لخّصلي

2.2 Subgrade filling test overview
2.2.1 Test purpose
The main purpose of dynamic triaxial test of subgrade fillings consists of three aspects: First, through dynamic triaxial tests, the stress state of subgrade fillers under simulated vibration loads of the train is approximated, and the influence of various experimental control conditions on the results is discussed. Second, the study of heavy loads The dynamic characteristics and long-term deformation law of the roadbed packing under train load are used to fit the formulae. The third is to provide the data foundation for the establishment of the dynamic model of subgrade filling.
2.2.2 Equipment

In 1934, the American scholar Renudh first measured the strength parameters of soil through the triaxial apparatus. Since a large number of scholars have continuously used and developed the process, the test technology has developed over 80 years. Whether it is the study of the static or dynamic characteristics of soil, the three axes The test has become one of the main indoor geotechnical test methods, and it is also the main means for studying the relationship between soil and soil. The dynamic triaxial test has the advantages of convenient application of various stresses, definite stress state, ability to control drainage conditions of the test piece, more accurate control of the stress and strain of the test piece, and measurement of pore water pressure, etc., which has been continuously improved by experimental researchers. The triaxial test can meet the requirements of practical engineering whether it is accuracy or specimen size. At present, the triaxial test is being developed toward large-scale, high confining pressure, power, and non-saturated technologies, and has achieved considerable results.
The dynamic triaxial test equipment used in this test was the DYNTTS-60KN dynamic triaxial test system jointly developed by the Institute of Engineering Mechanics, China Earthquake Administration and GDS (Geotechnical Digital Systems Instruments). The test system was assembled at the Institute of Engineering Mechanics, China Seismological Bureau in October 2013. The commissioning test proved that the system has stable performance and is an advanced power triaxial test equipment. The system is capable of performing tests from a standard soil sample of 39.1 mm to a soil sample of 300 mm large diameter. The test can be performed from a clay test piece to a composite soil sample containing a crushed (egg) stone group with a particle size of less than 60 mm. The instrument also reserves sensor data interfaces, which can be upgraded according to research needs, such as: mid-plane pore pressure test device, local strain measurement system (Hall element or LVDT). Figure 2-1 shows a working photograph of the experimental consolidation stage.