共查询到20条相似文献，搜索用时 78 毫秒
1.
In this paper, the finite element analysis software ABAQUS is used to analyze the ultimate bearing capacity of three-dimensional rectangular footing of marine structures. The deformation law and the failure mode of homogeneous seabed soil beneath the rectangular footing are analyzed in detail. According to the equivalent plastic strain of soil under rectangular footing, an allowable velocity field of homogeneous seabed soil is reasonably constructed. Based on the plastic limit analysis theory of soil mass and by using the Mohr-Coulomb yield criterion, an upper bound solution of the ultimate bearing capacity of three-dimensional rectangular footing on general homogeneous seabed soil is derived, and a correction factor of ultimate bearing capacity of three-dimensional rectangular footing is given. To verify the rationality and applicability of this theoretical solution, some numerical solutions are achieved using the general-purpose FEM analysis package ABAQUS, and comparisons are made among the derived upper bound solution, the solution of Vesic, and the solution of Salgado et al. The results indicate that the upper bound solution of the three-dimensional shallowly embedded rectangular footing proposed in this paper is accurate in calculating the bearing capacity of homogeneous seabed soil. For undrained saturated clay foundation and sandy foundation with smaller internal friction angle, this upper bound solution can evaluate the ultimate bearing capacity of rectangular footing; with the gradual increase of the internal friction angle of the soil, the ultimate bearing capacity of the proposed upper bound solution is slightly higher than that of the rectangular footing. 相似文献
2.
3.
为了研究软岩地基桥桩的荷载传递性状、破坏机理,并获取在该地质条件下更为可靠的桩基计算参数,对秦巴山区软岩地基3根钻孔灌注试桩进行竖向静载试验.结果表明:秦巴山区软岩地基桥桩试桩荷载沉降曲线呈陡降型,实测竖向极限承载力为20500kN,桩的破坏方式为桩身材料强度破坏;淤泥质亚黏土地层中的碎石起到一定的骨架作用,增强了此地层桩极限侧阻力,发挥极限侧阻力所需的桩土(岩)相对位移为4~8mm;强风化砾岩表现为加工软化型,发挥极限侧阻力所需的桩土(岩)相对位移为3~8mm;中风化砂砾岩表现为明显的加工硬化型,所需的桩岩相对位移大,且桩极限侧阻力的特征点不明显;淤泥质亚黏土地层桩侧阻力占总荷载的60%~70%,随着桩顶荷载的逐步加大,该地层桩侧阻力所占比例不断下降,而嵌岩段桩侧阻力所占比例逐渐上升,达到55%~65%,嵌岩段桩侧阻力沿桩深的分布曲线表现出非线性的特征;试桩为端承摩擦桩,桩端阻力约占桩顶荷载的20%左右,且未充分发挥,在上部结构允许的沉降范围内,适当增加桩端的沉降有利于端阻力的发挥;桩侧阻力先于端阻力发挥,建议单桩承载力设计时分别采用不同的端阻力和侧阻力安全系数. 相似文献
4.
The stability of soil-rock mixtures(SRMs) that widely distributed in slopes is of significant concern for slope safety evaluation and disaster prevention. The failure behavior of SRM slopes under surface loading conditions was investigated through a series of centrifuge model tests considering various volumetric gravel contents. The displacement field of the slope was determined with image-based displacement system to observe the deformation of the soil and the movement of the block during loading in the tests. The test results showed that the ultimate bearing capacity and the stiffness of SRM slopes increased evidently when the volumetric block content exceeded a threshold value. Moreover, there were more evident slips around the blocks in the SRM slope. The microscopic analysis of the block motion showed that the rotation of the blocks could aggravate the deformation localization to facilitate the development of the slip surface. The high correlation between the rotation of the key blocks and the slope failure indicated that the blocks became the dominant load-bearing medium that influenced the slope failure. The blocks in the sliding body formed a chain to bear the load and change the displacement distribution of the adjacent matrix sand through the block rotation. 相似文献
5.
The level-trench method is a traditional tillage operation to develop a drainage system on slope land in the Three Gorges region.Before crops are planted,farmers prepare the land with level trenches spaced 3-10 m apart,depending on the slope gradient:steeper slopes require shorter distances.Little scientific analysis has been done on the use of traditional level trenches for soil conservation.We conducted a field investigation and simulation experiments,and present a comparison between the spacing of level trenches and the slope length required for rill initiation.The results indicate that the spacing of level trenches in farmland is close to the slope length required for rill initiation in the experimental plots,and regression models of trench spacing with the gradient and the slope length required for rill initiation with the gradient have similar formats;the coefficients of determination (R2) for the two equations are 0.99 and 0.88,respectively.There were some differences between the field survey and experiments,but we conclude that the traditional level-trench method has an important role in preventing rill initiation. 相似文献
6.
Rainfall is an important factor to trigger the debris flow.Numerical simulation on the responses of slopes and the initiation of debris flow under rainfall was processed by using the software FLAC2D based on the soil parameters in Weijia Gully,Beichuan County,Sichuan Province,China.The effects of the slope angle,rainfall intensity,soil parameters on the developments of the stress and pore pressure and deformation of the slope were studied.It indicates that large displacements of the slope are mainly located near the slope toe.With the increase of the rainfall intensity the stability of the slope decreases and so the debris-flow is easy to occur. 相似文献
7.
以加拿大多伦多市某工程为例,介绍了在复杂地质条件下采用局部桩筏基础(PPRF)的设计及施工问题;探讨了设计PPRF的决定性因素;在保持PPRF设计的完整性前提下,提出了单位沉降量的准则,并用于筏板和桩的设计;计算了PPRF的滑移及转动;最后,采用有效方法对该工程采用的局部桩筏基础进行了计算分析.结果表明,PPRF的设计主要取决于侧向土压力、分布不均的建筑荷载以及地基土的非均匀承载力,工程桩应主要布置在沉降较大的区域,即位于筏板基础承受高压力而土体承载力较低的西北部.探讨局部桩筏基础的设计与施工为该类型工程的基础设计提供了一个新的解决途径. 相似文献
8.
In recent major earthquakes, the researchers have found the need for consideration of vertical seismic acceleration for the stability analysis of the man-made and natural slopes. However, in most past studies, the performance of slopes has been assessed by accounting only the horizontal seismic component of the ground motion, without giving due weightage to the effect of vertical component. In the present study, analytical expressions are derived to determine the factor of safety, yield seismic coefficient and consequently the seismic displacement of cohesionless soil slope under combined horizontal and vertical components of the ground motion. The derivation uses the Newmark’s sliding block approach, in which the soil slope with a planar failure surface within the framework of conventional pseudo-static analysis is assumed to follow the Mohr-Coulomb failure criterion. The effects of vertical seismic coefficient on the stability of cohesionless slope have been studied through a set of graphical presentations for a specific range of soil parameters. It is observed that overlooking the effect of the vertical component of the ground motion on factor of safety and the displacement while designing the slope may be detrimental, resulting in the slope failure. The general expressions presented in this paper may be highly useful in the field of earthquake geotechnical engineering practice for designing the cohesionless soil slopes under combined horizontal and vertical seismic loads. 相似文献
9.
Distributed fiber optic monitoring and stability analysis of a model slope under surcharge loading 总被引：2，自引：1，他引：1
In the discipline of geotechnical engineering, fiber optic sensor based distributed monitoring has played an increasingly important role over the past few decades. Compared with conventional sensors, fiber optic sensors have a variety of exclusive advantages, such as smaller size, higher precision, and better corrosion resistance. These innovative monitoring technologies have been successfully applied for performance monitoring of geo-structures and early warning of potential geo- hazards around the world. In order to investigate their ability to monitor slope stability problems, a medium-sized model of soil nailed slope has been constructed in laboratory. The fully distributed Brillouin optical time-domain analysis （BOTDA） sensing technology was employed to measure the horizontal strain distributions inside the model slope. During model construction, a specially designed strain sensing fiber was buried in the soil mass. Afterward, the surcharge loading was applied on the slope crest in stages using hydraulic jacks and a reaction frame. During testing, an NBX-6o5o BOTDA sensing interrogator was used to collect the fiber optic sensing data. The test results have been analyzed in detail, which shows that the fiber optic sensors can capture the progressive deformation and failure pattern of the model slope. The limit equilibrium analyses were also conducted to obtain the factors ofsafety of the slope under different surface loadings. It is found that the characteristic maximum strains can reflect the stability of the model slope and an empirical relationship was obtained, This study verified the effectiveness of the distributed BOTDA sensing technology in performance monitoring of slope. 相似文献
10.
近年来由于人类活动强度超出当地的地质环境承载能力,破坏了人与自然的平衡,带来了一系列地质灾害、地下水污染等环境问题。为科学合理地分析泰安市高新区地质环境的承载能力,本文在分析研究区内地质灾害、构造稳定性、水土环境等地质环境特征基础上,构建了地质环境承载能力评价的5项本底因子和4项状态评价指标,采用 GIS 空间分析技术将各评价指标进行空间叠加,建立了评价矩阵,对高新区地质环境承载承载能力进行了评价研究。结果表明研究区地质环境承载能力整体状况较好,承载能力中等以上区占比86.15%,承载能力较弱区占比10.2%,承载能力弱占比3.52%。本研究成果为资源环境承载能力监测预警提供靶区,同时也为国土空间规划的编制提供依据。 相似文献
11.
文章通过钻孔灌注桩施工方法对土的承载力影响的分析,提出了解决影响承载力的方法和措施,对提高施工质量进行了有益的探讨。 相似文献
12.
PS测井技术是地震勘探方法之一,也是一种简便、快速、准确的原位测试技术。该文介绍了单孔法PS测井的原理及其在铁路工程勘察中的应用,主要包括根据等效剪切波,进行建筑抗震场地类别划分,铁路工程抗震场地类别划分。根据岩土动力学参数,达到评价岩体质量和划分围岩类别目的,利用剪切波速法估算岩土的承载力基本值。通过青岛机场隧道场地的工程实例说明了PS测井技术在岩土工程勘察设计中的应用情况及应用效果。 相似文献
13.
Soil moisture, a critical variable in the hydrologic cycle, is highly influenced by vegetation restoration type. However, the relationship between spatial variation of soil moisture, vegetation restoration type and slope length is controversial. Therefore, soil moisture across soil layers (0-400 cm depth) was measured before and after the rainy season in severe drought (2015) and normal hydrological year (2016) in three vegetation restoration areas (artificial forestland, natural forestland and grassland), on the hillslopes of the Caijiachuan Catchment in the Loess area, China. The results showed that artificial forestland had the lowest soil moisture and most severe water deficit in 100-200 cm soil layers. Water depletion was higher in artificial and natural forestlands than in natural grassland. Moreover, soil moisture in the shallow soil layers (0-100 cm) under the three vegetation restoration types did not significantly vary with slope length, but a significant increase with slope length was observed in deep soil layers (below 100 cm). In 2015, a severe drought hydrological year, higher water depletion was observed at lower slope positions under three vegetation restoration types due to higher transpiration and evapotranspiration and unlikely recharge from upslope runoff. However, in 2016, a normal hydrological year, there was lower water depletion, even infiltration recharge at lower slope positions, indicating receiving a large amount of water from upslope. Vegetation restoration type, precipitation, slope length and soil depth during a rainy season, in descending order of influence, had significant effects on soil moisture. Generally, natural grassland is more beneficial for vegetation restoration than natural and artificial forestlands, and the results can provide useful information for understanding hydrological processes and improving vegetation restoration practices on the Loess Plateau 相似文献
14.
Spatial and seasonal variation in soil respiration along a slope in a rubber plantation and a natural forest in Xishuangbanna,Southwest China 总被引：1，自引：0，他引：1
Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO2 levels. The conversion of tropical forests to rubber plantations in SE Asia is increasingly common, and there is a need to understand the impacts of this land-use change on soil respiration in order to revise CO2 budget calculations. This study focused on the spatial variability of soil respiration along a slope in a natural tropical rainforest and a terraced rubber plantation in Xishuangbanna, Southwest (SW) China. In each land-use type, we inserted 105 collars for soil respiration measurements. Research was conducted over one year in Xishuangbanna during May, June, July and October 2015 (wet season) and January and March 2016 (dry season). The mean annual soil respiration rate was 30% higher in natural forest than in rubber plantation and mean fluxes in the wet and dry season were 15.1 and 9.5 Mg C ha-1 yr-1 in natural forest and 11.7 and 5.7 Mg C ha-1 yr-1 in rubber plantation. Using a linear mixed effects model to assess the effect of changes in soil temperature and moisture on soil respiration, we found that soil temperature was the main driver of variation in soil respiration, explaining 48% of its seasonal variation in rubber plantation and 30% in natural forest. After including soil moisture, the model explained 70% of the variation in soil respiration in natural forest and 76% in rubber plantation. In the natural forest slope position had a significant effect on soil respiration, and soil temperature and soil moisture gradients only partly explained this correlation. In contrast, soil respiration in rubber plantation was not affected by slope position, which may be due to the terrace structure that resulted in more homogeneous environmental conditions along the slope. Further research is needed to determine whether or not these findings hold true at a landscape level. 相似文献
15.
莱州湾瀰河三角洲滨海盐渍土,为近代松散沉积物。因海水入侵和蒸发浓缩作用,导致盐渍土(多属氯盐渍土)。根据土的物理力学性质指标,天然湿度下载荷试验和浸水载荷试验,认为:盐渍土是具有中等压缩性和湿陷性的土。盐渍土受水浸润后,土的压缩模量Es,承载力[R]明显下降,一般为浸水前的0.6倍。滨海盐渍土地区,地下水中硫酸根离子含量常大于3000毫克/升,具强结晶侵蚀性,应采取特殊防腐措施。 相似文献
16.
Study on Dynamic Response of the ＂Dualistic＂ Structure Rock Slope with Seismic Wave Theory 总被引：2，自引：1，他引：1
Currently, scant attention has been paid to the theoretical analysis on dynamic response mechanism of the ＂Dualistic＂ structure roek slope. The analysis presented here provides insight into the dynamic response of the ＂Dualistie＂ structure rock slope. By investigating the principle of energy distribution, it is shown that the effect of a joint plays a significant role in slope stability analysis. A dynamic reflection and transmission model （RTM） for the ＂Dualistic＂ structure rock slope and explicit dynamic equations are established to analyze the dynamic response of a slope, based on the theory of elastic mechanics and the principle of seismic wave propagation. The theoretical simulation solutions show that the dynamic response of the ＂Dualistic＂ structure rock slope （soft-hard） model is greater than that of the ＂Dualistic＂ strueture rock slope （hard-soft） model, especially in the slope crest. The magnifying effect of rigid foundation on the dynamic response is more obvious than that of soft foundation. With the amplitude increasing, the cracks could be found in the right slope （soft-hard） crest. The crest failure is firstly observed in the right slope （soft-hard） during the experimental process. The reliability of theoretical model is also investigated by experiment analysis. The conclusions derived in this paper could also be used in future evaluations of Multi-layer rock slopes. 相似文献
17.
公路膨胀土路堑边坡防护方案探讨 总被引：5，自引：3，他引：2
毛新虎 《地球科学与环境学报》2004,26(4):49-53
针对膨胀土路堑边坡的公路工程特点，总结以往膨胀土路堑边坡的防护措施，根据以往膨胀土路堑边坡的防护成败资料和经验。以保持边坡土体天然含水量状态的相对稳定，保持边坡土体结构的相对完整性。保持边坡土体足够的抗剪强度和防护工程应能适应边坡膨胀土体可能产生的膨胀变形与膨胀力不遭破坏。首先用DAH混合溶液改良膨胀土边坡的表层土，使DAH混合溶液与膨胀土产生离子交换发生化学反应，从而使表层膨胀土体改变性能，成为正常土，然后结合以往路堑边坡处理方法进行综合处理。实践证明，此方法不但充分利用了膨胀土．节约了工程投资，而且又绿化、美观了边坡，使其与周围环境相协调，从而为膨胀土地区公路路堑边坡处理提供了一种切实可行的防护措施。 相似文献
18.
《山地科学学报》2021,(8)
Rainfall infiltration on a soil slope is usually an unsaturated seepage process that can be described by a water-air two-phase flow model. The effect of pore air pressure on rainfall infiltration has been widely recognized and validated by means of numerical simulations and laboratory experiments. However, whether a slope can actually seal pore air continues to be debated by researchers. In this study, a water-air two-phase flow model is used to simulate the rainfall infiltration process on a soil slope, and a field experiment is conducted to realistically test the sealing conditions of a slope. According to the numerical simulation, the areas of water and air flow in and out on the slope surface are relatively stable and can be classified as the "inhalation zone" and "overflow zone", respectively. Intermittent rainfall on the soil slope has an amplifying effect on pore air pressure because rainfall intensity is usually at the millimeter level, and it causes pore air pressure to reach the cm level. A field experiment was performed to determine whether a slope can realistically seal pore air and subsequently verify the regularity of rainfall infiltration. Air pressure sensors were buried in the slope to monitor the pore air pressures during the rainfall process. The monitoring results show that the pore air pressure in the slope changed, which indicates that the slope can seal air. Moreover, the amplification effects of intermittent rainfall on pore air pressure were observed for natural rainfall, which agrees well with the numerical simulation results. 相似文献
19.
SPATIAL ANALYSIS OF SOIL EROSION AND NON-POINT SOURCE POLLUTION BASED ON GIS IN ERLONG LAKE WATERSHED, JILIN PROVINCE 总被引：1，自引：1，他引：0
Data collection, factor composition, nappe analysis and integrative simulation of natural geographical factors in Erlong Lake
watershed have been carried out based on GIS. The risk areas where non-point source pollution may occur were compartmentalized
and assessed, and the total soil erosion and the runoffs of N and P with rainfall in this valley were worked out by experiment
and GIS mapping. The study indicated that the main type of soil erosion was moderate (erosion modulus is 1000–2500t/(km2·a)) at present, and the intense erosion areas are located in dry land with variable slope east of the lake and the middle-south
parts of steep slope mountainous region (erosion modulus is more than 5000t/(km2·a)). Though the area is small, it should be paid attention to. The trend of non-point source pollution (NSP) of nitrogen
and phosphorus loss was corresponded with the soil erosion. Spatial distribution and the reasons of the distribution difference
have been presented and it was emphasized that the human activities among the influence factors was the most important. It
surely offers a scientific basis to control and prevent non-point source pollution in the watershed.
Foundation item: Under the auspices of the National Natural Science Foundation of China (No.50139020-5-2) and Science & Technology
Committee of Jilin Province (No. 20010602)
Biography: WANG Ning (1952–), female, a native of Beijing, associate professor, Ph.D., specialized in water and soil conservation
and pollution control. E-mail: nwang@nenu.edu.cn 相似文献
20.
Dong Yuan Jin-feng Liu Yong You Dao-chuan Liu Hao Sun Li Zhang Wen-bing Zhou 《山地科学学报》2018,15(1):100-113
Siltation gradient and siltation length are important parameters for designing gravity check dams for debris flows, which directly affect the accuracy of estimates of interception capacity. At present, siltation gradient calculations are based primarily on empirical values, and range from 0.4 to 0.95 times the channel slope coefficient. The middle reaches of the Bailong River are one of the four areas in China that are most severely affected by debris flow hazards. Gravity dams are widely employed in this mountainous area. However, field studies of their capacity are lacking. In this paper, the operations of check dams were investigated. Based on field investigation results and theoretical analysis, calculations for siltation gradient, siltation length, and dam storage capacity are established. The impact of debris flow density, channel slope, and particle size weight percentages are discussed. The calculations show that the theoretical values for siltation gradient are consistent with measured values with 83.6% accuracy; and theoretical values of siltation length are consistent with measured values with 91.6% accuracy. The results of this research are an important reference for optimal height and spacing of dams, estimation of dam storage capacity, and disaster prevention. 相似文献