水压下开裂混凝土中水分渗透红外试验

为了研究水下隧道开裂混凝土中水分渗透过程和影响因素，基于Richards方程和立方定律提出了外水压力下水分在开裂非饱和混凝土中的运动方程，根据水下隧道一侧承受外水压力、一侧接触大气的服役环境，设计了混凝土内部孔洞和裂缝承受冷却压力水的渗透试验，采用红外热像仪可视化研究水分入渗开裂混凝土的过程；通过红外辐射特性来分析裂缝几何特征、外水压力和初始饱和度对开裂混凝土中水分渗透的影响，并将试验结果与水分运动方程的影响因素进行对比。结果表明：外水压力越大、混凝土初始饱和度越小，则开裂混凝土试块的内外温差越大，表面温度变化曲线越陡峭，说明水分流速相应地越快，入渗深度越大，证明外水压力和初始饱和度都是开裂混凝土中水分运移的驱动因素；裂缝宽度越大、裂缝长度越长，混凝土试块表面红外温度越低，试块内外温差越大，说明裂缝面积越大导致冷却水入渗流量越大和渗透深度越深，证明裂缝宽度与开裂混凝土的渗透性正相关；另外垂直裂缝方向相比平行裂缝方向的红外热图观测效果更明显。在进行水下隧道渗漏预测时不宜忽略裂缝几何特征、外水压力和初始饱和度，不然会低估水流速度和流量，影响水下隧道的长期安全和耐久寿命。

Experimental Infrared Study on Water Transport in Cracked Concrete Under Pressure

To study the water transport process and influencing factors on the cracked concrete in underwater tunnels, a motion equation in cracked unsaturated concrete under external water pressure was proposed based on the Richards equation and cubic law. Penetration experiments with cooling pressure water on the internal holes and cracks of concrete were designed according to the service environment, namely, the wall side of the underwater tunnel bearing external water pressure, and the contacting atmosphere. Infrared thermography was used to visually study the water infiltration process in cracked concrete. The influence of the geometrical fracture characteristics, external water pressure, and initial saturation on the water transport in cracked concrete was analyzed based on the infrared radiation characteristics. Meanwhile, the test results and the influencing factors in the equation of water motion were compared. The results show that, the greater the water pressure, or the lower the initial saturation of concrete, the greater the temperature difference is between the inside and outside of the cracked concrete test block, and the steeper the change in the surface temperature curve, which indicates that the water velocity is correspondingly faster and the penetration depth is greater. As a result, it was verified that the external water pressure and initial saturation are both driving factors in the water transport in cracked concrete. The greater the crack width or the longer the crack length, the lower the infrared temperature of the concrete block surface is, and the greater the temperature difference between the inside and outside of the test block, which demonstrates that a greater crack area results in a greater infiltration flow of cooling water and a greater penetration depth, thereby proving the positive correlation between the crack width and permeability of cracked concrete. In addition, the observed effect of an infrared heat map from the direction of the vertical fracture is more obvious than that from the direction of a parallel fracture. When predicting the leakage of an underwater tunnel, it is suggested that the geometric characteristics of the crack, the external water pressure, and the initial saturation not be neglected; otherwise, the water velocity and flow will be underestimated, which will affect the long-term safety and durability analysis of underwater tunnels.