Soil was solidified with both lime and fibers to investigate the mechanical properties of the soil. Wheat straw, rice straw, jute and polypropylene fiber was added to the soil and lime-soil respectively. Unconfined compressive test of the fiber-soil was conducted to confirm the optimal fiber content and optimal fiber length. Triaxial compressive test of fiber-lime-soil was carried out to study the shear strength, deviatoric stress-strain properties and sample failure pattern. The results are as follows: Optimal fiber content was 0.2% or 0.25%, and the optimal fiber length was 30% or 40% of the sample diameter. Reinforcement significantly increased the cohesion and lightly improved the internal friction angle. The cohesion increments of polypropylene fiber-lime-soil, jute-lime-soil, rice straw-lime-soil and wheat straw-lime-soil were decreased in turn. The four kinds of fiber may all improve the strength and deviatoric stress-strain properties of soil and lime-soil, in which polypropylene fiber for reinforcement is the best.

以稻草和麦秸秆加筋滨海盐溃土,可提高土的强度和抗变形能力.使用SH胶对稻草和麦秸秆进行防腐处理,完成了防腐前后的吸水实验和极限拉伸实验.对比实验结果得知:①天然和浸胶稻草的吸水率均比麦秸秆的大;②浸胶提高了稻草与麦秸秆的极限拉力和极限延伸率;③浸胶稻草的吸水率的降低率、极限延伸率的增长率和极限拉力的增长率均低于浸胶麦秸秆的;④天然、浸海水、浸胶、浸胶后再浸海水稻草的极限延伸率和极限拉力均高于相应麦秸秆的.稻草和麦秸秆均适宜作加筋材料使用.应用在加筋土中,稻草比麦秸秆具有更良好的抗拉性能及协调土的变形能力.在浸胶后的防腐效果及其增强抗拉性能上,麦秸秆优于稻草.

Saline soil is reinforced with anti-corrosive rice straw marinated in SH agent, and the unconfined com-pressive test and triaxial shear test (UU) on reinforcement are carried out immediately in the condition of three dry densities and three water content of saline soil. It has been proved that (1) compressive strength and shear strength are high, and anti-deformation is remarkable in great density, (2) the strength are high and anti-deforma- tion of reinforced soil reduces with the increase of water content, (3) reinforcement with rice straw increases the cohesion and anti-deformation, but has small impact on internal friction angle, (4) reinforcing effect is very well in the con-dition of maximum dry density and optimum water content. Research results can be used as a guide for engineering construction.

Such problems of saline soil,as inferior strength and more deformation which result from crystallizing and dissolving of the salt in soil can be treated by reinforcing the anti-decayed rice straw by means of unconfined compressive test and triaxial shear test on the saline soil reinforced with the rice straw under the condition of six reinforcing length and five reinforcing rate.The results indicate that the suitable reinforced condition on the sample in diameter of 50 mm is of the reinforcing length of 15 mm and of reinforcing rate of 0.2% for unconfined compressive test,and the reinforcing length and the reinforcing rate of 20 mm and 0.2% is suitable reinforced condition on triaxial shear sample in diameter of 61.8 mm,with the best reinforcement effects.The reinforcement increases mainly the cohesion and exerts little influence on the internal friction angle.The rice straw decreases evidently the lateral deformation of the reinforced saline soil only when the sample going a certain axial strain.The results give the guidance for studying the strength and deformation of the reinforced saline soil at some reinforcing condition and some size of sample.

The reinforcement effect and strength of reinforced soil depending on a suitable reinforced position and triaxial shear test for reinforced lime-soil with wheat straw in three positions was carried out in this paper.First,reinforced position mainly affects the cohesion of reinforced soil,but has little influence on the internal friction angle;reasonable reinforced position plays an important role in improving strength of reinforced soil.Second,lime-soil displays failure in brittle manner;failure of reinforced lime-soil is located in un-reinforced region;the deformation in reinforced region decreases.Third,shear angle of lime-soil and reinforced lime-soil with wheat straw conform to the Mohr-Coulomb failure criterion and SMP(spatial mobilization plane) failure criterion.By the function of high tensile strength,space interweaving and load-sharing of wheat straw,the strength and anti-deformation of reinforced soil is improved.

Anti-decayed rice straw may be used to reinforce saline soil in inshore of Northern China. Water absorption, maximum elongation and maximum tension of rice straw, including rice straw soaked in seawater, running water and seawater after SH agent has been tested, and anti-decay effect is evaluated based on grey correlative method. The experimental results showed that water absorption of rice straw soaked in seawater and running water increased with soaking time. And maximum elongation and maximum tension decreased with soaking time. The reduction rate of water absorption was the greatest when the rice straw was soaked in seawater after SH agent for 14-day and which had the biggest maximum elongation and maximum tension yet. According to grey correlative method, the relational degrees of water absorption, maximum elongation and maximum tension for 14-day are the biggest. It means that anti-decay effect is the best in this condition. Taking rice straw which soaked in seawater after SH agent for 7-day as example, correlation coefficients of water absorption, maximum elongation and maximum tension increase with soaking time. It indicates that the longer soaking time is, the better anti-decay effect of rice straw is. Evaluating anti-decay effect of rice straw according to grey correlative method and analyzing the laboratory results respectively, they are highly consistent. Grey correlative method is a suitable one for evaluating the anti-decay effect of rice straw.

Saline soil in inshore has some problems which were resulted from crystallizing and dissolving in salt and water absorption of soil.It must be treated in the stage of engineering construction.It has been suggested that rice straw can be anti-decayed with SH agent and used for reinforcing saline soil.Some tests were carried out in order to study the water content,maximum tension and maximum elongation of rice straw in condition of natural,soaked in water,soaked in SH agent and soaked in water after SH agent respectively.The results indicate that:(1) The water content of rice straw soaked in SH agent is obviously less than of natural rice straw,the biggest decreasing rate is 50%.(2) The maximum elongation and maximum tension of rice straw soaked in SH agent is more than those of natural rice straw,with the biggest increasing rate of 26% and 23%.(3) The maximum elongation and maximum tension of rice straw soaked in seawater after in SH agent is more than those soaked in seawater,with the biggest increasing rate of 12% and 11%.(4) Results of SEM and EDS test show that SH agent infiltrates into voids of rice straw and enhances the connection of fiber.In future,SH agent can be used to slow down the decay of rice straw and reinforcing saline soil with rice straw is feasible.

Strength and stability of reinforced soil depends on intercrossing and tensility of reinforced materials, and friction between reinforced material and soil. By means of SEM photos, it is observed that SH agent is infiltrated through the pore of wheat straw, and adhered to its surface. For studying its tensility, maximum tensile and elongation of wheat straw with one stem node and without stem node, is tested in the condition of original, soaked in sea water, marinated in SH agent, and soaked in sea water after marinating in SH agent. It has been certified that the maximum tensile and elongation of wheat straw without stem node is more than that of wheat straw with one stem node. Respectively comparison on the marinated in SH agent and original, and soaked in sea water after marinating in SH agent and soaked in sea water, the maximum tensile and elongation of wheat straw marinated in SH agent is more than that of original wheat straw. SH agent benefits to increase the tensility of wheat straw.

Triaxial compression tests of reinforced saline soil with wheat straw and lime,reinforced uniformly at upper,lower and whole positions,were carried out to research the effect of reinforced position on stress-strain and shear strength characteristics. Moreover,strength model of reinforced saline soil with wheat straw and lime was discussed by WU model theory. The results show as follows:(1) Shear strength and anti-deformation capacity of lime soil in three reinforced positions are improved. (2) Reinforced position is related to the increase in cohesion, but has little effect on the internal friction angle. (3) Shear strength of reinforced saline soil with reinforcement in lower position is larger than that in whole and upper positions;and the reinforcement of lower position is helpful to the reinforcement function. (4) Strength model of reinforced soil with wheat straw shows that strength of reinforced soil is closely related to the distribution pattern of wheat straw. The research results are of important guidance for understanding the reinforcement mechanism of reinforced soil with natural fiber material.