风化砂改良膨胀土特性试验研究

发布时间：2018-02-13 14:11

本文关键词： 风化砂改良膨胀土物理特性胀缩特性强度特性工后沉降　出处：《三峡大学》2014年硕士论文　论文类型：学位论文

【摘要】：在膨胀土地区修建公路时，往往需要对膨胀土进行改良处理，目前工程实践中常用石灰、粉煤灰和水泥等无机结合料改良膨胀土，利用无机结合料改良膨胀土，可以改善膨胀土的工程性质，但是存在施工控制困难、污染环境、成本过高等不足之处。本文结合宜昌市风化砂广泛分布的特点，依托小溪塔至鸦鹊岭一级公路改建工程，对不同比例风化砂改良膨胀土的物理性质、胀缩特性以及力学强度特性进行了室内试验研究，得到了不同掺砂比例下风化砂改良膨胀土的特性指标，以及掺砂比例对改良土工程特性的影响规律，同时结合小溪塔至鸦鹊岭一级公路改建工程进行了现场试验监测。本文的主要结论如下：对质量比0%、10%、20%、30%、40%、50%风化砂改良膨胀土的物理性质、胀缩特性和强度特性进行了研究。通过对物理性质研究可知，掺砂能够改善膨胀土的含水特性、压实特性、及超固结性，且改善的效果随着掺砂比例的增加先增大后逐渐趋于平缓；通过对胀缩特性的研究表明，掺入风化砂能够有效的抑制膨胀，改善膨胀土的收缩特性；改良膨胀土的胀缩指标随着掺砂比例的增大逐渐减小，无荷膨胀率随着掺砂比例的改变呈线性减小；当掺砂比例大于20%时，改良土的胀缩总率小于0.7%，自由膨胀率小于40%,达到路基施工技术规范对路基填料要求；通过对力学强度指标的研究可知，掺砂可以明显的提高膨胀土的强度，达到路基填料的要求；掺入风化砂对于膨胀土的内摩擦角的影响较小，对膨胀土的黏聚力影响较大；随着掺砂比例的增大，改良土的无侧限抗压强度和回弹模量先增大后减小，当掺砂比例为10%时，此时无侧限抗压强度和回弹模量达到最大值；随着掺砂比例的增大，改良膨胀土的CBR值逐渐增大，且增长趋势先快后慢。综合技术经济指标分析，确定施工配合比，同时进行了试验路段的铺筑和现场试验监测。综合考虑技术经济指标，，确定掺入20%风化砂为施工配合比；同时对小溪塔至鸦鹊岭一级公路风化砂改良膨胀土填筑路基连续3个月的工后沉降进行观测，观测结果显示月平均沉降速率2.1mm，满足设计小于3mm的要求，从第三周开始，该试验路段路基的沉降基本趋于稳定，从工程实际上验证了风化砂改良膨胀土的可行性。
[Abstract]:In the construction of highway in expansive soil area, it is often necessary to improve the expansive soil. In current engineering practice, inorganic binders such as lime, fly ash and cement are commonly used to improve expansive soil, and inorganic binder is used to improve expansive soil. The engineering properties of expansive soil can be improved, but there are some shortcomings such as difficult construction control, environmental pollution, high cost and so on. According to the characteristics of widespread distribution of weathered sand in Yichang City, this paper relies on the reconstruction project of Xiaoxita to Yakueling first class highway. The physical properties, dilatation and shrinkage characteristics and mechanical strength characteristics of expansive soil improved by weathered sand with different proportion were studied in laboratory. The characteristic indexes of weathered sand modified expansive soil with different proportion of sand were obtained. The influence of sand ratio on the characteristics of the improved soil is also studied. Combined with the first class highway reconstruction project from Xiaoxita to Ya que Ling, the field test monitoring is carried out. The main conclusions of this paper are as follows:. In this paper, the physical properties, dilatation and shrinkage characteristics and strength characteristics of the expansive soil improved by 50% weathered sand are studied. Through the study of the physical properties, it can be seen that the mixing sand can improve the water-bearing, compaction, and over-consolidation properties of the expansive soil. With the increase of the ratio of sand to sand, the effect of improvement increases first and then tends to be gentle. The study of dilatation and shrinkage characteristics shows that the addition of weathered sand can effectively inhibit the expansion and improve the shrinkage characteristics of expansive soil. The swelling and shrinkage index of the improved expansive soil decreases with the increase of the ratio of sand to sand, and the load free expansion rate decreases linearly with the change of the ratio of sand to sand, and when the ratio of sand to sand is greater than 20, The total expansion rate of the improved soil is less than 0.7 and the free expansion rate is less than 40, which can meet the requirements of the subgrade filling in the technical specifications of subgrade construction. Through the study of the mechanical strength index, it can be seen that the strength of the expansive soil can be obviously increased by adding sand, The influence of weathering sand on the internal friction angle of expansive soil is small, and on the cohesion of expansive soil is greater, with the increase of sand ratio, the unconfined compressive strength and modulus of resilience of the improved soil first increase and then decrease. When the sand ratio is 10, the unconfined compressive strength and modulus of resilience reach the maximum; with the increase of the ratio of sand, the CBR value of the improved expansive soil increases gradually, and the growth trend is first fast and then slow. According to the analysis of the technical and economic indexes, the construction mix ratio is determined, and the paving and field test monitoring of the test section are carried out. Considering the technical and economic indexes, the mixing of 20% weathered sand is determined as the construction mix ratio. At the same time, the post-construction settlement of weathered sand improved expansive soil filling subgrade for 3 months on the first class highway from Xiaoxita to Ya que Ling is observed. The results show that the average monthly settlement rate is 2.1 mm, which meets the requirement of design less than 3 mm and starts from the third week. The settlement of the roadbed in this experimental section tends to be stable, and the feasibility of improving expansive soil by weathering sand is verified by the project.
【学位授予单位】：三峡大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU443;TU411

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