Experimental study on countermeasure against liquefaction-induced flotation of manhole using recycled materials packed in sandbags

The 2004 Niigata-ken Chuetsu earthquake in Japan caused serious damage to sewage facilities such as uplift of manholes and settlement of pavement above backfill soil for pipes.This paper deals with shake table tests in a 1 g gravity field on application of recycled materials for ground improvement to mitigation of liquefaction-induced flotation of manhole during earthquakes.The recycled materials used in tests were tire chips made of waste tires and crushed gravels made of waste reinforced concrete,and they were packed in sandbags.From the test results,it was confirmed that the recycled materials packed in sandbags could be treated as one of the countermeasures to restrain the flotation of manholes and settlement of ground surrounded by sandbags.     

西安地铁隧道穿越饱和软黄土地段的地表沉降监测

以西安地铁一号线朝阳门站—康复路站区段饱和软黄土地铁隧道为研究对象,通过施工期现场地表沉降变形监测,分析了在饱和软黄土特殊地层条件下隧道浅埋暗挖法施工引起的该区段地表沉降变形规律以及地表沉降槽分布特征。结果表明:在饱和软黄土隧道开挖时,随着掌子面的推进,隧道顶地表沉降可分为沉降微小阶段、沉降显著发展阶段、沉降缓慢阶段和沉降稳定阶段;单线隧道开挖后的最大地表沉降量为18.89mm,双线隧道开挖后的最大地表沉降量为36.4mm;已开挖隧道对围岩土体的扰动作用使得后开挖隧道的地表沉降发展较大;双线隧道的地表沉降槽宽度接近单线隧道沉降槽宽度的2倍,因此可以将其近似为单线隧道地表沉降槽宽度与双线隧道轴线中点距离之和;单线隧道开挖后地表沉降槽宽度为8.4～9.3m,双线隧道开挖后地表沉降槽宽度为16.2～17.5m;隧道开挖施工的沉降槽宽度参数为0.435～0.467,单线隧道开挖后的地层损失率为0.765%～1.324%,双线隧道开挖后的地层损失率为1.231%～2.200%。     

地裂缝分类及地面沉降区构造地裂缝防治对策

地裂缝类型多样,灾害严重.根据主导因素及动力类型,将地裂缝分为构造地裂缝和非构造地裂缝两大类和16个类别;基于地裂缝的工程地质特征、水文地质特征和活动特征,认为地面沉降区构造地裂缝发生超常活动的本质原因是地裂缝错断了含水层,在过量抽取地下水时地裂缝两侧形成明显的水头差,产生不均匀压缩,从而导致地表发生较大的差异沉降;提...     

采用时序InSAR技术监测北京地铁网络沿线地面沉降

随着北京轨道交通的日益完善,地铁成为人们日常出行的重要交通工具,监测和治理地铁工程沿线地面沉降成为保障线性工程正常运营的一项重要基础性工作。本文基于55景覆盖北京地区的3 m高分辨率TerraSAR-X数据,采用时序InSAR分析技术获取2010年4月至2016年12月地铁网络沿线的地面沉降形变信息,系统分析了北京地铁网络沿线地面沉降时空演变规律。同时,结合Peck公式将InSAR监测结果进行建模,以7号线磁器口-广渠门内站区段为例,估算地面沉降槽的空间发展特征。研究发现：北京市地铁线路沿线表现出不同程度的形变,形变严重的路段主要集中在东部及东北部区域,最大沉降速率超过了100 mm/a;相对于其他线路,4号、10线整体情况比较稳定,14号、亦庄线次之,6号、7号线不均匀沉降最为严重;此外,地铁在不同建设时期路段表现出不同的形变特征,施工期路段较运营期沉降严重;7号线磁器口与广渠门内站间沉降槽的宽度和最大值沉降值在2010-2016年呈现增加趋势,沉降槽最大宽度约达180 m。     

Effects of topography on dynamic responses of single piles under vertical cyclic loading

This paper describes model tests of single piles subjected to vertical cyclic compressive loading for three kinds of topography: sloping ground, level ground, and inclined bedrock. Comprehensive dynamic responses involving cyclic effects and vibration behaviours are studied under various load combinations of dynamic amplitude, mean load,frequency and number of cycles. Test results show that permanent settlement can generally be predicted with a quadratic function or power function of cycles.Sloping ground topography produces more pronounced settlement than level ground under the same load condition. For vibration behaviour,displacement amplitude is weakly affected by the number of cycles, while load amplitude significantly influences dynamic responses. Test results also reveal that increasing load amplitude intensifies nonlinearity and topography effects. The strain distribution in a pile and soil stress at the pile tip are displayed to investigate the vibration mechanism accounting for sloping ground effects. Furthermore, the dynamic characteristics among three kinds of topography in the elastic stage are studied using a three-dimensional finite method. Numerical results are validated by comparing with experimental results for base inclination topography. An inclined soil profile boundary causes non-axisymmetric resultant deformation, though a small difference in vertical displacement is observed.     

Measured Performance and Analysis of the Residual Settlement of a PVD-Improved Marine Soft Ground

Prefabricated vertical drains(PVDs) are commonly used to shorten the drainage path for consolidation as part of the improvement of marine soft ground. Many studies that focus on the primary consolidation settlement of PVD-improved soft ground have been conducted; however, residual settlement has been scarcely investigated. Residual settlement is the net effect of secondary compression and the remaining primary consolidation and generally occurs while the facilities are operating. In this study, residual settlement was investigated using the measured field settlement data obtained from the surface settlement plate and multilayer settlement gauges. This study determined that PVD still has some effect on residual settlement and can reduce the settlement times. Residual settlement is only related to the PVD-improved soil layer and only occurs significantly in the middle zone of that layer over a few months. The middle zone may be related to the time delay of excess pore water pressure dissipation. This study concluded that the remaining primary consolidation in the PVD-improved soil layer is the primary cause of residual settlement, whereas secondary compression in the PVD-improved soil layer is only a minor cause.     

大直径深埋顶管施工对地表沉降的影响

顶管施工因非开挖或少开挖而在城市建设中应用广泛, 但顶管施工引起的地表沉降不容忽视。依托佛山市某电力隧道顶管工程, 通过现场实测、数值模拟及Peck经验公式的方法研究了顶管施工引起的地表沉降规律, 探讨了管-土摩擦、注浆压力及支护压力对地表沉降的影响。结果表明: 顶管施工引起的横向地表沉降在距轴线约4倍管径范围内变化较大, 管-土摩擦的改变对横向地表距轴线约3倍管径范围内的地表沉降影响较大, 对纵向地表距开挖面约1倍管径范围内的地表沉降影响较小; 注浆压力的增大能够抑制地表沉降; 支护压力的改变对横向地表距轴线约2倍管径范围内的地表沉降影响较大。研究结果可为控制顶管施工引起地表沉降措施的制定提供参考; 同时, 实测值、模拟值及Peck经验公式所得到的地表沉降变化趋势和大小相近, 验证了数值模拟及Peck经验公式在实际工程中预测地表沉降的可行性。      

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页岩气藏清水压裂悬砂效果提升实验

针对页岩气藏压裂中清水压裂悬砂效果较差问题,分析压裂液和支撑剂性质,通过实验提出增强清水压裂悬砂效果方法:纤维复合清水压裂液技术和超低密度支撑剂技术.结果表明:纤维的加入不仅使清水压裂液的悬砂性能得到提高,同时还可以显著降低液体摩阻.低密度支撑剂可以降低沉降速度50%以上.综合采用纤维复合清水压裂液技术和超低密度支撑剂技术,支撑剂2h的沉降率为17%.不仅可以提高清水压裂的开发效果,还可以降低对地面泵车排量的要求,对于页岩气藏的开发具有指导意义.     

Characteristics of thawed interlayer and its effect on embankment settlement along the Qinghai-Tibet Railway in permafrost regions

The formation of thawed interlayer beneath embankment can result in embankment settlement in permafrost regions. Based on the data on ground temperatures and deformations beneath the embankment, observed in-situ along the Qinghai-Tibet Railway in permafrost regions from 2006 to 2013, characteristics of the thawed interlayer beneath the embankment and its influence on the embankment settlement are studied. The results indicate that the thawed interlayer hardly forms beneath the natural field, and beneath the embankments from the Qinghai-Tibet Railway the thawed interlayer develops widely, and it can be refrozen totally in the regions with lower mean annual ground temperature, and developed further in the regions with higher mean annual ground temperature. The thawed interlayer is closely related to the embankment settlement. The ice content of permafrost underlying the thawed interlayer influences the settlement of embankment. The higher the ice content is, the larger the settlement is, and vice versa. The increase in thickness of thawed interlayer mainly results from the decline of artificial permafrost table in high-temperature permafrost regions.     

鲁北平原地面沉降现状与机理分析

该文详细论述了鲁北地区水文地质条件、工程地质条件。以多期水准测量数据为基础,以校验后的多年insar解译数据辅助,获取了鲁北地区地面沉降速率及多年累积地面沉降量。结果表明,鲁北平原年沉降速率大于50mm/a的地区面积502.73km~2,区内存在2个显著的沉降中心,一个位于德州市城区西北部张庄,地面累积沉降量超过1.3m,一个位于广饶县县城东北部,多年地面累积沉降量达1.605m,200mm沉降等值线圈闭面积14 904km~2,占鲁北平原区面积的34.34%。分析了鲁北平原地区地面沉降机理,建立了地面沉降与地下水水位相关关系,并针对现状问题提出了防治措施与建议。     

嘉兴市地下水资源开发区域规划

本文通过区域水文地质条件、地下水动态及环境地质问题的分析研究,针对当前嘉兴市地表水遭受污染,地下水严重超采,造成区域地下水位下降及地面沉降等环境地质问题,利用长期监测资料进行地下水开来资源评价,提出合理开发利用地下水资源的区域规划意见,为政府部门水资源综合规划、确定地下水开采量、实施地下水资源开发利用监督管理提供了科学依据。     

Assessments on slope instabilities triggered by engineering excavations near a small settlement (Turkey)

In this study, the mechanisms of slope instabilities triggered by engineering excavations at location of a planned tunnel portal in the northwest region of Turkey were assessed, and stability of the current slopes which has impacts on safety of a settlement (village) and agricultural fields was investigated. In the first stage of the study, in order to identify the geological units and structural properties of the sedimentary rocks in the area, to clarify the mechanisms of instabilities and to characterize discontinuity and rock mass properties field works were conducted. In this content, geotechnical boreholes, geophysical explorations between the boreholes, line surveys to explore discontinuity properties, preparation of slope profiles using topographical techniques and sampling of rock blocks and discontinuity planes were performed. In the second stage, laboratory tests were carried out on the samples to determine the geomechnical properties of the slope forming materials and discontinuities. Then, back analyses of the instabilities were made to assess the responsible shear strength parameters of the geological units during failures by considering laboratory shear test results too. Based on the backanalyses of the failures, the strength properties of the slope debris were estimated, and it has been clarified that the residual shear strength properties are the factors controlling slip mechanism along the beddings. Following the stability analyses, it is understood that a further instability along the mass or bedding planes in the failed and redesigned area are not expected, if the current slope geometry is not changed. However, safety factor calculated for the slope in the debris is 1.1 which is well below the recommended value in the literature. The minimum safety factor for currently stable slopes which were cut at the eastern part of the failed area is 1.22 which is also less than that suggested in literature. Some remedial measures such as mini-pile or slope flattening are suggested after analyses to increase the factor of safety for this part below the settlement.     

常用粮仓地坪沉降观测方法及精度分析

中央直属储备粮库是国家重要的基础设施,为确保新建粮库储粮安全,必须进行粮库新仓初始装粮压仓试验,利用仓内地坪沉降观测数据对云梯升降法、悬尺法、倒尺法的精度进行分析,得出倒尺法是仓内地坪沉降观测的最佳方法。     

圆形网箱浮架结构有限元分析

在开放的海洋环境中,网箱浮架结构的强度和变形对网箱的安全有重要的意义。以某圆形HDPE网箱浮架结构为研究对象,采用壳单元和板单元,建立了三维有限元模型,分析了浮架结构在分布阻力、锚绳力及迭加载荷作用下的应力和变形,对浮架结构在不同的缆绳系附下的承载极限进行了评估。计算结果表明:缆绳系附处应力水平高,是浮架结构的危险点;浮架结构的变形和应力与网箱系统的载荷特点及缆绳系附方式密切相关;缆绳系附方式不同,浮架结构的承载极限有很大差别。     

阿博高速公路软土地基沉降监测分析

沉降观测是验证软土地基设计、指导施工的重要手段,对阿荣旗至博克图高速公路K42+400～K42+500段软土地基处理后现场沉降观测结果及差异沉降量进行分析,表明沉降主要发生在集中填筑期内,沿路基横断面沉降量的分布是不均匀的;验证了采用砂垫层+土工格栅法处理软土地基对减小横向差异沉降和提高地基承载力效果良好。     

Study on adverse effects of groundwater level rising induced by land creation engineering in hilly and gully area of the Loess Plateau

Land creation projects have been implemented in China to expand urban space in mountainous areas. In addition to the predictable settlement brought about by filling construction,varying degrees of land subsidence and engineering failures have a demonstrated relationship to groundwater level fluctuation induced by land creation engineering. In this work, we adopted a typical large-scale land creation project, Yan'an New City in Shaanxi province, West China, as our study area. Prior to conducting the main experiment,preliminary field investigation and groundwater level monitoring were conducted to determine the groundwater fluctuation trend induced by land creation engineering. Although a blind drainage system was implemented, the depth aspect of groundwater level changes after large-scale land creation still needed to be addressed. To study the degree of impact and the settlement mechanism induced by the rising groundwater level, we conducted a Water Immersion Test(WIT) in a typical land creation site for 107 days. The rising groundwater level was simulated by injecting water from the bottom of the filling foundation. During the WIT, the soil water content, surface subsidence, and internal settlement of soil at different depths were obtained. Surface subsidence development could be categorized into four stages during the water level increase. The second stage, which is defined as the point when the groundwater level rises to 10 m,marked the critical point in the process. Furthermore,it was ascertained that the local settlement in regions that were originally composed of steep slopes is larger than that in originally flat areas. In addition, ground cracks and sinkholes in the study area were inspected;and it was determined that they would become new channels that would accelerate water infiltration and exacerbate the settlement. Based on the results from our field investigation and testing, several suggestions are proposed for land creation projects to mitigate issues associated with construction-induced groundwater level rising.     

利用SBAS-InSAR技术监测菏泽市地面沉降

采用SBAS-InSAR技术对菏泽市65景Sentinel-1A SAR数据进行处理,获取菏泽市2017-05-20~2021-05-23的沉降结果,并结合地下煤矿工作面的开采对各成像时期的地面沉降情况进行精细化分析,最后利用实际水准数据对SBAS-InSAR监测结果进行精度验证。结果表明,研究时段内,菏泽市地面沉降不断加速,郓城地区沉降较为严重,最大年平均沉降速率达-311 mm/a,最大累积沉降量达-1 269 mm。SBAS-InSAR监测到的沉降位置和沉降变化趋势与水准测量结果相符,但在沉降严重区域,SBAS-InSAR监测到的沉降量与实际水准测量结果有一定差异。     

曹县梁堤头地区第四系地裂缝成因及防治

鲁豫交界的曹县黄河故道地区,地势较高的自然堤堤缘区是地裂缝等地质灾害的高发区。地裂缝主要由地表厚粘土层干湿胀缩产生,有一定的隐蔽性,并受地形和大气影响。地下水动态变化对地裂缝影响不大。地表裂隙张力的直接作用、建筑物的非均质土地基不均匀沉陷等因素的存在共同导致了该区民房开裂。可以采取加固地基和搬迁避让等方法进行防治。     

西南山区交通工程弃渣的工程特性评价及其分类

山区交通工程弃渣力学参数的准确测定,一直是弃渣场边坡稳定性评价面临的基础科学问题。在山区交通工程弃渣场运行特点和弃渣固体废弃物特征认知的基础上,探讨弃渣取样和试验代表性问题的物理根源,依托实际工程累计数据尝试提出简单实用的弃渣工程特性评价和分类方法。结果表明:①常规交通工程弃渣的密度、颗粒分析和强度试验,由于弃渣的粒径范围差异大、颗粒空间分布不均、弃渣来源复杂等固体废弃物特征造成取样和试验代表性难题;用多阶段坡角测量和颗粒分析试验代替传统的弃渣边坡试验,解决了试验和取样代表性难题。②利用弃渣粗细比可将弃渣分为细粒弃渣、混合型弃渣和粗粒弃渣。③根据弃渣粗细比、天然休止角和整形坡率,将西南山区交通工程弃渣分为细粒弃渣、混合型弃渣和粗粒弃渣等3类。细粒弃渣,弃渣粗细比小于0.3,天然休止角小于31.5°,整形坡率为1.00∶2.00;混合型弃渣,弃渣粗细比为0.3~1.0,天然休止角为31.5°~39.5°,整形坡率为1.00∶2.00~1.00∶1.50;粗粒弃渣,弃渣粗细比大于1.0,天然休止角大于39.5°,整形坡率为1.00∶1.50。④用多阶段坡角测量、颗粒分析试验和无黏性土边坡稳定性系数计算公式代替传统的弃渣边坡试验和稳定性系数计算方法,方法简单,结果保守,可以作为弃渣边坡稳定性评价和安全控制技术的有益补充。