Papers by Keyword: CPT

Abstract: A wide range of industrial applications, on land and offshore, require the solution of time domain problems and an associated understanding of rate effects in clay soils. In recent decades many researchers have examined the correlation between shear strength of soils and variation of shear strain rate and it is generally accepted that the strength increases by 1-5% for each order of magnitude increase in shear strain rate. This paper discusses the effects of penetration rate on the penetration resistance (q_c) by using cone penetration test (CPT) test setup. The research had been conducted at RECESS and cone penetration test were used in three selected range of rate which were 0.5 cm/s, 1cm/s and 5cm/s. In addition, Mackintosh probe testhad been considered as comparison with CPT test for the unconfined compressive strength. The result shows different penetration rate influenced the soil shear strength. For the slowest rate (0.5 cm/s), the shear strength was approximately 0.15% less compared to the standard rate (2 cm/s). However, for the highest rate (5 cm/s), the shear strength was 0.22% more than the reference rate (0.5 cm/s). In conclusion, it is suggested that the RECESS clay soil influenced by the rate effect and in agreement with previous research findings.

Abstract: The computing of end-bearing capacity of pile has vital significances for foundation design while the foundations analysis is usually problematic due to those diverse soils and engineering conditions. Though various CPT-based methods which have already been applied in numerous huge engineering practices are available for the analysis of pile foundation bearing capacity home and abroad, there still seemed lacking legitimate guidance assisting to select these formulations quite effectively. In this paper, five CPT-based design methods are compared in deep, the realization through computer program is also presented, with the capacity data accumulated from pile engineering coming into mind, we are on the way to making designers choose better methods during the designing process.

Abstract: On February 22, 2011 a M_W 6.2 earthquake struck Christchurch in New Zealand, which is the first time that liquefaction acts as the main cause of damage since there is survey record of historical earthquakes. On the basis of field investigation and in-situ test data, domestic and foreign liquefaction evaluation methods based on CPT including Chinese code, Robertson and Olsen methods are examined and their applicability and reliability are assessed. Analysis shows that the method adopted in Chinese code is more dangerous, whose success rates of liquefaction and non-liquefaction evaluation are 70% and 94%.The other two methods abroad are severely conservative, for the success rates of liquefaction and non-liquefaction evaluation of Robertson method are 100% and 40%, and Olsen method 100% and 11% respectively. Liquefaction evaluation methods need further research to be improved.

Abstract: Density is one of the most important soil parameters. However, it is difficult to measure the density of soil model during centrifuge in flight. The cone penetration test (CPT) with robot provides a useful tool to determine the soil density of different models, as the cone resistance is closely related to soil density. This paper presents the correlation between cone resistance and relative density of sand, by doing centrifuge tests with robot CPT. Based on the test results, a formula that describes the correlation between cone resistance and sand relative density of Fujian standard sand is proposed for IWHR CPT attached to centrifuge robot.

Abstract: Based on survey of the Bachu-Jiashi earthquake liquefaction sites, much new basic liquefaction information were obtained and China’s liquefaction database was enriched. A detailed investigation of the Bachu earthquake liquefaction site was conducted, in which three kinds of in situ test measures were used to obtain the site information, and given China mainland SPT data of liquefaction site increase by 40%. By site investigation, international standard liquefaction site CPT data were obtained, and also, the first measurement of liquefaction site data by SPT and CPT index was conducted. With the new data, the feasibility of liquefaction discrimination methods of China was inspected.

Abstract: In geotechnical engineering, assessment of the depth location of stratigraphic interfaces and the depth and thickness of thin layers can be critical in the design process. For example, stratigraphic interfaces can promote anisotropic soil strength response and potentially provide preferential slip planes that create slope instability. Similarly, the presence of thin, high permeability layers can alter groundwater flow regimes and rates of consolidation, which can hinder or accelerate methods of ground improvement. The piezocone penetration test (PCPT or CPTU) is an extension of the cone penetration test (CPT) and is able to measure cone tip resistance, sleeve friction and generated pore-water pressures simultaneously. The piezocone’s functionality is through the measured excess pore pressure profile, which reflects changes in the drainage conditions, and therefore soil conditions. In this paper the relationship between CPTU parameters and soil types and strata is analyzed, and the structure of a general regression neural network (GRNN) is designed, and the application program is programmed with MATLAB language. The results, identifying soil strata by CPTU, have confirmed that GRNN can be used to carry out the automatically identifying soil strata.

Abstract: The serious soil liquefaction phenomenon in Bachu-Jiashi earthquake on 24th February, 2003, which is the most prominent phenomena of sand liquefaction since the Tangshan Great Earthquake in 1976. Based on the earthquake liquefied investigation, inspect SPT and CPT applicability in situ tests. The results show that our country SPT specification and CPT specification of non-liquefied sites evaluation rate is higher than liquefied sites evaluation success rate, the liquefied sites evaluation rate are 88% and 88% respectively, but for liquefied sites evaluation rate are 38% and 55%. The result is tends to danger and the reason need further investigation, so establish a suitable liquefied prediction method should be to the future work in the local area.

Abstract: Lean duplex stainless steels have been developed in Korea for the purpose of being used in the seawater systems of industries. The flow velocity of some part of seawater systems in nuclear power plants is high and damages of components from corrosion are severe. Therefore, this environment requires using high strength and high corrosion resistant steels. The newly developed lean duplex stainless steels STS329LD(20.3Cr-2.2Ni-1.4Mo) and STS329J3L(22.4Cr-5.7Ni-3.6Mo) are evaluated for the compatibility in seawater systems of nuclear power plants. In this study, the physical & mechanical properties and corrosion resistance of two alloys were quantitatively evaluated in comparison with commercial stainless steel 316L. Microstructures and mechanical properties of them were analyzed and the electrochemical properties related to corrosion resistance were measured such as pitting potential, passive current density, and corrosion rates from Tafel analysis. Critical pitting temperatures were measured in accordance with ASTM G48E method. The pitting initiation time and lifetime for replacement were predicted from the PRE values of test alloys and empirical equations that have been formulated from the condenser tubes of a nuclear power plant.