| As the increase of domestic high-rise buildings, more and more deep foundation trench supporting constructions have come into existence . Among the general geographical condition of the urban district in Qingdao , most of regions, which mainly consist of strong de composed rocks, are in quite good condition .except for the sandy soil and oozy soil along sea sides .But the development of rock cracks and breaking zones and unstable lamprophyre still exist , so blasting is needed during constructions of foundation trench. Blasting have bad influence on the stability of slopes .moreover .the slope-liding has happened for several times , so the engineering project of foundation trench attracts more attention of people.In order to find out an economical, practical and reliable supporting method, some relevant technical personnel and I , based on successful experiences and project instances, designed the Pre-stress Anchor Board Supporting System, which is to exert pressure on the anchors and to independently support slopes. This system has successed and replaced thePile-Anchor Supporting System used in past . In Qingdao, this system has become one of main technologies in the field of Deep Foundation Trench.The technology of Anchor Shot, which appeared 50 years ago in foreign countries, was only a temporary supporting measure during constructing. The pouring anchor and shot concrete as used from the middle of 1950' s, while the technology of anchorage, which was used as foundation support was popular in Europe in I960' s , and this method was used to strengthen the tunnels' ceilings and support mines from 1970' s in China. Since 1980' s, it was used in deep foundation supporting construction with the steel piles, pouring piles and diaphragms together .As a measure of anchoring in supporting system, it has got satisfying effect.The supporting mechanism of pre-stress anchor is given in following sentences in this paragraph: Make full use of sectional stability, put-up steel-net shot concrete to the stratified earth as the trench is being excavated, and by this means, the little liding of soil layers and small broken slumps of rock slopes can be avoided . Furthermore , the pressure of soil can be exerted on anchor boards , so the stressed anchor can balance the pressure of soi1 through the anchoring .Before the trench displaces, the anchoring pressure begins to work through the exertion of pre-stress .Meanwhile, the stress pressure of anchor changes and is adjusted through shot concrete and its stressed steel. So the whole supporting system, which is similar with thePile-Anchor supporting system, is finally formed, and it can limit the displacement of trenches.The Pre-stress Anchor Board Supporting Technology is economical, speedy and safe enough. It can broaden the constructing space and can promote the efficiency and quality of excavation and restructuring construction. The equipments and the needed worksite of this technology are small, so they apply to every kind of geographical conditions and areas. Meanwhile, it does not need a extra time to be carried out . It can continuously work during the excavation of trenches , so whole work cycle can be reduced. Anchors and layers of shot concrete have replaced the traditional steel frames and piles, including concrete piles, steel piles, and they can largely economize construction materials, such as steel and concrete, reduce the amount of soil that would be excavated out, and improve work conditions. The pre-stress of anchors can be acquired by stress locking. So the design is safe enough to control displacement of slopes .During the process of construction, we adopted the security monitoring measures to the stability of slopes. These measures included the slope horizontal displacement monitor, the supporting structure swag monitor, the subsidence monitor, the pre-stress of Anchor monitor, the ribbed beam steel stress monitor .We monitored the whole process and got feedback information in time, so the trend and development of slope' s displa... |
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