Research on the effect of straw mulching on the soil moisture by field experiment in the piedmont plain of the Taihang Mountains

To reveal the influencing effect of the long-term straw mulching on the soil moisture, this paper employed the field experiment data in 2010 of a typical area of Taihang Mountains plain, observed the soil moisture dynamic regularities under different mulching patterns by virtue of depressimeter and neutron probe, analyzed the characteristics of soil water content and storage in different depths and seasons under the long-term straw mulching. The results showed that the long-term straw mulching can keep the soil moisture conservation of the deep, while decreased the shallow.(1) The long-term straw mulching can changed the type of soil water movement. If no straw mulching, the type is mainly evaporation-infiltration. And with straw mantle the type would change into infiltration. The number of zero flux plane would be reduced or absent.(2) The long-term straw mulching can increase the soil water reserves of the whole soil profile with the depth between 0 cm and 220 cm. But the soil water content of the layer from 30 cm to 80 cm decreased and the soil water content of the layer from 80 cm to 220 cm increased instead., The effect of soil moisture conservation on winter wheat is not obvious;(3) With no straw mulching, the depth of infiltration recharge by rainfall or irrigation is shallower than 80 cm. In a straw mulching, the influence depth is can extend to 120 cm;(4) With no straw mulching, there is a deep layer on the depth of 220 cm between March and June, while this layer will disappear with a long-term straw mulching.

Modeling spatio-temporal distribution of soil moisture by deep learning-based cellular automata model

Soil moisture content （SMC） is a key hydrological parameter in agriculture,meteorology and climate change,and understanding of spatio-temporal distributions of SMC in farmlands is important to address the precise irrigation scheduling.However,the hybrid interaction of static and dynamic environmental parameters makes it particularly difficult to accurately and reliably model the distribution of SMC.At present,deep learning wins numerous contests in machine learning and hence deep belief network （DBN） ,a breakthrough in deep learning is trained to extract the transition functions for the simulation of the cell state changes.In this study,we used a novel macroscopic cellular automata （MCA） model by combining DBN to predict the SMC over an irrigated corn field （an area of 22 km^2） in the Zhangye oasis,Northwest China.Static and dynamic environmental variables were prepared with regard to the complex hydrological processes.The widely used neural network,multi-layer perceptron （MLP） ,was utilized for comparison to DBN.The hybrid models （MLP-MCA and DBN-MCA） were calibrated and validated on SMC data within four months,i.e.June to September 2012,which were automatically observed by a wireless sensor network （WSN） .Compared with MLP-MCA,the DBN-MCA model led to a decrease in root mean squared error （RMSE） by 18%.Thus,the differences of prediction errors increased due to the propagating errors of variables,difficulties of knowing soil properties and recording irrigation amount in practice.The sequential Gaussian simulation （s Gs） was performed to assess the uncertainty of soil moisture estimations.Calculated with a threshold of SMC for each grid cell,the local uncertainty of simulated results in the post processing suggested that the probability of SMC less than 25% will be difference in different areas at different time periods.The current results showed that the DBN-MCA model performs better than the MLP-MCA model,and the DBN-MCA model provides a powerful tool for predicting SMC in highly non-linear forms.Moreover,because modeling soil moisture by using environmental variables is gaining increasing popularity,DBN techniques could contribute a lot to enhancing the calibration of MCA-based SMC estimations and hence provide an alternative approach for SMC monitoring in irrigation systems on the basis of canals.

Response of Surface Soft Soil and Fine-Grained Sand Layers to Seismic Waves

Shanghai is located in eastern China and is built on overburden soil layers. It can be seen from the Mexico M S=8.1 earthquake on September 19, 1985 and the Hanshin M S=7.4 earthquake on January 17,1995 that heavy casualties and property losses have a direct relationship with overburden soil layers. Ground motions caused by earthquakes are significantly amplified when passing through the soil layers. Under the influence of these amplified motions, building structures, whose nature frequency is within the frequency band of soil amplification response, will experience more severe damage than those built on bedrock. Therefore, engineering seismologists have paid considerable attention the amplification responses in the Shanghai overburden soil layers. The amplification responses of soil and sand layers in this paper are given by the M L=4.1 earthquake in Nantong, Jiangsu Province on December 25, 2001 at 31.8° N, 120.9° E. It can be seen that the responses of soil and sand layers are very different. That is important.

Experimental studies on curling development of artificial soils

Soil curling is an important phenomenon associated with volume changes induced by increasing soil suction upon desiccation.The study of soil behaviors associated with drying in soils(e.g.soil shrinkage,desiccation cracks and curling)has received increasing attention over the last few years,which has been mainly driven by the forecast climate change that will warm up our planet.There are significant gaps in the current knowledge related to the factors that control the development of curling deformations in soils.For this,the curling phenomenon is investigated through laboratory desiccation tests on different mixtures of artificial soils.The effects of soil grain size distribution,mineralogy,soil microstructure,and soil water content on the curling deformation are analyzed.Digital photos were taken at regular time intervals during the tests to understand the volume changes in the soil samples during drying.It is found that soil fabric and soil water content have significant effects on curling scenario.It is observed that the percentage of sand particles and the initial water content play a critical role in the development of soil curling.Samples of pure clayey minerals experienced shrinkage without or with minor curling during drying.

Fenlong Tillage System by the Theory of “Natural Forces” and Possibility of “Fenlong Agriculture” Establishment

"Natural forces" ——core theory of Fenlong technique is explored in this paper. We break through key core technique of farming and agriculture,and invent new method of Fenlong tillage. Broad-spectrum Fenlong tillage technique system based on "full-layer and bottom-layer superdeep tillage without disturbance of soil layer" is established,which provides the possibility for establishing "modern Fenlong agriculture". When applied in 35 kinds of crops in 24 provinces of China,yield could be increased by 10%-50%,and even 1 times. In the transformation of severe saline-alkali land,corn yield could increase by 73. 0%,and Na,Cl and Mg ions in grain decrease by 20. 81%,1. 47%,and 9. 36% respectively. The newly developed "scarification tillage( reclamation) in the bottom area" could cover "bottom tillage" of dryland,paddy field,degraded grassland,perennial sugarcane,forest and fruit land,traditional Chinese medicine land,and ecological reconstruction of desertification land. It is point out that if Fenlong technique is used in 666 666. 67 km2 of farmland,200 000 km2 of saline-alkali land,666 666. 67 km2 of degraded grassland,and fisheries in rivers and offshore waters are used,trillion yuan of Fenlong economy could be formed,and the nationals will walk towards a healthier new era.Fenlong technique involves agriculture,forestry,water,grass,environment and other aspects,and its global promotion could improve eco-environment and change world development pattern.

杂填土地层深基坑微型桩-锚-撑组合支护体系受力特性原位试验

为深入研究杂填土地层深基坑桩-锚-撑组合支护体系受力特性,依托青岛市某深基坑工程开展微型桩-锚-撑原位试验,分析不同开挖工况下双排微型钢管桩桩身弯矩与预应力锚索轴力的演化规律,揭示该支护体系下前、后排桩的受力性状、预应力锚索应力分布特征,探讨邻近建筑物、基坑暴露时间及钢支撑拆除对该支护体系内力的影响。研究结果表明:1)在基坑开挖过程中,前排桩在受力中起主导作用;当开挖至基底时,桩身最大正、负弯矩极值呈现增大趋势,且极值点不断下移,开挖面以上桩身弯矩均呈正“S”型分布。2)开挖深度增加引起开挖面上、下1.0 m范围内桩身弯矩显著增大,前排桩桩身的反弯点分别位于钢支撑下方0.5 m、开挖面位置。3)在开挖过程中,锚索轴力沿埋深方向呈现减小趋势,锚固段前端1.5 m之后的轴力基本不变或呈微小波动。4)锚索锚固段应力高度集中在锚固段前端4.0 m以内的区域,约为锚固段长度的44%,锚固段末端基本未产生轴力,可对该段长度进行优化处理。5)邻近建筑物对微型钢管桩桩身受力影响较小;随着基坑暴露时间增加,桩身弯矩呈微小增长趋势;钢支撑拆除后,前排桩的弯矩变化集中在0.38H~0.96H(H为基坑开挖深度)。6)桩-锚-撑组合支护体系能够较好地限制基坑变形,选择合理的支撑预应力是该类基坑设计的关键。

长期连作茭白增加水田深层土壤有机碳的积累

为了解长期连作茭白后水稻土有机碳库及其组分的变化,选择了连续种植茭白时间分别为0(对照)、2~5、5~10、10~20、20~30、30~35 a等6组种植茭白前土壤类型相同的18块农田,通过挖掘标准土壤剖面采集0~20、20~40、40~60、60~80 cm分层土样,分析了土壤有机碳、不同稳定性有机碳组分和微生物生物量碳。结果表明:随着茭白种植时间的增加,土壤容重由上层至下逐渐下降;各土层中有机碳总量、高活性有机碳、中活性有机碳、低活性有机碳和惰性有机碳及微生物生物量碳均逐渐增加,增幅以20~40、40~60 cm等2个土层最为明显。同时,深层土壤中高活性有机碳比例呈现显著的增加,20~80 cm土层中有机碳总量及其各形态有机碳贮量占0~80 cm土层有机碳总量的比例逐渐增加,呈现有机碳向深层土壤积累的特点。分析认为,深耕、长期浸水及茭白生产过程田间人为频繁踩踏,导致土壤犁底层逐渐消失、软糊层形成是造成茭白田深层土壤有机碳快速积累、有机碳活性增加的主要原因。

单层大直径圆环支撑在软土深大复杂基坑工程中的应用与研究

以浙江省台州中心城区某深大复杂软土基坑工程为背景,根据基坑周边环境,结合工程特点及方案选型分析,采用大直径圆环支撑结构体系,有效解决了周边环境复杂、施工场地狭小及支撑下土方开挖效率低等问题。通过数值模拟分析基坑开挖对周边道路及建筑物的影响,计算结果和实际监测数据显示,采用单层大直径圆环支撑体系能较好控制基坑变形,确保基坑周边环境的安全,为类似地质和边界条件下深大基坑工程设计提供一定经验。

复杂周边环境下的深基坑支护及开挖施工技术优化

为探究复杂周边环境下的深基坑支护及开挖施工技术优化问题,首先,通过对深基坑周边复杂环境、工程特点和工程难点进行重点分析,提出切实可行的保障措施。其次,基于复杂环境下的深基坑施工重难点,对基坑支护和开挖方式进行优化,并通过有限元分析软件进行施工过程模拟,提出相关施工技术优化方向。最后,对基坑支护和开挖过程进行自动化监测,确保对周边建构筑物产生的影响在可控范围内。

软土地层地铁深基坑施工智能化监测技术研究

为了确保地铁深基坑的施工安全,需通过监测手段实时掌握周围地层、支护系统、管道、水位及建筑物的状况。而在软土地层地铁深基坑所处的复杂且危险的环境中,由于人工监测的延迟,可能会导致意外事故的发生。研究结果表明,通过采用智能化的监测手段,可以在软土地层深基坑项目中,显著提高监测预警的效率,极大地填补人工监测“滞后反应”的不足,从而有力地预防工程损害和环保问题的出现。

深层搅拌桩砂土层钻进过程的受力分析

为研究深层搅拌桩砂土层钻进过程中钻具受力情况,对钻具叶片切削搅拌土层的运动轨迹以及钻具钻进砂土层过程中的轴向阻力及阻力矩进行分析,应用PFC3D软件构建钻具及地基砂土仿真模型,对不同钻进速度、旋转速度下颗粒位移、钻头承受的轴向阻力和阻力矩等进行监测与分析。最后将排涝泵站工程泵房基础防渗工程砂土层深层搅拌现场钻进过程实际观察结果与模拟结果进行比较,结果表明吻合度高,验证了模拟结果的准确性。本文分析结果可为深层搅拌桩在砂土层地质条件中的较好应用提供借鉴。

超深厚表土层特殊凿井技术探究

为了开发超深厚土层下的固体矿物资源,以2000m深厚表土层建井为工程背景,通过总结深厚土层中井筒建设成果,并参考深土层井筒施工经验与理论研究,对冻结法、钻井法及混凝土帷幕法等特殊凿井法进行了可行性分析。研究表明:在本工程背景下,使用单一的冻结法或使用单一的钻井法作为建井技术尚不成熟且实现难度较大;而采用冻结-帷幕凿井工艺具有一定的可行性。由于深井建设面临“高地应力、高地温、高水压”问题,为确保工程安全性,提出了冻结-帷幕凿井法,为后续超深厚土层凿井方法的选取提供了方向性的参考。

基于应变测量的桩基础轴力和横向变形同步监测方法

深厚软土层地区超长桩基础的轴向受力、水平变形对工程结构正常使用与安全性起着重要影响,而实现二者同步监测尚无可用方法。本文提出基于应变测量的桩基础轴向压力和水平位移同步监测方法,以应变片感知应变变化来反映桩基础轴向压力和水平位移情况,通过振弦式钢筋计进行验证。依托某立交桥工程,建立深厚软土层超长桩基础无线智能监测系统,采用无线智能采集仪采集传感器数据,借助于Lora模块形成局域网并汇总各传感器的监测数据,再通过4G模块将汇总数据上传至云平台。通过无线监测数据与传统采集器数据进行对比,发现二者数据误差在微小(0.3 Hz)以内,表明无线智能监测系统可靠性好、精度高;传统振弦式钢筋计所测应变与智能测斜管的误差在-11.32%~6.03%之间,表明智能测斜管具有较高的准确度和稳定性,采用智能测斜管进行桩基础受力性能监测是可行的。研究可为桩基础轴向压力和水平位移监测提供新的思路。

Characteristics of Dried Soil Layers Under Apple Orchards of Different Ages and Their Applications in Soil Water Managements on the Loess Plateau of China

Negative soil water balance(i.e., water input < water output) can lead to soil desiccation and subsequently the occurrence of a dried soil layer(DSL). The DSLs are generally studied at a specific sampling depth(e.g., 500 cm), and the actual extent of DSLs remains unknown due to the challenge of collecting deep soil samples. To investigate the characteristics of actual DSLs under different ages of apple orchards and ascertain the optimal age of apple orchards for avoiding/controlling the formation of DSLs, soil samples were collected to a depth of 1 800 cm under apple orchards of different ages in Changwu on the Loess Plateau of China. As the ages increased, soil water content(SWC) and mean SWC in DSLs showed an overall decreasing trend, whereas while DSL thickness and the quantity of water deficit(QWD) in DSLs demonstrated an increasing trend. The DSL was the thickest(1 600 cm) under the 17-year-old orchard, the forming velocity of DSL thickness was the highest at the apple tree growth stage of 9–17 years(168 cm year-1), and the highest increasing velocity of QWD(-181 mm year-1) was also observed at this stage. The thickness of DSL was significantly correlated with growth age and root depth of apple trees(r > 0.88), whereas the QWD and mean SWC in DSLs were found to have no correlation with them. The optimal age of apple orchards for avoiding/controlling the formation of DSLs was about 9 years. This information provided pertinent references for the management of deep water resources by controlling the growth age of plants.

水稻高产耕层构建及地力保育技术模式

辽宁省是我国重要的水稻产区,稻田长期重用轻养导致土壤肥力下降、耕层变浅变硬,严重制约了该区域水稻可持续高产能力。以秸秆还田和深耕为核心的水稻高产耕层构建及地力保育技术是黑土地保护与利用的有效技术之一。简述了“高留茬+深翻”和“秸秆粉碎+深旋”两种模式的高产耕层指标、秸秆促腐还田、合理深耕、养分精准调控和适宜密植栽培等主要措施、技术应用效果及存在问题。

基于深度强化学习的耕作层土壤水分、温度预测

【目的】利用土壤近表面空气温湿度与土壤内部参数的关联关系对耕作层土壤水分、温度进行精准预测,为实现精细化农业种植管理提供服务。【方法】针对土壤耕作层水分、温度预测在训练集获取与模型验证等方面的实际需求,设计了基于嵌入式系统及窄带物联网(Narrow band internet of things,NB-IoT)无线通信技术的物联网数据采集系统。在此基础上基于深度Q学习(Deep Q network,DQN)算法探索了一种模型组合策略,以长短期记忆(Long short-term memory,LSTM)、门限循环单元(Gated recurrent unit,GRU)与双向长短期记忆网络(Bidirectional long short-term memory,Bi-LSTM)为基础模型进行加权组合,获得了DQN-L-G-B组合预测模型。【结果】数据采集系统实现了对等间隔时间序列环境数据的长时间稳定可靠采集,可以为基于深度学习的土壤水分、温度时间序列预测工作提供准确的训练集与验证集数据。相对于LSTM、Bi-LSTM、GRU、L-G-B等模型,DQN-L-G-B组合模型在2种土壤类型(壤土、砂土)耕作层上水分与温度预测中的均方根误差(Root mean square error,RMSE)、平均绝对误差(Mean absolute error,MAE)、平均百分比误差(Mean absolute percentage error,MAPE)都有一定程度的降低,R2提高了约0.1%。【结论】通过该物联网数据采集系统与DNQ-L-G-B组合模型,可以有效地完成基于土壤近表面空气温、湿度对耕作层土壤中水分、温度的精准预测。

黄土旱塬区苹果园生草覆盖对深层土壤水分和根系分布特征的影响

研究苹果园长期生草覆盖后深层土壤水分及果树根系的分布规律,以期阐明旱作条件下果园根水互作关系,为黄土旱塬区果园生草覆盖实践的优化提供依据。试验于甘肃庆阳草地农业生态系统国家野外科学观测研究站苹果园中进行,设置果园生草覆盖(生草为鸭茅草,2014年建植)和清耕处理,以一年生作物田为对照;连续两年夏季测定果树行上和行间距离树干100和200 cm共4个位置0~500 cm土层的土壤水分和果树细根长密度,分析生草覆盖对果园深层水分亏缺及细根长密度的影响。清耕果园0~300 cm土壤水分较对照农田下降了6.7%~8.3%(P<0.01),而300~500 cm土层土壤水分与对照农田差异不显著(P>0.05);生草覆盖果园0~500 cm整个剖面的土壤水分均低于清耕果园,平均下降了11.5%~12.3%。果园生草覆盖6~7年后0~500 cm土层土壤较对照农田水分亏缺量为163.9~172.1 mm,是清耕果园水分亏缺量的3.2~4.2倍。果树根系在0~100 cm土层的细根长密度最高,平均密度为0.187 cm·cm^(-3),生草覆盖促进了0~100 cm土层果树根系的分布,对深层根系影响不显著。清耕果园和生草覆盖果园0~500 cm土层土壤水分的含量随果树细根长密度的增加而降低,二者呈线性负相关关系,生草覆盖后二者相关性提高,干旱年份二者相关性更高。黄土旱塬区苹果园长期生草可促进果树根系生长,降低深层土壤水分,加剧土壤干燥化,对苹果树的利用年限和农田水分循环具有负面效应。旱作条件下应加强果园生草覆盖管理以保障水分的可持续性。

深厚软土地层条件下地铁车站基坑支护体系变形特征及控制研究

深厚软土地层对地铁车站基坑开挖施工可能影响基坑支护体系的安全性,甚至会诱发基坑坍塌等重大工程灾害。根据车站施工监测以及科研监测数据,结合相关规范对支护体系变形机理和控制技术进行分析。结合工程实践及科研分析,提出了增加立柱桩长度、优化地墙方案等控制措施,可有效控制立柱隆起量。研究成果对今后地铁车站工程支护体系的安全性评价及指导现场安全生产具有重要意义。

高架桥桥基与地下车站深基坑近距离施工相互影响分析

基于某地下车站深基坑与高架桥桥基近距离施工难题,利用Midas GTS NX软件,土体采用修正摩尔库伦本构模型,对基坑开挖、桥基施工、支撑拆除以及车站主体结构回筑进行施工全过程数值模拟,分析施工全过程基坑和桥基的相互影响规律,并结合现场实测数据对数值模拟结果进行对比验证。研究发现,基坑开挖阶段,由于土体水平卸荷,基坑变形不断增大,基坑地表最大沉降发生在距基坑边缘约0.4倍基坑宽度处,地连墙最大侧移发生靠近基底处;桥基施工后,基坑地表沉降和地下连续墙侧向位移进一步增加,桥基本身也产生了一定沉降;基坑支撑拆除和车站主体结构回筑阶段,由于围护结构的作用,基坑和桥基的变形增长并不明显。

淤泥质土层明挖地铁车站深基坑施工技术

结合工程实践,从围护结构施工、基坑降排水、支撑架设以及土方开挖等工序入手,针对性地提出了各个工序最优的施工方法,总结形成了一套淤泥质土层明挖地铁车站深基坑施工的关键技术。