大坂山隧道地下水动态分析及对隧道作用评估

Base on the groundwater yield, water temperature and hydrochemistry change of the groundwater, we can analyze that the summer water content is obviously greater than winter water content where the in and-out wall rock of the Daban Mountain tunnel. The groundwater supply has the extensity and the seasonality. The groundwater content of the middle tunnel wall rock changes relatively steady, mainly supply through horizontal direction. And the total groundwater content is relatively little and steady in winter. The water pressure of the wall rock cranny is little. It has the fluent drainage system to dredge groundwater, which cannot constitute a threat to the tunnel lining. And the cold-proof sluice hole can normally work to drain water.     

Modification of Stokes and Vening-Meinesz formulas for the inner zone of arbitrary shape by minimization of upper bound truncation errors

Traditionally, the evaluation of geoidal height by Stokes formula and the vertical deflection by Vening-Meinesz one, and the estimation of the influence of neglecting the distant zone on computing the geoidal height and the vertical deflection were done by taking the inner zone as a spherical cap. It is not very convenient from the point of view of modern numerical methods such as fast Fourier and Hartley transforms where the inner zone is not a spherical cap, but a spherical trapezoid. So, we generalized the known formulas for evaluating the geoidal height and the vertical deflection for an integration area of arbitrary shape. The corresponding formulas for computing the effects of neglecting the distant zone have been derived. Some issues on computation techniques have been investigated. As an example, the case where the inner zone is modeled as a spherical trapezoid was given special attention, and practical computations were performed.     

不同晶形石盐沉积生长特征及对包裹体温度的影响

石盐晶体生长过程中捕获流体包裹体，利用冷冻测温法得到的均一温度信息与古水温存在良好的相关性。在部分地区，利用包裹体最大均一温度评价古气候时，温度数据与孢粉学反映的气候特征存在冲突，不同晶形的石盐沉积特征，及其晶体条纹内包裹体温度代表的地质含义需进一步探讨。笔者在分析经典测温数据的基础上，观察常温蒸发实验中漏斗晶和人字晶的形成及生长过程，分析了不同温度段均一温度与气温、水温之间的关系。结合现代气象记录数据，分析了最大均一温度评价气候时存在的局限性。研究认为：漏斗晶晶核形成与卤水表面，包裹体温度受温度和气压共同影响，漏斗晶在卤水底部绕核生长，漏斗晶外围包裹体温度对应水底温度，沉入水下后漏斗晶生长缓慢，包裹体最大温度可能代表年度最高温度，以此为指标评价气候得出的结论过于炎热；人字晶是多个漏斗晶之间的桥接部分，大部分形成于卤水蒸发将近结束之时，人字形条纹内包裹体温度受气温和地表温度共同影响，地表温度远大于气温是造成包裹体最高温度过高的主要原因。     

青藏高原南部及邻区深部碳释放规模与成因

不同构造背景下的深部碳释放通量与机制研究对于深刻理解长时间尺度的气候变化具有重要意义,以往的相关研究多集中在洋中脊、大洋俯冲带和大陆裂谷等地质单元,缺少对大陆碰撞带深部碳释放规模与机理的关注,从而制约了对大陆碰撞带深部碳循环过程及其气候环境效应的进一步认识。青藏高原起源于印度和欧亚大陆的碰撞,是研究大陆碰撞带深部碳循环的理想地区。为此,在近年来青藏高原温室气体释放野外观测与研究的基础上,本文估算了高原南部及邻区火山-地热区的CO₂释放规模并探讨了其释放模式。气体He-C同位素地球化学与温泉水热活动特征等显示,青藏高原南部及邻区的深部碳释放主要受深部岩浆房、断裂和浅部水热系统等因素的控制。依据深部流体源区和上升运移控制因素的差异,可以将青藏高原南部及邻区的深部碳释放划分为三大类:(1)以壳内水热系统脱碳为主的藏南地区;(2)深大断裂控制的以水热系统脱碳为主的川西地区;(3)深部岩浆房和浅部水热系统共同控制的滇西南地区。青藏高原南部土壤微渗漏CO₂释放通量介于18.7~52.3Mt/yr之间,温泉溶解无机碳释放通量约为0.13Mt/yr;高原邻区的川西、滇东南断裂带温泉CO₂释放规模为0.1Mt/yr;腾冲火山区CO₂释放通量介于4.5~7.1Mt/yr之间。本研究认为,青藏高原南部及邻区每年向大气圈释放CO₂的规模为23.4~59.6Mt,这一规模与全球其他构造背景(如洋中脊、大洋俯冲带、大陆裂谷等)火山区深部碳释放规模相当,表明以青藏高原为代表的大陆碰撞带是地质源CO₂释放的重要场所。     

Monotonic and cyclic characteristics of K0-Consolidated saturated soft clay under a stress path involving a variable confining pressure

In certain field conditions such as offshore projects under wave loads or embankments under traffic loads, both the vertical and horizontal stresses are variable. However, previous investigations rarely considered the variation in horizontal stress. To better understand the characteristics of natural saturated soft clay, a series of monotonic and cyclic triaxial tests with a K₀-consolidation state were carried out under a variable confining pressure (VCP) stress path. The development of axial strain, pore water pressure and effective stress path is analysed. The results show that with the increase in η (the ratio of the variation in the mean effective principal stress to that of the deviatoric stress), the undrained shear strength (q_f) decreases continuously. The pore water pressure generation is slightly improved under a stress path with increasing confining pressure. Based on the test results, a unified formula was established to predict the pore water pressure under VCP stress paths. The unique p–q–e relationship of normally consolidated clay in monotonic VCP triaxial tests was also demonstrated. Under VCP stress paths, the amplitude of the pore pressure increases, and the effective stress path tilts more sharply to the right. Moreover, a unified formula was established that can provide a good reference for predicting effective stress paths under cyclic VCP triaxial tests.

     

Accelerating consolidation of soft ground by aerosol injection technique: a field study

We present an aerosol injection technique (AIT) to accelerate the consolidation of soft soils for ground improvement. We employ high-pressure aerosol injections at different depths to enhance the drainage in soft soils for faster consolidation. The technique is briefly described. A well-instrumented field test is carried out to demonstrate its performance. Compared to the traditional methods, our approach gives rise to faster dissipation of excess pore pressure and larger ground settlement. This method is particularly attractive for the improvement in soft ground in medium depths.

     

Effect of freeze–thaw cycles on strength and ductility and microstructure of cement-treated silt with polypropylene fiber

Acta Geotechnica - In this paper, the strength, ductility and microstructure behavior of cement-treated silt with polypropylene fiber was studied by a host of experimental studies. The influence of...     

Movement process analysis of the high-speed long-runout Shuicheng landslide over 3-D complex terrain using a depth-averaged numerical model

Landslides - Flow-like landslide is one of the most catastrophic types of natural hazards due to its high velocity and long travel distance. In 2019, a large catastrophic landslide was triggered by...     

Comprehensive analysis control effect of faults on the height of fractured water-conducting zone in longwall mining

Natural Hazards - In order to examine the height of a fractured water-conducting zone due to the presence of a fault, a typical working face in the Baodian Coal Mine which is located in the Yanzhou...     

黔西北峨眉山玄武岩顶部Fe-Al岩系钪、铌、稀土分布特征与富集规律

在黔西北峨眉山玄武岩顶部与上覆宣威组(P3x)/龙潭组(P3l)不整合接触界面附近,常分布一套Fe-Al岩系,近年发现其中Sc、Nb和REE等关键金属富集特征显著,对这套铁铝岩系中Sc、Nb、REE的分布特征、富集规律和赋存形式研究.结果表明:1)Fe-Al岩系中富集的Sc、Nb和REE等关键金属,多数已达到综合利用标准,具有较好成矿前景;2)宣威组(P3x)Fe-Al岩系中,Sc、Nb和REE分布均匀、差异较小,Sc主要富集于下部,Nb主要富集于上部,REE主要富集于中下部,主要赋存岩性分别为含凝灰质铁质粘土岩、豆鲕状铝土质粘土岩和铝质粘土岩;3)龙潭组(P3l)Fe-Al岩系中,Sc主要分布于中部和南西部,Nb和REE主要分布于北部、南西部,Sc主要富集于下部,Nb和REE主要富集于上部及上覆煤系地层底部,主要赋存岩性分别为凝灰质粘土岩、植物屑粘土岩和碳质粘土岩;4)Sc和Nb主要以类质同象形式呈分散状态赋存于粘土矿物、独居石、金红石等中,REE以离子吸附态、类质同象和独立矿物等多种赋存;5)Sc、Nb,REE富集经历了风化作用初始富集,后期成岩改造作用再次富集过程,此外,还与Fe-Al岩系完整性有关.