This report was prepared by a task force drawn from Working Group 07 'Foundations' of Cigre Study Committee 22 and provides an overview of the design of overhead transmission line support foundations.

This report was prepared by a task force drawn from WG07 'Foundations of Cigre Study Committe 22' and provides a guide to the design and Installation of Micropiles and Ground Anchors for Overhead Line Support Foundations. Micropiles are small diameter cast-in-place piles with a diameter less than 300 mm and can be installed vertcally or with an inclination up to 20 degrees to the horizontal surface, they are principally loaded by axial forces. If micropiles are used only to resist tension loading they can also function as ground or rock anchors. Nevertheless micropiles are nonprestressed foundation elements no matter whether they are used as piles or as ground anchors.

This report prepared a task force drawn Working Group 07 'Foundations' of Cigré Study Committee 22. provides an outline of good practice on the refurbishment and upgrading of existing overhead transmission line support foundations. Possible reasons for foundation deterioration are reviewed, whichmay result from such diverse causes as early-age concrete cracking to damage by frost forces. The critical nature of the inspection and testing strategy are considered, with attention focussed on the economics of the inspection/testing regime, the use of alternative strategies and the different levels of foundation inspection together with the actual inspection test methods. The latter ranging from a simple visual approach to full scale load testing of the foundation. The interrelationship between the foundation's applied loading and strength is examined as part of the overall assessment of weather to refurbish, upgrade or accept foundation. Techniques for refurbishment and upgrading are outlined both for the internal structure of the foundation and the external geotechnical strength.

The techniques outlined in this guide apply to foundation testing for overhead transmission line towers and pole structures. They are also applicable to telecommunication towers. The folowing modes of applied loadings are considered. (a) axial (vertical, either in uplift or compression; (b) lateral (horizontal) shear, including those which give rise to high overturning moments; (c) combined axial and lateral loads. Only static monocycle or multicycle loadings are considered in this guide. In this context a cycle is defined as a complete loading stage from an unloaded state, through a series of load increments and back to an unloaded state.

In recent years dam failures in the United States have focused much attention on dam safety resulting in a requirement for all Federal and States agencies to review practices affecting the safety and integrity of dams. Extensive care is taken in the field of legislation, technical regulations, design, construction and operation of dams. Through my research work at the U of W I obtained an overview of the current situation of dam safety on the Federal level as well as on the Washington State level. Despite the fact, that the magnitude of the Slovenian dam engineering from all points of view does not compare with the US reality, some experiences gained in this country will be helpful in organizing the dam safety system in our county. On the other hand, there exist possibilities for cooperation on research projects.

Pomembno koordinativno vlogo med vsemi subjekti, ki zagotavljajo varnost pregrad v USA, igra FEMA (Federal Emergency Management Agency), ki je pripravila Nacionalni program za zagotovitev varnosti pregrad (National Dam Safety Program) s katerim udejanja Navodila in tudi vpliva na lastnike nezveznih pregrad, da razvijajo svoje varnostne programe, ki morajo biti na določenem tehničnem novoju. Cilji delovanja se lahko izrazijo v obliki doktrine. Pregrade morajo biti projektirane, grajene, uporabljane in vzdrževane tako, da lahko govorimo o varnih objektih. Zagotavljanje varnosti ni pasivna aktivnost. Odgovornost za zaščito življenj in lastnine se nikoli nekonča. Potrebno je stalno razvijati nove pristope in politiko varnosti, ter to vključevati v vsakodnevno življenje ter skrbeti za razvoj. Skrbeti je potrebno za stalno kadrovsko obnovo. Novi kadri se vključujejo v aktivnosti vedno v skupini že izurjenih ekspertov. Uvajati je potrebno nove programe in obnavljati starejše, ki ne odgovarjajo novim zahtevam. Lidership, awareness, dedication in aktivnost morajo biti zagotovljeni stalno. Priložnosti se ne sme spregledati.

V pričujočem delu je obravnavano obnašanje kontakta med gravitacijsko betonsko pregrado in temeljnimi tlemi. Telo pregrade je obravnavano kot idealno togo telo sestavljeno iz več med seboj konstrukcijsko neodvisnih blokov. Vsak od teh blokov lahko ob nastopu močnega potresa preide v relativno gibanje glede na podlago. Ugotovljeno je, da pri analitičnem obravnavanju drsenja konstantni koeficient trenja ne daje primernih rezultatov. Zaradi tega je bil definiran spremenljiv koeficient trenja $\mu (t)$. Časovna odvisnost koeficienta trenja je določena na osnovi teorije gibanja togega telesa na togi podlagi.$\mu (t)$ predstavlja vpliv, ki ga ima potresno vzbujanje tal in implicitno materialne in reliefne karakteristike kontakta med pregrado in tlemi. Na osnovi tega in razvitega matematičnega modela za posamezne načine gibanja telesa lahko določamo relativne pomike telesa glede na tla. Razvoj teorije je bil spremljan z obsežnim eksperimentalnim delom.