北京昌平区某CFG桩复合地基处理工程简介     

尹改梅 《城市地质》2012,7(2):52-54

以北京市昌平区某地基处理工程为例,介绍了CFG桩设计方法、施工工艺与检测技术。  相似文献   

Chaotic dynamics analysis and control of iterative procedure of capacity spectrum method     

Dixiong Yang  Gang Li 《Soil Dynamics and Earthquake Engineering》2009

The capacity spectrum method (CSM), capable of predicting the demands of forces and deformations of the inelastic system, has been applied in the ATC and FEMA guidelines. The deformation of an inelastic system is solved iteratively by using the equivalent linearization for CSM, which actually forms a nonlinear map or discrete dynamical system. However, the iterative procedure of CSM did not converge for some inelastic systems, and the complicated dynamical phenomena for the solutions such as the periodic oscillation, period-doubling bifurcation and chaos may occur, which were shown in the bifurcation plots of iterative map of the simplified CSM in ATC40 and FEMA440. This paper presents a novel method to analyze and control the non-convergence of the iterative procedure of CSM from the perspective of chaotic dynamics. The Lyapunov exponent of the dynamical system is employed to identify the evolutional state and stability of solutions. Finally, the stability transformation method as a simple, versatile and effective chaos feedback control approach is applied to control the convergent failure of CSM in ATC40 and FEMA440. The numerical results illustrate that the stability transformation method can capture the desired fixed points of the dynamical system and obtain the stable convergent solutions of CSM.  相似文献   

Static and seismic bearing capacity of shallow strip footings     

《Soil Dynamics and Earthquake Engineering》2016

In this study, the evaluation of static and seismic bearing capacity factors for a shallow strip footing was carried out by using the method of characteristics, which was extended to the seismic condition by means of the pseudo-static approach. The results, for both smooth and rough foundations, were checked against those obtained through finite element analyses.Under seismic conditions the three bearing capacity problems for N_c, N_q and N_γ were solved independently and the seismic bearing capacity factors were evaluated accounting separately for the effect of horizontal and vertical inertia forces arising in the soil, in the lateral surcharge and in the superstructure.Empirical formulae approximating the extensive numerical results are proposed to compute the static values of N_γ and the corrective coefficients that can be introduced in the well-known Terzaghi׳s formula of the bearing capacity to extend its applicability to seismic design of foundations.  相似文献   

Undrained capacity of a surface circular foundation under fully three-dimensional loading     

《Computers and Geotechnics》2017

Circular foundations are widely employed in offshore engineering to support facilities and are generally subjected to fully three-dimensional loading due to the harsh offshore environmental load and complex operational loads. The undrained capacity of surface circular foundations on soil with varying strength profiles and under fully three-dimensional loading is investigated and presented in the form of failure envelopes that obtained from finite element analyses. The combined ultimate limit state of circular foundations is defined as the two-dimensional failure envelopes in resultant H-M loading space accounting for the vertical load and torsion mobilisation. The effects of vertical load and torsion mobilisation, soil shear strength heterogeneity and loading angle from moment to horizontal load on the shape of normalised H-M failure envelopes are explored. A series of expressions are proposed to describe the shape of failure envelopes obtained numerically, enabling essentially instantaneous generation of failure envelopes and optimisation of a circular foundation design based on constraint of any input variable through implementation in an automated calculation tool. An example application is ultimately provided to illustrate how the proposed expressions may be used in practice.  相似文献   

Bearing capacity of rectangular footings in uniform clay with deep embedment     

《Computers and Geotechnics》2017

This letter is concerned with the undrained bearing capacity of rectangular footings with various aspect ratios and embedment ratios in uniform clay. It covers thin plate foundations with low aspect ratios and high embedment depth with embedment ratio up to 150. The work is based on small strain finite element analysis (FEA). After verification of the FEA model against existing solutions of the bearing capacity factors of rectangular footings, a series of FEA results are obtained. Based on the FEA results, a simple formulation is proposed to calculate the bearing capacity factor for rectangle footing with different aspect ratio in any embedment depth, extending the existing solutions to cover a wider ranges of footing aspect ratios and embedment ratios.  相似文献   

滇东南铝土矿成矿物质来源探讨   总被引：3，自引：1，他引：2  

冯晓宏  王臣兴  崔子良  刘宇淳  张兴恒 《云南地质》2009,28(3):233-242

滇东南含铝岩系为上二叠统吴家坪组（龙潭组）底部和第四系,铝土矿床类型分原生沉积型和第四系岩溶红土堆积型两大类,成矿物质分别来源于峨眉山大火成岩省的基性玄武岩的风化、剥蚀、淋沥所形成的含铝土矿碎屑-红土物质,以及邻近的原生沉积型铝土矿的风化残积、残坡积。  相似文献   

Factors Influencing Adoption and Implementation of Conservation Development Ordinances in Rural United States     

Heidi E. Kretser  Elliot Dale  Leslie Karasin  Liba Pejchar  Sarah E. Reed 《社会与自然资源》2019,32(9):1021-1039

Conservation Development (CD) is a land-use tool to reduce the impacts of development on natural resources, yetthe use of CD is highly variable. We used a collaborative conservation model to examine factors influencing adoption and implementation to improve the future application of CD. We interviewed 2–3 individuals including planners, board members, and developers (n?=?46) from 16 rural communities in the intermountain west and northeast U.S. Motivations to preserve rural character or comply with state statutes drove adoption. Greater capacity such as outside expertise, model regulations, and iterative revisions of ordinances was associated with stronger ordinances. Adoption processes including ample dialog across diverse constituents, especially those overseeing subdivision development, facilitated higher rates of implementation. Concerns over open space management, lack of successful CD examples, and inexperience with CD posed barriers to implementation. Understanding social context revealed the strengths and shortcomings of CD and provided guidance for strategically engaging communities in private lands conservation.  相似文献   

Measured and calculated spudcan penetration profiles for case histories in sand-over-clay     

《Applied Ocean Research》2019

This paper reports five case histories of jack-up rig installation in layered soil profiles where a dominate feature was a stronger sand layer overlaying a weaker clay layer. In all cases a relatively continuous load-penetration profile was measured during installation of each of the three spudcan foundations. Summary site-investigation data is provided and consisted of mainly torvane, minature vane, unconsolidated undrained triaxial and pocket penetrometer tests for determining undrained shear strength of the clays and blow counts for deriving the relative density of sand. A statistical averaging method recommended in the InSafeJIP guidelines was used to provide the best fit of the undrained shear strength profile in the clay as this then allowed for spudcan load-penetration profiles to be estimated without introduction of user interpretation or bias. Sand properties were taken as provided in the original site-investigation report. Comparisons between load-penetration profiles calculated using the industry-standard ISO guideline, more recently proposed mechanism-based calculation method and three-dimensional large deformation finite element simulations are made with the measured data, leading to valuable insights for practitioners for estimating behaviour of jack-up installations in problematic sand-over-clay soil profiles.  相似文献   

近地下水库理论与工程实践现状   总被引：1，自引：0，他引：1  

姜媛  沈媛媛  魏连伟  刘久荣 《城市地质》2012,7(3):26-30

地下水库作为一种水资源调控工程措施,具有重要意义。在过去的40年,国内外进行了大量的地下水库建设工程实践,取得了较大的社会、经济和环境效益。本文回顾了地下水库研究和工程实践的历史,讨论了地下水库的概念、分类、建设条件、效益及存在问题。  相似文献   

广东省湛江市区第四纪沉积层工程地质特征     

黄文县  陈水安 《城市地质》2012,7(2):30-31,48

湛江市区工程建设持力层选择是第四系土层,为海相及海陆交互相沉积。近海地段以淤泥、淤泥质土、粘土、粉质粘土与砂层呈互层状分布为主;远离海滨地带以海陆交互相沉积层为主,岩土以粘性土及中粗砂为主。  相似文献