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凝灰岩是一种典型的分布不规律、易崩解、难取样火山碎屑岩,其强度参数难以准确评估。本文依托华丽高速公路金沙江特大桥工程,判定丽江岸为反倾坡,为陡倾结构面或卸荷裂隙带剪入、缓倾结构面剪出组合滑移模式,破坏规模有限;华坪岸为顺层坡,为陡倾结构面或卸荷裂隙带剪入、凝灰岩层主滑、缓倾结构面剪出组合滑移模式,破坏规模较大。T3和T2凝灰岩软弱层为关键层,其强度参数对岸坡稳定性影响很大。针对此种情况提出了经验、试验、数值反分析相结合综合识别凝灰岩强度参数的方法。利用这种方法,在工程岩体分级标准GBT50218-2014、水利水电岩石力学参数手册、室内外试验、数值反分析的基础上,综合确定了凝灰岩带泥化参数为内摩擦角24°、粘聚力50k Pa、泥化率60%;凝灰岩层内摩擦角29°、粘聚力90k Pa,在工程经验取值的范围之内;玄武岩内摩擦角36°、粘聚力600k Pa,在水利水电工程岩石力学手册推荐值范围之内;IV陡倾结构面强度参数内摩擦角35°、粘聚力150k Pa,符合一般结构面试验经验值。经计算复核,埋深浅、局部分布的T3凝灰岩主滑模式下安全系数为1.65~2.15;埋深大、分布连续的T2凝灰岩主滑的安全系数为1.32~1.67,T2主控下的安全系数要比局部分布T3情况小约0.33~0.48,平均降低约21%。虽然T2主控下的最不利工况安全系数也大于1.30,但是在实际施工和运行过程中仍需关注T2凝灰岩层可能形成的深大滑移问题。类似和临近工程可参考该凝灰岩强度参数或强度参数综合识别方法。
Tuff is a typical distribution of irregular, easily disintegrated, difficult to sample volcaniclastic rocks, the intensity parameters are difficult to accurately estimate. Based on the project of Jinsha River Bridge of Gorgeous Expressway, this paper determined that the Lijiang River bank is anti-incline, cut into the steeply inclined structure surface or unloading fracture zone, and the gently-inclined structural surface cut out the combined slip mode, and the scale of the damage is limited; For the bedding slope, the steep-dumping surface or the unloading fracture zone, the main slippery tuff layer, the slow-dip structure cut the combined slip mode, the larger the damage. The weak layers of T3 and T2 tuffs are the key layers, and their strength parameters have a great influence on the stability of the bank. In view of this situation, a combination of experience, experiment and numerical back analysis is proposed to comprehensively identify the strength parameters of tuff. Based on the GBT50218-2014 standard of rock mass classification, manual of rock mechanics parameters of water conservancy and hydropower, indoor and outdoor tests and numerical back analysis, the mud parameters of the tuff zone are determined as follows: internal friction angle 24 °, cohesion 50k Pa, mud rate 60%; tuff friction angle 29 °, cohesion 90k Pa, within the range of engineering experience; basalt angle of 36 °, cohesion 600kPa, in the water conservancy and hydropower Engineering Manual of Rock Mechanics recommended value range; IV steep structural surface strength parameters of the internal friction angle of 35 °, the cohesion of 150k Pa, in line with the experience of the general structural plane test experience. The safety factor of main tuff of T3 tuff with the shallow buried depth and local distribution is 1.65 ~ 2.15. The safety coefficient of main slip of T2 tuff with large buried depth and continuous distribution is 1.32 ~ 1.67, and the safety factor under T2 main control Than the local distribution of T3 small about 0.33 ~ 0.48, an average reduction of about 21%. Although the most unfavorable operating condition safety factor under T2 control is more than 1.30, it is still necessary to pay attention to the deep slip problem that T2 tuff may form during the actual construction and operation. Similar and adjacent projects may refer to the tuff strength parameters or comprehensive identification of strength parameters.