Dense clay can be used for sealing of boreholes and isolation of waste containers. Expansion of the clay to fill the space between containers and confining rock takes place by uptake of water of the clay, which thereby provides effective isolation. The issue is to prepare clay inserts with properly selected water content. The paper describes preparation of clay seals by mixing air-dry clay powder with nanoparticles of water droplets coated with very thin shells of a hydrophobic silicious substance (“dry water”). It behaves as dry powder and is easily mixed with dry clay. On compaction to the desired density the shells break into microscopic fragments while water becomes homogeneously distributed in the mass. Laboratory tests verify that the properties of clay prepared in this way are the same, or better, than of commonly saturated clay.

On peut utiliser de l'argile dense pour sceller les forages et isoler les conteneurs de déchets. L'expansion de l'argile pourremplir l'espace entre les récipients et la roche confinant a lieu par absorption d'eau de l'argile, ce qui fournit ainsi un isolement efficace. La question est de préparer des inserts d'argile avec une teneur en eau correctement sélectionnée. L'article décrit la préparation de joints d'argile en mélangeant de la poudre d'argile séchée à l'air avec des nanoparticules de gouttelettes d'eau revêtues de coquilles très minces d'une substance siliceuse hydrophobe ("eau sèche"). Il se comporte comme une poudre sèche et se mélange facilement avec de l'argile sèche. Lors du compactage à la densité souhaitée, les coquilles se cassent en fragments microscopiques tandis que l'eau se répartit de manière homogène dans la masse. Des essais en laboratoire vérifient que les propriétés de l'argile préparée de cette façon sont les mêmes, ou mieux, que les argiles couramment saturées.

The input-output relationship of an accelerometer depends on parameters that are sensitive to temperature and air humidity. High accuracy field measurements therefore require simple in-field estimation of these parameters.We present an extension of a simple non-iterative six-parameter calibration method for triaxial accelerometers with orthogonal input axes to a nine-parameter method that also handles non-orthogonal axes and cross-axis interference.We derive necessary and sufficient conditions on the accelerometer output that guarantee that the nine parameters can be uniquely determined from the calibration measurements in an idealized scenario with no noise or quantization errors. The method is based on measurements of the Earth gravity with the accelerometer placed at rest in at least nine different orientations.The choice of orientations is important for measurement accuracy. We compare two different setups, one called A090-45, which is based on 90 and 45 degree rotations of the accelerometer and one called A0max sep that has maximized smallest angle between any two of the orientations. For the A090-45 setup we have constructed a simple test equipment for quick positionings of the accelerometer. For the A0max sep setup, a similar equipment is more complicated to construct, but equally simple to use.We have done Monte Carlo simulations with accelerometer orientations deviating at most D degrees from the desired A090-45 or A0max sep and with D ranging from 1◦ to 30◦. For real-world noisy environments and D up to 18◦, our simulations showed slightly smaller errors for the A0max sep than for the A090-45 setup. For noise standard deviation typical for our field measurements, the measurement errors after nine-parameter calibration were about 100 times smaller than those for six-parameter calibration both for the A0max sep setup and, as long as D ≤ 13◦ for the A090-45 setup. For the A090-45 setup, however, we found that combinations of large noise levels and/or large D can makesix-parameter calibration the better choice.

Under periodenn 1992-94 har gasemissioner studerats vid testceller ingående i projektet "Samordnad deponigas-FUD" (i Malmö, Helsingborg och Upplands Bro). Syftet med dessa mätningar har varit att bestämma gasbildningen och gasutvinningens effektivitet i olika celler