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A new Croatia-Japan Joint Project “Risk identification and land-use planning for disaster mitigation of landslides and floods in Croatia” was initiated in 2009. A new transportable undrained ring shear apparatus, ICL-1, was designed for laboratory soil test and landslide simulation test as a part of Project activities. The aim of ICL-1 was to develop much inexpensive and transportable undrained ring shear apparatus to be used in different counterpart organizations with a standard electricity available anywhere. To make this apparatus effectively and practically used in Croatia and also in other countries, a detailed manual has been made based on the experiences of students and researchers invited from Croatia to Japan. This paper introduces the manual including the concept, design and construction of this apparatus as well as test procedures and data analysis. The ring-shear apparatus was designed to investigate the residual shear resistance under the drained condition along the sliding surface at large shear displacements in landslides because it allows unlimited deformation of the specimen. Sassa et al have developed undrained high speed ring shear apparatus (DPRI-5, 6, 7) to reproduce a rapid landslide motion after failure and to measure the generated pore pressure and the shear resistance mobilized on the sliding surface during motion. It needs high electricity and the great capacity of servo-motor of 37 kW to shear soils at a high velocity up to 2-3 m/sec in the center of the sample. High velocity required a high power motor and a great size of apparatus. However, the series of test results presented that the generated pore pressure and the mobilized shear resistance at the steady state motion is hardly affected by the velocity, but they significantly depend on the shear displacement. The developed transportable ring-shear apparatus (ICL-1) has weight of app 100 kg, maximum height of 95 cm, and dimensions 50x50 cm and it is set on a handcart. The dimensions of the sample box are 100 mm of inner diameter and 140 mm of outer diameter. The significant reduction in dimensions of the latest apparatus was possible because of smaller shear velocity and new loading system in which the normal stress is loaded by pulling the central axis of the apparatus. The large and tall loading frame to give vertical load is not necessary. The shear velocity of ICL-1 is only 5.4 cm/s. The 200 W servo-motor is used for normal stress loading and the 400 W servo-motor is used for shear stress loading. Electricity is single phase 100 V or 200 V. Beside the smaller dimensions, ICL-1 can succeed to maintain undrained condition up to 1 MPa of pore water pressure which is almost double than in previous apparatus (300-350 kPa of pore water pressure in DPRI 5, 6 and 7 apparatus). This became possible because of new loading system with a short loading axis and higher precision of upper and lower ring height ; and the smoothing of inner and outer rubber edge height. Since one of the goals of this apparatus was to be transportable and used in Croatia, the modifications were made in order to be easily maintained outside of Japan. Most of these modifications have practical meaning. Rubber edges can be easily replaced because they are not pasted with glue, but fixed by screws through a Teflon ring and a stainless steel ring. In original design of DPRI apparatus, full round length of annular metal filters with pore sizes of 100 μm and 40 μm (from inside) were pushed and placed inside the annular gutter. Those metal filters were often filled with mostly used fine grained materials taken from Croatia. In ICL- 1 apparatus, a half round length of 100 μm and 40 μm filters were fixed by screws, which has enabled filter changing and cleaning, only by unscrewing of the gutter. The height of the lower half of the shear box can be adjusted by adding porous metals so it can be used for testing of low permeable soils, like it is the case in the tested Croatian landslides. |
