The Research Of Construction Technology Of Concrete Cutoff Wall In Complex Strata

The concrete cutoff wall, an effective method for permeable mass's impervious disposal, is one kind of diaphragm wall generally used in water resources & hydropower and municipal engineering. With special pore-creating mechanical equipments, this technology firstly forms slotted holes, which are grouted with mud to prevent the hole-wall from slumping, then replaces the mud with concrete to form a wall. The walls could be stiff as well as flexible, in which the former are mainly used for the foundation's bearing and earth-retaining in industrial and civil buildings, and the later for the cutoff and reinforcement of rivers, lakes and reservoirs' embankments. After dozens of years of domestic and oversea application and exploring, the concrete cutoff wall engineering technology has been approved mature. For example, this technology effectively solves numbers of leakage problems in embankments and their foundations of many large and medium hydropower stations as well as foundations' earth-retaining and bearing problems of municipal projects. Furthermore, it has been developed to a whole set of code system. On the basis of engineering practice, this paper summarizes plentifully valuable experiences which set an foundation and orientation for the technology.In collaboration with the author's years of engineering experiences, and on the basis of empirical summaries, this paper carries out a preliminary study on various problems of engineering crafts from analyzing multiple aspects of drilling method selection, drilling devices' selection and the connection between walls in cutoff walls' engineering in complex strata. Based on the above work, this paper draw some conclusions as follows: 1.Concrete cutoff wall presents a bigger safety and reliability in aspects of the reinforcement of reservoirs' loss, and foundations' cutoff in large-medium hydropower stations' deep overlying strata.2.Thanks to the technology's characteristics, it is difficult and expensive to deal with the problems occurred during engineering progress because of complex geological conditions or unsuitable engineering methods.3.For different geological conditions, the selection of drilling methods and devices requires complexity. In some cases, only a good combination of several methods and devices could result in maximum benefits.4.Whether the connection between walls and segments is reliable is the key joint in cutoff wall engineering. Although there are some possible connections, they are still in development and improvement.5.During the progress of creating holes, mud principally acts as the part of stabilizing hole-wall, floating and carrying drill cuttings and cooling the drill bit. Selecting prime bentonite mud and suitable additives according to different geological conditions is an effective confirmation for hole-wall's stability and shortening engineering time limit.6.It is a must to add various additives in wall materials to meet different cutoff requirements against the cutoff wall's functions. Through summarizing and analyzing this technology, the author furthered his knowledge about cutoff wall engineering crafts, which set an example and provide a rather complete database for future application. Predictably, with the acceleration of hydropower exploitation in west China and rapid development of municipal foundation engineering, the concrete cutoff wall engineering technology will definitely get more application and spreading and should contribute more to the development of economy in our country.