裂隙砂岩注浆前后渗流特性及注浆后力学特性试验研究

Experimental study of seepage characteristics before and after grouting and mechanical characteristics after grouting of fractured sandstone

为探究裂隙砂岩注浆前后渗流特性及注浆后力学特性变化规律,利用Rock Top多场耦合试验仪在不同围压下以0.02 mm/min的恒定速率对砂岩进行三轴压缩试验得到裂隙砂岩并进行渗流试验,进而采用自主研制的注浆加固系统对裂隙砂岩进行注浆加固,再利用Rock Top多场耦合试验仪对注浆后的裂隙砂岩在不同围压下进行三轴压缩渗流试验。结果表明:(1)裂隙砂岩注浆后的渗透率相对于注浆前显著降低,下降幅度在24.26%~96.55%之间,但均大于原岩渗透率;(2)裂隙砂岩注浆前、后的渗透率随静水压等梯度增加呈现出不同的阶段性变化规律,并且当静水压达40 MPa及以上时,5 MPa以内的渗透压差对渗透率影响较小,渗透率曲线趋于水平;(3)裂隙砂岩注浆后仅在10 MPa围压下表现出同原岩类似的脆性破坏特征,在20~60 MPa围压下则失去了原岩的脆性破坏特征,表现出很强的延性破坏,并在峰后出现塑性流动现象;(4)裂隙砂岩注浆后的峰值强度、峰值应变皆随围压的增大而增大,并呈现出满足二次函数关系的非线性变化特征,其峰值强度介于原岩峰值强度的44%~59%之间;(5)裂隙砂岩注浆后的破坏形式以滑移剪切破坏为主,低围压下会伴随有新破坏形式产生,随着围压增大,破坏程度减弱;(6)岩-浆界面电镜扫描试验表明,钙矾石与C-S-H(水化硅酸钙)凝胶相互搭接形成了稳定的水化产物,从而提升了岩石承载力。

This study aims to explore the seepage characteristics of fractured sandstone before and after grouting and the change rule of mechanical properties after grouting.Firstly,Rock Top multi-field coupling tester was used to conduct triaxial compression test on sandstone under different confining pressures at a constant rate of 0.02 mm/min to obtain fractured sandstone and conduct seepage test.Then,the self-developed grouting reinforcement system was used to reinforce the fractured sandstone,and the Rock Top multi-field coupling tester was used to conduct the triaxial compression seepage test on the fractured sandstone under different confining pressures.The results show that:(1)The permeability of fractured sandstone decreases significantly after grouting compared with that before grouting,with a decrease range of 24.26%-96.55%,but it is greater than the original rock permeability.(2)The permeability of fractured sandstone before and after grouting shows different periodic changes with the increase of hydrostatic pressure.When hydrostatic pressure reaches 40 MPa or above,the permeability difference within 5 MPa has a little effect on permeability,and the permeability curve tends to be horizontal.(3)After grouting,the fractured sandstone only exhibits brittle failure characteristics similar to the original rock only under 10 MPa confining pressure,but loses the brittle failure characteristics of the original rock under 20−60 MPa confining pressure,showing strong ductility failure and plastic flow phenomenon after the peak.(4)The peak strength and strain of the fractured sandstone after grouting both increase with the increase of confining pressure and show nonlinear variation characteristics satisfying the quadratic function relation.The peak strength ranges from 44%to 59%of the peak strength of the original rock.(5)The failure mode of fractured sandstone after grouting is mainly slip-shear failure,and new failure modes will appear under low confining pressure.With the increase of confining pressure,the failure effect weakens.(6)Scanning electron microscopy test on rock-slurry interface shows that ettringite and C-S-H(calcium silicate hydrate)gel are bonded to form stable hydration products,thus improving the bearing capacity of rock.