Issue 41

S. Zhao et alii, Frattura ed Integrità Strutturale, 41 (2017) 412-423; DOI: 10.3221/IGF-ESIS.41.52 418 concrete test block with the addition of carbon fiber cannot have better dispersion of the fiber in the mixing process, and the strength of the test block compared with the test block of ordinary concrete test block decreases significantly, the pressure value gets shows a rapid decline after reaching a certain point during the compressive process, but the test block body does not get suffer obviously damaged, retaining the its original shape well; (c) compared with the ordinary concrete, the strength of the steel fiber concrete is obviously improved, but the damage is more thorough and the damage interface is clearer from the macro observation. From the analysis of the test data, it can be seen that the compressive strength and anti-splitting strength of the test blocks in the fifth group of materials are the largest in the orthogonal tests. That is, the composite Portland cement is used as the cementitious material, and the steel fiber is used as the reinforcement material. The ratio of the composition in each 20 kg of concrete can be seen in Tab. 5. No. Combination Steel fiber(g) Graphite (g) Copper slag(g) Fine aggregate(kg) Coarse Aggregate(kg) Cementations materials(kg) Water (kg) 5 A 2 B 2 C 3 D 1 372.6 8.4 262.4 5.07 9.02 3.86 1.78 Table 5: Proportion Optimization Table E XPERIMENTAL RESEARCH ON MECHANICAL PROPERTIES OF THE ENERGY PILES hrough the experimental ratio obtained by orthogonal experiments as well as the actual mixing process of each group, the composite Portland cement with steel fiber is selected to carry out the experiment with buried pipes in the piles, so as to further obtain the actual property indexes of the fiber- reinforced concrete of the energy piles. Test plan The test of mechanical properties of the energy piles is to involves testing the compressive strength of the pile body mainly through the static loading test of a pile. The heat-transfer tubes are supposed to be embedded in the energy piles, greatly weakening the vertical load of the foundation piles. This test is to verify the strength of the material of the energy piles so as to verify the correctness of the optimal ratio by conducting the pile loading without lateral force towards the energy piles through the compressive strength data and the damage mode of the piles. Figure 12: Hydraulic pressure testing machine. Figure 13: Preparation before the pile pile's static pressure. In this test, three groups of concrete test piles are made and three identical concrete piles are made in for each set group. So, there are Nnine concrete piles are shared total in the test. As the standard pieces, the first group of the three concrete piles is the reinforced concrete piles with a normal ratio of material without reinforced fibers or embedded heat-transfer tubes. The second group of the three concrete piles is the reinforced concrete piles with a normal ratio of material with a group of single U-type heat-transfer tubes embedded in the piles, whose material is fits the PPR profile. The third group of the three piles is the energy piles whose material ratio is A 2 B 2 C 3 D 1 , with a group of single U-type heat-transfer tubes embedded in the piles, whose material is fits the PPR profile. The sizes of the test piles are that they have a diameter of T