基于单三轴试验与直剪试验的层状软岩模拟

为探究模型试验中层状软岩模拟方法，依托九绵高速层状软岩隧道现场取样的室内试验结果，多次试验确定重晶石粉、石英砂、石膏粉、滑石粉和水的最优配比以模拟软岩基体，采用带孔薄膜模拟层理弱面的黏结作用，并通过直剪试验确定孔隙率，最后对不同层理角度与层理厚度的试样开展直剪与单、三轴试验以反映各向异性情况。结果表明：软岩基体模拟最优配比为0.55:0.15:0.07:0.06:0.17，重晶石粉对强度及破坏变形起决定作用，含量过低易压溃，含量过高产生上下贯通裂缝；采用30%孔洞率的薄膜模拟层理效果最佳；土样强度随层角呈U形变化，层厚减小（不小于2 cm），强度减小。直剪试验中，45º层理剪切面朝层理方向倾斜，90º层理导致剪切面上下产生裂缝与碎裂，单三轴结果中，0º层理会产生小角度倾斜裂缝，45º层理产生垂直层理面的斜裂缝及二次破裂，90º层理产生顺层理的竖向劈裂；与现场结果对照后确定最优层厚为 3 cm，对层角与层厚的直剪与单三轴试验结果整体一致，揭示土样孔隙压密闭合?弹性?塑性胀裂破坏?徐变的过程。

Layered soft rock simulation based on uniaxial and triaxial tests and direct shear test

In order to explore the simulation method of layered soft rock in model experiment, relying on the indoor test results of samples selected from a layered soft rock tunnel of Jiuzhaigou-Mianyang Expressway, the optimal ratio of barite powder, quartz sand, gypsum powder, talc powder and water was determined by many tests to simulate soft rock matrix. The film with holes was used to simulate the adhesion of weak surface of bedding, and the porosity was determined by direct shear test. And direct shear and uniaxial and triaxial tests were carried out on the samples with different bedding angles and thickness to reflect the anisotropy. The optimal ratio of soft rock matrix simulation is 0.55:0.15:0.07:0.06:0.17. Barite powder plays a decisive role in strength and failure deformation. Barite content is too low for easy crushing and too high for producing top-to-bottom penetration cracks. The film with 30% porosity has the best effect on simulating bedding. The strength of soil sample changes in U-shape with the layer angle, and the strength decreases with the decrease of the thickness of layers (no less than 2 cm). In the direct shear test, the shear plane of 45º bedding is inclined to the direction of bedding, while the shear plane of 90º bedding leads to cracks and fractures on both sides of the shear plane. In uniaxial and triaxial results, for 0º bedding, small angle inclined cracks generate, for 45º bedding inclined cracks perpendicular to the bedding plane and secondary cracks arise, and for 90º bedding vertical splitting along bedding plane emerges. The optimal layer thickness is determined to be 3 cm after compared with the field results. The direct shear test of layer angles and thickness is consistent with the results of uniaxial and triaxial tests, revealing the process of pore compaction closure-elastic-plastic expansion crack failure-creep of soil samples.