The material with which to build underground structures, must have a high resistance, water resistance, erode, frost resistance and fire resistance. Due to the complexity of reconstruction of underground facilities, their service life should be longer than the land-based structures, respectively, the materials for the manufacture of such structures needs to be better. Materials which meet such requirement are: steel, cast iron, concrete and reinforced concrete. When erecting concrete structures concrete its hardness should not be less than “B15”, and the thickness of load-bearing elements not less than 20 cm. For prestressed concrete structures the concrete grade shall not be less than “B25”. Mark of concrete on water resistance should not be less than “B-6” for structures located in soil moisture hanged. Estimated supports of concrete in concrete and reinforced concrete structures take accordingly to the current normative document. Continue reading
This is the most magnificent building built by man – the only one that can be seen from space with the naked eye. An impregnable fortification. Symbol of antiquity and power of the Chinese civilization. Heard about it every, but. no one saw it whole!
The construction of the Millennium
Look in any encyclopedia about the great wall of China can be found only a short article. And, alas, the data in different sources will often contradict each other. Nevertheless, officially recognized is considered such a story.
The great wall of China is a chain of fortifications, extending in the North of Ancient China from the Yellow sea to the Gobi desert. The total length of the wall is more than 6500 kilometers. The wall was built over two millennia.
It all started long before our era. At the time of the ancient Chinese state, about which we know almost nothing, collapsed into many small principalities that fought each other. And the richest of them began to build fortifications, so that it was easier to defend their borders. Continue reading
Krakow is without doubt one of the most beautiful cities of Poland, with its specific and unique character. It’s here for centuries, met different people, cultures and religions, creating an exceptional atmosphere of this city. Krakow is one of the few places in the world, which was listed as a World Cultural Heritage site by UNESCO. The architectural team of the old town, which has endured all historical cataclysms, while retaining unchanged since the middle ages, the system was recognized as one of the most precious treasures of architecture in the world. Only within the boundaries of the old Centre of Krakow there are more than 300 historic stone houses, churches and palaces. Their rich interior decoration testifies to the hard work of long-time residents of this town, about their sense of beauty and aesthetics. Its fame Krakow obliged, also, to outstanding people who lived here, such as N. Copernicus, Continue reading