| Together with the development of engineering projects and the deepening in the slope problems research, more and more attention has been drawn to the research of transformation stability of slope rocks. Traditional appraisal and control of slope and relative geological disasters such as collapse and slide are based on intensity stability theory and statics-based criterion design. The guiding principles have some obvious disadvantages. First of all, the basic starting point is the extreme balance theory which deals with the simple destructive pattern of even medium. It is far from the truth in most rocksoil structure and structure control. Secondly, the key of design—rocksoil pressure should be the result of the reciprocity of rocksoil transformation and supporting structure. While in the traditional way, a destructive surface is assumed, then stability coefficient can be calculated in the extreme balance way. In order to overcome the above-mentioned disadvantages, the construction of a new engineering theory, which is based on the limited and nerve fiber network, about geological disasters control has become a necessity. Against this background, in this paper,"simulation and control of slope stability process"is used to carry out an engineering geological research of the slopes of the nuclear island district of the Hong Yan He Nuclear Power Plant in Liaoning Province. Massive on-the-spot investigation, testing experiments and simulative research and analysis lead to the following major results.1. Through analysis of the attainable information and on-the-spot investigation, engineering surroundings and geological conditions are revealed. What's more, stability appraisal and research are conducted on the slopes of the nuclear island by way of bare even projection and extreme balance methods.2. The method based on limited and nerve fiber network is put forward to carry out the research of slope problems. And reasonable and objective research results have been obtained.3. The slope stability conclusion has been drawn.(1) The west slope is generally considered as unsatisfactory in stability. Seen on the bare even projection chart of the structural surface, the unstable cuniform sliding objects on the west slope have obliquities less than 50o. The calculation results are analyzed by extreme balance method, and the following conclusion can be reached: for the seriously airslaked rocks, when the slope rate is 1:1.5, the stability coefficient for engineering condition two seriously airslaked granite is 1.346, whilst the stability coefficient for engineering condition two seriously airslaked gneiss is 1.284. These make the temporary slope in a state of stability.(2) The south slope is not stable.The above part of the south slope is seriously airslaked granite which is 6.00m～14.20m in thickness. The other parts are mainly moderately airslaked granite and gneiss. Based on the bare even projection of the south slope, the structural surface combination that most likely causes trouble is the cuniform sliding object combined by advantage section group J1 and J3, with a leaning angle of 25o. The digging experience of nuclear island tells us that in the south slope, section group of directing NEE with leaning NW, or directing NW with leaning VE, may cause cuniform sliding object. Sliding and collapsing of different scales may arise as the result of the digging of the slope. Generally speaking, the south slope is not stable. It is strongly recommended that reinforcement measures are taken to guarantee the stability.(3) The east slope is not stable.In the east slope, the rock above the base is mainly moderately airslaked granite. Based on the bare even projection of the east slope, the advantage structural surface combination that most likely causes trouble is the cuniform sliding object combined by advantage section group J1 and J3, and J4 and J5, with leaning angles of 25o and 18o respectively. The engineering geological testing information of the slope part reveals that in the pump room part exist several section crannies which are not good for the stability of the east slope (315°∠63°,260°∠60°). These sections are massive in size and combined together they may cause various scales of sliding and collapsing. Therefore, the general appraisal of the east slope is unstability. Engineering reinforcement measures are recommended.(4) The stability of the north slope is really bad.The rock above the base in the north slope is mainly composed of seriously airslaked gneiss. In the 45m long slope, the middle part is moderately airslaked granite, 5.0m～12.0m in thickness, whilst the above and the base are seriously airslaked gneiss. The north slope has the worst geological condition among all the four slopes surrounding the pump room foundation. The geological conditions are complicated. The above base seriously airslaked blackcloud gneiss has loose structure with split core or even soil core. It is easily collapsed or dissolved when meeting water, and it may appear a loose sand or mud condition when agitated mechanically. When the digging of the foundation begins, under the influence of mechanical agitation, underground water, and surface water, the seriously airslaked gneiss is very likely to slide and collapse. Based on the bare even projection of the north slope, the stability angle of the north slope is less than 45o. Since seriously airslaked rocks are revealed in the north slope, the stability slope rate should be recalculated by the extreme balance method. The analysis shows us when 3-meter steps are reserved at the top of temporary slope as well as the 12m permanent slope foot, the stability coefficient for engineering condition two seriously airslaked gneiss is 0.986. Considering the 12m permanent slope can not be destroyed when the foundation is dug, supporting measures should be used to protect the slope when digging.4. In this paper, a non-linear prediction model based on plane limited and three-dimensional BP nerve fiber network is put forward for the first time. It promises a new way to predict the slope stability by way of non-linear methods. It can solve practical problems by providing scientific evidence for the slope unstability research and slope security. The significance of the choice of this subject lies in its practicality and innovation.5.In this paper, BP artificial nerve fiber network is applied in the predictive research of the stability condition of the four slopes of nuclear island. The construction of the network is based on the Matlab 7.3. In the nerve fiber network prediction model set up in the paper, the section of input layer, hidden layer, and output layer can all be chosen randomly, it also makes use of multiple ways of calculation about the training function, passing function, value function, valve matrix, etc.6. If the limited simulation results are in accordance with the BP nerve fiber network based slope unstability prediction research results, they guarantee more liability and objectivity. Nerve fiber network based slope stability prediction can solve practical constructional problems, that's why it possesses the value to be applied and promoted. 7.When studying similar slope stability problems, non-linear theory methods can be used with reference to the non-linear appraisal and prediction system put forward in this paper. This, together with slope extreme balance theory calculation methods and three-dimensional digital simulation methods, provide more information for the slope stability conditions.8.The stability of slopes are influenced by numerous factors, that is why it is a global problem, just like the prediction and forecast of earthquake and sliding. In the future, deeper research should by conducted about the factors affecting slope stability and their destroying patterns, so that a better precaution model can be set up about slope security.9.In the design of slope projects, methods and economic benefits should be both taken into consideration. At the same time, precautions should be taken. The predicting research results about slope stability, which is drawn in this paper, can provide scientific references for the slope engineering design of the nuclear island in Hong Yan He.10.The geology should be given enough attention during the construction process. The concrete geological structure changes in slopes must be observed, especially in the part where seriously airslaked gneiss is abundant. Special treatment measures should be used when meeting with splitting parts which may affect the stability of the slopes. If necessary, manual dynamic design and construction of slopes can be performed.11.The intensity of seriously airslaked gneiss will drop dramatically when frozen and melted repeatedly in winter, which may affect the stability of slopes a lot. For this reason, the engineering units should carefully arrange the time of construction in case the temporary slopes are destroyed by freezing and melting.
|
PDF Full Text Request