Since the 1950’s， 212 earth fissures have been discovered in the Wei River Basin. During a field survey in 2016， an additional 48 earth fissures were discovered in Anren area， northeast of the Wei River Basin. The characteristics and formation mechanisms of these fissures were studied through field investigations， measurements， trench excavation， and drilling. On-site investigations indicated that these earth fissures were distributed along a fault-controlled geomorphic boundary. Fissures trended at 60°–80° NE and were divided into five groups. Trenches revealed multiple secondary fissures， exposing severe soil ruptures in the shallow earth surfaces. Drilling profiles revealed that earth fissures dislocated several strata， and resembled synsedimentary faults. Seismic reflection profiles revealed buried faults beneath the earth fissures. The Anren area fissures formed in the following three stages: regional extension that initially generated multiple buried faults; seismic activity rupturing multiple strata， resulting in multiple buried fractures; and finally， erosion processes that propagated the buried fractures to the surface， forming the current earth fissures.

Red sand is widely distributed on the west coast of Africa, south of the Sahara, and is an essential material for local engineering construction. Red sand possesses orthostasis and high sensitivity to water, exhibiting characteristics that are different from ordinary sandy soil. Laboratory and in-situ tests were conducted to assess its engineering characteristics, including collapsibility, shear characteristics, and bearing capacity. The water sensitivity of red sand was analyzed along with the images from a scanning electron microscope. The findings indicate that red sand can be classified as silty sand. It demonstrates strong collapsibility, with the collapsibility coefficient decreasing as water content increases. The critical water content for red sand to avoid collapsibility is 13%. The shear strength, internal friction angle, and cohesion of undisturbed and remolded red sand decrease with increasing water content. The critical water content for red sand to lose cohesion is 13%. The bearing capacity and deformation modulus of red sand decrease with increasing water content. Red sand exhibits a softening property, with a softening coefficient of 0.4. The water sensitivity of red sand can be attributed to the cementing effects of fine-grained clay minerals adhering to the surface of large particles or aggregating at particle contacts.

A healthy water ecosystem within a river basin is essential for maintaining ecological security, preserving species diversity, and ensuring sustainable socio-economic development. Unfortunately, human activities have significantly threatened the health of water ecosystems in various basins. Consequently, timely restoration and targeted protection of damaged river ecosystems have become crucial objectives in watershed management. As a prerequisite and cornerstone for river protection and management, assessing river ecological health has emerged as a primary focus in current research. In this study, we selected the Wei River Basin, a representative area of the Yellow River Basin, as our research subject. We identified multiple influencing factors, including society, biology, water quality, and habitat, which collectively impact this semi-arid region. To assess the overall impact of these factors on ecological health, we developed a comprehensive River Ecological Health Assessment Index (REHAI) system. The research findings indicate that the Wei River system, as a whole, is currently in a healthy state, while the Jing and Luo River systems are classified as sub-healthy. Furthermore, we observed variations within the Wei River system itself; the upper reaches of the Wei River exhibit higher levels of health compared to the middle reaches, whereas the water environment in the lower reaches is the most compromised. This degradation can be attributed to downstream subsidence, increased pollution, and rapid urbanization. By establishing a river ecosystem health assessment methodology and conducting a comprehensive evaluation of the health status of river ecosystems, this paper puts forward management recommendations for river basins. These findings provide a scientific basis for the sustainable utilization of water resources in river basins and promote the harmonious coexistence of humanity and nature.

Collapsibility is a typical engineering characteristic of Angola red sand. It is of great significance to study its influencing factors for geotechnical investigation and evaluation in red sand area. Based on laboratory compression tests of undisturbed and remolded Angola red sand specimens, the effects of structure, pressure, moisture content, dry density and fine-grained soil content on the collapsibility of Angola red sand were examined. Test results show that when the pressure is larger than 100 kPa, the collapsibility of remolded red sand is 2.0 times that of the undisturbed red sand. The collapsibility coefficient of red sand has a positive correlation, i.e. to increase with increasing test pressure and fine-grained soil content, with peaking pressure and fine-grained soil content reaching 300 kPa and 60%-80%, respectively. Contrarily, the collapsibility coefficient of red sand is, in general, negatively correlated with dry density and water content. The critical moisture content for eliminating and completely losing the collapsibility of undisturbed red sand is 9% and 13%, respectively, and those of remolded soil 11% and 13% respectively. The critical dry density of remolded soil is 1.80 g/cm~3 and 1.90 g/cm~3 respectively, and the corresponding compaction coefficient is 0.92 and 0.97 respectively. For engineering construction, the collapsibility of red sand can be eliminated by increasing dry density.

孔内深层超强夯法(SDDC)挤密桩是处理湿陷性黄土地基的一种新型工法.为研究SDDC挤密桩对湿陷性黄土地基的处理效果,开展了室内试验、载荷试验和浸水载荷试验.试验结果表明:SDDC挤密桩可有效消除桩长范围内黄土的湿陷性,提高桩间土和桩体土的干密度且挤密系数最大值分别可达0.98和1.04;SDDC挤密桩可显著提高桩间土的黏聚力和内摩擦角,也可显著提高桩体土的黏聚力;SDDC挤密桩不仅可有效消除天然黄土地基的软化特性,还可以显著提升地基承载力,处理后的复合地基分别是天然含水率黄土地基承载力和浸水饱和黄土地基承载力的1.33倍和2.03倍.研究结果对湿陷性黄土地基处理具有指导意义.

作为海外大型项目,促进中国技术标准的对外输出,在"一带一路"建设中具有重要意义.印尼北苏2X 5 000 t新型干法熟料水泥生产线配套专用码头位于近海区域,地基土体组成复杂,包括软土、饱和砂土及软化岩石.运用现场钻探、原位测试、室内试验等勘探手段和方法,对其物理力学性质进行分析研究,并对饱和砂土的液化进行判别,确定液化等级.工程成果为海外水运工程复杂地基土特性研究及地基基础方案的选择提供了参考.

安哥拉南部广泛发育花岗岩残积土,研究强夯法对花岗岩残积土地基处理效果对该区工程建设具有重要意义.依托安哥拉RED社会住房项目,通过钻探取样、室内试验、强夯试验、动力触探和荷载试验揭示了安哥拉花岗岩残积土的工程特性,分析了强夯法对安哥拉花岗岩残积土的处理效果.结果表明:安哥拉花岗岩残积土可定名为砂质黏土,具有湿陷和软化的工程特性,承载力软化系数为0.38,变形模量软化系数为0.31.强夯法可有效消除一定深度花岗岩残积土的湿陷性、提高花岗岩残积土的干密度、显著提高花岗岩残积土的地基承载力和变形模量,处理深度和提高系数与最后两击夯沉量和点夯间距有关,但强夯后花岗岩残积土仍具有软化性.

礁灰岩是珊瑚岛礁的主体部分,钻孔灌注桩是岛礁工程建设和海洋开发中最常用的深基础之一.为揭示礁灰岩地区钻孔灌注桩的承载特性,在印度尼西亚珊瑚礁地区开展了冲击钻孔和旋挖钻孔灌注桩的现场静载试验,对比分析了冲击钻孔和旋挖钻孔灌注桩的承载特性.结果表明,冲击钻孔灌注桩的施工周期和充盈系数分别是旋挖钻孔灌注桩的 24 倍和 1.09 倍;冲击钻孔灌注桩承载特性表现为摩擦端承桩特性,旋挖钻孔灌注桩表现为摩擦桩特性;旋挖钻孔灌注的承载特性优于冲击钻孔灌注桩,其竖向极限承载力是冲击钻孔灌注桩的 2.85 倍,其桩周地层极限侧摩阻力是冲击成孔灌注桩的 8.03 倍.冲击成孔过程中在孔周形成的泥皮是造成冲击钻孔灌注桩桩周地层极限侧摩阻力降低和单桩抗压极限承载力降低的主要原因.

研究孔内深层超强夯法(SDDC工法)地基处理效果对处理湿陷性黄土地基具有重要工程实际意义.以西安市白鹿原某在建项目为工程背景,通过原位试验、室内试验和理论计算,研究SDDC的单桩挤密效应,分析不同桩间距下SDDC的挤密效应和承载特性.结果表明:SDDC夯扩桩桩体中部挤密系数大于桩端,其消除桩周黄土湿陷性的水平距离是桩端的 3～4 倍.SDDC夯扩桩横向挤密系数随距桩心水平距离变化曲线可分为 3 段,数学关系可用logistic模型进行最优函数拟合.SDDC夯扩桩三角形布桩时,两桩中心挤密系数小于三桩形心,该结果与DDC桩不同,按现有公式设计桩间距偏保守.SDDC桩体、桩间土及其组成的复合地基承载力和变形模量均随桩间距增加而减小,桩间距相同时复合地基承载力提高系数远小于变形模量提高系数.

针对东南亚某水电站坝址区上游右岸古滑坡,通过钻探、地质调查及长期监测研究了滑坡地层特征、滑带特征及变形特征,并对古滑坡复活机制进行探究.结果表明:(1)坡脚卸载和强降雨是古滑坡复活的主要原因;(2)道路开挖导致应力场发生改变,滑坡沿浅表部第四系坡积物和板岩、砂岩接触面"复活",向临空面产生蠕变变形;(3)古滑坡变形与降雨呈正相关,雨季高强度降雨期间位移与变形速率急速增大,旱季无降雨时滑坡基本处于稳定状态;(4)深部位移监测数据显示,古滑坡深部未见位移突变,降雨对深部位移基本无影响.

Currently， the most of the geotechnical investigation of overseas engineering projects adopt European and American standards. Studying European and American standards in-depth will be helpful for Chinese survey and design enterprises to conduct implementing overseas projects. Aiming at the Flat Plate Dilatometer test and Dynamic Cone Penetrometer test that were commonly used in geotechnical engineering investigations in China and abroad， the differences between American ASTM standards and Chinese geotechnical engineering specifications and standards were analyzed and compared from four aspects: equipment specifications， scope of application， test technical requirements， and application of test results. The results showed that the specifications of flat dilatometer test equipment in Chinese and American standards were basically the same， with slight difference in local equipment， technical requirements， formulas， operations and data records. There was no significant difference in the technical requirements of Dynamic Cone Penetrometer test between China and the United States， but there were some differences in test termination conditions and test data recording requirements. The research results can provide reference for survey and design enterprises in China to implement the ‘go global’ strategy.

安哥拉红砂在工程建设上表现出与中国黄土相似的湿陷性和水敏性.通过浸水载荷试验和室内压缩试验揭示了红砂的湿陷特征,并探讨了红砂湿陷系数与含水率、干密度、孔隙比、饱和度的相关关系.结果表明:试验方法对红砂湿陷系数影响较大,室内压缩试验获得的湿陷系数是现场浸水载荷试验获得湿陷系数的1.7倍.红砂湿陷系数随压力增加而增加,但增加速率逐渐减小,红砂湿陷系数的起始压力小于等于50kPa.红砂湿陷系数与含水率、干密度、孔隙比、饱和度的相关性较好,其中湿陷系数与含水率、干密度、饱和度呈负相关关系,与孔隙比呈正相关关系.研究结果可为评价红砂地基的湿陷性与地基处理提供一定的借鉴和参考.

2016年野外地质调查发现渭河盆地东北侧安仁镇发育48条地裂缝,造成沿线房屋墙体开裂、道路错断和农田变形龟裂等,并严重威胁大西高铁安全运营.通过详细的地质调查和地质测绘发现其均位于地貌分界线两侧并发育在双泉-临猗断裂上盘,地裂缝走向为NE60°～80°,按发育位置可将其划分为5组地裂缝.选取典型地裂缝为研究对象,利用槽探和工程地质钻探揭示了地裂缝的剖面结构特征,发现地裂缝导致浅部土体破裂严重,地裂缝错断两侧地层且位错量随深度增加而增加,表现出同沉积断层的性质.在此基础上,对比西安地裂缝并详细分析了安仁镇地裂缝的成因机理,发现构造断裂、地震活动和表水潜蚀是地裂缝形成的主要因素.安仁镇地裂缝成因机理可概化为:构造控缝、地震启缝和表水扩缝.

老挝南俄四水电站右岸边坡发育F22断裂,穿越大坝10#坝段坝基,将其划分为碎裂岩带和软弱构造岩带(岩屑夹泥型).为了提供该水电站工程设计所需的工程地质资料,在查明F22断层发育几何学特征的基础上,通过勘探技术、取样室内物理力学性质试验、压水试验研究,查明断裂破碎带的性状,包括分布及规模、矿物成份、物理力学性质、工程特性,同时研究对应的处理措施.结果表明:泥质板岩内未发现蒙脱石等高膨胀性矿物;崩解试验发现泥质板岩在浸水后很快发生软化分散,证明泥质板岩水理性质较差,粉砂质板岩水理性尚可;在坝基F22断层带上游侧布置有齿槽,可解决坝基渗透问题;在断层带附近采用混凝土垫座"桥接"跨越断层,可解决坝基变形问题.研究成果可为其它工程类似断层性状研究提供参考.

The Zezhang ground fissure in the Linfen Basin, China was first observed in 2004 where it damaged the infrastructure in and around the town. Field and laboratory investigations now confirm that the fissure has had a complex origin, ranging from likely recurrent fault offset with almost synchronous local sedimentation (synsedimentary), to accelerated groundwater withdrawal, soil erosion and ultimately to geomorphic expression of surface subsidence, local linear scarps and sinkholes. Trench exposures and interpretation of borehole data indicate that at least four tectonic events took place during the latest Pleistocene and Holocene generally localizing the zone of fissure expression. In contrast to other tectonic ground fissures, the ground fissures in Zezhang are highlighted with major synsedimentary characteristics. The formation mechanism of ground fissures was caused by several factors, initial and later underlying fault displacements, initial fissures with land subsidence caused by groundwater withdrawal and widening into linear sinkholes under soil erosion. The Zezhang ground fissure, its investigation techniques and the technical findings, provide a case study for assessing previously unrecognized synsedimentary fissures elsewhere.

通过一系列地质调查研究了黄土湿陷地裂缝的发育特征,结合浸水试验分析了地裂缝的成因机理和形成过程.研究结果表明:黄土湿陷地裂缝与浸水坑平行,兼具水平拉张和竖直位错,地裂缝发展演化过程可分为四个阶段.黄土湿陷地裂缝上宽下窄,其宽度和竖直位移均随深度增加而减小,地裂缝发育深度约等于黄土湿陷土层厚度.黄土渗透浸润线与竖直面的夹角随时间逐渐增加,导致湿陷地裂缝逐渐向外扩展.黄土湿陷产生的差异沉降和拉张应变是湿陷地裂缝形成的直接因素,当地面倾斜率达到0.6％,拉应变达到0.002％时,地裂缝出露地表.基于悬臂梁理论提出了湿陷差异沉降产生拉张应力的计算公式,根据本公式可预测黄土湿陷地裂缝的发育位置.

依托巴基斯坦塔尔矿区风积砂土湿陷性研究课题,基于前期勘察成果和相关湿陷性试验结果,对塔尔沙漠风积砂土的湿陷性特征及其基本物理指标与湿陷性的相关性进行分析研究.结果 表明:风积砂土的湿陷性主要分布在①、②层,湿陷性系数平均值为0.039,湿陷性程度属于轻微-中等;风积砂土的颗粒组成和易溶盐特征是湿陷变形的主要内在基础;风积砂土湿陷性系数与含水率之间离散性较强,与孔隙比基本呈正相关关系,与干密度之间基本呈线性负相关,当孔隙比＜0.65或干密度＞1.60 g/cm3时,风积砂土不具有湿陷性.

以东南亚某在建水电站引水隧洞粉砂质板岩段洞室开挖工程为依托,在现场地质调查测绘的基础上,对粉砂质板岩段围岩变形破坏特征进行分析,结果表明:粉砂质板岩段围岩的变形破坏主要分两种,一种由Ⅳ级结构面相互切割引起的局部垮塌掉块;另一种由断层引起的大规模垮塌变形.并基于有限元软件模拟断层分布发育特征对洞室稳定性的影响,结果表明:断层倾角在30°～60°对洞室稳定性影响较大,当断层位于隧洞中心上部时,对围岩变形的影响最大,特别左侧腰线部位岩体;当其位于隧洞中心下方,影响次之;与隧道中心相交时,影响最弱.研究成果可为后续类似洞段开挖支护方案提供参考借鉴.

随着人类活动向海洋深入,岛礁工程建设涉及到越来越多的吹填珊瑚砂地基.本文以马尔代夫某吹填珊瑚砂房建工程为研究背景,利用现场载荷试验和标准贯入试验,探究并分析了吹填珊瑚砂地基的承载特性和评价方法.试验结果表明,吹填珊瑚砂地基的荷载—沉降曲线可分为两个阶段:比例变形阶段和破坏阶段,地基承载力特征值为130kPa,变形模量为14.9MPa,压缩模量为16.6MPa.吹填珊瑚砂地基荷载的传递深度为1倍的承压板宽度,水平传递范围随着深度的增加而增加,传递扩散角约为38.7～45°.根据标贯击数计算吹填珊瑚砂地基承载力的经验公式可取fk= 11N.研究结果可为岛礁工程建设评价吹填珊瑚砂地基承载力提供一定的借鉴和参考.

振动碾压是浅部地基处理的常用方法,对砂土、粉土和粉质黏土等陆相沉积物碾压效果较好.与陆相沉积物物理性质相差较大的珊瑚砂是岛礁工程的主要持力层,为探究振动碾压对吹填珊瑚砂地基的处理效果,本文以马尔代夫房建工程为研究背景,利用室内试验、标准贯入试验、现场载荷试验和动力触探试验研究了不同振动碾压遍数下吹填珊瑚砂地基的工程特性.试验结果表明:振动碾压对吹填珊瑚砂地基工程特性影响显著,随碾压遍数增加,吹填珊瑚砂地基密实度、承载力和变形模量均不同程度增加,且不均匀性降低;振动碾压对浅部地基处理效果好,最大处理深度约为2 m;干密度与碾压遍数存在相关性,标贯击数与承载力和变形模量存在相关性,通过分析获得的经验公式可用于快速评价吹填珊瑚砂地基的干密度和承载力.研究结果可为岛礁工程建设的吹填珊瑚砂地基处理提供一定的借鉴和参考.