【摘要】：土石壩是壩工建設(shè)中首選的壩型之一,而其中采用黏土和礫石摻合而成的礫質(zhì)黏土(本文稱為寬級配礫質(zhì)土)經(jīng)碾壓后具有較高的密實度、抗剪強度、低壓縮性的特性,同時能滿足設(shè)計要求的防滲性能并有效降低了工程成本。因此對其工程性質(zhì)的研究已經(jīng)成為土石壩工程的一項重要研究內(nèi)容。本文依托國家自然科學(xué)基金(NO.41102167)、福州大學(xué)科技發(fā)展基金(NO.2011-XQ-12),對寬級配礫質(zhì)土開展三軸CD試驗研究。試驗分析了影響其固結(jié)歷時的相關(guān)因素,探討了對其剪切速率的選定,并修正了Gibson破壞歷時公式。首先,選取了影響三軸CD試驗固結(jié)歷時的四個重要因素,即摻礫量、圍壓、壓實度和排水條件。研究表明,摻礫量對固結(jié)歷時的影響主要和寬級配礫質(zhì)土的結(jié)構(gòu)性有關(guān),隨著摻礫量的增加,固結(jié)歷時相應(yīng)的減�。粨降[量在60%以上的試樣其固結(jié)歷時陡然減小。圍壓對固結(jié)歷時的影響是圍壓越大排水量越大,固結(jié)歷時也相應(yīng)增大。壓實度對固結(jié)歷時的影響相對較小,不同壓實度下試樣的固結(jié)系數(shù)相差不大。排水條件對固結(jié)歷時的影響是在同一摻礫量下,雙向排水的的試樣比單向排水的試樣其固結(jié)歷時大大減小,且在摻礫量較小時其固結(jié)歷時減少的程度更大。其次,研究了寬級配礫質(zhì)土三軸試驗剪切速率的選取。為此進行了不同剪切速率下的三軸CD試驗,然后通過改變摻礫量和壓實度,分析了不同剪切速率下試樣中未消散孔隙水壓力的變化規(guī)律。研究表明,試樣剪切速率越大,試樣中未消散孔隙水壓力的峰值也越大。在同一剪切速率下,孔壓上升的峰值會隨著摻礫量的增大而變小,且在剪切速率變大的情況下,摻礫量小的試樣其孔壓峰值的增幅越大。在同一剪切速率下,改變壓實度對剪切試驗中孔壓的影響較小。再者,基于寬級配礫質(zhì)土三軸CD試驗成果,討論了Gibson三軸剪切破壞歷時公式對寬級配礫質(zhì)土的適用性,在此基礎(chǔ)上,通過結(jié)合試驗實測值與Gibson公式理論計算值的進行對比分析總結(jié),對Gibson三軸剪切破壞歷時公式進行了改進,在原有公式的基礎(chǔ)上增加了一個系數(shù)A,A是一個與摻礫量有關(guān)的參數(shù),使其能適用于寬級配礫質(zhì)土。最后用試驗佐證了未消散孔隙水壓力的峰值與剪切速率的關(guān)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.
【學(xué)位授予單位】：福州大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TV41

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