注浆堵漏常用于盾构隧道渗漏事故的抢险过程中，合理的注浆能够有效封堵渗漏点，避免险情进一步恶化。为研究不同地层中隧道渗漏后不同堵漏材料的作用机制，基于不同地层侵蚀状态下盾构隧道发生渗漏险情后的发展特征，提出渗流型和空洞型2种渗漏事故类型；进一步考虑注浆材料物理化学性质的差异，将堵漏浆材划分为膨胀型和黏结型2种不同类型，从而通过模型试验研究不同类型浆液在不同渗漏事故类型中的作用机制。研究表明： 1）注浆封堵的机制是浆液固化物通过膨胀性或者黏结性在接触面上形成较强的正应力，当接触面正应力超过水压力时，外部流水无法进入隧道内部，堵漏成功； 2）渗流型地层中浆液扩散距离主要受到浆液凝结时间、地层渗透系数、浆液黏度、注浆压力、水力梯度等因素的影响，并通过试验给出浆液扩散距离的经验公式； 3）渗流型地层中，油性聚氨酯反应生成固化物膨胀挤压周边地层，通过挤压力抵抗外水压力，水性聚氨酯的接触面挤压力小于油性聚氨酯，通过包水性消耗孔隙水，同时结合挤压力实现堵漏； 4）空洞型地层中，油性聚氨酯固化物以自密封的形式、水性聚氨酯以黏结力和自密封共同作用的形式实现堵漏效果； 5）空洞型地层中，堵漏注浆的浆液扩散过程受浆液及其生成物密度的影响，针对不同渗漏位置需要选用不同的浆液类型。
Grouting is commonly used
in shield tunnels to stop water and sand inrushes by effectively sealing
leakage points to prevent their further deterioration. To investigate the
mechanism of different sealing materials for tunnel leakage in various strata,
leakage accidents are divided into "seepage-type" and "cave-type" based on the deterioration characteristics of shield tunnels under
various erosion stages of strata. Furthermore, the sealing grout is divided
into "expansion type" and "bonding type" according to the chemical
properties of the grouting materials. The working mechanisms of different types
of slurries for various leakage issues are investigated through modeling tests.
Results reveal the following. (1) The consolidated material exerts high positive
stress on the contact surface through expansion or adhesion. When this positive
stress on the contact surface exceeds the water pressure, the external flow of
water cannot enter the tunnel, thereby stopping the leakage. (2) In the seepage-type strata, the spreading distance of slurry is primarily affected
by the condensation time of slurry, permeability coefficient of strata,
viscosity of slurry, grouting pressure, and hydraulic gradient. The empirical
formula for the spreading distance of the slurry is given by tests. (3) In the
seepage-type strata, the expansion of oil-based polyurethane generates a large positive stress that resists
the external water pressure. The pressure on the contact surface of waterborne
polyurethane is lower than that on oil-based
polyurethane. This is because waterborne polyurethane consumes pore water and
achieves leakage sealing under expansion pressure. (4) In the cave-type strata, oil-based polyurethane stops
leakage by self-sealing, while waterborne polyurethane
stops leakage by the combined action of adhesion and self-sealing. (5) In the cave-type strata, slurry
diffusion is affected by the density of the slurry and its products. Further,
appropriate slurries should be selected based on leakage locations.
