湖淤积高液限粘土用作路基填料的物理力学特性研究

发布时间：2019-06-09 13:31

【摘要】：黄泛区湖淤积高液限粘土或以湖相沉积层、或以粉土夹层广泛分布于鲁西南-鲁西北平原区,其塑性和粘性较高,水稳定性差,难以压实。目前在此类地区修建道路时,一般按规范要求,采用换填或改性处理的方法,造成土地资源的浪费,增加工程造价。因此,研究湖淤积高液限粘土的直接利用与经济改性技术,具有重大的理论意义与工程应用价值。本研究选取济徐高速公路沿线的典型湖淤积高液限粘土,通过室内试验研究其物理、力学特性,以揭示该类土的压实特性以及在不同含水率与压实度状态下的强度变化规律。同时,针对路床区填料强度要求,对该类土进行改性研究。采用FLAC3D软件分析该类土填筑路基的变形稳定性,提出该类土用作路基填料碾压控制含水率、压实度的临界指标。室内试验及数值模拟结果表明：(1)黄泛区湖淤积高液限粘土的颗粒组成以粉粒和粘粒为主,粘土矿物含量高,其塑性指数高而塑限偏低。因此,该类土兼有粉土与高液限粘土的性质,表现出高的粘滞力、强的吸湿性和保水性,其压实过程中对水敏感性强,高于最佳含水率以后4%后饱和度较高,压实易出现弹簧现象。(2)该类土的CBR值、抗剪强度、回弹模量及压缩模量等力学性质指标表现出相同的规律性,随压实度的增加而增加,随含水率的增加而降低。该类土的水稳定性差,含水率是影响其力学性质的主要因素。在含水率不高于最佳含水量4%、压实度90%以上时,其强度较高,不浸水CBR值满足规范对路堤区填料最低要求。(3)石灰改性和小剂量石灰与粉煤灰的改性效果较好,掺灰拌合后的闷料时间宜为3～4天。改性土的CBR强度在压实度90%以上时可达10%以上,满足规范对路床区填料的最小承载比要求。(4)黄泛区湖淤积高液限粘土用作路基填料时,路堤区的碾压控制含水率在最佳含水率的基础上提高4%、压实度较规范标准降低3个百分点后,路基的变形与稳定性可满足路用要求。
[Abstract]:The lake siltation of high liquid limit clay or lacustrine sedimentary layer or silt interlayer is widely distributed in the southwest Shandong-northwest Shandong plain in the Yellow River flooding area. The plasticity and viscosity of the lake are high and the water stability is poor, so it is difficult to compaction. At present, when building roads in this kind of area, according to the requirements of the code, the method of replacement and filling or modification is generally adopted, which results in the waste of land resources and increases the cost of the project. Therefore, it is of great theoretical significance and engineering application value to study the direct utilization and economic modification technology of high liquid limit clay in lake siltation. In this study, the typical lake silted high liquid limit clay along Jixu Expressway was selected to study its physical and mechanical properties through laboratory tests in order to reveal the compaction characteristics of this kind of soil and the variation of strength under different water content and compaction conditions. At the same time, according to the requirement of packing strength in road bed area, the modification of this kind of soil was studied. The deformation stability of subgrade filled with this kind of soil is analyzed by FLAC3D software, and it is put forward that this kind of soil can be used as a critical index to control moisture content and compaction degree of subgrade filling. The results of laboratory test and numerical simulation show that: (1) the particle composition of high liquid limit clay in lake siltation in the flood area of the Yellow River is mainly silt and clay, the clay mineral content is high, the plastic index is high and the plastic limit is on the low side. Therefore, this kind of soil has the properties of both silt and high liquid limit clay, showing high viscosity, strong hygroscopicity and water retention, and has strong sensitivity to water in the compaction process, which is higher than that of 4% after the optimum moisture content. Compaction is easy to appear spring phenomenon. (2) the mechanical properties of this kind of soil, such as RR value, shear strength, springback modulus and compression modulus, show the same regularity, increase with the increase of compaction degree, and decrease with the increase of moisture content. The water stability of this kind of soil is poor, and the moisture content is the main factor affecting its mechanical properties. When the moisture content is not higher than the optimum water content 4% and the compaction degree is more than 90%, the strength is higher, and the CBR value of non-immersion meets the minimum requirements of the code for embankment filling. (3) the modification effect of lime modification and low dose lime and fly ash is better. The stuffing time after mixing with ash should be 3 times 4 days. The CBR strength of the modified soil can reach more than 10% when the compaction degree is more than 90%, which meets the requirements of the code for the minimum bearing ratio of the filling in the road bed area. (4) when the lake siltation high liquid limit clay is used as subgrade filling in the flood area of the Yellow River, After the rolling control moisture content of embankment area is increased by 4% on the basis of the optimum moisture content, and the compaction degree is reduced by 3% compared with the standard, the deformation and stability of subgrade can meet the requirements of road use.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U416.1

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