基于Fluent软件小型非连通型溶洞注浆数值模拟及裂隙数量影响

[目的]溶洞的注浆处理是地铁隧道工程中的难点,施工时溶洞的不恰当处理极易引发事故,因此有必要对小型溶洞裂隙数量和注浆压强之间的关系进行研究。[方法]针对需注浆填充的城市小型非连通型溶洞(体积不大于8 m 3)的裂隙数量不确定问题,采用Fluent数值模拟软件中的多相流Mixture模型进行不同裂隙数量的溶洞注浆数值模拟,计算模拟注浆时,测试区的注浆压强随时间的变化情况,并与实际工程溶洞注浆压强数据进行对比分析。[结果及结论]对于体积不大于8 m 3的小型非连通型溶洞,其模拟注浆时测试区的注浆压强与裂隙数量呈平方反比关系,注浆压强随着裂隙数量的增加而降低;当裂隙面积达到0.048 m 2时,注浆压强不再降低;注浆压强随着裂隙位置的增高而降低。在实际工程中,可通过对比同类型体积不超过8 m 3小型非连通溶洞之间的注浆压强数据,判断溶洞的相对裂隙数量,调整与优化后续的注浆方案。

Mechanical properties of anti-seepage grouting materials for heavy metal contaminated soil

Cement-based composite grouting materials were used to construct grouting cutoff wall for heavy metal contaminated soil in non-ferrous metal mining areas. Cement, fly ash, and slag as principal ingredients were mixed with water glass in different ways to produce three composite grouting materials. In order to investigate the effect of water glass mixing ratio, Baume degree, fly ash and slag contents on the mechanical properties of the composite grouting materials, particularly their gel time and compressive strength, the beaker-to-beaker method of gel time test and unconfined compressive strength test were conducted. In addition, the phase composition and microstructure of the composite grouting materials were analyzed by the X-ray diffraction（XRD） and scanning electron microscope（SEM） techniques. The test results show that their gel time increases when water glass mixing ratio and Baume degree increase. The gel time increases dramatically when fly ash is added, but decreases slightly if fly ash is partly replaced by slag. When the mixing ratio of water glass is below 20%, their compressive strength increases with the increases of the ratio; when the ratio is above 20%, it significantly decreases. The compressive strength also tends to increase as Baume degree increases, and improves if fly ash and slag are added.

Mechanical properties and failure characteristics of fractured sandstone with grouting and anchorage

Based on uniaxial compression experimental results on fractured sandstone with grouting and anchorage, we studied the strength and deformation properties, the failure model, crack formation and evolution laws of fractured sandstone under different conditions of anchorage. The experimental results show that the strength and elastic modulus of fractured sandstone with different fracture angles are significantly lower than those of intact sandstone. Compared with the fractured samples without anchorage,the peak strength, residual strength, peak and ultimate axial strain of fractured sandstone under different anchorage increase by 64.5–320.0%, 62.8–493.0%, and 31.6–181.4%, respectively. The number of bolts and degree of pre-stress has certain effects on the peak strength and failure model of fractured sandstone. The peak strength of fractured sandstone under different anchorage increases to some extent, and the failure model of fractured sandstone also transforms from tensile failure to tensile–shear mixed failure with the number of bolts. The pre-stress can restrain the formation and evolution process of tensile cracks, delay the failure process of fractured sandstone under anchorage and impel the transformation of failure model from brittle failure to plastic failure.