Grant Technology (China)

Deep excavation and lateral support (ELS) are integral components of urban development, particularly in the construction of multi-storey basements. The conventional ELS design employs the Mohr-Coulomb (M-C) Failure Criterion for both soil and rock parameters, even when bedrock is encountered at shallow depth. This may lead to over-conservative design by underestimating the rock mass strength and stiffness in the overall rock-structure interaction analysis. This paper explores an alternative design approach by suggesting the application of the Hoek-Brown (H-B) Failure Criterion for ELS design in the presence of shallow bedrock. While the M-C parameters are well-established for soil, the conservative nature of M-C Failure Criterion for rock parameters derived from rock joints or discontinuities defect shear strength properties can lead to avoidable costs. Additionally, the paper addresses common scenarios involving the design of temporary piled walls socketed into bedrock for deep excavation, which involve the design of groundwater seepage in rock. The paper suggests a more nuanced approach, advocating for an assessment of the likelihood of possible rock joint failures to derive sensible and cost-effective solutions. By reconsidering conventional design criteria and incorporating alternative geotechnical principles while highlighting the importance of rock testing and field observation, the proposed methodologies contribute to more efficient and economically viable deep excavation practices in rock.

Abstract The reactions proceed by in situ formation of C60(OH)2·‐ which reduces the aryl iodides to the corresponding aryl radicals which in turn arylate benzene.

Abstract Review: 57 refs.

Abstract Review: 10 refs.

Abstract Review: 89 refs.

Abstract Ethyl 5,6,7,8-tetra-O-acetyl-3,4-dideoxy- d -arabino-oct-2-ulosonate and ethyl 3,4-dideoxy-5,6:7,8-di-O-isopropylidene- d -arabino-oct-2-ulosonate have been synthesised from peracetylated and bisacetonated aldehydo- d -arabinose respectively by a two stage procedure: Wittig reaction and catalytic hydrogenation. Deprotection of the blocked ethyl oct-2-ulosonate afforded the 3,4-dideoxy- d -arabino-oct-2-ulosonic acid (4-deoxy-KDO), isolated as its calcium salt in an overall yield of 37% from d -arabinose. Likewise reactions of d -xylose gave calcium 3,4-dideoxy- d -xylo-oct-2-ulosonate in an overall yield of 34%. Both calcium salts were derivatised as crystalline quinoxaline tetraacetates. Other routes attempted are also described.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Phenylethynyl Fischer carbene complexes of chromium 1 and tungsten 2 were found to undergo chemoselective, regioselective and rate-enhanced 1,3-dipolar cycloadditions with phenyl N-t-butyl nitrone 3 at room temp. to give 2,3-dihydroisoxazole carbene complexes 4 and 5 in excellent yields.

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.