On The Law Of Variation And Energy Consumption Of Red Sandstone Soil Under Single-point Impact Loading

Red sandstone, as one kind of rocks distributed widely in our country, is exploited largely and used to backfill all kinds of ground, red sandstone soil foundation as a result. The intensity of red sandstone soil is lower, foundation formed by red sandstone soil is thick and uneven and its engineering-property is poor. In order to meet the construction requirements,the foundation need to be reinforced. Due to simple construction equipment, significant reinforcement and low cost, dynamic consolidation is the first choice and used to reinforce the foundation, but currently, the theoretical study of impact loading for reinforcing foundation is a little bit lag behind. On the basis of previous studies, this paper aims at red sandstone soil,using compaction test equipment which is refitted to do laboratory compaction experiment,comparative study on laws of physical and mechanical properties of different thickness soil under impact loading is done; by setting different test parameters, discusses the displacement laws of soil under different impact energy; based on the change of the soil’s settlement amount and density and the relationship between the settlement amount and the reinforcement depth under impact energy, explores the consumption law and reinforcement scope of impact energy in soil, the main conclusions are as follows:(1) The effect of impact energy in red sandstone soil is given priority to vertical and influence on the level is complementary; there is a certain influence depth in the soil for the transmission of impact energy and it is increasing with the increase of the energy within a certain range, but the growth rate is gradually reduced.(2) The cumulative settlement amount of soil under 25 N ? m, 30 N ? m, 35 N ? m and 40 N ?m presents two stages including the fast growth and slow growth, the demarcation point is the7 th hit, 8th hit, 9th hit and 10 th hit and this phenomenon is pushed back obviously; the changes of cumulative settlement amount of red sandstone soil under 15N·m、20N·m、25N·m、30N·m、35N·m、40N·m with the best tamp count has good linear characteristics.(3) With the increase of single impact energy(25N·m, 30N·m, 35N·m and 40N·m), the impact of reinforcement effect is obvious, the notable displacement action ranges of the soil change from 4.5~5.0cm to 6.0~6.5cm in horizontal direction and from 13.5~14.0cm to 17.0~19.0cm in vertical direction.(4) The valid reinforcement depth of soil when soil thickness is H/3, 2H/3 and H is5.5~7.3cm, 10.6cm, 13.7cm; ratio between the settlement amount of soil and the validreinforcement depth calculated is 0.4 to 0.6 under the effect of the impact energy, so the valid reinforcement depth may be estimated by settlement amount of soil, and the research results have certain referenced value.(5) The influence scope of soil’s density is a ellipsoid sphere under impact energy; based on the change of the soil’s density and the relationship between the settlement amount and the reinforcement depth, the theoretical formula of reinforcement depth and width is deduced.Results of this study enriches the impact reinforcement theory of red sandstone soil and have a certain reference value for the further study to red sandstone soil, and some guidance is provided to engineering practice of similar foundation treatment.