01628163

Component

The Atlantic razor clam (Ensis directus) possesses an exceptional penetration performance via the periodical expansion/contraction motion of its body during burrowing. In essence, the burrowing process is a soil-penetrator interaction problem where the penetrator has a time-varying shape. The mechanism is very similar to that of the pressuremeter test used in geotechnical site characterization, but different in that such an expansion/contraction process is a dynamic one with relatively high frequency. Although various experimental and analytical researches have been conducted to explore the burrowing mechanism, the understanding on the interaction between a shape-changing structure, such as as a clam, and the surrounding soil is far from complete. This paper provides insights into the cyclic burrowing process in uniform non-cohesive dry granular sands from Discrete Element Method (DEM) modeling. While it is not attempted to explore the burrowing mechanics with realistic burrower geometry and kinematics, a simplified 2D model is developed to study the key feature of the burrowing behavior of the razor clam: dynamic interaction between soil and a circular penetrator with a radius changing in a sinusoidal fashion. Different expanding/contracting frequencies are considered in order to explore their effects on penetration resistance. Various stages of the penetration process including initial movement, progressive expansion and contraction are captured. Results show that the cyclic expansion/contraction has significant effects on penetration resistance and consuming penetrating energy. Patterns of soil displacement and contact force chain are investigated to shed light on the underlying mechanism. To further the exploration of burrowing efficiency, these results are also compared with the data from static penetration simulation. It is found out that there exists a unique critical expansion/contraction frequency, under which the penetration energy consumption is lowest.

This paper was sponsored by TRB committee AFP30 Standing Committee on Soil and Rock Properties. Alternate title: Penetrating in Granular Materials with Changing Shape.

01618707

17-05598

English

14p

2017

Transportation Research Board 96th Annual Meeting

Digital/other

Figures; References; Tables

Contraction; Dislocation (Geology); Expansion; Sand; Shellfish; Simulation; Soil mechanics; Static penetration test

Geotechnology; Transportation (General)

Transportation Research Board Annual Meeting 2017 Paper #17-05598

TRIS, TRB, ATRI

Dec 8 2016 12:13PM