【作者】 石茜；

【导师】 韩文峰； 谌文武；

【作者基本信息】 兰州大学 ， 地质工程， 2011， 博士

【摘要】 滨海盐渍土具有吸湿软化、盐胀和溶陷等不良工程特性,未经处理不能满足填筑高等级公路路堤的强度和变形要求,需要对盐渍土进行加筋或固化处理。通过无侧限抗压强度实验和三轴压缩实验,研究了稻草加筋土、稻草加筋石灰土的强度和应力应变。研究内容与取得成果如下：(1)完成了不同加筋条件的稻草加筋土、稻草加筋石灰土的无侧限抗压强度实验,直径50 mm高度50 mm试样的适宜加筋率和适宜加筋长度为0.2%和15 mm。在适宜加筋条件下,加筋土、加筋石灰土的抗压强度和抗变形能力明显提高。(2)加筋土的无侧限抗压强度随土干密度的增加而增加。低于或高于最优含水率时,土的强度均降低。均匀加筋方式的加筋效果优于层面加筋方式。二分之一圆管状稻草加筋土的强度最大。(3)浸水后加筋石灰土试样的抗压强度比相应未浸水的均有不同程度的降低。随养护龄期、石灰掺量的增加,加筋石灰土试样的强度和水稳系数有明显增长。加筋使水泥土的强度有所提高；石灰土、加筋石灰土的强度和水稳系数均高于水泥土、加筋水泥土的。(4)稻草的加筋作用能提高土的粘聚力,但对内摩擦角影响较小。直径61.8mm高度125 mm试样的适宜加筋率和适宜加筋长度分别为0.2%和20 mm。加筋能有效地约束土样的横向变形。只有达到一定的轴向应变时,稻草的加筋作用才能发挥出来。借助WU模型理论,建立了稻草加筋土的抗剪强度模型。(5)随干密度的增加,加筋土的峰值主应力差逐渐增加,粘聚力增加。含水率20%和24%加筋土的峰值主应力差、粘聚力和内摩擦角均比22%的小。中部均匀加筋土的峰值主应力差和粘聚力均高于上部均匀和下部均匀加筋土的。中部平铺加筋土的峰值主应力差和粘聚力比上部平铺、下部平铺加筋土的大。均匀加筋方式加筋土的强度大于平铺加筋的。与剥皮稻草加筋土相比,不剥皮稻草加筋土的峰值主应力差和粘聚力较小。与圆管状稻草加筋土相比,碾压状稻草加筋土的峰值主应力差和粘聚力较小,二分之一圆管状稻草的较大。不浸胶稻草加筋土试样的峰值主应力差、粘聚力与浸胶的相差不多。(6)进行CU实验的试样以塑性破坏为主,应力应变曲线接近应变硬化型。邓肯一张双曲线模型可较好的反映盐渍土和稻草加筋盐渍土的应力应变特性。CU实验中加筋土试样的粘聚力比UU的大,两种实验条件的内摩擦角相差不多。(7)石灰土具有明显的45。剪切面,呈脆性破坏；加筋石灰土不具有明显的剪切面,体现为较弱的塑性破坏。加筋石灰土的峰值主应力差、粘聚力和内摩擦角与加筋土的变化趋势基本相同。水泥土和加筋水泥土的粘聚力与内摩擦角均比石灰土和加筋石灰土的小。经加筋固化后,稻草加筋土的无侧限抗压强度和抗剪强度指标具有显著提高,实现了土质改性与加筋固化的目标。研究结果对于深入认识稻草加筋滨海盐渍土的加筋作用机制具有理论指导意义,可在滨海新区高等级公路路堤处理中推广应用,同时也为其它盐渍土地区的公路路堤处理提供技术参考。更多还原

【Abstract】 Saline soil in inshore has some problems, such as softening, expansion and depression, which make saline soil not meet the requirement of strength and deformation for road embankment if untreated. It could be considered that saline soil may be reinforced or solidified.Unconfined compressive strength tests and triaxial tests were carried out in order to understand the stress-strain relationship and strength property of reinforced soil and reinforced lime soil. Main contents and results are as follows:(1) The unconfined compressive strength in different conditions of reinforced soil and reinforced lime soil was tested. The best reinforced effect is of 15 mm reinforced length and 0.2% reinforced rate which the size of sample is diameter 50 mm and height 50 mm. Under the right reinforced condition, unconfined compressive strength and resistance to deformation of reinforced soil and reinforced lime soil significantly improved.(2) The unconfined compressive strength increased with the increasing of dry density. Below or above the optimum water content, the strength decreased. Homogeneous method of reinforced soil was better than the tiled. The strength of half round tubular rice straw was bigger than other form of reinforced material.(3) The unconfined compressive strength of reinforced lime soil after immersion in water decreased. With the increasing of conservation periods and lime content, the strength and water stability coefficient increased. Strength of cement soil increased after reinforced. Strength and water stability coefficient of cement soil and reinforced cement soil is less than that of lime soil and reinforced lime soil.(4) The triaxial test (UU) of reinforced soil indicated that the reinforcement improved mainly cohesion and less influence to the internal friction angle. The reinforced effect is best at reinforced length and rate of 20 mm and 0.2% separately which the size of sample is diameter 61.8 mm and height 125 mm. Rice straw may decrease availably the lateral deformation of reinforced saline soil. The reinforcement effect plays out only when soil sample arriving a certain axial strain. Strength model of reinforced soil with rice straw by WU Model theory was discussed.(5) Peak of deviator stress and cohesive increased along with dry density increasing. Peak of deviator stress, cohesive and internal friction angle of reinforced soil with 20% and 24% water content were less than that of 22%.Peak of deviator stress and cohesive of middle homogeneous and middle tiled were bigger than that of upper and lower. Homogeneous method of reinforced soil was better than the tiled.Compared with peeled rice straw, peak of deviator stress and cohesive of unpeeled rice straw were smaller. Compared with tubular rice straw, peak of deviator stress and cohesive was smaller than that of laminated rice straw, and bigger than that of half round tubular rice straw. The shear performance of reinforced soil with original rice straw was almost as same as that of anti-decayed rice straw.(6) The samples which doing CU tests showed plastic failure, their stress-strain were close to the hardening. By means of Duncan-Chang model, the stress-strain characteristic of saline soil and reinforced saline soil with rice straw can be well indicated. Cohesion of CU experiment sample was more than that of UU test. Their internal friction angle was almost the same.(7) Lime soil showed significantly 45°shear planes and brittle failure, while reinforced soil with lime showed insignificant shear planes, reflecting the weak plastic failure. Peak of deviator stress, cohesive and internal friction angle of reinforced soil with lime were almost as same as that of reinforced soil under different conditions when making samples. Cohesive and internal friction angle of cement soil and reinforced cement soil was less than that of lime soil and reinforced lime soil.After reinforced and solidified, unconfined compressive strength and shear strength parameters of reinforced soil with rice straw and lime have been significantly improved to achieve the objectives of improving strength of soil. The research results are of importance for understanding the mechanism of reinforced saline soil with rice straw. And it can be applied in dealing with high grade road embankment in Tianjin Binhai New Area while can provide technical reference for other saline soil region.更多还原