Research samples were taken from an ancient gravel stratum which is not only a representative soil layer along the middle-lower reaches of the Yangtze River in East China, but also one of the primary Neozoic strata in...Research samples were taken from an ancient gravel stratum which is not only a representative soil layer along the middle-lower reaches of the Yangtze River in East China, but also one of the primary Neozoic strata in Naming district. Located mostly on the second and third terraces, the ancient gravel strata formed the geomorphic landscapes of terrace and step. They were complex in constitution, varied widely in stability, of multiple sources, locally derived, and associated with braided streams in the deposition environment. A CIPW (Cross, Iddings, Pirsson and Washington) method modified by the author was used to analyze the soil-rock-forming materials of finer grains (less than 2 mm in size) of the ancient gravel stratum. Results of the analysis showed that the sandy grains were composed of apatite, ilmenite, potassium feldspar, plagioclase, enstatite and free quartz, the clay mainly of kaolinite, and the cement of a combination of silicon, aluminum and iron at a ratio of 46:44:10. In the soil-rock-forming processes, including compactional solidification, water-stable illuviation-cementation t homogeneous overgrowth and so on, the loose soil-rock-forming components gradually changed into consolidated soil and further to the early stage of lithification. Meanwhile, from the analysis, we found that the ancient gravel stratum had been protected by the overlying Xiashu loess or basalt and the overloading resulted in overconsolidated strata. The modified CIPW method was applicable and effective for semi-quantitative analysis.展开更多
为解决土压平衡盾构及车站基坑开挖过程中产生大量废弃粉质黏土的现状,提出一种利用废弃粉质黏土调制泥浆改良盾构渣土的新方案。以沈阳地区粉质黏土为研究对象,通过添加不同的外加剂对粉质黏土泥浆进行改性,研究泥浆土水比、外加剂种...为解决土压平衡盾构及车站基坑开挖过程中产生大量废弃粉质黏土的现状,提出一种利用废弃粉质黏土调制泥浆改良盾构渣土的新方案。以沈阳地区粉质黏土为研究对象,通过添加不同的外加剂对粉质黏土泥浆进行改性,研究泥浆土水比、外加剂种类及掺量变化对改性泥浆的漏斗黏度、酸碱度、滤失量和胶体率的影响。通过扫描电镜(scanning electron microscope, SEM)研究了粉质黏土泥浆的微观改性机理。结果表明:纯粉质黏土泥浆自身稳定性差、泌水量大,无法有效改良渣土;碳酸钠和焦磷酸钠对粉质黏土泥浆的改性效果较好,合理掺入量为1%~3%;改性后的粉质黏土泥浆可有效改良砾砂地层渣土的塑流性,合理粉质黏土泥浆土水比为9∶11、焦磷酸钠掺量为3%,注入比为24%~28%。研究结果验证了粉质黏土泥浆用作盾构渣土改良剂的可行性,为废弃粉质黏土再利用提供了新思路。展开更多
文摘Research samples were taken from an ancient gravel stratum which is not only a representative soil layer along the middle-lower reaches of the Yangtze River in East China, but also one of the primary Neozoic strata in Naming district. Located mostly on the second and third terraces, the ancient gravel strata formed the geomorphic landscapes of terrace and step. They were complex in constitution, varied widely in stability, of multiple sources, locally derived, and associated with braided streams in the deposition environment. A CIPW (Cross, Iddings, Pirsson and Washington) method modified by the author was used to analyze the soil-rock-forming materials of finer grains (less than 2 mm in size) of the ancient gravel stratum. Results of the analysis showed that the sandy grains were composed of apatite, ilmenite, potassium feldspar, plagioclase, enstatite and free quartz, the clay mainly of kaolinite, and the cement of a combination of silicon, aluminum and iron at a ratio of 46:44:10. In the soil-rock-forming processes, including compactional solidification, water-stable illuviation-cementation t homogeneous overgrowth and so on, the loose soil-rock-forming components gradually changed into consolidated soil and further to the early stage of lithification. Meanwhile, from the analysis, we found that the ancient gravel stratum had been protected by the overlying Xiashu loess or basalt and the overloading resulted in overconsolidated strata. The modified CIPW method was applicable and effective for semi-quantitative analysis.
文摘为解决土压平衡盾构及车站基坑开挖过程中产生大量废弃粉质黏土的现状,提出一种利用废弃粉质黏土调制泥浆改良盾构渣土的新方案。以沈阳地区粉质黏土为研究对象,通过添加不同的外加剂对粉质黏土泥浆进行改性,研究泥浆土水比、外加剂种类及掺量变化对改性泥浆的漏斗黏度、酸碱度、滤失量和胶体率的影响。通过扫描电镜(scanning electron microscope, SEM)研究了粉质黏土泥浆的微观改性机理。结果表明:纯粉质黏土泥浆自身稳定性差、泌水量大,无法有效改良渣土;碳酸钠和焦磷酸钠对粉质黏土泥浆的改性效果较好,合理掺入量为1%~3%;改性后的粉质黏土泥浆可有效改良砾砂地层渣土的塑流性,合理粉质黏土泥浆土水比为9∶11、焦磷酸钠掺量为3%,注入比为24%~28%。研究结果验证了粉质黏土泥浆用作盾构渣土改良剂的可行性,为废弃粉质黏土再利用提供了新思路。
