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RISS 인기검색어
- 검색키워드
- 저자 : Dante Fratta (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Field Measurements for the Effectiveness of Compaction of Coarse-grained Soils
김규선,Dante Fratta,Haifang Wen 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.2
Most earthwork construction specifications recommend a lift thickness of 0.2 m for subgrade soils during road construction. Theselimits were originally implemented to ensure uniform compaction across the entire depth of the soil lifts. However, it has also beenargued that the larger footprints and weight available in modern compaction equipment could potentially compact thicker layerswithout sacrificing the mechanical performance of subbases. This paper describes a field study on the effects of the lift thickness andcompactors on the quality of compacted subbases. The effectiveness of two compactors was evaluated on coarse-grained soils. Different types of geotechnical instruments were used to determine variations in the mechanical properties of soils under appliedcompaction energy. The main goal was to combine the information of different testing types to determine whether it is possible to usea thicker lift of coarse-grained subgrade soils during compaction. The field test results show that compaction energy propagates up tothe 0.3-m depth into the soil lift. Therefore, the conventional 0.2-m lift thickness specification for road construction may be updatedto potentially save construction costs without compromising mechanical performance.
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Effect of Wave-Inclusion Interactions in the Crosshole Tomographic Imaging of Heterogeneous Media
김규선,Dante Fratta 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.2
This paper describes a series of physical and numerical experiments designed to evaluate elastic wave-inclusion interactions and the ability of crosshole travel-time tomography to detect anomalies in heterogeneous media. The effects of diffraction-driven time delays on wave propagation detection methodologies are considered using a simple circular Plexiglas plate with a carved slot. Then, the quality of the tomographic inversion for different wavelengths to ray-path lengths and anomaly size ratios are tested using a rectangular Plexiglas plate containing a circular cavity. Guidelines for establishing the proper measurement configuration are developed based on the observed wave-inclusion interactions. Finally, numerical simulations are performed to extend the proposed guidelines for stress-dependent field applications. The simulated results show that crosshole travel-time tomography, with a measurement configuration (e.g., choice of wavelength and ray-path length) considering diffraction phenomena, can detect the size of an anomaly in a stress-dependent heterogeneous medium with a 10% error.
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비파괴시험과 관입시험에 의한 노상토의 물리 · 역학적 특성
김규선(Kim Kyu-Sun),김동휘(Kim Dong-Hee),프라타 단테(Fratta Dante),이우진(Lee Woojin) 대한토목학회 2011 대한토목학회논문집 C Vol.31 No.1
본 연구에서는 도로 성토현장에서 파 기반의 비파괴시험법과 관입시험의 현장 다짐품질 측정에 대한 적용성을 평가하였다. 현장에서 다짐 노상토의 물리 · 역학적 특성을 평가하기 위해 흙강성 측정기(SSG), 시간영역 반사측정기(TDR), 소형 전기-기계 시스템(MEMS) 가속도계 등의 비파괴시험을 이용하여 다짐 전후 흙의 응답을 평가하였고, 동적 콘관입시험기(DCP)를 이용하여 다짐 후 전단특성을 평가하였다. 현장시험은 두 가지 흙의 종류에 대해 네 가지의 다짐장비 및 다짐에너지로 조성된 성토지반에서 수행되었다. 시험결과, 조사 매커니즘이 다른 시험법인 SSG, TDR, MEMS 가속도계 및 DCP로 측정된 흙의 파라메터들은 상호 연관성이 있는 것으로 분석되었으며, 다짐지반의 전체적인 품질 및 공학적인 응답을 고려하여 시험방법들을 현장에 적용할 경우, 기존의 다짐도 평가 방법들을 대체 또는 보완하여 현장에서 신속한 다짐품질 평가를 수행할 수 있는 것으로 나타났다. This paper evaluates the applicability of wave-based nondestructive methodologies and a penetration test for compaction quality measurements during road construction. To evaluate the physical and mechanical properties of compacted subgrade soil layers, soil stiffness gauge (SSG), time domain reflectometry (TDR), and miniature electro-mechanical systems (MEMS) accelerometers were used to nondestructively evaluate the soil response during and after compaction and dynamic cone penetrometer (DCP) profiles were used to evaluate the soil shear strength after compaction was completed. At the field site, two types of soils were compacted with four different compaction equipments and energies. Field testing results indicate that soil parameters evaluated by different testing methods, which are SSG, TDR, MEMS accelerometer, and DCP, are highly correlated. In addition, it is shown that the physical and mechanical tests deployed in this study can be used as alternative methods to the conventional compaction quality evaluation methods when assessing the overall quality and the engineering response of compacted lifts.
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