Construction of both plant facilities and transportation lines demand conduction of extensive geotechnical studies. The purpose of the studies is obtaining of trustworthy information about subsurface geology and geotechnical conditions of the area of interest by the way of soil sampling with minimal damage of monolith structure. In compliance with existing regulatory documents for sampling in squashy soft grounds – sands of mean density and clay-bearing grounds having plasticity index no more than ,75 – it is recommended to use striking type devices. Domestic and foreign practice shows that together with such advantages as structural reliability, possibility to on wide scale control process parameters, such as: hammer head, height of lift, striking frequency, drop samplers usage is defined by consuming much of time on hole drilling as a result of small surge power. Sampler’s surge power also makes influence on quality of a sample being drawn. The more the power of a generated stroke, the less quantity of strokes will be necessary to take a sample of the required height. In the end the sample will come out less damaged. Due to this research of existing devices performance and also due to searching for technical solutions, directed at drilling rate raise while preserving of sampling reliability, stays vital.
Project’s objective is to establish dynamic processes’ regularities on a drop sampler that ensures undamaged ground samples drawing.
Research Tasks:
- Numerical scheme development of hammer head’s movement at power stroke in respect to the current constructions of stroke unit of a drop sampler.
- Refinement of calculation methodology of soft ground mass, which takes part in striking interference of hammer head with coring tool in procedure of sampling.
- Depth value estimate at a single stroke in sand-shale grounds and drilling rate at the chosen energetic and design values of the tool taking into account sample’s depth.
Obtaining of maximum possible percussion rate of hammer head with anvil of sampler’s stroke unit can ensure an effective ground samples drawing of shallow boreholes drilling.
Numerical schemes are developed and comparisons of hammer head’s movement at power stroke under the sole weight impact are performed, of follow-up spring and pressure fall in the housing of stroke unit of sampler after the stroke.
Sand-shale grounds mass is defined, which takes part in striking interference of hammer head with coring tool, which improves calculation accuracy of movement rate of the coring tool after the stroke.
Mathematical formulation has been suggested of a stroke hole by drop sampler into soft grounds, which differs by taking a sample’s depth into account. This allows defining a value of making a hole most precisely at a single stroke and duration of sampling.
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