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There distribute the soft soil in great guantities in the seaside district, medium downstream of Yangtze river and Pearl river downstream etc, in our country. It has the following engineering feature: high water content, high compress, low water permeability and low strength. Construcing various importang engineering stucture, the soft soil foundation must be processed in order to insure engineering safety and normally performing.To process above-mentioned this soft soil foundation, must to cosider thus three basic problems:1.Settlement problem,the buiding doesn’t produce harmful settlement and differential settlement during the period of application.2.Stability problem, accelerate to increase shear shear strength of the foundation soil, raise the bearing capacity and stability.3.Under the premise of resolving two above-mentinged problems, it can shorten the work period, lower the engineering cost, obtain the best processing effect.With preloading method to process the foundation is valid and this method is a kind of method that use extensively in current engineering. Based on vacuum preloading method and piled-load preloading method, the vacuum-piled-load preloading method ahich is the new generation effective soft soil processing method is developed. Currently, many important engineering, such as the piling field of extensive harbor, airport runway and expressway etc, all of them adopt the vacuum-pile-load preloading method to process the soft soil foundation, and carried on a great deal of trial research, obtion satisfactory processing effect.Through comparative analysis among the vacuum stack preloading and other methods and instances. And based on the consolidation mechanism of vacuum preloading method and piled-load preloading method,the possibility of applying the vacuum-piled-load preloading method is discussed furthermore. Based on the former researchers’work,the consolidation mechanism of vacuum-piled-load preloading method is studied out from the principle of effective stress. According to the test data of some soft soil reinforcing engingeering of Tianjin harbor, the rationality of this mechanism is argued, get a beneficial conclusion is obtained. It is shown that the stress is added up under the positive pressure and negative pressure,the consolidating effect is added up from the engineering. With this method, the growth of subsoil strength is very effective to compare with vacuum preloading method and piled-load preloading method, and the construction technology is simple, the construction is convenient, the engineering cost is lowered, the work period is shortened, the engineering is economic. It shows that the vacuum preloading concerting stack preloading technology is increasingly maturing, the method is simply, and it can not only strengthen ground, but also shorten total period efficiently. It may be expanded further as a mean for harbor soft ground treatment. There with, it indicates that the consolidation principle between vacuum drainage preloading and vacuum stack preloading is similar, but some aspects such as drainage mechanism exist large differences, and attention shall be paid to during designing and construction.
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