Analytical investigations of in situ stress inversion from borehole breakout geometries

This study aims to investigate the feasibility of deriving in situ horizontal stresses from the breakout width and depth using the analytical method.Twenty-three breakout data with different borehole sizes were collected and three failure criteria were studied.Based on the Kirsch equations,relatively accurate major horizontal stress(sH)estimations from known minor horizontal stress(sh)were achieved with percentage errors ranging from 0.33%to 44.08%using the breakout width.The Mogi-Coulomb failure criterion(average error:13.1%)outperformed modified Wiebols-Cook(average error:19.09%)and modified Lade(average error:18.09%)failure criteria.However,none of the tested constitutive models could yield reasonable sh predictions from known sH using the same approach due to the analytical expression of the redistributed stress and the nature of the constitutive models.In consideration of this issue,the horizontal stress ratio(sH/sh)is suggested as an alternative input,which could estimate both sH and sh with the same level of accuracy.Moreover,the estimation accuracies for both large-scale and laboratory-scale breakouts are comparable,suggesting the applicability of this approach across different breakout sizes.For breakout depth,conformal mapping and complex variable method were used to calculate the stress concentration around the breakout tip,allowing the expression of redistributed stresses using binomials composed of sH and sh.Nevertheless,analysis of the breakout depth stabilisation mechanism indicates that additional parameters are required to utilise normalised breakout depth for stress estimation compared to breakout width.These parameters are challenging to obtain,especially under field conditions,meaning utilising normalised breakout depth analytically in practical applications faces significant challenges and remains infeasible at this stage.Nonetheless,the normalised breakout depth should still be considered a critical input for any empirical and statistical stress estimation method given its significant correlation with horizontal stresses.The outcome of this paper is expected to contribute valuable insights into the breakout stabilisation mechanisms and estimation of in situ stress magnitudes based on borehole breakout geometries.

淘宝村城镇化转型的社会网络植入与演替机制——以广州市里仁洞村为例

伴随互联网向村落空间的快速渗透,"淘宝村"这一特殊的乡村产业聚集模式不断完善,并成为促进乡村产业发展的城镇化路径之一。然而,现有研究多数集中于村落的空间环境层面,很少提及近郊型淘宝村的社会网络植入与更替过程及其演化机制。以广州市里仁洞淘宝村为例,通过实地调研与深度访谈,探索社会网络变迁与其发展兴衰的内在联系。研究表明,随着城市化的推进,部分城郊村落演化为流动人口高度集中的淘宝村,潮汕社会网络的"链式迁移"特征在早期有效促进村庄产业发展,并在城镇化过程中成为淘宝村高强度再开发的重要诱因;随着增量开发难以为继,潮汕社会网络的"排外"特征反而成为阻滞淘宝村产业发展的重要因素。原住村民物业惜租/选择住户等行为导致里仁洞村日渐转向同质化的居住功能。消解植入型电商群体和本地居民之间的分离状态,是确保淘宝村产业融入本地社区网络、可持续发展的关键。

Diffraction of plane SH waves by a semi-circular cavity in half-space

This paper presents a closed-form solution for diffraction of plane SH waves by a semi-circular cavity in half-space by using wave function expansion method. Accuracy of the solution is checked by the displacement residual and stress residual along the boundaries. Numerical results show that there are notable differences for response amplitudes between a semi-circular cavity and a whole-circular cavity in a half-space.

Anti-plane (SH) waves diffraction by an underground semi-circular cavity:analytical solution

Diffraction of a two-dimensional （2D） semi-circular cavity in a half-space under incident SH-waves is studied using the classic wave function expansion method with a new de-coupling technique. This so-called ＂improved cosine half- range expansion＂ algorithm exhibits an excellent performance in reducing displacement residual errors at two rim points of concern. The governing equations are developed in a manner that minimizes the residues of the boundary conditions. Detailed derivation and analysis procedures as well as truncation of infinite linear governing equations are presented. The semi-circular cavity model presented in this paper, due to its simple profile, is expected to be used in seismic wave propagation studies as a benchmark for examining the accuracies of various analytical or numerical methods for mixed-boundary wave propagation problems.

Seismic response control with density-variable tuned liquid dampers

In this paper, the seismic effectiveness of a density-variable tuned liquid damper （DVTLD） with a sloping bottom is experimentally investigated through a series of shake table tests on a 1/4-scale, 3-story frame structure and numerically simulated by a new semi-analytical model. Special attention was given to reducing the first peak and maximum response under near- and far-field ground motions, and the robustness of a density-variable control system consisting of multiple DVTLDs with closely-spaced frequencies. Adaptable to earthquake excitations, the density-variable control system has been demonstrated to be more effective and more robust than its corresponding traditional tuned liquid damper in suppressing story drift and floor acceleration of the structure. Numerical simulations of the DVTLD-controlled structure agreed very well in phase with experimental results but somewhat overestimated the amplitude of the structural response.

Soil-structure interaction on shallow rigid circular foundation:plane SH waves from far-field earthquakes

A closed-form wave function analytic solution of two-dimensional scattering and diffraction of incident plane SH-waves by a fl exible wall on a rigid shallow circular foundation embedded in an elastic half-space is presented. This research generalizes the previous solution by Trifunac in 1972, which tackled only the semi-circular foundation, to arbitrary shallow circular-arc foundation cases, and is thus comparatively more realistic. Ground surface displacement spectra at higher frequencies are also obtained. As an analytical series solution, the accuracy and error analysis of the numerical results are also discussed. It was observed from the results that the rise-to-span ratio of the foundation profi le, frequency of incident waves, and mass ratios of different media(foundation-structure-soil) are the three primary factors that may affect the surface ground motion amplitudes near the structure.

Out-of-plane (SH) soil-structure interaction： a shear wall with rigid and flexible ring foundation

Soil-structure interaction （SSI） of a building and shear wall above a foundation in an elastic half-space has long been an important research subject for earthquake engineers and strong-motion seismologists. Numerous papers have been published since the early 1970s; however, very few of these papers have analytic closed-form solu- tions available. The soil-structure interaction problem is one of the most classic problems connecting the two dis- ciplines of earthquake engineering and civil engineering. The interaction effect represents the mechanism of energy transfer and dissipation among the elements of the dynamic system, namely the soil subgrade, foundation, and super- structure. This interaction effect is important across many structure, foundation, and subgrade types but is most pro- nounced when a rigid superstructure is founded on a rela- tively soft lower foundation and subgrade. This effect may only be ignored when the subgrade is much harder than a flexible superstructure： for instance a flexible moment frame superstructure founded on a thin compacted soil layer on top of very stiff bedrock below. This paper will study the interaction effect of the subgrade and the super- structure. The analytical solution of the interaction of a shear wall, flexible-rigid foundation, and an elastic half- space is derived for incident SH waves with various angles of incidence. It found that the flexible ring （soft layer） cannot be used as an isolation mechanism to decouple asuperstructure from its substructure resting on a shaking half-space.

Development and Evaluation of Intersection-Based Turning Movement Counts Framework Using Two Channel LiDAR Sensors

This paper presents vehicle localization and tracking methodology to utilize two-channel LiDAR data for turning movement counts. The proposed methodology uniquely integrates a K-means clustering technique, an inverse sensor model, and a Kalman filter to obtain the final trajectories of an individual vehicle. The objective of applying K-means clustering is to robustly differentiate LiDAR data generated by pedestrians and multiple vehicles to identify their presence in the LiDAR’s field of view (FOV). To localize the detected vehicle, an inverse sensor model was used to calculate the accurate location of the vehicles in the LiDAR’s FOV with a known LiDAR position. A constant velocity model based Kalman filter is defined to utilize the localized vehicle information to construct its trajectory by combining LiDAR data from the consecutive scanning cycles. To test the accuracy of the proposed methodology, the turning movement data was collected from busy intersections located in Newark, NJ. The results show that the proposed method can effectively develop the trajectories of the turning vehicles at the intersections and has an average accuracy of 83.8%. Obtained R-squared value for localizing the vehicles ranges from 0.87 to 0.89. To measure the accuracy of the proposed method, it is compared with previously developed methods that focused on the application of multiple-channel LiDARs. The comparison shows that the proposed methodology utilizes two-channel LiDAR data effectively which has a low resolution of data cluster and can achieve acceptable accuracy compared to multiple-channel LiDARs and therefore can be used as a cost-effective measure for large-scale data collection of smart cities.

Ultra-High Performance Concrete: An Advanced Solution for Accelerated Bridge Pier Cap Rehabilitation and Bearing Replacement

The objective of this paper is to propose and illustrate feasibility, approach, validation as per prevailing codes and design standards, specification to rehabilitate bridge pier cap by using Ultra-High Performance Concrete (UHPC). The evaluation of existing pier caps and bearings indicates that the complete removal of existing bearing is undesirable due to 1) massive size of bearing 2) difficulty in cutting through the thick components of existing bearing 3) deeply anchored lower shoe of existing bearings 4) huge cost and time required to erect temporary support system for superstructure to facilitate the construction of new piers. To overcome these difficulties, UHPC could be cast around the lower shoe up to the existing bearing pin. This UHPC cast could be used to support jacks and temporary bearings. The new low height permanent bearing could then be installed after removing the upper shoe of the existing bearing. In the present research, first properties of UHPC are summarized followed by evaluation of case studies to check feasibility of the solution to rehabilitate pier cap by using UHPC. The complex load paths in pier cap are idealized by using validated strut and tie model as per prevailing AASHTO LRFD Bridge Design Specification.