerprogram is created. The geodynamic model representsa hierarchical system of models: imitative andoptimizational, balanced and dynamic, graphic and