Drag anchors, including the vertically loaded plate anchors, play a very important role in deepwater mooring systems. However, the behavior of the anchor has never been clearly known, especially the trajectory of the anchor in soils when pulled into the seabed. Positioning in seabed soils is especially important for drag anchors because the working performance of the anchor is closely related to the embedment depth and orientation of the anchor and the properties of the surrounding soils. Hence, studying the trajectory by analytical and experimental methods is critical for the further application of drag anchors in offshore engineering. An overview of the present trajectory measurements demonstrates that there has not been an acceptable measurement technique for laboratory model flume experiments. In this paper, a contact measurement technique, which is based on the knowledge of the motion characteristic of the drag anchor in soils, is developed and applied in measuring the trajectory of the anchor models. This technique is easier to perform and has little effect on the behavior of drag anchors in soils. The measurement precision and applicability of the technique are verified through specially-designed experiments. Being an important application, the measurement technique can be adopted to detect the movement direction of the anchor with an arbitrary fluke section. The present work has demonstrated that through model tests and employing the developed technique, the movement direction of any type of drag anchor can be effectively and easily determined.

The aim of the study is the deep understanding of the essential reactivity of the environmentally friendly mortar by which its applicability can be justified. Created in the study was the environmentally friendly mortar, which helped relieve the increasing requirements on conventional building materials that are produced from exhausted freshwater and river sand nowadays. Seawater (SW) and sea sand (SS) collected from the Eastern Seas of China were used to produce the mortar at various ages, including 10-day, 33-day, and 91-day. Both the curing and working conditions of the mortar were natural marine ones. The physicochemical-mechanical behaviors were investigated using uniaxial compression tests (UCTs), Energy Dispersive Spectrometer (EDS), X-ray Diffraction (XRD), and thermal-field emission scanning electron microscopy (SEM) analysis to understand the essential reactivity of the mortar with age accumulation. The results indicated that hydration products and favorable components were generated promisingly in the mortar: the C-S-H (xCaO·SiO2·zH2O) development was certainly achieved in the critical environment during the curing and working period; the extensive generation of C-A-S-H (CaO·Al2O3·2SiO2·4H2O) helped densify the C-S-H grid, which caused the promising development of the uniaxial compression strength (UCS); the framework porosity of the mortar was restrained effectively due to the development of Friedel’s salt that re-bonded the interfacial cracks between SS and the hydration products with the age accumulation in the critical environment. Consequently, UCS and the resistance against damage of the mortar showed increasing behavior even in the critical environment. The study established Friedel’s salt working models and strength and damage models to interpret the physicochemical reactivity of the mortar as: the source of the strength and toughness was the proper polymerization between the native saline components and the hydration product mixture generated throughout the production, curing, and application without the leaching phenomenon. The novel models and interpretation of the physicochemical reactivity ensured the applicability of the mortar produced with SW and SS in the critical environment.

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