The upper section of the foundation of one substation building, which is located on a dyke section of the south side of Yangtze River, contains a thick layer of slit. The static-press poles of precast steel reinforced concrete were adopted. All static-loading examinations on test piles met requests of design, but among the same examinations on engineering piles, there were only 50 percentage of piles the requests. The article analyses the engineering geological condition of the site at first, discusses in details on construction factors, squeezing-effect and time-effect of group-pile which affect static-load examinations on engineering piles; at last, based on the main causes, some corresponding measures are given to meet the design in the article.