宽级配砾质土三轴CD试验研究
发布时间：2018-09-11 14:26
【摘要】：土石坝是坝工建设中首选的坝型之一,而其中采用黏土和砾石掺合而成的砾质黏土(本文称为宽级配砾质土)经碾压后具有较高的密实度、抗剪强度、低压缩性的特性,同时能满足设计要求的防渗性能并有效降低了工程成本。因此对其工程性质的研究已经成为土石坝工程的一项重要研究内容。本文依托国家自然科学基金(NO.41102167)、福州大学科技发展基金(NO.2011-XQ-12),对宽级配砾质土开展三轴CD试验研究。试验分析了影响其固结历时的相关因素,探讨了对其剪切速率的选定,并修正了Gibson破坏历时公式。首先,选取了影响三轴CD试验固结历时的四个重要因素,即掺砾量、围压、压实度和排水条件。研究表明,掺砾量对固结历时的影响主要和宽级配砾质土的结构性有关,随着掺砾量的增加,固结历时相应的减小；掺砾量在60%以上的试样其固结历时陡然减小。围压对固结历时的影响是围压越大排水量越大,固结历时也相应增大。压实度对固结历时的影响相对较小,不同压实度下试样的固结系数相差不大。排水条件对固结历时的影响是在同一掺砾量下,双向排水的的试样比单向排水的试样其固结历时大大减小,且在掺砾量较小时其固结历时减少的程度更大。其次,研究了宽级配砾质土三轴试验剪切速率的选取。为此进行了不同剪切速率下的三轴CD试验,然后通过改变掺砾量和压实度,分析了不同剪切速率下试样中未消散孔隙水压力的变化规律。研究表明,试样剪切速率越大,试样中未消散孔隙水压力的峰值也越大。在同一剪切速率下,孔压上升的峰值会随着掺砾量的增大而变小,且在剪切速率变大的情况下,掺砾量小的试样其孔压峰值的增幅越大。在同一剪切速率下,改变压实度对剪切试验中孔压的影响较小。再者,基于宽级配砾质土三轴CD试验成果,讨论了Gibson三轴剪切破坏历时公式对宽级配砾质土的适用性,在此基础上,通过结合试验实测值与Gibson公式理论计算值的进行对比分析总结,对Gibson三轴剪切破坏历时公式进行了改进,在原有公式的基础上增加了一个系数A,A是一个与掺砾量有关的参数,使其能适用于宽级配砾质土。最后用试验佐证了未消散孔隙水压力的峰值与剪切速率的关系。
[Abstract]:Earth-rock dam is one of the preferred dam types in dam construction, and the gravel clay mixed with clay and gravel has the characteristics of high compactness, shear strength and low compressibility after compaction. At the same time, it can meet the design requirements and effectively reduce the project cost. Therefore, the study of its engineering properties has become an important research content of earth-rock dam engineering. Based on the National Natural Science Foundation (NO.41102167) and Fuzhou University Science and Technology Development Foundation (NO.2011-XQ-12), this paper carried out triaxial CD test on boulder soil with wide gradation. The related factors affecting the consolidation duration were analyzed, the selection of shear rate was discussed, and the Gibson failure duration formula was revised. Firstly, four important factors affecting the consolidation duration of triaxial CD test are selected, that is, the amount of gravel, the confining pressure, the compaction degree and the drainage condition. The results show that the influence of gravel content on the consolidation duration is mainly related to the structure of boulder soil with wide gradation. With the increase of gravel content, the consolidation duration decreases correspondingly, and the consolidation duration decreases sharply when the gravel content is more than 60%. The effect of confining pressure on consolidation duration is that the larger the confining pressure, the greater the discharge, and the more the consolidation duration is. The influence of compaction degree on consolidation duration is relatively small, and the coefficient of consolidation is not different under different compaction degrees. The effect of drainage condition on consolidation duration is that the consolidation duration of bidirectional drainage specimen is much smaller than that of unidirectional drainage sample with the same amount of gravel, and the consolidation duration of bidirectional drainage sample is much larger than that of unidirectional drainage sample, and the consolidation duration of bidirectional drainage sample decreases more than that of unidirectional drainage sample. Secondly, the selection of shear rate of wide gradation grained gravel soil under triaxial test was studied. The triaxial CD test at different shear rates was carried out, and the variation of undissipated pore water pressure at different shear rates was analyzed by changing the amount of gravel and compaction. The results show that the higher the shear rate, the greater the peak value of the undissipated pore water pressure. At the same shear rate, the peak value of pore pressure will decrease with the increase of gravel content, and the larger the shear rate, the larger the increase of pore pressure peak. At the same shear rate, the change of compaction degree has little effect on the pore pressure in shear test. Furthermore, based on the results of triaxial CD test of boulder soil, the applicability of Gibson triaxial shear failure time formula to boulder soil is discussed. By comparing and analyzing the experimental data and the theoretical calculation value of Gibson formula, the formula of triaxial shear failure duration of Gibson is improved. Based on the original formula, a coefficient A A is added as a parameter related to the amount of gravel added. So that it can be used in wide grained gravel soil. Finally, the relationship between the peak value of undissipated pore water pressure and shear rate is verified by experiments.
【学位授予单位】：福州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV41
本文编号：2236953
[Abstract]:Earth-rock dam is one of the preferred dam types in dam construction, and the gravel clay mixed with clay and gravel has the characteristics of high compactness, shear strength and low compressibility after compaction. At the same time, it can meet the design requirements and effectively reduce the project cost. Therefore, the study of its engineering properties has become an important research content of earth-rock dam engineering. Based on the National Natural Science Foundation (NO.41102167) and Fuzhou University Science and Technology Development Foundation (NO.2011-XQ-12), this paper carried out triaxial CD test on boulder soil with wide gradation. The related factors affecting the consolidation duration were analyzed, the selection of shear rate was discussed, and the Gibson failure duration formula was revised. Firstly, four important factors affecting the consolidation duration of triaxial CD test are selected, that is, the amount of gravel, the confining pressure, the compaction degree and the drainage condition. The results show that the influence of gravel content on the consolidation duration is mainly related to the structure of boulder soil with wide gradation. With the increase of gravel content, the consolidation duration decreases correspondingly, and the consolidation duration decreases sharply when the gravel content is more than 60%. The effect of confining pressure on consolidation duration is that the larger the confining pressure, the greater the discharge, and the more the consolidation duration is. The influence of compaction degree on consolidation duration is relatively small, and the coefficient of consolidation is not different under different compaction degrees. The effect of drainage condition on consolidation duration is that the consolidation duration of bidirectional drainage specimen is much smaller than that of unidirectional drainage sample with the same amount of gravel, and the consolidation duration of bidirectional drainage sample is much larger than that of unidirectional drainage sample, and the consolidation duration of bidirectional drainage sample decreases more than that of unidirectional drainage sample. Secondly, the selection of shear rate of wide gradation grained gravel soil under triaxial test was studied. The triaxial CD test at different shear rates was carried out, and the variation of undissipated pore water pressure at different shear rates was analyzed by changing the amount of gravel and compaction. The results show that the higher the shear rate, the greater the peak value of the undissipated pore water pressure. At the same shear rate, the peak value of pore pressure will decrease with the increase of gravel content, and the larger the shear rate, the larger the increase of pore pressure peak. At the same shear rate, the change of compaction degree has little effect on the pore pressure in shear test. Furthermore, based on the results of triaxial CD test of boulder soil, the applicability of Gibson triaxial shear failure time formula to boulder soil is discussed. By comparing and analyzing the experimental data and the theoretical calculation value of Gibson formula, the formula of triaxial shear failure duration of Gibson is improved. Based on the original formula, a coefficient A A is added as a parameter related to the amount of gravel added. So that it can be used in wide grained gravel soil. Finally, the relationship between the peak value of undissipated pore water pressure and shear rate is verified by experiments.
【学位授予单位】：福州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV41
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