This article analyzes four major reasons for frequent breakage of rock drill rods: 1. **Raw‑material defects**: Poor‑quality steel contains impurities and air bubbles. These hidden internal flaws develop into cracks under impact and torsion, leading to premature fracture. 2. **Violent drilling operation**: Forcing against hard rock, empty firing, and operating with bent drill rods subject the

This article addresses a common field issue: PDC bits fail quickly after replacing tricone bits, which is usually blamed on bit quality. In most cases, however, damage results from applying tricone‑based operating habits to PDC bits. Tricone bits work with high weight‑on‑bit for impact‑crushing rock, while PDC bits cut rock by shearing and are sensitive to excessive WOB. When operated within pr

This paper (Part II) mainly discusses typical construction troubles in horizontal directional drilling crossing projects, including stuck‑pipe and difficult pull‑back caused by unclean boreholes, pull‑back failures from improper pipe launching and entry angles, as well as mud leakage. It analyzes the root causes from mud performance, pump capacity, geology and operating practices, and puts forward practical countermeasures: optimize mud parameters and circulation modes during reaming and borehole cleaning, select proper pipe launching ways for long‑distance large‑diameter pipelines, and adopt process adjustment, reasonable mud formulation, reaming control and auxiliary on‑site facilities to prevent mud leakage and environmental pollution, so as to reduce construction accidents and ensure crossing project success.