影像城市简

1999年9月,立得空间信息技术股份有限公司（以下简称“立得空间”）正式成立。时光荏苒。光阴如梭,立得空间走过了十四年曲折的创业历程。这十四年也代表着中国移动测量和实景地图事业的发展历程。如今,立得空间已发展成为移动测量与实景三维技术领域的国际领先企业,将实景地图首创性地应用于100多个城市的信息化管理,开创了城市信息化领域崭新的应用模式,迈向大数据时代,为中国智慧城市建设打下了坚实的基础。     

与世界同步简

随着新的建筑节能标准施实,中国建筑行业迎来了一场前所未有的变革,为了使建筑能达到新的节能标准,所有人的目光都瞄向了建筑能量损耗最大的部分--建筑门窗,门窗耗能占到了建筑耗能50%,所以提高门窗节能是实现建筑节能的重中之重。而要提高门窗节能性能,生产是关键,先进的生产设备和技术决定了门窗性能。     

地下车库设计策略简

地下车库（非人防）相对地上,因其功能相对单一、建设成本高、结构复杂而成为各个设计及优化的重中之重。论文以停放小型汽车为主、不舍人防的地下车库为研究对象。地下车库出入口及坡道,地下车库车位、车道及柱网,地下车库层高,地下车库安全、疏散及防火、防烟,地下车库设备用房,地下车库内地面排水,地下车库顶板覆土深度及埋深等8个章节进行阐述,并结合实例列举相应的设计失误及产生原因。     

松石绿的诱惑简

舞蹈、音乐、时装等不同的艺术形式,在很大程度上是相关联的。设计师对于项目的设计灵感来自一场国际时装show ：当着一袭钻石黑色礼物的模特,转身露出一小截精妙的“松石绿色”鞋跟时,通体的黑色与小范围绿色的点缀搭配,惊艳全场。这个项目通过对空间、比例、工艺的精细考究,展示了国际化、东方味、现代感的融合,将小小的设计灵感演绎为一场大空间的艺术盛宴--“松石绿的诱惑”。     

生态文明国家战略简

2013年12月3日,中共中央政治局召开会议决定出台实施国家新型城镇化规划,提出要＂坚持绿色低碳清洁发展,加强生态文明制度建设,走新型城镇化道路＂。人们进一步认识到低碳发展、生态文明的重要性。     

Practical application of failure criteria in determining safe mud weight windows in drilling operations

Wellbore instability is reported frequently as one of the most significant incidents during drilling operations.Analysis of wellbore instability includes estimation of formation mechanical properties and the state of in situ stresses.In this analysis,the only controllable parameter during drilling operation is the mud weight.If the mud weight is larger than anticipated,the mud will invade into the formation,causing tensile failure of the formation.On the other hand,a lower mud weight can result in shear failures of rock,which is known as borehole breakouts.To predict the potential for failures around the wellbore during drilling,one should use a failure criterion to compare the rock strength against induced tangential stresses around the wellbore at a given mud pressure.The Mohr–Coulomb failure criterion is one of the commonly accepted criteria for estimation of rock strength at a given state of stress.However,the use of other criteria has been debated in the literature.In this paper,Mohr–Coulomb,Hoek–Brown and Mogi–Coulomb failure criteria were used to estimate the potential rock failure around a wellbore located in an onshorefield of Iran.The log based analysis was used to estimate rock mechanical properties of formations and state of stresses.The results indicated that amongst different failure criteria,the Mohr–Coulomb criterion underestimates the highest mud pressure required to avoid breakouts around the wellbore.It also predicts a lower fracture gradient pressure.In addition,it was found that the results obtained from Mogi–Coulomb criterion yield a better comparison with breakouts observed from the caliper logs than that of Hoek–Brown criterion.It was concluded that the Mogi–Coulomb criterion is a better failure criterion as it considers the effect of the intermediate principal stress component in the failure analysis.     

A statistical evaluation of intact rock failure criteria constrained by polyaxial test data for five different rocks

In this study we examine seven different failure criteria by comparing them to published polyaxial test data (σ₁>σ₂>σ₃) for five different rock types at a variety of stress states. We employed a grid search algorithm to find the best set of parameters that describe failure for each criterion and the associated misfits. Overall, we found that the polyaxial criteria Modified Wiebols and Cook and Modified Lade achieved a good fit to most of the test data. This is especially true for rocks with a highly σ₂-dependent failure behavior (e.g. Dunham dolomite, Solenhofen limestone). However, for some rock types (e.g. Shirahama Sandstone, Yuubari shale), the intermediate stress hardly affects failure and the Mohr–Coulomb and Hoek and Brown criteria fit these test data equally well, or even better, than the more complicated polyaxial criteria. The values of C₀ yielded by the Inscribed and the Circumscribed Drucker–Prager criteria bounded the C₀ value obtained using the Mohr–Coulomb criterion as expected. In general, the Drucker–Prager failure criterion did not accurately indicate the value of σ₁ at failure. The value of the misfits achieved with the empirical 1967 and 1971 Mogi criteria were generally in between those obtained using the triaxial and the polyaxial criteria. The disadvantage of these failure criteria is that they cannot be related to strength parameters such as C₀. We also found that if only data from triaxial tests are available, it is possible to incorporate the influence of σ₂ on failure by using a polyaxial failure criterion. The results for two out of three rocks that could be analyzed in this way were encouraging.     

A simplified three-dimensional extension of Hoek-Brown strength criterion

The Hoek-Brown(HB) strength criterion has been applied widely in a large number of projects around the world.However,this criterion ignores the intermediate principal stress σ_2.Many evidences have demonstrated that the rock strength is dependent on σ_2. Thus it is necessary to extend the HB criterion into a three-dimensional(3D) form.In this study,the effect of σ_2 on the strength of rocks is identified by reviewing the true triaxial tests of various rock types reported in the literature.A simple 3D strength criterion is developed.The modified criterion is verified by the true triaxial tests of 13 rock types.The results indicate that the modified criterion can achieve a good fit to most of rock types.It can represent a series of criteria as b varies.For comparisons,several existing 3D versions of the HB criterion are selected to predict the strengths of these rock types.It is indicated that the proposed criterion works better than other criteria.A substantial relationship between parameter b and the unconfined compressive strength is established,which guarantees that the proposed criterion can still work well even in the absence of true triaxial test data.     

Three-dimensional FDEM numerical simulation of failure processes observed in Opalinus Clay laboratory samples

This study presents the first step of a research project that aims at using a three-dimensional(3D) hybrid finite-discrete element method(FDEM) to investigate the development of an excavation damaged zone(EDZ) around tunnels in a clay shale formation known as Opalinus Clay. The 3D FDEM was first calibrated against standard laboratory experiments, including Brazilian disc test and uniaxial compression test. The effect of increasing confining pressure on the mechanical response and fracture propagation of the rock was quantified under triaxial compression tests. Polyaxial(or true triaxial) simulations highlighted the effect of the intermediate principal stress(s2) on fracture directions in the model: as the intermediate principal stress increased, fractures tended to align in the direction parallel to the plane defined by the major and intermediate principal stresses. The peak strength was also shown to vary with changing σ2.