Research on 3D mechanical properties of sludge solidified soil under the action of drying and wetting cycles
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摘要:
采用自主研发的新型固化剂对天津城市污泥进行固化处理，通过GCTS真三轴仪对污泥固化土进行不固结不排水试验，探讨其在干湿循环作用下的应力-应变特征和强度指标变化规律。试验结果表明：污泥固化土应力-应变曲线在初始阶段近似表现为线性关系，同等条件下，破坏应力随中主应力比b的增大而增大；相同b值下，破坏应力随干湿循环次数的增大而逐渐减小。经过干湿循环1，3，5，7，10次之后，不同围压下污泥固化土的破坏应力值均呈现下降趋势。当循环次数超过5次后，其降低幅度趋于平缓。在b值较小、循环次数小于3时，应力-应变曲线产生应变软化现象，随着围压和b值的增大表现为硬化型。污泥固化土c、φ值随干湿循环次数的增大呈现出降低趋势，并最终趋于稳定。在此基础上，对不同中主应力比条件下的c、φ值变化规律进行分析，分别建立其与干湿循环次数和中主应力比之间的关系式，并构建出能够考虑不同围压及中主应力比影响的初始弹性模量Ei和主应力差渐近值（σ1−σ3）ulti预测公式。
Abstract:A novel curing agent produced by our independent research and development is used to solidify the municipal sludge taken from Tianjin. GCTS true triaxial apparatus is used to conduct unconsolidated and undrained tests on the sludge solidified soil under different drying-wetting cycles. The stress-strain characteristics and strength index variation of the sludge solidified soil under drying-wetting cycles are investigated. The test results indicate that the stress-strain curve of the sludge solidified soil is approximately linear in the initial stage, and the failure stress increases with the increasing medium principal stress ratio b under the same conditions. At the same value of b, the failure stress decreases with the increasing number of drying-wetting cycles. After 1, 3, 5, 7 and 10 cycles, the failure stress values of the sludge solidified soil under different confining pressures all show the downward tendency. When the cycles are over 5 times, the reduction in the failure stress tends to be flat. When the value of b is small and the number of cycles is less than 3, strain softening occurs in the stress-strain curve, which appears as hardening with the increase of the confining pressure and the value of b. The values of c and φ of the sludge solidified soil show a decreasing trend with the increasing number of drying-wetting cycles, and finally tend to be stable. On this basis, the variation of values of c and φ under different principal stress ratios are analyzed, and the relationships between the values of c and φ and the number of drying-wetting cycles and the principal stress ratio are established respectively. Moreover, the prediction formula for the initial elastic modulus Ei and the asymptotic value of deviator stress (σ1−σ3)ulti which considers the influence of different confining pressures and the principal stress ratio is constructed.
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表 1 正交试验因素和水平
Table 1. Factors and levels of the orthogonal test
水平 影响因素 A B C D E 1 20%:80% 25% 5% 0.2% 0.1% 2 25%:75% 30% 10% 0.3% 0.2% 3 30%:70% 35% 15% 0.4% 0.3% 4 35%:65% 40% 20% 0.5% 0.4% 5 40%:60% 45% 25% 0.6% 0.5% 注：固化剂主剂、固化剂辅剂和水的质量均按照污泥和干土总质量的百分比添加。 
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表 2 正交试验结果分析
Table 2. Analysis of the orthogonal test results
指标 影响因素 A B C D E S1 1 039.40 803.90 387.30 768.70 771.60 S2 893.20 837.80 513.20 773.70 593.90 S3 805.40 876.40 805.40 902.70 840.70 S4 737.20 781.90 1 159.10 838.70 795.70 S5 639.10 998.70 875.60 891.90 897.80 M1 207.88 160.78 77.46 153.74 154.32 M2 178.64 167.56 102.64 154.74 118.78 M3 161.08 175.28 161.08 180.54 168.14 M4 147.44 156.38 231.82 167.74 159.14 M5 127.82 199.74 175.12 178.38 179.56 极差R 80.06 43.36 154.36 26.80 60.78
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表 3 不同中主应力比下的参数值
Table 3. Parameter values under different medium principal stress ratios
参数 b=0.00 b=0.25 b=0.50 b=0.75 b=1.00 A 4.298 4.412 4.803 5.067 5.278 B 2.808 3.389 3.818 4.261 4.430 D 23.165 23.896 25.637 26.350 26.677 R2 0.951 0.990 0.959 0.980 0.971 P 0.0225 0.0272 0.0283 0.0314 0.0323 S 1.1087 1.3929 1.6345 1.9064 2.0546 T 0.1992 0.1932 0.1862 0.1720 0.1576 R2 0.9744 0.9967 0.9815 0.9654 0.9942
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表 4 ε1/（σ1−σ3）～ ε1关系曲线趋势线
Table 4. Tendency lines of the relationship between ε1/（σ1−σ3）and ε1
应力-应变曲线 围压/kPa 趋势线 R2 第一段 20 y= 0.105x+0.095 0.986 40 y= 0.089x+0.094 0.989 60 y= 0.078x+0.082 0.991 第二段 20 y= 0.23x−0.02 0.994 40 y= 0.19x+0.01 0.999 60 y= 0.17x+0.01 0.999
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