Vízügyi Közlemények, 1970 (52. évfolyam)
4. füzet - Rövidebb közlemények és beszámolók
(59) plastics in Hungary is illustrated in Chapter 2, containing data on the annual per capita consumption lor a few countries in Table II. The manufacture and chemical Structure of polivynilchloride (PVC) are described in Chapter 3, while the processing of PVC powder to different products is outlined in Chapter 4. Information on the properties of PVC products is contained in Chapter 5, and for purposes of comparison the specific gravities of some of the structural materials are given in Table III. PVC is seen to be among the lightest structural materials. A comparison of strength properties is presented in Table IV. Subsequently the factors affecting the strength properties of PVC are listed, Table V indicating the influence of temperature on the tensile strength of PVC, Table VI the effect of water-content on the strength of emulsified PVC. The thermal properties of PVC are compared in Table VII with those of some of the "conventional" building materials. The relative resistances of PVC and some other building materials to the more commonly encountered chemicals are listed in Table VIII, whence it will be appreciated that PVC can be used as a protecting material against most aggressive substances. Guidance for the working and shaping of PVC is given in Chapter 6, concerning mainly a ) mechanical working, b ) warm shaping, с ) welding and d ) glueing. BRIEF PUBLICATIONS AND REPORTS 1. Sárváry, I., Civ. Engr. : Surface subsidences due to the extraction of artesian waters (Symposium on Land Subsidence, Symposium sur les Affaissements) (For the Hungarian text see pp. 367) On the Tokyo symposium greatest attention has been devoted to the subsidences caused by the extraction of a variety of fluids (water, oil, etc.). Altogether 53 papers have been submitted on related subjects, mostly by participants from Japan and the United States. Subsidences caused considerable damages in both countries. For preventing damages, or for predicting subsidences networks of well equipped observing stations have been erected in the areas affected by subsidence. A diagram showing the design principle for subsidence observation points is shown in Fig. 2. Processing of subsidence data from the observation network has shown area settlement due to fluid extraction to be proportionate to the volume of fluid extracted or the drop of piezometric level on the average over longer periods. For short extractions and for such of longer duration the role of elastic and plastic processes, respectively, becomes predominant. Forecasts are in general issued on the basis of actually observed variations and these data are extrapolated as functions of different factors. The introduction of subsidence observations in Hungary is suggested and an observation point design of low-cost installation is recommended (Fig. 3). Ibad Zade, Ju. A., Doctor of Techn. Sc. and Samelov, Ii. 1., Civ. Engr. : Scouring ill spillway channels (For the Hungarian text see pp. 371) Along the Ghirdimantshai and Akhsoutshai rivers on the southern slopes of the Caucasus range spillway relief channels have been constructed, the bed changes of which permit interesting conclusions to be arrived at. Formulae are given for the bottom slope that is always characteristic for stable channels. The stability of natural channels was found to depend not only on hydraulic parameters, and material properties of the bottom and the slopes, but also on the angle of hydrodynamical stability of the slopes (Eq. (11)). For determining the longitudinal profile characteristic for stable channels Eq. (13) is derived under the assumption that the size of particles forming the channel vary along length according to the exponential expression given in Eq. (12). The profile thus computed is compared with results actually observed in Fig. 2. 3. Hörcher, F., Civ. Engr. : The watertightness of standard gate designs (For the Hungarian text see pp. 377) According to operational watertightness requirements gates are classified into three groups, namely:
