• Journal of the Korean GEO-environmental Society
• /
• v.7 no.6
• /
• pp.67-73
• /
• 2006

In this study, basic physical tests and mechanical tests of crushed rock were performed in order to investigate the field application of crushed rock as substitute materials of sand that is commonly being used as foundation and backfill materials of sewer conduit. Particle-size distribution curve of crushed rock is similar to sand and also it is well-graded soil than common sand. Maximum dry unit weight in proctor compaction test for crushed rock is higher than the values of common sand. So we can estimate that the crushed rock has advantages in workability than sand for the backfill compaction after construction of sewer conduit. When we investigate the results of direct shear test and triaxial compression test on the crushed rock, it has a similar value of shear strength parameters to sand at the same stress state and as time goes by, it tends to increase the unconfined compression strength. But, because the strength reaches at the constant value after 6~7 days, we expect that it can absorb the lateral strain of flexible conduit well. All the above experimental results just proves that crushed rock can substitute for sand as backfill materials and foundation of sewer conduit.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09a
• /
• pp.1190-1200
• /
• 2010

A method was developed to determine resilient modulus for crushed rock-soil mixtures whose usage has been increased recently without engineering specifications. The method is based on the subtle different modulus called nonlinear dynamic modulus and was lately implemented in residual soils and engineered crushed-stones. Hereby. the same method was expanded to crushed rock-soil mixtures containing as large grain diameter as 300mm. The method utilize field direct-arival tests for the determination of maximum Young's modulus, and a large scale free-free resonant column test, which is recently developed to is capable to test as large grain diameter as 25mm, for modulus reduction curves. The prediction model of resilient modulus was evaluated for crushed rock-soil mixtures of a highway construction site at Gimcheon, Korea.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.03a
• /
• pp.607-616
• /
• 2006

More strict construction control of railway roadbeds is demanded in high speed railway system because of heavier repeated dynamic loading than conventional railways. The aim of this study is to propose a compaction control methodology of crushed-rock-soil-fills including as large particles as $200\sim300mm$ in diameter, which are easily encountered in high speed railway roadbed. Field tensity evaluation and in turn compaction control of such crushed-rock-soil-fills are almost impossible by conventional methods such as in-situ density measurements or plate loading tests. The proposed method consists of shear wave measurements of compaction specimens in laboratory and in-situ measurements of fills. In other words, compaction control can be carried out by comparing laboratory and field shear wave velocities using as a compaction control parameter. The proposed method was implemented at a soil site in the beginning and will be expanded to crushed-rock-soil-fills in future. One interesting result is that similar relationship of shear wave velocity and water content was obtained as that of density and water content with the maximum value at the optimum moisture content.

• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.955-963
• /
• 2008

There are lots of tunnel intervals in the KTX II stage construction line for the linearity of railway line passing mountain region. In order to use the rocks from tunnel excavations, railway subgrades are constructed with crushed rock-soil mixtures. In this study, plain strain test using large scale box was conducted in order to analyze the characteristics of deformation behavior of railway subgrades composed of crushed rock-soil mixtures. The effects of variation of degree of saturation, stress level of applied loadings, and number of loading cycles on the resilient and permanent deformation behavior were analyzed. The results show that degree of saturation have a great effect on the deformation behavior of crushed rock-soil mixtures. The axial strain ranges between $0.1{\sim}0.8%$ with variation of degree of saturation, in assumption that deviatoric stress applied on the subgrade by high-speed train load is 55kPa.

• Journal of the Korean Society of Safety
• /
• v.27 no.6
• /
• pp.127-132
• /
• 2012

In this study, ambient temperature curing artificial aggregate were developed by using crushed-stone sludge. In order to evaluate the mechanical properties, the artificial aggregate was tested on 7 items. Test results showed that the artificial aggregate mostly satisfied the basic requirements of normal aggregate. The concrete with the artificial aggregate made by weathered rock and granite sludge was tested on the compressive test and flexural test. From the test results, It is confirmed that the concrete with the granite artificial aggregate develope the higher compressive strength than the crushed rock aggregate and the concrete with artificial aggregate concrete have the lower elastic modulus and flexural strength than the concrete with crushed rock aggregate.

• Journal of the Korean Society for Railway
• /
• v.12 no.2
• /
• pp.183-189
• /
• 2009

The track structure of Gyungbu High Speed Railway line from Daegu to Busan is concrete track. It has a very strict specification for residual settlement because of its rigid type structural characteristics. The residual settlement of it comes from the residual settlement of the subgrade and the ground. The residual settlement of railway subgrade composed of crushed rock and soil might be major parts of total residual settlement depending on the field compaction qualities. Therefore, it is a key to minimize the residual settlement of the subgrade for a successful concrete track construction. In this paper, total 31 large scale compaction tests were performed to understand the compaction behaviors of the crushed rock-soil mixture. The test specimens were constituted with soil, crushed shale and mudstone taken from two sites under construction. The compaction tests were performed with the variations of rock types, #4 sieve passing contents, maximum particle size, and moisture contents. The influence of those factors on maximum dry unit weights of crushed rock-soil mixture was evaluated.

• Geomechanics and Engineering
• /
• v.16 no.3
• /
• pp.273-284
• /
• 2018

A detailed understanding of the mechanical behaviors for crushed coal rocks after grouting is a key for construction in the broken zones of mining engineering. In this research, experiments of grouting into the crushed coal rock using independently developed test equipment for solving the problem of sampling of crushed coal rocks have been carried out. The application of uniaxial compression was used to approximately simulate the ground stress in real engineering. In combination with the analysis of crack evolution and failure modes for the grouted specimens, the influences of different crushed degrees of coal rock (CDCR) and solidified grout strength (SGS) on the mechanical behavior of grouted specimens under uniaxial compression were investigated. The research demonstrated that first, the UCS of grouted specimens decreased with the decrease in the CDCR at constant SGS (except for the SGS of 12.3 MPa). However, the UCS of grouted specimens for constant CDCR increased when the SGS increased; optimum solidification strengths for grouts between 19.3 and 23.0 MPa were obtained. The elastic moduli of the grouted specimens with different CDCR generally increased with increasing SGS, and the peak axial strain showed a slightly nonlinear decrease with increasing SGS. The supporting effect of the skeleton structure produced by the solidified grouts was increasingly obvious with increasing CDCR and SGS. The possible evolution of internal cracks for the grouted specimens was classified into three stages: (1) cracks initiating along the interfaces between the coal blocks and solidified grouts; (2) cracks initiating and propagating in coal blocks; and (3) cracks continually propagating successively in the interfaces, the coal blocks, and the solidified grouts near the coal blocks. Finally, after the propagation and coalescence of internal cracks through the entire specimens, there were two main failure modes for the failed grouted specimens. These modes included the inclined shear failure occurring in the more crushed coal rock and the splitting failure occurring in the less crushed coal rock. Both modes were different from the single failure mode along the fissure for the fractured coal rock after grouting solidification. However, compared to the brittle failure of intact coal rock, grouting into the different crushed degree coal rocks resulted in ductile deformation after the peak strength for the grouted specimens was attained.

• Journal of the Korean Geosynthetics Society
• /
• v.18 no.4
• /
• pp.1-13
• /
• 2019

The purpose of this study is to examine the effect of soft ground improvement by dynamic replacement with utilizing crushed rock. In order to understand the ground improvement effect when applying dynamic replacement method with crushed rock, the laboratory test and field test were performed. The internal friction angle and apparent cohesion were derived through direct shear test. The dynamic replacement characteristics were identified by analyzing the weight, drop, and number of blows needed for dynamic replacement. Through the field plate bearing test and density test, the bearing capacity and settlement of the improved ground were measured, and the numerical analysis were conducted to analyze the behavior of the improved ground. In this study, it proposes modified soil experimental coefficient(C_DR) to 0.3~0.5 in the dynamic replacement method with crushed rock. Also when applying the dynamic replacement method using crushed rock, the particle size range is less than 100 mm, D₉₀ is less than 80 mm and D₁₅ is more than 30 mm.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.447-450
• /
• 2005

The purpose of this study is to investigate properties of compressive strength of concrete using the shale rock as coarse aggregates. To evaluate properties of compressive strength of concrete using crushed shale rock, we performed the expriment according to the proportioning strength of $10MPa\~40MPa$ and the slupm of $12\%\~15\%$. The result of this study is as follow. The compressive strength of concrete using crushed shale rock is lower than those of granite aggregates. The proportioning strength is higher, the reduction of comperssive strength of concrete using the shale rock is higher.

• Geomechanics and Engineering
• /
• v.18 no.4
• /
• pp.417-426
• /
• 2019

Gangue filling in the goaf is an effective measure to control the surface subsidence. However, due to the obvious deformation of gangue compression, the filling effect deserves to be further studied. To this end, the deformation of coal gangue filling in the goaf is analyzed by theoretical analysis, large-scale crushed rock compression test, and field investigation. Through the compression test of crushed rock, the deformation behaviour characteristics and energy dissipation characteristics is obtained and analysed. The influencing factors of gangue filling and predicted amount of main deformation are summarized. Besides, the predicted equation and filling subsidence coefficients of gangue are obtained. The gangue filling effect was monitored by the movement observation of surface rock. Gangue filling can support the roof of the goaf, effectively control the surface subsidence with little influence on the ground villages. The premeter and equations of the main deformation in the gangue filling are verified, and the subsidence coefficient is further reduced by adding cemented material or fine sand. This paper provides a practical and theoretical reference for further development of gangue filling.