Abstract:
The composite soil nailing systems are considered to be effective to reduce deflections of excavations,so that they can be applied to the excavated cases which are close to roads,pipes,and structures where surrounding strate movements are not permitted.A case of application of the composite retaining structure of soil nails,anchors and micro-piles in excavation engineering close to an expressway,was demonstrated.The technical essentials of design,construction,and field measurement of the engineering were expounded in considerable detail.The stability analysis was carried out based on different engineering cases considering load distribution of expressway automobiles and the deflection control standards and measures were drawn up.The anchor hole was bored by pushing jacket tube to prevent drill bit from being withheld in the uneven distributed subsoil which consisted of gravel and clay filling to be filled layer by layer.The measured data shows that the maximum horizontal displacement of the expressway pavement on the excavation top is limited to the value less than 10 mm and meets the requirements of deflection control standard,and the pre- stressed anchors are effective measures to control the horizontal displacements.