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381.
非开挖技术在市政管道铺设中的应用越来越广泛,从直径50mm通讯光缆-直径3000mm混凝土管道,采用非开挖安装各种管道都变得很普遍。同时,鉴于非开挖技术综合效益优越性、环境友好型施工特点,也逐渐被工程建设方、社会所接受和认可。泥水平衡顶管技术是非开挖最为成熟的技术之一,在城市市政设施建设中也起着举足轻重的作用。采用泥水平衡顶管技术进行城市雨污分流改造已经在国内大量城市取得应用,但是,采用泥水平衡顶管在岩层中铺设直径达2000mm埋深在5m电力管道,在国内为数不多,在福建厦门地区也是尚属首次。通过在工程施工中对设备、施工工艺的摸索和改进,最后采用泥水平衡顶管施工技术成功铺设建设方所要求的电力管道。本工程将为在福建地区采用预管技术铺设大口径长距离、曲线管道提供了指导和借鉴。 相似文献
382.
383.
384.
岩体力学试验的理论分析 总被引:1,自引:2,他引:1
本文通过对岩石力学试验中岩石试件破坏方式的分析, 在理论上解释了岩体力学试验中经常遇到的一些力学现象并且作出了定量的回答, 同时还建立了岩石的各种破坏模式的判据。 相似文献
385.
This paper presents an application of rock engineering system (RES) in an attempt to reveal and assess the inherent instability
potential of 388 sites where equivalent landslides have been manifested and recorded in the region of Karditsa County, Greece.
The main objective has been defining the principal causative and triggering factors responsible for the manifestation of landslide
phenomena, quantify their interactions, obtain their weighted coefficients, and calculate the instability index, which refers
to the inherent potential instability of each natural slope of the examined region. From the statistical interpretation of
the data reported in a well-documented database and concerning the examined failure sites, a clear correlation between the
instability index and the area affected by a single landslide event has been revealed. Almost the entire failure sites, 98%
of the examined slope sites, exhibit an instability index value over 55, a value which is thought to be a critical threshold
for landslide manifestation concerning natural slopes in Karditsa County. It is argued that the presented RES methodology,
engaging the selected set of parameters, could be considered as an effective expert's tool for ranking, in an objectively
optimal and simple way, the instability potential of natural slopes in Karditsa County, and thus providing a tool for sound
zoning landslide hazard. 相似文献
386.
Assessing soil erosion in Mediterranean karst landscapes of Lebanon using remote sensing and GIS 总被引:10,自引:0,他引:10
Maps showing the potential for soil erosion at 1:100,000 scale are produced in a study area within Lebanon that can be used for evaluating erosion of Mediterranean karstic terrain with two different sets of impact factors built into an erosion model. The first set of factors is: soil erodibility, morphology, land cover/use and rainfall erosivity. The second is obtained by the first adding a fifth factor, rock infiltration. High infiltration can reflect high recharge, therefore decreasing the potential of surface runoff and hence the quantity of transported materials. Infiltration is derived as a function of lithology, lineament density, karstification and drainage density, all of which can be easily extracted from satellite imagery. The influence of these factors is assessed by a weight/rate approach sharing similarities between quantitative and qualitative methods and depending on pair-wise comparison matrix.The main outcome was the production of factorial maps and erosion susceptibility maps (scale 1:100,000). Spatial and attribute comparison of erosion maps indicates that the model that includes a measure of rock infiltration better represents erosion potential. Field investigation of rills and gullies shows 87.5% precision of the model with rock infiltration. This is 17.5% greater than the precision of the model without rock infiltration. These results indicate the necessity and importance of integrating information on infiltration of rock outcrops to assess soil erosion in Mediterranean karst landscapes. 相似文献
387.
The strain developed due to creep is mainly proportional to the logarithm of the time under load, and is mostly proportional
to the stress and temperature. At higher temperature the creep rate falls slowly with respect to time, and the creep strain
is proportional to a fractional power of time, with the exponent increasing as the temperature increases and reaching a value
approximately one-third at temperatures of about 0.5°C. At these temperatures, the creep increases with stress according to
a power greater than unity and possibly exponentially. It increases with temperature as (−U/kT), where U is an activation energy and k is Boltzman’s constant. There are different methods to determine the creep strain and the energy of Jog (B) including experimental
methods, multivariate regression analysis, and by numerical simulation. These methods are less cumbersome and time consuming.
In the present investigation, artificial neural network technique has been used for prediction of the creep strain and energy
of Jog (B). Two different networks have been tested and validated. Both the networks have four input neurons and one hidden
layer with five neurons, and one output neuron. The data for different rocks at temperatures up to 750°C under conditions
of compressive or tortional stress are taken from the literatures. The training and testing data sets used were 163 and 14,
respectively. To deal with the problem of overfitting of data, Bayesian regulation has been used and network is trained with
suitable training epochs. The coefficients of correlation among the predicted and observed values are found high and they
improve the confidence of the users. The mean absolute percentage error obtained are also very low. 相似文献
388.
内蒙古达茂旗宝音图岩群是在达茂旗、查干呼绍地区 1:5万区调和白云鄂博幅 1:2 5万区调过程中从过去的巴特敖包群和白云鄂博群未分岩组解体出来的中级变质岩系。通过对宝音图岩群中阳起钠长片岩、二云片岩 (原岩均为基性火山岩 )进行单颗粒锆石U -Pb法年龄测定 ,获得了两条不一致线上交点年龄 (2 486± 42 )Ma、(2 496± 2 6 )Ma ,代表了宝音图岩群基性火山岩及宝音图岩群的形成时代 ;在不一致线之外不同成因的锆石的2 0 7Pb/ 2 0 6Pb表面年龄 (2 2 2 7± 15 )Ma ,寓示着 2 2 0 0Ma左右发生了一次区域性变质热事件 ;下交点年龄 (319±486 )Ma和 (40 6± 46 )Ma ,代表了 2 5 0~ 480Ma时期该区大面积岩浆侵位及宝音图岩群后期变形变质改造的时期 ,两个年龄样的获得为研究古元古代古陆的裂解及白云鄂博海槽的形成提供了直接依据。 相似文献
389.
Summary Although wedge and plane sliding stability analyses are well established in the geotechnical literature, certain geologic environments produce blocks which cannot be adequately modelled as either wedges or plane slides. An example is blocks forming in cylindrically folded sedimentary rocks, where the surface of sliding is neither a single plane nor a double plane but is curved. This type of block may be idealized as a prismatic block with multiple sliding planes, all with parallel lines of intersection. If the sliding planes number three or more, the distribution of normal forces, and hence the factor of safety, is indeterminate. A new analytical model for sliding stability analysis is described in which the distribution of normal forces on the contact planes is chosen to minimize the potential energy of the system. The classic wedge and plane solutions are shown to be special cases of this more general model, which allows determination of the safety factor for any shape of prismatic contact surface. An example from Tennessee concerning a block with a curved sliding surface is described and the factor of safety compared with the standard wedge analysis. It is shown that with three or more contact planes, the safety factor may be significantly lower than that calculated from the wedge model, which provides an upper limit on stability. 相似文献
390.
The energy balance of a solid subject to fracture has been explored using heat and mass transfer equations with regard to the volumetric and superficial components. In the suggested model, brittle fracture of a cracked solid considered as a heterogeneous two-phase medium is described by an equation analogous to the Griffith’s criterion for propagation of a single crack. The derived equation is used, together with estimates of relative change in specific interface area, to study the respective change of free strain energy and pressure in rocks associated with failure. 相似文献