New methods of safety evaluation for rock/soil mass surrounding tunnel under earthquake

The objective of this work is to obtain the seismic safety coefficient and fracture surface and proceed with the seismic safety evaluation for the rock mass or soil mass surrounding a tunnel,and the limitation of evaluating seismic stability is considered using the pseudo-static strength reduction.By using the finite element software ANSYS and the strength reduction method,new methods of seismic safety evaluation for the rock mass or soil mass surrounding a tunnel are put forward,such as the dynamic finite element static shear strength reduction method and dynamic finite element shear strength reduction method.In order to prove the feasibility of the proposed methods,the results of numerical examples are compared with that of the pseudo-static strength reduction method.The results show that 1) the two methods are both feasible,and the plastic zone first appears near the bottom corners; 2) the safety factor of new method Ⅱ is smaller than that of new method I but generally,and the difference is very small.Therefore,in order to ensure the safety of the structure,two new methods are proposed to evaluate the seismic stability of the rock mass or soil mass surrounding a tunnel.A theoretical basis is provided for the seismic stability of the rock mass or soil mass and the lining surrounding a tunnel and also provided for the engineering application.

Kinetic Mass Transfer Between Non-aqueous Phase Liquid and Gas During Soil Vapor Extraction

The mass transfer between non-aqueous phase liquid(NAPL) phase and soil gas phase in soil vapor extraction(SVE) process has been investigated by one-dimensional venting experiments. During quasi-steady volatilization of three single-component NAPLs in a sandy soil, constant initial lumped mass transfer coefficient (λgN,0) canbe obtained if the relative saturation (ξ) between NAPL phase and gas phase is higher than a critical value (ξc), andthe lumped mass transfer coefficient decreases with ξ when ξ＜ξc. It is also shown that the lumped mass transfercoefficient can be increased by blending porous micro-particles into the sandy soil because of the increasing of theinterfacial area.

A ^(210)Pb_(ex) mass balance model in cultivated soils in consideration of the radionuclide diffusion

The existing^(210)Pb_(ex)mass balance models for the assessment of cultivated soil erosion are based on an assumption that^(210)Pb_(ex)is quite evenly mixed within the plough layer.However,the amount of^(210)Pb_(ex)distributed in the soils below the plough depth,like a downward tail in the lower part of the^(210)Pb_(ex)profile,has been largely ignored.In fact,after the initial cultivation of undisturbed soils,^(210)Pb_(ex)will diffuse downward from plough layer to the plough pan layer due to the concentration gradient.Assuming^(210)Pb_(ex)inventory is constant,the depth distribution in the two layers of the cultivated soils will achieve a steady state after continuous cultivation for 10.37 years,when^(210)Pb_(ex)is evenly distributed in the soils of the plough layer with an exponential concentration decline with depth in the soils of the plough pan layer,and the^(210)Pb_(ex)concentration at any depth will be invariable with time.The work reported in this paper attempts to explain the formation of the^(210)Pb_(ex)tail in the soil profile below the plough depth by theoretical derivation of the^(210)Pb_(ex)depth distribution process in the two layers of the cultivated soils,propose a^(210)Pb_(ex)mass balance model considering^(210)Pb_(ex)diffusion based on the existing model,and discuss the influence of the^(210)Pb_(ex)tail to the existing model.

Multiple Tuned Mass Damper Based Vibration Mitigation of Offshore Wind Turbine Considering Soil–Structure Interaction

The dynamics of jacket supported offshore wind turbine （OWT） in earthquake environment is one of the progressing focuses in the renewable energy field. Soil-structure interaction （SSI） is a fundamental principle to analyze stability and safety of the structure. This study focuses on the performance of the multiple tuned mass damper （MTMD） in minimizing the dynamic responses of the structures objected to seismic loads combined with static wind and wave loads. Response surface methodology （RSM） has been applied to design the MTMD parameters. The analyses have been performed under two different boundary conditions： fixed base （without SSI） and flexible base （with SSI）. Two vibration modes of the structure have been suppressed by multi-mode vibration control principle in both cases. The effectiveness of the MTMD in reducing the dynamic response of the structure is presented. The dynamic SSI plays an important role in the seismic behavior of the jacket supported OWT, especially resting on the soft soil deposit. Finally, it shows that excluding the SSI effect could be the reason of overestimating the MTMD performance.

Mathematical Model of Coupled Heat and Mass Transfer in Unsaturated Soils

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A Simplified Method for the Stress Analysis of Underground Transfer Structures Crossing Multiple Subway Tunnels

According to the design specifications,the construction of extended piles involves traversing the tunnel’s upper region and extending to the underlying rock layer.To address this challenge,a subterranean transfer structure spanning multiple subway tunnels was proposed.Deliberating on the function of piles in the transfer structure as springs with axial and bending stiffness,and taking into account the force balance and deformation coordination conditions of beams and plates within the transfer structure,we established a simplified mechanical model that incorporates soil stratification by combining it with the Winkler elastic foundation beam model.The resolved established simplifiedmechanicalmodel employed finite difference technology and the Newton-Simpsonmethod,elucidating the mechanical mechanism of the transfer structure.The research findings suggest that the load carried by the upper structural columns can be transferred to the pile foundation beneath the beams through the transfer structure,subsequently reaching the deep soil layer and ensuring minimal impact on adjacent tunnels.The established simplified analysis method can be used for stress analysis of the transfer structure,concurrently considering soil stratification,pile foundation behavior,and plate action.The pile length,pile section size,and beam section size within the transfer structure should account for the characteristics of the upper load,ensuring an even distribution of the beam bending moment.

民勤荒漠区不同植物群落土壤微生物生物量碳氮及生态化学计量特征

以甘肃民勤连古城荒漠区5种典型植物群落为对象,测定了土壤微生物生物量碳(MBC)和土壤微生物生物量氮(MBN)及其影响因素,分析土壤MBC、MBN的空间变化特征。结果表明:(1)不同植物群落间,土壤MBC的最大值出现在红砂群落(282.90 mg/kg),土壤MBN最大值出现在膜果麻黄群落(28.27 mg/kg)。(2)不同植物群落间,白刺群落的微生物量熵(qMB)最大,最小值出现在人工梭梭群落,5种植物群落间土壤qMB差异不显著。土壤微生物生物量碳氮比(MBC/MBN)的最大值出现在白刺群落,显著高于膜果麻黄群落和人工梭梭群落。(3)土壤MBC、MBN与生态化学计量之间存在相关关系。其中,土壤MBC与土壤全氮(TN)和有效磷(EP)呈显著正相关(P<0.05),与土壤硝态氮(NO_(3)^(-)-N)和含水率(WC)呈极显著正相关(P<0.01)。土壤MBN与土壤WC显著正相关(P<0.05),与土壤EP和速效钾(AK)呈极显著正相关(P<0.01),与土壤TN、NO_(3)^(-)-N呈正相关,且相关性达到极显著水平(P<0.001)。冗余分析进一步显示,NO_(3)^(-)-N和TN是影响土壤MBC、MBN的主要因子。综上所述,不同植物群落间土壤MBC、MBN不同,以红砂群落和膜果麻黄群落最为显著;土壤TN、EP、土壤NO_(3)^(-)-N和WC是影响土壤MBC的主要因子,土壤WC、土壤EP、AK、土壤TN和NO_(3)^(-)-N是影响土壤MBN的主要因子。

液相色谱-串联质谱法测定土壤、沉积物和水中3种新型除草剂残留

除草剂在杂草和有害植物防控上发挥着重要的作用,但其有效利用率低,大量除草剂进入环境中,对生态环境和人类健康构成了潜在威胁,因此建立环境样品中除草剂的残留分析方法尤为重要。该文采用电喷雾正离子源模式,建立了液相色谱-串联质谱法(LC-MS/MS)测定土壤、沉积物和水中异噁唑草酮、吡唑草胺和苯嘧磺草胺残留量的方法。土壤和沉积物样品经乙腈振荡提取、盐析后经C18固相萃取小柱净化,水样过滤后经C_(18)固相萃取小柱净化;再用LC-MS/MS测定样品中异噁唑草酮、吡唑草胺和苯嘧磺草胺的残留量。实验优化了仪器检测和前处理条件,考察了方法的线性关系、基质效应、检出限和定量限,并选取4种土壤、2种沉积物和水样进行了方法验证。在0.0005~0.02 mg/L范围内,异噁唑草酮、吡唑草胺、苯嘧磺草胺的线性关系均良好,r≥0.9961。3种除草剂在土壤、沉积物和水中的基质效应为-10.1%~16.5%。异噁唑草酮、吡唑草胺和苯嘧磺草胺的检出限分别为0.05、0.02、0.01μg/kg,定量限分别为0.2、0.05、0.05μg/kg。异噁唑草酮、吡唑草胺和苯嘧磺草胺在土壤、沉积物和水样中3个水平(0.005、0.1、2.0 mg/kg)下的加标回收率分别为77.2%~101.9%、77.9%~105.1%、80.8%~107.1%;相对标准偏差(RSD)分别为1.4%~12.8%、1.2%~7.7%、1.5%~11.5%。结果表明:本方法操作简单,方法稳定,定量准确,实用性强,可用于土壤、沉积物和水中异噁唑草酮、吡唑草胺和苯嘧磺草胺残留量的检测。

富水卵漂石地层盾构近距离下穿运营地铁隧道施工技术研究

[目的]富水卵漂石地层盾构下穿既有地铁线路施工过程中,易导致既有地铁线路上方土体不规则沉降超出控制范围,进而可能引发地下水喷涌和地面塌陷问题。为此,需要对富水卵漂石地层盾构近距离下穿运营地铁隧道的施工技术进行研究。[方法]以新建成都地铁17号线凤溪大道站盾构下穿既有地铁4号线为案例,在阐述工程概况的基础上,选取了4个地面沉降测点和4个深层土体沉降测点,分析了盾构掘进过程中地层的沉降变化规律。采用MIDAS GTS软件建立了三维有限元模型,对采用38 m超长管棚与斜向注浆相结合的加固施工进行模拟,对4号线隧道预加固效果进行了分析。基于此,明确了地面跟踪注浆的时机,进一步分析了地面跟踪注浆的效果。[结果及结论]该加固措施有效提高了4号线结构底部土体的整体性,改善了4号线结构的受力状况,有效控制了4号线的结构沉降。

液相色谱-质谱法测定土壤中的溴敌隆

本研究建立了乙醇超声提取后直接上机测定土壤中溴敌隆的液相色谱-串联质谱法。基于多反应监测离子对信息以及保留时间完成目标物的定性分析,根据定量离子对的峰面积采用外标法进行定量分析。结果表明,溴敌隆在0.5~100 ng/mL范围内线性关系良好,相关系数大于0.99;方法的检出限为0.795 ng/g,定量限为2.55 ng/g;平均回收率为88.4%~93.9%,相对标准偏差为3.1%~6.7%。本方法灵敏度高、准确性好、样品用量少且操作简单,适用于土壤中溴敌隆的定性定量分析,可为评估环境土壤中的溴敌隆残留提供技术支持。

真空冻干/快速溶剂萃取-气相色谱-质谱法测定土壤中35种不同种类半挥发性有机物

建立了真空冻干/快速溶剂萃取-气相色谱-质谱法(GC-MS)测定土壤中35种不同种类半挥发性有机物(SVOCs)的方法。样品经真空冷冻脱水、快速溶剂萃取、旋转蒸发浓缩以及固相萃取SPE小柱净化后,氮吹定容,采用GC-MS上机测定。结果表明:土壤中35种SVOCs在10~1000μg/L范围内线性相关系数r^(2)≥0.991,方法检出限为0.034~0.40μg/kg,方法定量限为0.14~1.20μg/kg;以空白样品为基体进行加标回收实验,所得加标回收率为71.2%~113%,相对标准偏差(RSDs,n=7)为0.38%~13.3%,替代物荧蒽-D 10回收率为84.0%~92.5%;经实际样品检测验证,该方法灵敏、快速、准确可靠,适用于土壤中35种不同种类SVOCs的分析检测。

高效液相色谱串联质谱法分析沉积物中壬基酚和双酚A

建立并优化了基于超高相液相色谱-三重四级杆串联质谱技术测定沉积物中壬基酚和双酚A含量的方法。沉积物样品经HLB-SPE萃取柱处理后,以甲醇-5 mmol甲酸铵为流动相,通过Agilent Eclipse Plus C18 RRHD超高效液相色谱柱进行分离和分析,选择电喷雾离子源,多反应监测负离子模式下进行测定。结果表明,壬基酚和双酚A在质量浓度5~100μg/L范围内均呈良好的线性关系,R^(2)≥0.99,检出限范围为0.066~0.14μg/L,平均回收率为88.9%~105%,精密度为2.97%~8.20%。方法的选择性、灵敏度及准确性均良好,可实现沉积物中壬基酚和双酚A含量的同时准确测定。

Temperature Sensitivity of Soil Respiration Probed by Numerical Analysis of Field-Observed Data Sets

Temperature sensitivity of soil respiration is essential to predict possible changes in terrestrial carbon budget on various scenarios about atmospheric and soil climates. Although it is often evaluated by using respiratory quotient “Q10”, Q10 values of soil respiration seem to vary depending on methods or scales of evaluation. Aiming at probing how Q10 values of soil respiration are evaluated differently for a field, this study used a model of soil respiration rate, and numerically evaluated soil respiration rates along depth by fitting the model to depth distributions of CO2 concentration measured in a field. And temperature sensitivity of soil respiration rate was evaluated by comparing the determined soil respiration rates with atmospheric and soil temperatures measured in the field. The results showed that the relation between surface CO2 emission rates and atmospheric temperatures was represented by lower Q10 values than that between soil respiration rates and soil temperatures, presumably because the top soil layers had acclimatized in more extent to the existing thermal regime than the underlying deeper layers. Thus, for evaluating effects of long-term rise in atmospheric temperature on soil respiration, it is necessary to precisely predict the long-term change in depth distribution of soil temperature as well as to quantify temperature sensitivity of soil respiration along depth. The evaluated sensitivity of surface CO2 emission rate to atmospheric temperature showed hysteresis, implying the needs for more knowledge about temperature sensitivity of soil respiration evaluated in both warming and cooling processes for better understandings and predictions about terrestrial carbon cycling.

QuEChERS-气相色谱质谱法测定土壤中5种氨基甲酸酯农药残留

建立QuEChERS-GC/MS法测定土壤中5种氨基甲酸酯农药残留的方法。实验结果表明,5种氨基甲酸酯农药标准曲线在5.00~400μg·L^(-1)浓度范围内线性关系良好,相关系数均大于0.995,加标回收率在88.7%~105.5%之间,相对标准偏差为1.86%~4.08%。该方法操作简单、灵敏度好、测试高效准确,可用于土壤中多种痕量氨基甲酸酯农药残留的测定。

软土地区大体积混凝土水化热数值模拟分析

针对上海软土地区某深大基坑底板施工工况,建立大底板浇筑过程的数值计算模型,并对大体积混凝土浇筑过程后的温度场分布等因素进行分析。结果表明,在该基坑大底板混凝土浇筑过程中,大底板混凝土的最高温度出现在中心位置,混凝土内外最大温差约为25.3℃。混凝土上表面的最大拉应力达到2.5 MPa。本工程需要采取相应措施对混凝土温升进行控制。本研究可为类似工程提供一定的理论指导。

下沉式深基坑工程信息化施工监测分析

以某处理厂为视角,针对其下沉式深基坑开展全面的工程监测工作:合理使用控制网,获取较为精确的测量数据,对围护、基坑各个点位进行有效监测。经实践监测发现:围护各项监测结果,虽然均处于警报值以外,但整体围护结构具有较强的平稳性,能够保证基坑工程有序进行。

长沙市某区浅层地埋管岩土体热响应试验性能研究

长沙市某区为高新技术发展示范基地,能源冷热需求量大,该片区地质条件复杂,邻近少有地源热泵热响应测试数据,通过性能研究,揭露研究区地层以第四系覆盖层及元古界泥岩、砂岩、板岩为主,10~40 m存在上层少量上层滞水;通过线热源模型热响应试验,测试岩土体综合平均导热系数为1.78~1.95 W/(m·K),钻孔热阻值为0.18~0.23(m·K)/W,并与钻孔取芯和室内热物性测试进行对比,吻合度较好。考虑长沙地区气候特征,在不考虑大量钻孔换热过程中存在热干扰和长时间持续运行情况下,通过换热计算,夏季每延米换热量最大可达51~53 W/m,冬季每延米换热量最大取值为47~49 W/m。

引黄灌区连续减施化肥对春小麦产量稳定性的影响

【目的】探索宁夏引黄灌区连续减施化肥对土壤氮、磷、钾养分供应及春小麦产量的影响,并分析影响产量稳定性的因素,为化肥合理减施、春小麦高产稳产提供理论依据。【方法】以宁春4号春小麦为供试作物,2019-2022年连续4年开展化肥减施田间定位试验,试验设置常规施肥(CF,N 270 kg·hm^(-2)、P_(2)O_(5)150 kg·hm^(-2)、K_(2)O 75 kg·hm^(-2))、减量施肥下限(RF1,N 180 kg·hm^(-2)、P_(2)O_(5)45 kg·hm^(-2)、K_(2)O 30 kg·hm^(-2),与传统施肥相比减N 33.3%、减P_(2)O_(5)70.0%、减K_(2)O 60.0%)、减量施肥上限(RF2,N 225 kg·hm^(-2)、P_(2)O_(5)75 kg·hm^(-2)、K_(2)O 45 kg·hm^(-2),与传统施肥相比减N 17.0%、减P_(2)O_(5)50.0%、减K_(2)O 40.0%)及不施肥(CK)处理,分析春小麦生育期间气候因素,播前土壤水分含量,播前和收获期土壤矿质态氮、速效磷、速效钾含量,收获期春小麦地上部干物质累积量、籽粒产量及产量构成因素的差异及相互关系。【结果】2019-2022年播前土壤水分含量存在年际差异,其中2022年的较低,平均值仅为19.5%;除2020年受施肥处理显著影响外,其余年份各施肥处理之间无显著差异。播前和收获期土壤矿质态氮、速效钾和速效磷含量均以常规施肥(CF)处理较高,RF2处理次之,且两者之间无显著差异,而RF1处理的趋于降低。2019年,地上部干物质累积量和产量均以CF处理最高,分别为23261.7和9449.0 kg·hm^(-2),较RF2处理增幅分别为2.8%-4.5%和3.2%-16.0%,而2020-2022年均以RF2处理较高,但与CF处理之间无显著差异,且4年籽粒产量表现最稳定;从年际变化来看,所有施肥处理的公顷穗数、千粒重、产量均呈逐年下降的趋势,因此施肥量并不是造成产量年际差异的主要原因,而是与播前土壤水分、降水量、气温、湿度和风速有密切关系,其中2022年产量的降低主要与较低的播前土壤水分、灌浆期的干热风现象及氮肥基追比的改变有关。【结论】宁夏引黄灌区连续适量减施化肥(N225 kg·hm^(-2)、P_(2)O_(5)75 kg·hm^(-2)、K_(2)O 45 kg·hm^(-2),相对常规施肥减N 17.0%,减P_(2)O_(5)50.0%,减K_(2)O 40.0%)不会显著降低土壤氮、磷、钾的供应能力,且一定程度上提高了春小麦公顷穗数、穗粒数和千粒重,促进地上部干物质量向籽粒的转移和积累,从而趋于提高春小麦的籽粒产量。但是,春小麦产量受降雨、风速、湿度等气候因素和土壤墒情、连作障碍、氮肥追施比等的影响而存在年际差异,其中,气温、相对湿度和风速是影响小麦产量差异的主要因素,其对施肥效果的影响需做进一步研究。

土岩复合地层深基坑桩锚支护数值分析

为探究土岩复合地层基坑中不同桩锚支护形式的结构响应规律,该文依托梧州市某民用深基坑工程,采用PLAXIS数值分析软件分别建立吊脚桩与落底桩两种支护形式的二维数值分析模型,分析对比两者的桩体水平位移变化规律与基坑外土体沉降模式。结果表明:基坑开挖过程中,吊脚桩的整体变形模式由“悬臂式”逐渐向“悬臂+平动”转变,而落底桩的整体变形模式是由“悬臂式”逐渐向“凸肚形”转变;吊脚桩与落底桩的坑外土体沉降模式分别呈现倒三角形分布与凹槽形分布,同时吊脚桩的沉降影响范围较小。该研究对日后相似的工程应用具有一定的参考价值。

电感耦合等离子体质谱(ICP-MS)法测定土壤中6种重金属元素的不同前处理方法比较

样品前处理是测定土壤中重金属元素的关键步骤,为保障测定结果能如实反应土壤环境状况,比较不同的前处理方法对土壤中6种重金属元素的同时提取能力。基于电感耦合等离子体质谱技术,采用微波和石墨消解装置,探索消解过程中酸种类、加酸方式、消解装置、赶酸温度等因素对测定土壤标准品和实际样品结果的影响。结果表明,样品通过依次加入盐酸、硝酸、氢氟酸、高氯酸,并在160℃赶酸的石墨消解方式进行前处理能快速、准确地测定土壤中的Cu、Pb、Zn、Cd、Cr、Ni等6种元素,其前处理时长约8.5 h,并且消解成本比微波消解更低。在优化条件下,土壤标准样品中6种重金属元素检测结果的绝对回收率为91.5%~108%,相对标准偏差为0.80%~5.4%,方法检出限为0.02~2 mg/kg。表明方法的灵敏度高、准确度与精密度好,适用于批量土壤样品的分析。