Studies On Mechanism And Inspecting Methods For The Sea Dike Constructing Technique Of Explosion Replacement

Explosion replacement technique is a new ground treatment technique original created by Chinese. After more than 20 years'development, it was widely applied to construct sea dikes or cofferdams. According to the explosion replacement theory currently in effect,the thickness of the soft clay treated by explosion replacement technique should be less 12m. Actually, the thickness of the soft clay treated by this technique exceeds 40m. The actual consumed explosive is hardly less than the theoretical quantity. These indicate that the theory cannot adapt to the development of the explosion replacement. At the same time, there are some disputes about the inspecting method for the inspecting of the sea dikes, it is difficult to effectively control the quality and quantity of the sea dikes. Therefore, it is very necessary to study on the mechanism and inspecting methods of the explosion replacement.Firstly, the strength of the soft clay and its varying laws before and after the explosion have been concluded by collecting the engineering applications and other people's researching achievements. It is revealed that the soft clay is under undrained condition after explosion, the strength of the soft clay after the explosion will decrease. It is appropriate to express the ration of the strength of the soft clay before and after the explosion as the sensitivity. The disturbed zone of the soft clay after explosion was also divided according to the actual projects. The radius of the first disturbed zone is about 6~8m. The radius of the second disturbed zone is about 4m.According to the traditional limit balance theory, the formula of the thickness of the sea dike was deduced. The relation between the height of the sea dike above the soft clay and the thickness of the sea dike underneath the soft clay was studied. The thickness of the sea dike underneath the soft clay varies as the strength of the soft clay. The section shape of sea dike was inferred from the above research. The results were verified by actual inspecting data.The study on the process of squeezing soft clay by stone under complex condition also did with finite element simulation method. The results were compared with the results achieved by limit balance analysising and verified by actual inspecting data. According the actual engineering, a finite element model was established. The full process of explosion replacement was simulated through varying the strength of the soft clay in the place ahead to the forepart of the sea dike. The similarity between the simulating result with the actual inspecting result indicates that the thought of the slide of the stone is caused by the decreasing of the strength of the soft clay is right. The soft clay strongly disturbed mechanism of explosion replacement can be concluded as: After the process of squeezing soft clay by stone is completed. Ignites the explosive buried on the soft clay in the place ahead to the forepart of the sea dike, the strength of the soft clay will be decreased by the explosion. The balance between the stone and the soft clay formed at the squeezing soft clay stage was broke, then the stone slide into the soft clay until the new balance is created. More soft clay will be squeezed by the stone and the stable sea dike will be constructed through repeating the above processes.A lot of inspecting experiments had been conducted at various engineering sites. The experimental results indicates that the boring inspecting, surface wave inspecting, seismic imaging inspecting and ground penetrating radar inspecting methods are all effective to inspect the sea dike. But if doing inspecting with single method, the precision of the result may be very low, and even get the wrong results. Through comprehensive analysising, a comprehensive inspecting method which relies mainly on GPR inspecting and boring inspecting while making seismic imaging inspecting subsidiary was put forward. In order to increase the ratio between the signal and the noise of the GPR data and improve the interpretation ability of the abnormal objectives, the 2D-FK filtering, 2D-FK migration and Kirchhoff migration processing procedures were programmed. In some actual applications, the comparisons were also conducted between simulatingresults and actual inspecting results. It is revealed that both the simulating method and the inspecting method are right and reliable. A new formula of explosive quantity and a formula of buried depth of the explosive are given. Some designing advices are put up basing on the soft clay strongly disturbed mechanism of explosion replacement.At the end of the paper, some useful conclusions are concluded and some further studying advices are also put forward.