Changes of soil labile organic carbon in different land uses in Sanjiang Plain,Heilongjiang Province

In the Sanjiang Plain,Northeast China,the natural wetland is undergoing a rapid conversion into agricultural land,which has resulted in drastic ecological changes in the region. To investigate the effects of different land uses on soil labile organic carbon,soils of Calamagrostis angustifolia wetland,Carex lasiocarpa wetland,dry farmland,paddy field,forest land and abandoned cultivated land were collected for measuring the contents of soil microbial biomass carbon (MBC),dissolved organic carbon (DOC),readil...     

Effect of Freeze-Thaw Cycles on Mechanical Properties and Permeability of Red Sandstone under Triaxial Compression

Geological disasters will happen in cold regions because of the effects of freeze-thaw cycles on rocks or soils, so studying the effects of these cycles on the mechanical characteristics and permeability properties of rocks is very important. In this study,red sandstone samples were frozen and thawed with 0,4, 8 and 12 cycles, each cycle including 12 h of freezing and 12 h of thawing. The P-wave velocities of these samples were measured, and the mechanical properties and evolution of the steady-state permeabilities were investigated in a series of uniaxial and triaxial compression tests. Experimental results show that, with the increasing of cyclic freeze-thaw times, the P-wave velocity of the red sandstone decreases. The number of freeze-thaw cycles has a significant influence on the uniaxial compressive strength, elastic modulus, cohesion, and angle of internal friction. The evolution of permeability of the rock samples after cycles of freeze-thaw in a complete stress-strain process under triaxial compression is closely related to the variation of the microstructure in the rock. There is a highly corresponding relationship between volumetric strain and permeability with axial strain in all stages of the stress-strain behaviour.     

Phosphorus sorption-desorption characteristics of ditch sediments from different land uses in a small headwater catchment in the central Sichuan Basin of China

Investigation of phosphorus (P) sorption-desorption characteristics of drainage ditch sediments is important for better understanding on sediment P transport behaviors in ditches. Surface ditch sediment samples were collected from headwater sub-catchment of forestland, sloping cropland, paddy field, and residential area in a representative catchment in the central Sichuan Basin. These sediment samples were used for determination of P sorption-desorption characteristics by a batch equilibrium technique. Results showed that the maximum P sorption capacities (Qm) in the sediments ranged from 159.7 to 263.7 mg/kg, while higher Qm were observed in the ditch sediments from the paddy fields. The Qm was significantly and positively correlated with oxalate-extractable Fe and Al oxides (r=0.97 and 0.98, p < 0.01), clay fraction (r = 0.78, p < 0.05) and organic matter (r = 0.95, p < 0.01). Sediment pH, clay and organic matter influenced the P sorption through amorphous Fe and Al oxides. CaCO3 content was negatively correlated with the Qm (r = -0.83, p < 0.05), implying that saturated CaCO3 (> 50 g/kg) would not increase P sorption capacity in the ditch sediments. The ditch sediments featured a linear desorption curve, suggesting that P release risk would be enhanced with the increase of the P adsorption. The P desorption rate was positively correlated with Olsen P (r = 0.94, p < 0.01), but negatively related to the fine particle-size fractions (r = -0.92, p < 0.01), the sum of the amorphous Fe and Al oxides (r = -0.67, p < 0.05) and the P sorption capacity (r = -0.59, p < 0.05). The ditch sediments from residential area had a higher P release risk than that from the other ditches of forestland, sloping cropland and paddy field. The P sorption index (PSI) derived from single-point measurement was significantly correlated with the P sorption capacity (r = 0.99, p < 0.01), and could be used for estimating Qm as 1.64 times PSI plus 24.0 (Qm = 1.64 PSI + 24.0) for similar sediments with highly calcareous soils and sediments. Ditch cleaning and sediment removal for the ditch in residential area were recommended in this area to reduce the P release risk.     

SORPTION AND DESORPTION CHARACTERISTICS OF CADMIUM BY FOUR DIFFERENT SOILS IN NORTHEAST CHINA

1IN TR O D U C TIO NA s a persistentand toxic pollutant, cadm ium (C d) canresultin m any adverse health effects in a variety oftis-suesand organssuch asthe lung,kidney,urinary,blad-der,pancreas,breast and prostate (SA TA R U G etal.,2003).C adm ium in so…     

The impact of nitrogen amendment and crop growth on dissolved organic carbon in soil solution

Dissolved organic carbon (DOC) is an important component of the terrestrial carbon cycle. However, the sources and controlling factors of DOC in soils remain uncertain. In this study, the effects of nitrogen (N) amendment and crop growth on DOC in soil solution were examined at a maize-wheat rotated field located in the central Sichuan Basin in southwestern China. Nitrogen treatments in this study included 150 kg N ha^-1 season^-1, 200 kg N ha^-1 season^-1 and the control without any fertilizer application. During the whole experimental period, we observed significant decreases (p<0.05) in DOC concentrations in the sampled soil solutions associated with increase in N inputs at the bare soil plots, but no change in DOC at the plots with crop growth. The estimated average contributions of plantderived DOC were 16%, 24% and 32% of total DOC in the summer maize season and 21%, 32% and 38% in the winter wheat season along with the gradient of N fertilizer application rates. The results implied that the crop growth could play a key role in the soil DOC production, and the N input enhanced DOC production by increasing crop growth. The relationship between the DOC concentrations and the crop root biomass was statistically significant for both the maize and winter wheat seasons. Our observations indicated that crop growth exerted greater influence on the seasonal variability of DOC concentration in soil solutions at the experimental site, which overwhelmed the effect of soil native organic matter decomposition on DOC concentrations in soil solutions.     

Role of organic acids in desorption of mercury from contaminated soils in eastern Shandong Province, China

Batch experiments were conducted to study the effects of low-molecular-weight organic acids(LMWOAs) on desorption of Hg from two kinds of soils in the eastern Shandong Province,China.Of all LMWOAs,oxalic and citric acids were chosen as the representatives in this experiment because they are most common in soils.Desorption of Hg increases with the increase of extracting time,until the highest desorption amount at 6-8 h,and then declines.It indicates that timeliness is very important when organic acids are used for phytoremediation in contaminated soils.When the concentrations of organic acids increase from 1.0 mmol/L to 10.0 mmol/L,Hg desorption increases significantly regardless of oxalic or citric acid.Compared with oxalic acid,citric acid is more effective to enhance the desorption of Hg,especially from fluvo-aquic soil.With the increase of initial pH value from 3 to 8,Hg desorption decreases directly in the presence of oxalic acid.However,Hg desorption first decreases,then increases,and eventually decreases again in the presence of citric acid due to the variation of competitive ability between chelating of citric acid and adsorption of soil in different pH values.Citric acid showed greater ability to release Hg from soils than oxalic acid.According to the results of the present study,it is found that the bioavailabilities of heavy metal can be improved with selecting suitable types and concentrations of organic acid amendment and reasonable soil condition.     

Labile and stabile soil organic carbon fractions in surface horizons of mountain soils–relationships with vegetation and altitude

Global and local climate changes could disturb carbon sequestration and carbon stocks in forest soils. Thus, it is important to characterize the stability of soil organic matter and the dynamics of soil organic carbon (SOC) fractions in forest ecosystems. This study had two aims: (1) to evaluate the effects of altitude and vegetation on the content of labile and stabile forms of organic carbon in the mountain soils; and (2) to assess the impact of the properties of soil organic matter on the SOC pools under changing environmental conditions. The studies were conducted in the Karkonosze Mountains (SW Poland, Central Europe). The content of the most labile fraction of carbon (dissolved organic carbon, DOC) decreases with altitude, but the content of fulvic acids (FA), clearly increases in the zone above 1000 m asl, while the stabile fraction (humins, non-hydrolyzing carbon) significantly decreases. A higher contribution of stabile forms was found in soils under coniferous forests (Norway spruce), while a smaller - under deciduous forests (European beech) and on grasslands. The expected climate change and the ongoing land use transformations in the zone above 1000 m asl may lead to a substantial increase in the stable humus fraction (mainly of a non-hydrolyzing carbon) and an increase in the SOC pools, even if humus acids are characterized by a lower maturity and greater mobility favorable to soil podzolization. In the lower zone (below 1000 m asl), a decrease in the most stable humus forms can be expected, accompanied by an increase of DOC contribution, which will result in a reduction in SOC pools. Overall, the expected prevailing (spatial) effect is a decreasing contribution of the most stable humus fractions, which will be associated with a reduction in the SOC pools in medium-high mountains of temperate zone of Central Europe.     

Effect of Wetland Reclamation on Soil Organic Carbon Stability in Peat Mire Soil Around Xingkai Lake in Northeast China

Content and density of soil organic carbon(SOC) and labile and stable SOC fractions in peat mire soil in wetland, soybean field and rice paddy field reclaimed from the wetland around Xingkai Lake in Northeast China were studied. Studies were designed to investigate the impact of reclamation of wetland for soybean and rice farming on stability of SOC. After reclamation, SOC content and density in the top 0–30 cm soil layer decreased, and SOC content and density in soybean field were higher than that in paddy field. Content and density of labile SOC fractions also decreased, and density of labile SOC fractions and their ratios with SOC in soybean field were lower than that observed in paddy field. In the 0–30 cm soil layer, densities of labile SOC fractions, namely, dissolved organic carbon(DOC), microbial biomass carbon(MBC), readily oxidized carbon(ROC) and readily mineralized carbon(RMC), in both soybean field and paddy field were all found to be lower than those in wetland by 34.00% and 13.83%, 51.74% and 35.13%, 62.24% and 59.00%, and 64.24% and 17.86%, respectively. After reclamation, SOC density of micro-aggregates( 0.25 mm) as a stable SOC fraction and its ratio with SOC in 0–5, 5–10, 10–20 and 20–30 cm soil layers increased. SOC density of micro-aggregates in the 0–30 cm soil layer in soybean field was 50.83% higher than that in paddy field. Due to reclamation, SOC density and labile SOC fraction density decreased, but after reclamation, most SOC was stored in a more complex and stable form. Soybean farming is more friendly for sustainable SOC residence in the soils than rice farming.     

Effects of Reclamation on Soil Carbon and Nitrogen in Coastal Wetlands of Liaohe River Delta,China

To evaluate the influence of wetland reclamation on vertical distribution of carbon and nitrogen in coastal wetland soils, we measured the soil organic carbon(SOC), soil total nitrogen(STN) and selected soil properties at five sampling plots(reed marsh, paddy field, corn field, forest land and oil-polluted wetland) in the Liaohe River estuary in September 2013. The results showed that reclamation significantly changed the contents of SOC and STN in the Liaohe River estuary(P 0.001). The SOC concentrations were in the order: oil-polluted wetland corn field paddy field forest land reed marsh, with mean values of 52.17, 13.14, 11.46, 6.44 and 6.16 g/kg, respectively. STN followed a similar order as SOC, with mean values of 1351.14, 741.04, 632.32, 496.17 and 390.90 mg/kg, respectively. Interaction of reclamation types and soil depth had significant effects on SOC and STN, while soil depth had significant effects on SOC, but not on STN. The contents of SOC and STN were negatively correlated with pH and redox potential(Eh) in reed marsh and corn field, while the SOC and STN in paddy field had positive correlations with electrical conductivity(EC). Dissolved organic carbon(DOC), ammonium nitrogen(NH_4~+-N) and nitrate nitrogen(NO_3~–-N) were also significantly changed by human activities. NH_4~+-N and NO_3~–-N increased to different degrees, and forest land had the highest NO_3~–-N concentration and lowest DOC concentration, which could have been caused by differences in soil aeration and fertilization. Overall, the results indicate that reed harvest increased soil carbon and nitrogen release in the Liaohe River Estuary, while oil pollution significantly increased the SOC and STN; however, these cannot be used as indicators of soil fertility and quality because of the serious oil pollution.     

The effects of estuarine processes on the fluxes of inorganic and organic carbon in the Yellow River estuary

Riverine carbon flux is an important component of the global carbon cycle. The spatial and temporal variations of organic and inorganic carbon were examined during both dry and wet seasons in the Yellow River estuary. Concentrations of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in the Yellow River during dry seasons were higher than those during wet seasons. The effective concentrations of DOC (C_DOC*) were higher than the observed DOC at zero salinity. This input of DOC in the Yellow River estuary was due to sediment desorption processes in low salinity regions. In contrast to DOC, the effective concentrations of DIC were 10% lower than the DIC measured at freshwater end, and the loss of DIC was caused by CaCO₃ precipitation in low salinity region. Particulate organic carbon (POC) and particulate inorganic carbon (PIC) contents of the particles stabilized to constant values (0.5%±0.05% and 1.8%±0.2%, respectively) within the turbidity maximum zone (TMZ) and showed no noticeable seasonal variations. A rapid drop of PIC and rise of POC occurred simultaneously outside the TMZ due to an intense dilution of riverine inorganic-rich particles being transported into a pool of aquatic organic-poor particles outside the TMZ. Annually, the Yellow River transported 6.95×10⁵ t of DIC, 0.64×10⁵ t of DOC, 78.58×10⁵ t of PIC and 2.29×10⁵ t of POC to the sea.     

冻融循环对GFRP锚杆锚固性能影响的试验研究

针对季冻区春融期岩锚失效的问题, 研究了玻璃纤维(GFRP)锚杆在冻融循环作用下的锚固能力。通过设计物理模型对经历25, 50, 75冻融周期的试块进行了加载试验, 根据试验数据和破坏现象分析了GFRP锚杆在冻融后锚杆应力和承载力的变化规律。研究结果表明: 冻融循环会导致环氧树脂砂浆与混凝土的黏结性能下降, 在25, 50, 75周期后承载力损失分别为38.24%, 42.65%, 52.94%。冻融循环加速黏结材料及围岩的材料性能劣化, 荷载向内部传递加速, 使得GFRP锚杆上各点之间的应力差值逐渐减小, 锚杆应力分布比常温状态下更趋于均匀, 但材料性能的劣化导致局部破坏提前, 锚杆整体承载性能降低。研究结果可以为GFRP锚杆的工程应用提供建议。      

裂隙岩体循环冻融变形特征及影响因素分析

高寒、高海拔地区由于反复冻融导致的岩体变形破坏,对区内工程建设有重大影响。为研究不同裂隙条件下岩体循环冻融特性,在汶马高速沿线选择具有代表性的千枚岩和砂岩,制备了不同裂隙条件（长度、张开度、裂隙组数）试样,在干燥和饱水两种状态下分别进行大温差（-20℃到20℃）循环冻融（50次）试验。试验揭示了饱水裂隙岩样冻融变形过程:冻缩→冻胀→冻缩（冻结阶段）→融胀→融缩→融胀（融化阶段）,干燥裂隙岩样冻融变形过程:冻缩（冻结阶段）→融胀（融化阶段）。进一步,选择冻胀量εd为指标,分析了两类岩样冻融循环次数与εd的关系,揭示了裂隙长度、宽度和组数对εr的影响规律;选择残余变形量εr为指标,揭示了千枚岩和砂岩试样在饱水条件下εr随εd的增加规律,获得了εd与εr间的定量关系;分析了干燥和饱水试样单轴抗压强度随冻融循环次数增加而减小规律,确定了冻融次数与试样劣化间的线性关系。最后,初步讨论了饱水条件、岩性和裂隙条件对岩体冻融循环变形的影响机制。      

融入土壤湿度指标的青藏高原近地表土壤冻融机器学习监测算法

青藏高原作为中低纬度地区最大的高山冻土区,多年冻土和季节冻土广泛分布。高精度的地表冻融监测结果对研究该区域的水热交换、碳氮循环和土壤冻融侵蚀非常重要。本文基于4个青藏高原典型地区的土壤温湿度观测网数据,开展利用LightGBM算法和随机森林算法进行土壤冻融循环监测的研究。在构建土壤冻融监测模型的过程中,发现土壤湿度是影响冻融判别的一个关键因子。使用AMSR2亮温数据和ERA5-Land土壤湿度数据,基于两种机器学习算法判别地表冻融状态,将结果与传统冻融判别式算法进行对比分析。结果表明：相比冻融判别式算法,LightGBM算法在白天和夜间的总体判对率提高了12.09%;14.45%,随机森林算法在白天和夜间的总体判对率提高了13.23%和14.96%。近80%的错分样本分布在-4.0℃～4.0℃之间,说明2个机器学习算法能够识别出稳定的土壤冻结状态和融化状态。另外,LightGBM算法和随机森林算法得到的日冻融转换天数的平均RMSE降低了112.82和117.00;冻结天数的平均RMSE降低了47.87和53.96;融化天数的平均RMSE降低了37.10和39.80。同时,基于随机森林算...     

Effects of freeze-thaw cycle on engineering properties of loess used as road fills in seasonally frozen ground regions,North China

Compacted loess is widely used as fills of road embankments in loess regions of northern China. Generally, densely-compacted loess can satisfy the requirements of embankment strength and post-construction deformation. I lowever, uneven subsidence, pavement cracks and other related damages can affect the integrity of loess subgrade after several years of operation, and even cause some hazards, especially in North China, where the strong freeze-thaw erosion occurs. In this study, cyclic freeze-thaw tests for both densely and loosely compacted loess samples were performed to determine the variation in engineering properties such as volume, void ratio, collapsible settlement, microstructure, and the related mechanisms were addressed. The experimental results showed that an obvious water migration and redistribution occurred within the samples during freeze-thaw cycles. Ice lenses and fissures could be identified in the upper frozen layers of the samples. After freeze-thaw cycles, the dry densities of the nipper layers of samples changed significantly due to strong freeze-thaw erosion. The dry densities decreased for the dense sample and increased for the loose sample. It can be found that dense samples become loose, while loose samples became dense with the increasing number of freeze-thaw cycles. Their related void ratios changed reversely. Both void ratios tended to fall into a certain range, which verified the concept of a residual void ratio proposed by Viklander. The loosening process of densely compacted samples involves the formation of large pores, volume increase and density reduction as well as the related changes in mechanical properties because freeze-thaw cycles may be important contribution to problems of loess road embankments. Adverse effects of freeze-thaw cycles, therefore, should be taken into account in selecting loess parameters for the stability evaluation of road embankment in seasonally frozen ground regions.     

神农架大九湖泥炭地溶解有机碳季节性变化及其影响因素

亚热带泥炭地在水源涵养、碳储存和生物多样性等方面有着重要的保护价值。溶解有机碳(DOC)是泥炭地中容易受到外界扰动的一部分碳，在气候变化和人类活动的双重影响下，DOC可能通过降解或横向迁移从泥炭地中流失，潜在地威胁了泥炭地的碳储存功能。然而，目前对于亚热带泥炭地DOC如何响应季节性尺度的环境变化还缺乏深入的认识。以位于北亚热带的神农架大九湖泥炭地为研究对象，开展了季节尺度的泥炭孔隙水DOC浓度和紫外-可见吸收光谱特征以及环境参数的监测。结果显示，在大九湖泥炭地中，表层0~10 cm的泥炭孔隙水DOC浓度和光谱参数具有明显的季节差异性，DOC浓度和光谱参数还表现出明显的深度差异性。相关性分析显示，DOC浓度及紫外-可见吸收光谱参数直接受控于泥炭孔隙水的电导率和氨态氮浓度，可能还间接受到泥炭地水位和孔隙水硝态氮浓度等因素的影响。以上结果表明，在亚热带季风气候条件下，季节性水位波动引起的泥炭水化学参数和营养盐的变化，可能显著改变表层泥炭DOC动态，需要重视这种季节性波动对亚热带泥炭地碳储存能力以及生态功能的影响。      

贵州省湿地碳储量与碳中和潜力分析

湿地作为缓解气候变化的关键生态系统, 在碳捕获与碳封存方面发挥着不可替代的作用。湿地碳储量和影响因素的分析以及固碳潜力的预测, 对湿地生态保护与管理、国家"双碳"目标实现具有重要意义。应用ArcGIS10.8对《贵州省湿地保护发展规划》(以下简称规划)的3个时期(分别是: 1999-2009年; 2010-2018年; 2018年至今)湿地分布图采用遥感目视解译的方式进行矢量化并根据贵州省岩溶发育强度进行分区。采用生命带研究法与生物量估算法等对贵州省湿地面积和碳储量变化进行估算分析, 对重要湿地碳储量与单位面积碳储量进行估算并与全省湿地进行对比, 采用固碳潜力计算模型对贵州省重要湿地固碳潜力进行估算, 应用Origin软件对各相关影响因子进行数据分析。结果表明: ①贵州省湿地规划前期的面积为216 526.95 hm2, 规划中期面积为209 726.85 hm2、规划后期面积为255 440.53 hm2, 总体表现为先下降再升高, 总体面积增加38 913.58 hm2; ②贵州省湿地碳储量变化为: 规划前期为5.97×105 t, 规划后期为3.78×106 t, 是规划前期的6倍以上, 碳储量增加明显。其中, 贵州省重要湿地碳储量为3.24×106 t, 占全省湿地碳储量85.71%, 固碳潜力十分显著; ③贵州省重要湿地的固碳潜力为1.14×104 t C/a, 预计到2030和2060年, 湿地总固碳量分别达到7.99×106 t C和8.34×106 t C; ④温度、DIC浓度、有机碳含量与面积对贵州省重要湿地的碳储量影响较大, 重要湿地碳储量与DIC浓度、有机碳含量以及面积呈正相关, 而与温度呈负相关关系。对贵州省的湿地碳储量估算与碳中和潜力分析不仅可以了解贵州省湿地碳封存现状, 还可为区域湿地生态系统在"3060"双碳目标的贡献上提供理论参考。      

Preliminary study on the dissolved and colloidal organic carbon in the Zhujiang River estuary

ＩＮＴＲＯＤＵＣＴＩＯＮＥｓｔｕａｒｉｅｓｃｏｍｐｒｉｓｅａｍａｊｏｒｂｉｏｇｅｏｃｈｅｍｉｃａｌｉｎｔｅｒｆａｃｅｃｏｎｎｅｃｔｉｎｇｔｈｅｌａｎｄａｎｄｔｈｅｓｅａ (Ｍａｎ ｔｏｕｒａ,1 987) .Ｔｈｅｂｅｈａｖｉｏｒａｎｄｆａｔｅｏｆａｐａｒｔｉｃｕｌａｒｒｉｖｅｒ ｂｏｒｎｅｓｕｂｓｔａｎｃｅｉｎｔｒｏｄｕｃｅｄｉｎｔｏａｎｅｓｔｕａｒｙｉｓｄｅｔｅｒｍｉｎｅｄｔｏａｌａｒｇｅｅｘｔｅｎｔｂｙｔｈｅｂｉｏｇｅｏｃｈｅｍｉｃａｌｐｒｏｐｅｒｔｉｅｓｏｆｔｈｅｓｕｂｓｔａｎｃｅａｓｗｅｌｌａｓｐ…     

针铁矿和蒙脱石对菲的吸附解吸行为与热力学研究

采用批量振荡吸附平衡法设计针铁矿和蒙脱石对菲的吸附解吸试验,对比研究了针铁矿和蒙脱石对菲的吸附解吸行为,并考察了不同K+浓度的溶液对蒙脱石吸附菲的影响,比较分析了线性吸附模型和Freundlich吸附模型描述矿物吸附等温线的准确性,并从吸附热力学角度探讨了矿物的吸附机理。结果表明:针铁矿和蒙脱石对菲的吸附解吸均表现出明显的非线性和解吸滞后现象;相对于线性吸附模型来说,针铁矿和蒙脱石对菲的吸附解吸更符合Freundlich吸附模型;与蒙脱石相比,针铁矿对菲的吸附更为显著,且具有更好的稳定性;溶液中软阳离子K+的存在使蒙脱石对菲的吸附能力得到显著提高;菲在蒙脱石和针铁矿上的吸附过程是一个自发放热,同时伴随着熵值减小的过程;随着温度的升高,蒙脱石和针铁矿对菲的吸附能力均减弱。     

Mechanism of slope failure in loess terrains during spring thawing

Slope failure in loess terrains of Northern China during spring thawing period is closely related to the freeze-thaw cycling that surface soils inevitably experienced. Field surveys were carried out on natural and artificial slopes in thirteen surveying sites located in the Northern Shaanxi, the center of Loess Plateau, covering five characteristic topographic features including tablelands, ridges, hills, gullies and valleys. Based on the scale that is involved in freeze-thaw cycling, the induced failures can be classified into three main modes, i.e., erosion, peeling and thaw collapse, depending on both high porosity and loose cementation of loess that is easily affected. Model tests on loess slopes with gradients of 53.1°, 45.0° and 33.7° were carried out to reveal the heat transfer, water migration and deformation during slope failure. The surface morphology of slopes was photographed, with flake shaped erosion and cracks noted. For three slope models, time histories for the thermal regime exhibit three obvious cycles of freeze and thaw andthe maximum frost depth develops downwards as freeze-thaw cycling proceeds. Soil water in the unfrozen domain beneath was migrated towards the slope surface, as can be noticed from the considerable change in the unfrozen water content, almost synchronous with the variation of temperature. The displacement in both vertical and horizontal directions varies over time and three obvious cycles can be traced. The residual displacement for each cycle tends to grow and the slopes with higher gradients are more sensitive to potentially sliding during freeze-thaw cycling.     

冻融循环作用下砂岩单轴压缩破坏断口特征分形研究

寒区岩石的力学特征往往受到冻融循环和荷载的共同影响,冻融岩石单轴压缩破坏断口蕴含着与冻融循环和荷载有关的损伤演化信息,冻融岩石单轴压缩破坏断口研究对冻融岩石断裂破坏机理分析有重要价值。为研究冻融岩石单轴压缩破坏断口形貌特征及其与宏观力学参数之间的关联性,通过摄影观测经历不同次数冻融循环的砂岩单轴压缩破坏断口形貌,采用像素点覆盖法计算断口分维值,探究了断口分维值与宏观力学参数之间的关系。结果表明:随着冻融次数的增加,冻融砂岩的力学性能劣化,单轴抗压强度、弹性模量、断口分维值、耗散能密度逐渐减小,峰值应变增大;单轴抗压强度、弹性模量、耗散能密度均与断口分维值之间存在指数关系,断口分维值越大,对应的单轴抗压强度、弹性模量、耗散能密度越大。冻融岩石单轴压缩破坏断口分维值可作为寒区岩体断裂破坏机理分析的有效参数。