Experimental Study On Ultimate Bearing Capacity Of Reinforced Cement Mortar Pile Of Soil Composition Model

With the economic development of the modern high-rise buildings have been expanding, increasingly high demand for pile foundation. Since the bearing capacity requirements, geological conditions-such as restrictions on soft ground, using a single cement pile often can not meet the project requirements, so the combination of the pile is the future of the cement pile. Reinforced concrete pile soil combination is a typical example, and it has the construction piling noise, vibration small advantages, in recent years, our research quite right combination of soil cement pile gradually increased.QS curve in order to improve the strength of cement soil caused by stiff lower combined model pile big difference, bonding with soil cement concrete core difference between the scope and impact of the use of soil bearing capacity of reinforced cement composite piles. Mixed with the right amount of sand in the soil cement to increase the compressive strength of cement soil. Sand compared with other additives, inexpensive, widely drawn sources.In this paper, by making three kinds of cement ratio was15%,20%,25%and5kinds of mixed sand is0%,5%,10%,20%,30%of the15groups of test blocks, cement mortar studied soil compressive mechanical properties. On this basis, the production as fellows①on the condition of cement ratio of20%, the amount of sand mixed with0%,5%,10%,20%,30%of the five kinds of reinforced cement mortar mix combined model pile soil②on the condition of cement ratio was15%, the ratio of reinforced cement mortar mixed with sand pile soil composition model of10%③on the condition of cement ratio of25%, the amount of sand mixed with10%of one kind of reinforced cement mortar mix soil composition model piles, piles model number for a total of seven.By soil cement mortar compressive strength test, the amount of sand mixed analysis, age, cement ratio on the compressive strength of cement mortar impacts and changes of soil. Through the static strength of the combined model of soil cement pile load test, got the combination compared with the situation in a variety of model pile ultimate bearing capacity, collecting QS curve and the stress strain curve analysis combined pile stress in the working state, internal force distribution, failure modes, and its findings are as follows: (1) When the cement ratio was15%,20%, mixed with a certain amount of sand in the soil cement, can significantly improve the early strength,7d strength will increase about50%. When cement ratio was15%,20%,25%, mixed with cement soil and form the optimal amount of sand mixed with soil cement mortar, late strength will increase by about20%. When15%of cement ratio, respectively,20%, the optimal amount of sand are mixed with10%. When cement ratio is25%, the optimal amount of sand mixed with5%.(2) The age greater impact on soil cement mortar compressive strength grows curing period, the strength of cement mortar will significantly improve the soil between7d-60d. Soil cement mortar compressive strength and age logarithmic function. qu=a In T+c(3) When mixed with sand is0%,5%,10%,20%,30%condition, in cement ratio less than20%cases, with the increase of cement mixed the compressive strength ar e increase; after20%, cement mortar compressive strength of soil cement ratio increases instead of decreases. In this paper, the proposed limit soil cement mixing ratio is20%. Compressive strength of cement mortar and soil cement ratio represents a quadratic function. qu=a(aw)2+b(aw)+c(4) Q-S can be seen in the graph, the cement ratio was20%cases, comparative analysis of the amount of sand mixed with each of10%and0%of the strength of the soil cement pile ultimate bearing capacity combined model the former than the latter increased by16.3%. In the same vertical load, the settlement value of the former than the latter decreased by22.2%.(5) when cement ratio is20%, the amount of sand mixed with10%for the failure modes of reinforced cement mortar pile of soil combined model can be seen, the destruction occurred in the bottom of the concrete core is crushed soil cement mortar, concrete core pile did not produce damage. Vertical cracks in the soil cement concrete core height is extended to the middle of the external periphery, are partially bonded, some are off, shedding part show that the adhesion of concrete core pile of soil with cement mortar has lost its effect.(6) Analysis the load-strain, the greater the compressive strength of soil cement, a combination of model pile at the top of the soil with cement mortar concrete core load sharing ratio increases.(7) Through the static load test results of five reinforced cement mortar composition model pile ultimate bearing capacity of the soil, and with reference to the research results of domestic and foreign scholars proposed reinforced cement pile ultimate bearing capacity of the soil composition model reference formula:Ra=0.141mfcA+0.349(1-m)fcuA, R2=0.916。(8) In the finite element analysis of reinforced cement mortar pile of soil composition model, you can get outside the core cement mortar mixed with soil mixed with sand optimal amount of reinforced cement mortar improved s oil composition model pile ultimate bearing capacity and reduce its settlement, consistent with the experimental conclusion.