地面塌陷地质特征和粉煤灰掺量对泡沫混凝土性能的影响发布时间：2019/3/26 12:27:21 浏览次数:768
空中塌陷地质特征：采空塌陷：普通较大，面积普通在几百米以上，大者如湖南杨梅山煤矿塌陷，长2km，宽1km，深12m，塌陷面积达几百万平方米。 黄土湿陷：湿性黄土在枯燥状态下能够接受一定荷重而变形不大。当浸水后，土粒间水膜增厚，水溶盐被溶解，土粒联合力显著削弱，从而惹起土体构造毁坏并产生湿陷。由于湿陷常常是忽然发作的，所以常使建筑物忽然发作沉陷，以至招致建筑物毁坏。 岩溶塌陷：岩溶塌陷的平面形态具有圆形、椭圆形、长条形及不规则形等，主要与下伏岩溶洞隙的启齿外形及其上复岩、土体的性质在平面上散布的均一性有关。其剖面形态具有坛状、井状、漏斗状、碟状及不规则状等，主要与塌层的性质有关。粘性土层塌陷多呈坛状或井状，砂土层塌陷多具漏斗状，松懈土层塌陷常呈碟状，基岩塌陷剖面常呈不规则的梯状。
Geological characteristics of air subsidence: goaf subsidence: generally large, the area is usually more than several hundred meters, such as the collapse of Yangmeishan Coal Mine, Hunan Province, 2 km long, 1 km wide, 12 m deep, the collapse area reaches several million square meters. Loess collapsibility: Wet loess can accept a certain load in a dry state and has little deformation. When immersed in water, the water film between soil grains becomes thicker, water-soluble salts are dissolved, and the combined force of soil grains is significantly weakened, which leads to the destruction of soil structure and collapsibility. Because collapsibility often occurs suddenly, it often causes buildings to collapse suddenly and even cause buildings to be destroyed. Karst collapse: The plane shape of karst collapse is circular, elliptical, strip and irregular, which is mainly related to the shape of the opening of the underlying karst cave and the uniformity of the distribution of the properties of the upper complex rock and soil in the plane. Its profile shape is altar-shaped, well-shaped, funnel-shaped, dish-shaped and irregular, mainly related to the nature of the collapse layer. The collapse of cohesive soil layer is mostly altar or well-shaped, the collapse of sandy soil layer is mostly funnel-shaped, the collapse of loose soil layer is usually dish-shaped, and the collapse profile of bedrock is often irregular ladder-shaped.
The influence of fly ash content on the properties of foam concrete: at the early stage, there was no volcanic ash reaction, so the compressive strength of concrete decreased with the increase of fly ash content. The performance of foam concrete blocks with fly ash is long and the dry density of foam concrete is very obvious. With the increase of curing age of foam concrete, the effect of fly ash pozzolanic action and the reaction of cement hydration, and the effect of fly ash micro aggregate, the compressive strength of foam concrete mixed with proper amount of fly ash can reach and surpass pure cement foam concrete (also called foam cement). In this study, the suitable content of fly ash is 20%.
Fly ash contains more than 70% vitreous body, the main components are SiO2 and al2o3. Under strong alkali excitation, gelling activity will appear. In foam concrete, cement is released from time to time to produce strong alkali Ca (OH) 2, which produces chemical reactivity with fly ash to produce calcium silicate hydrate, low sulfur type and high sulfur type calcium sulphoaluminate with gel properties, and promotes the strength growth of foamed concrete. The dry density of foamed concrete is 700kg/m, 800kg/m, 900kg/m and 1000kg/m, respectively. The corresponding water and material ratios are 0.56, 0.54, 0.52 and 0.50 respectively, and the content of fly ash is 0, 10%, 20%, 30% and 40%. The 28d compressive strength of foam concrete containing different amounts of fly ash is calculated in Figure 6. The results show that the proper proportion of fly ash in the cement fly ash foam water raw material foam concrete will help to improve the strength of foam concrete and reduce the cost, reduce shrinkage and improve crack resistance.