Numerical computation of anti-liquefaction effect of lattice-type cement-mixed soil countermeasure

Continuous soil-cement wall confinement method to resist liquefaction is a new kind of process. However, whether it also has a good effect on anti-liquefaction or not needs to be urgently answered for earthquake engineering. Quiet boundary is adopted on the lateral face while free field boundary is employed at the bottom. Byrne model on dynamic pore water pressure generation is accepted and natural seismic wave EI Centro whose peak acceleration is adjusted to 0.2 g in proportion is used for input. A double-layer foundation with sandy soil in the upper portion while clay soil in the lower part is chosen as the calculation model, which is 30 m in length and 20 m in width. The groundwater level is on the ground surface. Excess pore water pressure rate is considered as a liquefaction index in the three-dimensional non-linear earthquake response computation. The anti-liquefaction effectiveness and its influencing factors, such as confinement element area are studied. For the natural double-layer foundation, it is liquefied when the excess pore water pressure rate reaches 1.0 under the seismic load. Under the same earthquake load, the peak excess pore water pressure reduces to 0.56 after adopting reinforcement of the continuous soil-cement wall, which is 46% lower than before. It indicates that continuous soil-cement wall confinement method can attain the purpose of anti-liquefaction. Accordingly, it can be a sort of engineering measure to carry on the anti-liquefaction foundation treatment.

The Shaking Table Test on the Performance of Cement-mixed Piles in Liquefiable Railway Foundations

Cement-mixed piles,as countermeasure against liquefaction of silt and sand ground,can improve the shear strength and bearing capacity of foundation soil,meaning cement-mixed piles are capable of resisting displacement when an earthquake happens. However,investigations of cement-mixed piles by experimental methods such as the shaking table test is few and far between. It is especially true for the seismic performance of cement-mixed piles in liquefiable railway foundations in high seismic intensity regions. To this end,a cross-section of the Yuxi-Mengzi railway was selected as the prototype and studied by the shaking table test in this study. The results showed that composite foundation of cementmixed piles was not liquefied when the seismic acceleration was lower than 0. 30g. In the process of acceleration increasing from 0. 30g at 2Hz to 0. 60g at 3Hz,the upper middle silt outside slope toe was partly liquefied. The foundation soil under the shoulders and center of subgrade was far from the initial liquefaction criterion during the test. Cementmixed piles can effectively reduce the embankment settlement and differential settlement. It can be concluded that, the design of cement-mixed piles can ensure the seismic performance of the subgrade,and satisfy the seismic design requirements of the YuxiMengzi railway in areas of VIII degrees seismic fortification intensity.

水泥工业用混料机的对比研究

水泥工业中常用的混料机有单(双)轴混料机、气力+机械复合式混料机和组合式连续混料 机。单(双)轴混料机装机功率较高,配件更换周期短;气力+机械复合式混料机装机功率小,配件更换周 期长;组合式连续混料机装机功率低,配件更换周期长。在电石渣替代石灰石预分解窑水泥生产线生料制备 和分别粉磨水泥制成工艺中,对双级组合式连续混料机和单轴混料机、单级组合式连续混料机和气力+机械 复合式双轴混料机分别进行了对比研究,结果表明,上述两种工艺中,双级组合式连续混料机出料混合度相 对较高,单级组合式连续混料机运行功耗最低。