As an industry and a discipline, geotechnical investigation in China differs from that in the USA and European countries in its course of emergence and evolution. For over half a century, Chinese geotechnical investigation professionals witnessed continuous technical advances as they undertook independently almost all of China’s large-scale construction projects. Based on projects that won the “National Outstanding Engineering Investigation” Gold Medal Awards since the year 2000, this paper discusses the achievements of geotechnical investigation in the context of comprehensive technical ability, project evaluation and analysis, hi-tech applications and engineering monitoring, and analyzes several factors that have hindered the industry’s further development and alignment with international practice. Finally, some suggestions are given for future improvement.

Collapses of transmission towers were often observed in previous large earthquakes such as the Chi-Chi earthquake in Taiwan and Wenchuan earthquake in Sichuan, China. These collapses were partially caused by the pulling forces from the transmission lines generated from out-of-phase responses of the adjacent towers owing to spatially varying earthquake ground motions. In this paper, a 3D finite element model of the transmission tower-line system is established considering the geometric nonlinearity of transmission lines. The nonlinear responses of the structural system at a canyon site are analyzed subjected to spatially varying ground motions. The spatial variations of ground motion associated with the wave passage, coherency loss, and local site effects are given. The spatially varying ground motions are simulated stochastically based on an empirical coherency loss function and a filtered Tajimi-Kanai power spectral density function. The site effect is considered by a transfer function derived from 1D wave propagation theory. Compared with structural responses calculated using the uniform ground motion and delayed excitations, numerical results indicate that seismic responses of transmission towers and power lines are amplified when considering spatially varying ground motions including site effects. Each factor of ground motion spatial variations has a significant effect on the seismic response of the structure, especially for the local site effect. Therefore, neglecting the earthquake ground motion spatial variations may lead to a substantial underestimation of the response of transmission tower-line system during strong earthquakes. Each effect of ground motion spatial variations should be incorporated in seismic analysis of the structural system.

Recent research has shown that circular hollow section (CHS) joints may exhibit non-rigid behavior under axial load or bending. The non-rigid behavior significantly affects the mechanical performance of structures. This paper is concerned with the parametric formulae for predicting axial stiffness of CHS X-joints while braces are in tension. The factors influencing the axial stiffness of CHS X-joints under brace axial tension are investigated, including the joint geometric parameters, the axial force of the chord, and bending moments of braces in two directions, etc. Effects of various parameters on axial stiffness of CHS X-joints are examined by systematic single-parameter nonlinear analysis using shell finite element methods. The analysis is implemented in a finite element code, ANSYS. The observed trends form the basis of the formulae for calculating the joint axial stiffness under brace axial tension by multivariate regression technique. In order to simplify the formulae, two non-dimensional variables are introduced. The proposed formulae can be used to calculate the joint axial stiffness in the design of single-layer steel tubular structures.

A numerical investigation of thin-walled complex section steel columns with intermediate stiffeners was performed using finite element analysis. An accurate and reliable finite element model was developed and verified against test results. Verification indicates that the model could predict the ultimate strengths and failure modes of the tested columns with reasonable accuracy. Therefore, the developed model was used for the parametric study. In addition, the effect of geometric imperfection on column ultimate strength and the effect of boundary conditions on the elastic distortional buckling of complex section columns were investigated. An equation for the elastic distortional buckling load of fixed-ended columns having different column lengths was proposed. The elastic distortional buckling load obtained from the proposed equation was used in the direct strength method to calculate the column ultimate strength. Generally, it is shown that the proposed design equation conservatively predicted the ultimate strengths of complex section columns with different column lengths.

This paper proposes a new approach to the performance optimization of an auto-cascade refrigerator (ACR) operating with a rectifying column and six types of binary refrigerants (R23/R134a, R23/R227ea, R23/R236fa, R170/R290, R170/R600a, and R170/R600) at a temperature level of −60 °C. Half of the six binary refrigerants are nonflammable, of which the 0.5 and the 0.6 mole fractions of R23 for the R23/R236fa possess the most prospective composition for the medium and low suction pressure compressors, respectively. The remaining three binary refrigerants are flammable but with low global warming potentials, of which the 0.6 mole fraction of R170 for the R170/R600 is the most prospective one. The results show that the overall matching as well as local matching of heat capacity rates of hot and cold refrigerants in the recuperators are important for the improvement of coefficient of performance of the cycle, which can be adjusted through the simultaneous optimization of the pressure level and composition. The new approach proposed also offers a wider range of applications to the optimization in performance of the cycle using multi-component refrigerants.

This study presents experimental results focused on a performance comparison of a transcritical CO₂ ejector system without an internal heat exchanger (IHX) (EJE-S) to a transcritical CO₂ ejector system with an IHX (EJE-IHX-S). The comparison includes the effects of changes in operating conditions such as cooling water flow rate and inlet temperature. Experiments are conducted to assess the influence of the IHX on the heating coefficient of performance (COP_r), heating capacity, entrainment ratio, pressure lift, and other parameters. The primary flow rate of the EJE-IHX-S is higher than that of the EJE-S. The pressure lift and actual ejector work recovery are reduced when the IHX is added to the transcritical CO₂ ejector system. Using a more practical performance calculation, the compression ratio in the EJE-S is reduced by 10.0%–12.1%, while that of EJE-IHX-S is reduced only by 5.6%–6.7% compared to that of a conventional transcritical CO₂ system. Experimental results are used to validate the findings that the IHX weakens the contribution of the ejector to the system performance.

The controllable active thermo-atmosphere combustor (CATAC) has become a utilizable and effective facility because it benefits the optical diagnostics and modeling. This paper presents the modeling research of the auto-ignition and flames of the H₂/N₂ (H₂/CH₄/N₂, or H₂/H₂O₂/N₂) mixture on a CATAC, and shows curves varying with temperatures of auto-ignition delay, the height of the site of auto-ignition of lifted flames, and flame lift-off height. The results of auto-ignition delay and the lift-off height are compared the experimental results to validate the model. A turning point can be seen on each curve, identified with criterion temperature. It can be concluded that when the co-flow temperature is higher than the criterion temperature, the auto-ignition and lifted flame of the mixture are not stable. Conversely, below the criterion temperature, the mixture will auto-ignite in a stable fashion. Stabilization mechanisms of auto-ignition and lifted flames are analyzed in terms of the criterion temperature.

This paper describes the results of an investigation into the effect of the variation of curing temperatures between 0 and 60 (C on the hydration process, pore structure variation, and compressive strength development of activated coal gangue-cement blend (ACGC). Hardened ACGC pastes cured for hydration periods from 1 to 360 d were examined using the non-evaporable water method, thermal analysis, mercury intrusion porosimetry, and mechanical testing. To evaluate the specific effect of activated coal gangue (ACG) as a supplementary cementing material (SCM), a fly ash-cement blend (FAC) was used as a control. Results show that raising the curing temperature accelerates pozzolanic reactions involving the SCMs, increasing the degree of hydration of the cement blends, and hence increasing the rate of improvement in strength. The effect of curing temperature on FAC is greater than that on ACGC. The pore structure of the hardened cement paste is improved by increasing the curing temperature up to 40 °C, but when the curing temperature reaches 60 °C, the changing nature of the pore structure leads to a decrease in strength. The correlation between compressive strength and the degree of hydration and porosity is linear in nature.