Shield tunneling requires precise, continuous displacement monitoring to protect surface structures, adjacent utilities, and the tunnel alignment. A flange-mounted LVDT displacement sensor offers a practical solution for harsh underground conditions. Its linear variable differential transformer (LVDT) core provides high-resolution, friction-free measurement, while the flange mounting enables fast, stable installation on shield tails, segment rings, bulkheads, and monitoring frames. The rugged housing resists dust, moisture, vibration, and electromagnetic interference, ensuring reliable real-time data. In shield tunneling, these sensors monitor convergence, settlement, gap changes, and structural deformation. Flange mounting keeps the sensor aligned with the measurement axis, reduces installation error, and allows easy replacement without disturbing the monitored structure. When connected to data loggers and automated monitoring systems, the sensor helps engineers detect anomalies early, verify construction performance, and adjust tunneling parameters such as face pressure, grouting volume, and advance rate. Typical models offer measuring ranges from a few millimeters to 100 mm, analog or digital outputs, and IP-rated connectors for site integration. For projects that demand durability, repeatability, and efficient installation, a flange-mounted LVDT displacement sensor is an effective choice for safe, data-driven shield tunneling and long-term tunnel monitoring.