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Jun Cai,Guangyin Du,Han Xia,Changshen Sun 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.10
When pervious concrete is used as pile material, both high strength and water permeability will be available. By comparing the strength and permeability of pervious concrete with different aggregate size (3 − 5 mm and 4 − 6 mm) and porosity (20%, 25%, 30% and 35%), the recommended aggregate size (3 − 5 mm) and porosity (30%) can be achieved. To investigate the installation effect and bearing characteristics of the pervious concrete pile composite foundation, the excess pore water pressure, settlement, pile-soil stress ratio and skin friction were recorded in the model test. Results show that, compared with the impervious pile, the pervious pile can significantly accelerate the dissipation of excess pore water pressure after pile installation, and in the loading test can shorten the consolidation time by 30.3%, increase the skin friction 0.12 kPa averagely, reduce the peak value of excess pore water pressure by 30.2%, and increase the characteristic value of bearing capacity by 43.2%. When the linear penalty method is applied, and the friction coefficient is 0.6, compared with the test, the deviation of simulated skin friction is the largest, being about 15%, so in general the model test results are reliable.
Static and Dynamic Behaviors of Basalt Fiber Reinforced Cement-Soil after Freeze-Thaw Cycle
Changhui Gao,Guangyin Du,Qian Guo,Zhongxun Zhuang 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.12
This study investigated the effects of freeze-thaw (f/t) cycles on the static and dynamic behaviors of plain cement-soil (PCS) sample and basalt fiber reinforced cement-soil (BRCS), with a series of laboratory experiments like split Hopkinson pressure bar (SHPB), unconfined compression strength test (UCT), and ultrasonic pulse velocity testing. The results showed that the incorporation of basalt fibers improved the wave velocity, unconfined compression strength (UCS), and dynamic compression strength (DCS), absorption energy (WS) of cement-soil sample with f/t cycle. The UCS/DCS strength degradation was serious for both BRCS and PCS samples with 1 and 3 f/t cycle, after which the strength decreased slowly. With the strain rate increased from 150 s-1 to 190 s-1, the strength growth of BRCS against PCS gradually slowed down. Under different f/t cycle conditions, both power relationship and exponential relationship fitted well with the experimental data of wave velocity and UCS/DCS for the DCS of samples, but the UCS seems to be only suitable for the power relationship. The incorporation of basalt fibers changed the energy absorption mode of the sample under impact load and there was a positive correlation between the DCS and WS.
Yuxiao Wang,Guangyin Du,Songyu Liu,Dingwen Zhang 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.10
The resonance probe compaction (RPC) method is an effective technique for particular soils, which mainly includes sandy and loess. However, the application of RPC on contaioning clay interlayer area has never been seen. In this study, a successful case of using the RPB method to treat the clay interlayer foundation is presented in detail. The test results of Huaiyan high-speed railway construction project are introduced. The test is divided into the laboratory test and the field test, mainly including standard penetration test (SPT), cone penetration test (CPT) and seismic wave cone penetration test (SCPT). The test results indicated that the cone resistance of silt and silty sand layers increased to an average of 2.13 times compared with an average of 4.39 MPa before treatment, and the sleeve friction whose initial average is 54.17 kPaincreased to an average of 1.74 times. The existence of the clay interlayer does not affect the consolidation and drainage of the silt layer and the silt sand layer, and after the construction, the excess pore water pressure around the vibration point can be dissipated by more than 90% within 15 minutes. After reinforcement, the standard penetration number of subsoil, increased by about 15% − 95% compared with an average of 19 blows before treatment and the clay particle content of some clay interlayers are reduced to less than 10%. The shear wave velocity of the subsoil in the treatment depth increased by about 15% − 48% compared with 140 m/s before treatment. The RPC method was successful for the coastal phase liquefaction foundations.
Guanghua Cai,Songyu Liu,Guangyin Du,Liang Wang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.9
The natural soil will have a significant strength improvement when admixed with reactive magnesia (MgO) and subjected to CO2 carbonation, which has been identified as an innovative and environment-friendly technique in the domain of soil treatment. MgO activity has been revealed to have a significant influence on the treatment effectiveness during the carbonation process. With this in view, the effect of MgO activity index on physicochemical, electrical and strength properties of carbonated silt was investigated. Results show that the MgO activity index and initial water-MgO ratio play crucial roles in controlling the aforementioned properties. With the initial water-MgO ratio reducing or MgO activity index increasing, the mass increment ratio, growth rate of unit weight, pH, resistivity, strength and CO2 sequestration increase to different degrees, while the volume increment ratio, water content, specific gravity, porosity and saturation degree decrease. The unconfined compressive strength shows a better linear relation with resistivity, indicating the applicability of resistivity method in the strength evaluation of carbonated MgO-admixed soil. Moreover, the thermal and microstructural analyses have explained the changing mechanism of physicochemical, electrical and strength properties. Finally, the analysis of the CO2 sequestration indicates that the carbonated MgO-admixed silt could achieve a high carbonation degree when the initial water-MgO ratio is less than 2.0, showing the feasibility of MgO carbonation in the CO2 sequestration.