Current Issue : January - March Volume : 2020 Issue Number : 1 Articles : 5 Articles
Every year, a large amount of silt is generated by river dredging. For the characteristics\nof dredging silt, such as high moisture content, low strength and\nhigh compressibility, the traditional solidification method can no longer better\nsolve this kind of silt problem. This paper mainly studies the fluidized solidification\ntreatment of high water content sludge, not only makes the silt\nsoil achieve a good solidification effect, but also the project cost is lower, the\nconstruction method is more environmentally friendly and green. The influencing\nfactors of the solidified soil are mainly investigated by the unconfined\ncompression test and the fluidity test. The experiment result shows 1)\nWhen the cement to sludge mass ratio (RCS) is 0.09 - 0.16 and the fly ash to\ncement mass ratio (RFC) is 0.35 - 0.80, as the amount of RFC increases, the flow\nrate of the solidified soil gradually decreases. With the increase of time, the\nliquidity is significantly reduced, and the influence of cement on the fluidity\nis greater than that of fly ash. 2) When RCS = 0.09 - 0.16, the strength of the\nsludge solidified soil at 28 d age increased by 4.5 - 6 times. 3) When RCS = 0.09\n- 0.16 and RFC = 35% - 80%, the intensity of 14 d increased by 1.23 times than\nthat of 7 d, and the intensity of 28 days increased by 1.29 times than that of 14\nd. This experiment can provide the mix ratio design of solidified materials for\ndifferent needs of the project, which can better provide a basis for engineering\napplication and strength prediction....
The resilient modulus of subgrade is a design parameter of the pavement structure, which is significantly affected by the overlying\nload and traffic load. It is important to calculate the equivalent resilient modulus of the top surface of subgrade based on the\nnonuniform distribution of resilient modulus in subgrade. This paper takes the fully weathered granite soil as the research object.\nFirstly, the soil density of different layers of the subgrade structure is calculated by the degree of compaction of different subgrade\nlayers. Secondly, the overlying load of each point in the subgrade is determined based on the quality of subgrade. Thirdly, the\nsubprogram of the finite element software is compiled and redeveloped based on the elastic constitutive model, and the calculation\nmethod for the resilient modulus of each point in the subgrade under the traffic load is proposed when the convergence criterion is\nset up. Finally, according to the deflection equivalence of the elastic double layer and elastic half-space, the calculation and control\nmethods for equivalent resilient modulus of the top surface of subgrade under nonuniform stress distribution are put forward, and\nthe field verification tests are carried out. The results show that the error range between numerical calculation and field\nmeasurement of equivalent resilient modulus of subgrade is 10%. It shows that the calculation method for equivalent resilient\nmodulus of subgrade proposed in this study is reasonable and effective. The equivalent resilient modulus of subgrade decreases\nwith the increase of traffic load. And the resilient modulus of subgrade soil increases with the increase of subgrade depth. The\nresilient modulus of subgrade soil has a significant impact on the equivalent resilient modulus of subgrade after the overlaying\ngravel layer. The equivalent resilient modulus of the subgrade with the gravel layer increases with the increase of the resilient\nmodulus of the subgrade soil....
In order to explore the effects of moisture content and plasticity index on\nDuncan-Chang model parameters K, n, C and Rf , we selected 8 groups of soft\nsoil with water content of 69.1% - 94.3% and plasticity index of 32.2 - 54.1 for\ntriaxial unconsolidated undrained shear test. The results show that Cuu, K and\nn values all showed a downward trend, and Rf variation was not obvious with\nthe increase of moisture content. The variation rule of each parameter is not\nobvious with the increase of plasticity index. When moisture content is constant,\nCuu and n values do not change much, K increases with the increase of\nplasticity index within the range of 70% - 80% moisture content, and does not\nchange much with the increase of plasticity index when moisture content is\ngreater than 80%, Rf has no obvious rule. When the plasticity index is constant,\nCuu, K and n decrease with the increase of moisture content, Rf has no\nobvious rule. The maximum value of Cuu is 20.18 kPa, the minimum is 3.72\nkPa, and the maximum to minimum ratio is 5.42. The maximum value of K is\n0.517, the minimum is 0.022, and the maximum to minimum ratio is 23.5.\nThe maximum value of n is 1.198, the minimum is 0.150, and the maximum\nto minimum ratio is 7.99. The maximum value of Rf is 0.872, the minimum is\n0.679, and the maximum to minimum ratio is 1.28....
Despite its importance as one of the key parameters in the design of structural elements, the modulus of elasticity (MoE) is one of\nthe least researched areas in oil palm kernel shell (OPKS) concrete. In the present study, we determined the MoE of OPKS\nconcrete, using micromechanical models based on the classic approaches of homogenisation of Hashinâ??Shtrikman (HS) and\nMoriâ??Tanaka (MT). The MoE values for OPKSC (fcu < 35 MPa and OPKS volume fraction < 42%) estimated using the HS and MT\nmodels in the literature showed a good correlation with the experimental values. An empirical linear correlation between the\nvolume fraction of inclusions and the MoE was proposed. The results obtained can enable better control of the mix design of\nstructural concrete based on the proportion of OPKS coarse aggregate in tropical countries producing palm oil....
To study the seismic performance of hollow reinforced concrete piers under dynamic loads, nine hollow pier specimens with\ndifferent stirrup ratios, reinforcement ratios, and axial compression ratios are designed and manufactured. The El Centro wave,\nTaft wave, and artificial Lanzhou wave are selected as seismic excitation for the shaking table test. The effects of the reinforcement\nratio, stirrup ratio, and axial compression ratio on the failure mode, period, damping, acceleration and displacement response,\ndynamic magnification factor, ductility, and energy dissipation of specimens under different working conditions are studied. The\nresults show that all the nine reinforced concrete piers have good seismic performance. Subjected to ground motion excitation,\nhorizontal through cracks appeared on the pier surface. With the increase of ground motion excitation, the period of piers\nincreases but the maximum period does not exceed 0.62 s, and the damping ratio increases as well and ranges from 0.02 to 0.064.\nWith the increase of the ground motion excitation, the acceleration response of pier specimens increases, the dynamic magnification\nfactor decreases, the displacement ductility coefficient decreases, and the energy dissipation of the specimens increases.\nThe reinforcement ratio, stirrup ratio, and axial compression ratio have different effects on the above parameters. The test results\ncan provide reference for seismic design of hollow rectangular piers and have certain engineering significance and value....
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