| With the rapid development of the upper and middle reaches of the Yangtze Riverinland river shipping industry, the large-diameter rock-socketed piles have been widelyused. It takes to set up steel tubes to insure the construction of rock-socketed piles in thewater normally, and steel tubes need to be embedded in a certain depth of the rock as aconstruction measure, the steel tubes are retained to bear load together with pile ofconcrete after completion of the construction. It is inconsistent with the actual situationthat the role of steel tubes was not considered in the design and calculation previously.In this paper, a set of indoor direct shear test apparatus was designed to studymechanical properties of steel and sandstone mixed with mudstone interface and relatedfactors on the basis of relevant literature data. A finite element simulation method oflarge-diameter rock-socketed pile with steel tube was putted forward based on relevanttests data and pile load tests, and the bearing behavior of large-diameter rock-socketedpile with steel tube in the vertical and lateral load was studied. The main work andachievements were obtained as follows:(1) Mechanical properties of steel and sandstone mixed with mudstone interfacewere studied by using self-designed soil and structure interface direct shear testapparatus. Based on test results, the influencing factors were discussed that they contentparticle grading of sandstone mixed with mudstone, content ratio of sandstone versusmudstone, dry density and moisture content.(2) A finite element simulation method of large-diameter rock-socketed pile withsteel tube was putted forward. In addition to considering nonlinear rock and soilbehavior around pile, it was also taking into account nonlinear concrete and steel tubeand pile-rock (soil) interaction and steel tube-concrete interaction.(3) Taking a certain pier engineering as the prototype, vertical bearing behavior oflarge-diameter rock-socketed pile with steel tube was analyzed by finite element method.According to the results of load-settlement curve, axial force and pile shaft resistancedistribution, the influence of steel tube on vertical bearing behavior of large-diametersocketed pile was analyzed, and it was discussed that the influence of rock-socketeddepth, pile diameter, steel tube rock-socketed depth, overlaying soil and rock strengthparameters on vertical bearing behavior of large-diameter rock-socketed pile. The results show that large-diameter rock-socketed pile works as end-bearing frictional pileafter considering steel tube，and the presence of steel tube improves the vertical bearingcapacity of rock-socketed piles.(4) Lateral bearing behavior of large-diameter rock-socketed pile with steel tubewas analyzed by finite element method. According to the calculation results ofload-displacement curve, the lateral displacement curve and bending moment of pile,the influence of steel tube on lateral bearing behavior of large-diameter rock-socketedpile was analyzed, and it was discussed that the influence of rock-socketed depth, pilediameter, steel tube rock-socketed depth, overlaying soil and rock strength parameterson lateral bearing behavior of large-diameter rock-socketed pile. The results show thatthe lateral bearing capacity of rock-socketed piles has been improved after consideringsteel tube; steel tube carries a part of lateral bearing capacity of rock-socketed pile, andit can effectively constrain the lateral displacement of the pile above the ground,improve the stress of rock-socketed pile body concrete. |
