Calculation models for estimation of grout take in hard jointed rock

Detta är en avhandling från Institutionen för anläggning och miljö

Författare: Thomas Janson; Kth.; [1998]

Nyckelord: ;

Sammanfattning: The purpose of thls thesis is to descrrbe a method for thedetermination of an expec[ed grouting process, i.e. to have abetter understanding of the most important mechanisms ingroutlng. The aim of groutlng is, to create a watertight zoneagainst water flow. The zone must satisfy the specifiedwatenightnesh requirements with the aid of a specificpenetration and joint filling. However. owing to the complexstructure of the rock, it is difficult to check groutpenetration and joint filling in a simple way. Grout take canon the other hand be checked easily by measuring the amountpumped into the rock. The expected take can be calculated usingthe penetration length and the porosity of the rock withrespect to the grout used. It is further assumed that theporosity of the rock can be described easily by means ofsimpllfied joint geometrles. On the basis of the abovereasoing, it should therefore be possible to control indirectlythe penetration and joint filling by means of a model thatdescribes the grout rake. Three calcularlon models of varyingcomplexity have been developed. The first calculation modelsimulated joints to by grouted as circular discs. The secondcalculation model described the grouting in the same way as thefirst model but the grout only penetrates a certain section ofthe disc. The last calculation model, the most complex one,described the grout as penetrating a system of channels with ageometry characterised by a number of geologlcai descriptionparameters. The calculation models have been tested by fieldstudies and in laboratory tube models. The analysis of thetests confirms the importante of the three principal factorswhich together control the grouting : groutmg technology(pressure and grout properties). hydrogeology and geologydescriptions of the rock The calculation models show a goodagreement as regards the medium value of grouted volumes, for anumber of grouting holes. The most complex model gave the bestresults in the studies compared with the other models. For allmodels a good evaluation of the yield value of the groutingmaterial and the transmissivity of the rock mass are veryimportant. The tests in laboratory models yield differentdegrees of agreement between measured and calculated volumes.The greater the penetration of grout into the laboratory model,the better is the agreement. The reason is that the calculatlonmodels take no account of lotal variations tn the laboratorymodel. Further simulated tests show that when the variation ofthe tube radius is small the calculation models give a goodagreement with simulated volume and reverse.Key words: grouting. rock, joint, aperture, Binghamflow. penetration length. grout take

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