Formulation and procedure for in situ stress back-analysis from borehole strain changes measured during nearby underground excavation

Estimation of in situ stresses based on back-analysis of measured stress changes and displacements has become an alternative to the direct stress measurement methods.In order to help users conduct own measurement and analysis,this paper presents in detail a field stress back-analysis approach directly from borehole strain changes measured during nearby underground excavation.Essential formulations in major steps and the procedure for the entire analysis process are provided to allow users to follow.The instrument for borehole strain change measurement can be the CSIR or CSIRO stress cells and other borehole strain cells that can measure strains on borehole walls.Strain changes corresponding to the stress changes at a borehole location are calculated in borehole environment.The stress changes due to nearby excavation can be calculated by an analytical model for a single circular opening and simulated by a numerical model for non-circular and multiple openings.These models are based on isotropic,homogeneous and linear elastic assumptions.The analysis of borehole strain changes is accomplished by multiple linear regression based on error minimization and an integrated process provides the best-fit solution directly to the in situ stresses.A statistical technique is adopted for screening outliers in the measurement data,checking measurement compatibility and evaluating the reliability of analysis results.An application example is included to demonstrate the practical application and the analysis procedure.

Strain Engineering for Germanium-on-Insulator Mobility Enhancement with Phase Change Liner Stressors

We investigate the strain in various Ge-on-insulator （GeOI） micro-structures induced by three phase-change maferials （PCMs） （Ge2Sb2Te5, Sb2Te3, GeTe） deposited. The PCMs could change the phase from amorphous state to polycrystalline state with a low temperature thermal annealing, resulting in an intrinsic contraction in the PCM films. Raman spectroscopy analysis is performed to compare the strain induced in the GeOI micro- structures by various PCMs. By comparison, Sb2 Tea could induce the largest amount of tensile strain in the GeOI micro-structures after the low temperature annealing. Based on the strain calculated from the Raman peak shifts, finite element numerical simulation is performed to calculate the strain-induced electron mobility enhancement for Ge n-MOSFETs with PCM liner stressors. With the adoption of Sb2 Te3 liner stressor, 22% electron mobility enhancement at Xinv=1×10^13cm^-2 could be achieved, suggesting that PCM especially Sb2 Te3 liner stressor is a promising technique for the performance enhancement of Ge MOSFETs.

Co-seismic strain changes of Wenchuan Mw7.9 earthquake recorded by borehole strainmeters on Tibetan plateau

Co-seismic strain changes of the Wenchuan MwT. 9 earthquake recorded with three four-component borehole strainmeters showed NW-SE and roughly EW extensions, respectively, at two locations in the interior and northern part of Tibetan plateau, and NS shortening at a location south of the epicenter, in agreement with the tectonic stress field of this region retical values obtained with half-space effects, such as local crustal structure The observed values of as much as 10-7 are, however, larger than theo- and spherical-earth dislocation theories, implying the existence of other and initial stress.

Abnormal strain changes observed at Guza before the Wenchuan earthquake

An YRY-4 type borehole strainmeter at Guza station on the southwest end of the Longmenshan fault zone recorded anomalous changes from time to time since about one year before the Wenchuan earthquake.The anomaly is characterized by steps and/or asymmetrical pulses of short-periods(minutes-hours).Among about one hundred stations over the mainland of China,only Guza,the nearest one to the seismic area,observed such changes.A self-check function of the strainmeter helps confirm the credibility of the observation.The anomalous signals do not correspond to seasonal changes.The consistency in the sense of strain among long-term,anomalous interfering and coseismic changes suggests that they all resulted from the background tectonic movement.Results of an Overrun Rate Analysis further illustrate a close temporal relevance of the anomaly to the Wenchuan earthquake:its increase before,and decrease after the biggest changes during the main shock.The abnormal changes are attributed to local small-scale fractures with an evidential clue that the only Ms4.5 foreshock near Guza station on February 27,2008 produced the biggest anomalous change.By means of Wavelet Decomposition,it is revealed that longer period portion of the anomaly took place later before the main shock,consistent with the idea that scales of small fractures increase during earthquake preparation process.The anomalous strain changes are analogous to the stress changes observed before the 1976 Tangshan earthquake.

Identification of Connection Flexibility Effects Based on Load Testing of a Steel-Concrete Bridge

In the case of composite girders, an effective cooperation of both parts of the section is influenced by deformability of connectors. Limited flexural stiffness of welded studs, used commonly in bridge structures, does not provide full interaction of a steel beam and a concrete slab. This changes strain distribution in cross-sections of a composite girder and results in redistribution of internal forces in steel and concrete element. In the paper partial interaction index defined on the basis of a neutral axis position, which can be used for verification of steel-concrete interaction in real bridge structures rather than in specimens is proposed. The range of the index value changes, obtained during load testing of a typical steel-concrete composite beam bridge, is presented. The investigation was carried out on a motorway viaduct, consisting of two parallel structures. During the testing values of strains in girders under static and quasi-static loads were measured. The readings from the gauges were used to determine the index, characterizing composite action of the girders. Results of bridge testing under movable load, changing position along the bridge span is presented and obtained in-situ influence functions of strains and index values are commented in the paper.

China＇s Thirty Years of Reform and Its Future Road to a Rechtsstaat

Along with the deepening of China＇s marketization-oriented reform, the widespread corruption of government officials and whether or not the fast economic growth in the last 30 years in China is sustainable have become the two serious problems disturbing the Chinese government and people of all circles in China. This paper argues that something must be done in the construction of China＇s legal system and in its constitutional reform, otherwise the problems of prevalence of corruption will eventually hold back the high economic growth of China. Starting from the discussion of the differentiation of two concepts of ＂the rule by Law＂ and ＂the rule of Law,＂ this paper suggests that laws in China should be restored to their natural role as the incarnation of justice on the basis of jurisprudence reasoning, and instrumentalism, pragmatism and utilitarianism in China＇s current legal theory inherited from the traditional Chinese culture should be discarded. Otherwise, it will be impossible to restore the sacredness and authority of Law in China, and then it will take an unconscionable time to reach the state of ＂the Rule of Law＂ with constitutional democracy in China and there will be no way to tackle the problem of institutionalized corruption in the contemporary Chinese society once and for all.