암석지반의 진동삼축시험

암석지반의 진동삼축시험

 

영신컨설턴트 (02) 529 8803 ystcha@naver.com 2022 6

 

진동하중을 받는 암석 지반 (도로, 제방, 철도)에서 암석 흙의 강도와 압축성 평가를 위해 진동 삼축시험이 필요하다. 입경이 크면 삼축셀이 커서 삼축셀 비용이 증가합니다. 지표면 근처의 구속압력 작아 진공압력으로 큰 시료 직경의 삼축시험 가능합니다. 삼축셀이 없어 수평변형도 디지털 사진기술로 측정이 가능합니다.

 

삼축압축시험에서 시료의 최대입경은 시료직경의 1/6이고 구속압축 시 상 하단 top cap, pedestal에 의한 고정 영향을 적게 하기 위해 삼축 시료 높이와 직경 비는 2배 규정. (ASTM D5311-92).

암석직경 63.5mm x 6 = 381mm 시료 최소직경

 

구속압력 20–80kPa 철도, 구속압력을 진공압력으로

 

Two of the most important characteristics in the design of road beds, rock-fill embankments, and railroad structures are shear strength and compressibility of the granular material. Testing of these properties is typically performed using the triaxial testing apparatus. The triaxial test configuration allows a confining pressure to be applied through a flexible membrane surrounding the sample during axial loading. It has been demonstrated that the largest grain size that can be accurately examined in the triaxial apparatus must be one-sixth the diameter of the testing specimen. Additionally, a sample height to diameter ratio of two is necessary to alleviate end platen confinement of the specimen during testing (ASTM D5311-92).

 

It is not uncommon for railway ballast materials to contain individual particles of sizes up to 63.5 mm in railway ballast. If the 1/ 6 maximum particle size to sample diameter ratio is met, the minimum diameter of a triaxial specimen of this material should be approximately 381 mm.

 

This fact, combined with the acceptability of the relatively low confining stresses, in the range of 20–80kPa for testing railway ballast, led to the adoption of vacuum back pressure applied inside the specimen as an alternative means of apply confining pressure for the large grain-size triaxial testing apparatus. This method of confinement is only sufficient for materials relatively close to the surface, and therefore under relatively low confinement. The maximum confinement available usingvacuum is 101 kPa 1 atmosphere.

 

 

wire extensionometers were placed surrounding the samples circumference at 1/4H, 1/2H,and 3/4H.

 

membranes 419 mm in diameter and 889 mm in length.

 

진동하중 113 kg to 1815 kg

 

at 100, 200, 500 cycles and then every1000 cycles thereafter

 

디지털 사진에 의한 변형 측정 PIV patches on triaxial specimen and corresponding strains

 

 

수평변형 측정 PIV (line) and wire extensionometers (dots) measurements.

 

 

 

constant confining pressure 20.7 kPa

 

진동하중

Cyclic stress-strain curves at various number of cycles

 

 

 

A Large-Scale Triaxial Apparatus for Prototype Railroad Ballast Testing