垂直防渗帷幕渗漏条件下示踪剂迁移模拟

Simulation of tracer transportation under the leak of vertical flexible barrier system

为研究抽水-示踪联合检测垂直柔性污染阻隔屏障(VFBS)渗漏的可行性、灵敏度和影响因素,构建了相应的概念模型.利用等效渗透系数(EHC)方法耦合井筒-含水层水流运动,在此基础上利用多物理场仿真数值模型模拟了人工水力诱导下示踪剂通过VFBS缺陷的穿透过程和规律.结果表明:在抽水诱导下,VFBS两侧形成人为的水力压差加速了示踪剂穿过漏洞的速度.但整体上,穿过漏洞的示踪剂仍然是极少部分,大部分示踪剂围绕注入井分布.在典型条件下(漏洞深度2.2m、大小0.5m、注入浓度1000μg/L和流速1L/h),示踪剂在对侧监测井中于第4d检出,第5d达到峰值.漏洞越深,峰值浓度越低,检出时间越长.深度增至4m以上时,示踪剂无法在对侧检出.以典型条件中4m漏洞深度为例,漏洞水平位置的偏移也会降低峰值浓度,偏移4m时,示踪剂无法在对侧检出;投加浓度越大,峰值浓度越大,但峰值时间不变,浓度小于2000μg/L时,示踪剂无法检出;漏洞尺寸越大,峰值浓度越大,均在第6d达到峰值浓度,但均不能检出,预测漏洞边长至少为1.07m时,示踪剂方可在对侧检出.总体上,按照对示踪剂穿透过程影响大小排序:水平偏移距离>漏洞深度>漏洞大小>投加浓度.

In order to study the feasibility, sensitivity and influencing factors of pumping-tracer joint detection of vertical flexible pollution barrier(VFBS) leakage, a corresponding conceptual model was constructed. The Equivalent Hydraulic Conductivity(EHC) method was used to couple wellbore-aquifer flow, on this basis the multi-physics simulation numerical model was used to simulate the breakthrough process and law of the tracer passing through the VFBS defect under artificial hydraulic induction. The results showed that under pumping induction, an artificial hydraulic pressure difference is formed on both sides of the VFBS to accelerate the speed of the tracer passing through the leakage. But overall, the tracer passing through the leakage was still a very small part, most of the tracer is distributed around the injection well. Under typical conditions(leakage depth 2.2m, size 0.5m, injection concentration 1000μg/L and flow rate 1 L/h), the tracer was detected in opposite monitoring well on the 4th day and reached the peak on the 5th day. The deeper the leakage depth was, the peak concentration was lower and the detection time was longer. The tracer was not detected above 4m depth on the opposite side under typical conditions. Taking the 4m leakage depth under typical conditions as an example, With the deviation of the horizontal position of leakage, peak concentration was reduced, When the deviation was 4m, and the tracer was not detected on the opposite side;The greater the injected concentration was, the peak concentration was higher, but the peak time was unchanged, when the concentration was less than 2000μg/L, the tracer was not detected;The larger the hole size was, peak concentration was greater and reached on the 6th day, but all not detected. The side length of the leakage was predicted to be at least when it was 1.07m, the tracer was detected on the opposite side under typical conditions. In general, it is sorted according to the size of the impact on the tracer breakthrough process: horizontal offset distance> leakage depth> leakage size> injected concentration.