土石混合体的三轴数值模拟及宏细观变形分析

Triaxial Numerical Simulation and Macro-Micro Deformation Analysis of Soil-rock Mixture

筑坝料的力学特性能够直接影响心墙坝的沉降变形及结构稳定性,为究其根本原因,采用宏细观相结合的手段探究土石混合体的力学性能及内部变形破坏机制。以西藏澜沧江如美水电站工程为例,基于离散元颗粒流法开展大型三轴数值模拟试验,结果表明,随块石形态的不规则度提高,应力峰值出现节点提前、峰值强度明显增大并伴有显著软化特征,剪缩性不明显,剪胀性突出;剪切带由单一“工”字型向复杂“工”字型破坏形态演化,厚度由45 mm增至105 mm,最终鼓胀破坏面积成倍递增至35000 mm^(2);力链强度极值增大且数目增多。增大含石量也是提高试样峰值强度的关键;含石量较低时试样剪缩特性突出,剪胀特性不明显;随含石量增大,块石“齿轮”效应增强,剪切带破坏形态由光滑反“S”型向多条不规则剪切带过渡,厚度由47.5 mm增为105 mm,鼓胀破坏区面积从12800 mm^(2)演化至35000 mm^(2),强力链数目增长,力链强度极值由10.49 kN提高至164.30 kN。可选择不规则度高的块石并提高含石量以增强结构强度稳定性,研究结果可为工程后期稳定性评价及拟建大坝工作提供参考。

Since the mechanical properties of dam materials can directly affect the settlement deformation and structural stability of core wall DAMS,it is necessary to explore the mechanical properties of soil-rock mixture and the internal deformation and failure mechanism by means of macro and micro in order.Taking the Rumei Hydropower Station in Tibet in Lancang River as research background,particle flow code(PFC)method based on discrete element was used to carry out large-scale triaxial numerical simulation test.The results show that with irregular enhancement in the form of block stone,the stress peak nodes was in advance,peak strength increased obviously with significant softening characteristics,shear shrinkage was not obvious,and the dilatancy is prominent;The shear zone evolved from a single“工”shape to a complex“工”shape.The thickness increases from 45 mm to 105 mm,and the final swelling failure area increases exponentially to 35000 mm^(2).The extreme value and the number of force chain strength increased.Increasing the stone content was the key to improve the peak strength of the sample.When the rock content was low,the shear shrinkage characteristic was prominent,and the dilatancy characteristic was not obvious.With the increase of the stone content,the“gear”effect of the block stone was enhanced,and the shear zone failure mode was transitioned from smooth reverse“S”shape to multiple irregular shear zones,with the thickness increasing from 47.5 mm to 105 mm,the swelling failure area evolving from 12800 to 35000 mm^(2),and the number of strong chains increased.The extreme strength of the force chain was increased from 10.49 kN to 164.30 kN.In conclusion,it is suggested to select blocks with high irregularity and increase the stone content to enhance the structural strength stability.The research can provide reference for the stability evaluation of the project in the later stage and the work of the proposed dam.