Issue 41

S. Zhao et alii, Frattura ed Integrità Strutturale, 41 (2017) 412-423; DOI: 10.3221/IGF-ESIS.41.53 421 c — the specific heat of the material J / (Kg • K); T — time, 24 hours is set here. (a) Drying oven (b) Thermal conductivity tester Figure 16 : Main instruments for measuring the thermal conductivity Group Thermal conductivity(W/m.K) Group 1 1.85 Group 4 2.81 Group 5 4.41 Table 8: Test results of thermal conductivity The specific heat capacity of the concrete is: ∑ ∑ = i i i p w cw c (2) In the equation, c p — the specific heat capacity of the concrete J / (Kg • K) w i — mass fraction of different parts c i — specific heat capacity of different parts The specific heat capacity of different kinds of raw materials is: the specific heat capacity of the water is 4.186 ×10 3 J / (Kg • K); the specific heat capacity of the cement is 900 J / (Kg • K); the specific heat capacity of the fine aggregate is 920 J / (Kg • K); the specific heat capacity of the coarse aggregate is 850 J / (Kg • K); the specific heat capacity of the steel is 450 J / (Kg • K); the specific heat capacity of the graphite is 710 J / (Kg • K); the specific heat capacity of the copper slag is 1060 J / (Kg • K). It can be seen through calculation that the specific heat capacity of the first group of ordinary concretes is 1.175 ×10 3 J / (Kg • K), the specific heat capacity of the fourth group of the mixing material is 1.182 ×10 3 J / (Kg • K), the specific heat capacity of the fifth group of the mixing material A 2 B 2 C 3 D 1 is 1.172 ×10 3 J / (Kg • K). With formula 1 added, it can be seen that the heat storage coefficient of the first group of materials is 19.3 W / (m 2 • K) , the thermal storage coefficient of the fourth group of materials is 24.47 W / (m 2 • K) , and the heat storage coefficient of the fifth group of materials is 30.6 W / (m 2 • K) . That is to say, the thermal storage capacity of the energy pile using a mixing ratio of A 2 B 2 C 3 D 1 is 1.6 times than that of the ordinary reinforced concrete pile, whose effect of heat storage is relatively better. C ONCLUSION . Based on the mixing ratio of the material of the energy piles through the orthogonal test, the test piles made of the composite Portland cement with steel fiber are made, and the tests of the mechanical properties of the pile foundation are conducted to get the following conclusions: 1