In situ digital testing method for quality assessment of soft soil improvement with polyurethane

This study purposes an in situ testing method on quality assessment of soil improvement.Factual drilling data includes the spatial distribution and in situ strength of untreated and treated soil along three different drillholes measured by on-site drilling monitoring method.These factual drilling data can characterize the degree of soil improvement by penetration injection with permeable polyurethane.Result from on-site drilling monitoring shows that the linear zones represent constant drilling speeds shown in the plot of drill bit advancement vs.net drilling time,which indicates the spatial distributions of soil profile.The soil profile at the study site is composed of four layers,which includes fill,untreated silty clay,treated silty clay,and mucky soil.The results of soil profile are verified by the parallel site loggings.The constant drilling speeds profile the coring-resistant strength of drilled soils.By comparing with the untreated silty clay,the constant drilling speeds of the treated silty clay have been decreased by 13.0-62.8%.Two drilling-speed-based indices of 61.2%and 65.6%are proposed to assess the decreased average drilling speed and the increased in situ strength of treated silty clay.Laboratory tests,i.e.uniaxial compressive strength(UCS)test,have been performed with core sample to investigate and characterize in situ strength by comparing that with drilling speeds.Results show that the average predicted strengths of treated silty clay are 2.4-6.9 times higher than the average measured strength of untreated silty clay.The UCS-based indices of 374.5%and 344.2%verified the quality assessment(QA)results by this new in situ method.This method provides a cost-effective tool for quality assessment of soil improvement by utilizing the digital drilling data.

Theoretical calculation of high-pressure CO_(2)jet in cases of composite rock-breaking based on span-wagner equation of state

Although several theoretical calculation methods for high-pressure jet are available,there is currently no theoretical model for the high-pressure CO_(2)jet based on the high-precision equation of state(EOS).To investigate the flow field of the high-pressure CO_(2)jet in cases of the composite rock-breaking under the high-pressure CO_(2)Jet and PDC cutter,a semi-analytical approach of the high-pressure CO_(2)jet is developed based on the Span-Wagner EOS and CO_(2)jet theory.The semi-analytical calculations and the physical property calculations under the action of the high-pressure CO_(2)jet are conducted with consideration of the jet pressure,the jet distance,the nozzle diameter and the jet angle.The results indicate that the distribution of the physical properties calculated by the semi-analytical approaches is similar to that obtained by experimental monitoring and numerical simulation,which indicates that the calculation method of the high-pressure CO_(2)jet presented in this paper is effective and reliable.The properties of the CO_(2)jet obtained by the theoretical calculation see a significant difference between the initial region and the jet impact region.At the temperature of 300 K,the increase of the initial pressure can effectively increase the impact force and the cooling ability of the jet.The proportion of the jet core lengths in the jet on the axis increases with the increase of the ratio of the nozzle diameter to the jet length,accompanied with the increase of the impact force of the jet.The increase of the jet angle can effectively increase the impacting force of the jet,but hampers the fluid diffusion.The study combines the theoretical calculation of the jet with the calculation of the physical properties of the high-pressure CO_(2),for comprehensively understanding the CO_(2)jet field in the composite rock-breaking under the action of the high-pressure CO_(2)jet and PDC cutter.This theoretical calculation of the CO_(2)jet based on the high-precision EOS provides an option for the convenient calculation of the CO_(2)drilling in practical engineering.