饱和软黄土隧道围岩注浆加固参数研究

研究目的:饱和软黄土地层隧道围岩具有强度低、承载力差、抗变形能力弱等特性,因此对饱和软黄土地层隧道围岩注浆加固参数展开研究具有重要意义。依托西安地铁4号线火车站站暗挖西安火车站工程,进行室内黄土力学性能和现场注浆试验,研究含水率对黄土强度特性的影响,分析黄土劈裂注浆浆液扩散的基本规律及劈裂机理,并总结现场隧道围岩注浆加固参数。研究结论:(1)饱和软黄土的含水率降低,其强度呈线性增长,因此注浆后降低了原位土体的渗透性能以及提升土体的黏聚力,整体上提升土体的抗剪强度;(2)黄土劈裂注浆浆液扩散的基本规律及劈裂机理:浆脉夹角近似120°,且高度不一致,长度有差别,在注浆压力逐渐增大的情况下,浆液在黄土体内会先后三次劈裂土体,形成劈裂缝并在其中进行扩散、填充,最终形成黄土劈裂注浆的"Y"型浆脉;(3)加固后的开挖面土体无侧限抗压强度达到0.6 MPa,周边土体加固区达到1.2 MPa,渗透系数≤10-6cm/s,含水率由原先的约30%下降至10%;(4)得出了在饱和软黄土地层中下穿火车站暗挖隧道WSS注浆所使用的配合比、注浆压力控制值、黄土地层下填充系数等参数,可为饱和软黄土地层隧道围岩注浆加固参数的精细化设计提供必要的参考依据。

Research on the Grouting Reinforcement Parameters of Tunnel Surrounding Rock in Saturated Soft Loess

Research purposes: Tunnel surrounding rock in saturated soft loess has the characteristics of low strength,poor bearing capacity,weak deformation resistance,etc. So it is of great significance to study grouting reinforcement parameters of tunnel surrounding rock in saturated soft loess. Relying on the project of Xi’an Metro line 4 Huochezhan station undercutting railway station,the indoor loess mechanical properties and grouting test is conducted,the effects of water content on the strength properties of loess are studied,the basic law of grout diffusion and fracturing mechanism in loess fracturing grouting test are analyzed,and the grouting reinforcement parameters of the tunnel surrounding rock on construction site are summarized.Research conclusions:( 1) The water content of saturated soft loess decreases and its strength increases linearly,so after grouting,the permeability of undisturbed soils is reduced and the cohesion of the soil is improved,and the shear strength of the soil is improved overall.( 2) Basic law of grout diffusion and fracturing mechanism: angle of plasma vein is approximately 120°,and the height is inconsistent,the length is different. When the grouting pressure is gradually increased,the slurry will split the soil three times in the loess body,forming splitting cracks,and diffusing and filling them,and finally form the " Y" type vein of the loess fracture grouting.( 3) The unconfined compressive strength of the reinforced excavation surface soil reaches 0. 6 MPa, the strength of surrounding soil reinforcement area reaches1. 2 MPa,the permeability coefficient is no more than 10-6 cm/s,and the water content decreases from about 30% to10%.( 4) The paper obtained the parameters such as the mix ratio used for WSS grouting,the control value of grouting pressure,and the filling factor of loess in the project of saturated soft loess tunnel undercutting railway station,which can provide necessary reference for the precise design of grouting reinforcement parameters of tunnel surrounding rock in saturated soft loess.