In situ measurement of the dynamic characteristics of surficial soils is becoming more common in geotechnical practice for prediction of ground-surface motions from earthquake excitation and to evaluate foundations for vibrating equipment. Techniques for these measurements have been under development at the University of British Columbia (UBC) since 1980. The paper discusses many practical considerations with respect to equipment (sources, receivers, trigger, etc.) and procedures that can affect the interpretation and analysis of seismic cone results. A brief review is given of the cross-over method as used at UBC to determine interval shear velocity travel times from downhole seismic cone testing. A more detailed description is provided for the cross-correlation technique used in the frequency domain, which has recently been incorporated into the analysis procedure. Comparisons of these two methods are presented and discussed. It has been found useful to isolate the main shear wave before further calculations, and the effects of this procedure are provided. A summary of findings concerning the characteristics of the measured signals is also included. Key words : seismic, cone penetrometer, sources, receivers, accelerometers, shear wave, velocity, downhole, digital, signal processing.

The downhole seismic cone penetration test (SCPT) procedure has been extended to allow the measurement of material damping at small strains at minimum expense while one is measuring shear wave velocity. The nature of damping, the required equipment characteristics, and the recommended procedure and calculation methodology are presented in a practical way. SCPT results from four different sites give results that are in general agreement with laboratory measurements of damping for sands and clays and with values recommended by other authors. It appears, however, that previously reported measurements of damping by borehole methods are higher, by a factor of two or more, when compared with SCPT and laboratory results.

For anchors embedded in cohesive soil, the uplift capacity remains almost constant when the ratio of anchor embedment depth to anchor diameter (D/B) increases above about 4.5. The uplift capacity of anchors in cohesionless soil increases as D/B increases and the increase is greater with increased density of the cohesionless soil. Then, given that an anchor is embedded in cohesive soil, it may be possible to increase the uplift capacity of the anchor by placing a cohesionless overlay on the clay layer.The purpose of the model tests reported in this note was to investigate the effectiveness of placement of a cohesionless layer over a clay seabed in increasing the uplift capacity of a shallow anchor buried in the clay (D/B < 2.0). The sand overburden did increase the uplift capacity, but to obtain a substantial increase in capacity, a very large anchor displacement is required. In fact, the anchor had to displace through almost the entire clay layer before it mobilized the frictional resistance of the sand overlay. Key words: circular anchor, uplift, layered system.

A rational approach to calculating the drag embedment performance of marine anchors in cohesive soils is presented. The method considers the geotechnical and gravity/buoyancy forces acting on all components of the anchor system including various areas on the anchor and the attached mooring line which may be either chain or wire. The solution proceeds in a piece-wise linear manner until an equilibrium position is found for the anchor. This equilibrium position is described in terms of the anchor burial depth, the anchor drag distance, and an anchor angle of rotation in the soil. The equilibrium position may be such that the anchor holds the applied line load and no further movement occurs, or it may be such that the anchor can dig no deeper and horizontal movement is predicted with a given maximum resistance. The solution technique requires a computer program. Such program has been developed and the results from the program have been compared with large scale tests performed in the Gulf of Mexico in 1990. HISTORICAL ANCHOR DESIGN This paper is concerned primarily with relatively large marine drag embedment type anchors which areused in the offshore industry. However, it is worth considering the evolution of anchors in general. The first patent that was filed for describing an anchor was that by Hawkins in 1821. This patent described an anchor consisting of two flukes which were articulated about a pin perpendicular to the shank of the anchor. This concept has remained in use today and falls now into two main categories of stockless anchors and stock anchors. Stockless anchors are widely used today on warships and on merchant ships. They are not typically used inthe offshore industry. Articulated stock anchors are more widely used incommercial applications today than stockless anchors. The Danforth anchor is a typical example developed in the late 1930s. These anchors are used on barges and semi-submersible drilling rigs. Names in common use include Danforth, LWT, and Offdrill. The requirements of the offshore industry to provide ever larger capacities of anchors led to a scaling up ofexisting models. Stockless and stock anchors weighing up to 30 tons in air have been built. Special anchor handling vessels have been developed specifically for the placement and retrieval of these anchors. In the last decade, the increasing use ofpermanent mooring systems for floating production has resulted in the design of anchors specialized to certain types of soil conditions. In the soft cohesive soils typical of many deep water areas in the world, increasing use of anchors fabricated from steel plates has occurred. These fabricated anchors replace cast steel anchors. They are more efficient in terms of their holding capacity compared to their weight. However, they are very specific to individual applications and cannot be regarded as general purpose anchors.

Marine renewables have made great strides in recent years. The IEC, ABS, and DNV GL continue to generate standards and recommended practices in an effort to formulate approved processes as the renewable products make their way offshore and into the market. There are many similarities in some of the processes and designs when compared to oil and gas structures, especially when it comes to moorings. However, many design areas are uniquely related to renewables, even within the same field of energy conversion (e.g. multiple types of wave energy converters). As more renewable systems are installed, the standards will continue to transition from philosophical to more prescriptive recommendations. One area in which the lines are blurred between oil and gas and renewable industries is mooring systems. The interdependency between the mooring and power generation systems plays a crucial role early in the design phase. Modeling marine energy converters and the mooring system can be complex due the variability of moving parts, and without proper attention, it may be easy to underestimate the loads and fatigue cycles to which moorings will be exposed. Moorings for these structures should incorporate existing standards and recommended practices to ensure safety and reliability. Inspection, maintenance, repair, and replacement should also be considered. As the renewable industry continues to move forward from scaled prototypes to farms of devices, the oil and gas supply chain will contemplate when to become involved from a financial and resource perspective. However, there are still hurdles within the US authorization bodies like BSEE, BOEM, FERC, NOAA, USCG, etc. to overcome. This paper addresses the existing mooring related standards and delineates areas that need further refinement or conservatism as the renewable industry moves forward with the installation of offshore energy converters.