非饱和土双应力变量广义土水特征曲线理论模型构建

土水特征曲线(soil-water characteristic curve,SWCC)方程是非饱和土力学中最重要的土性表征手段之一。该文评价当前经典的SWCC方程,指出其未具有包容复杂因素的能力,具有灵活性的优点但却同时具有对试验数据量依赖性高的缺点,不能处理多孔隙尺度集群土体固-液-气共同运动及作用的水力-力学耦合效应问题。建立双应力变量广义SWCC概念图示并定义相对体积含水比,基于Fredlund双应力变量理论及van Genuchten土-水表征方程,构建考虑土体变形及多孔隙分布形态的双应力状态变量的广义SWCC方程。相较于2个参数的Brooks等的方程、3个参数的van Genuchten方程以及4个参数的Fredlund等的方程,广义SWCC方程仅3个参数,其中2个参数在双对数坐标系的"相对体积含水比-吸力"平面中进行最小二乘法线性拟合得到,仅1个参数需非线性最小二乘法拟合得到。该模型可利用不同应力状态下的至少3个土水试验数据点,绘制出1条具有适宜精度的单峰SWCC;方程考虑了多峰孔隙概率密度函数分布及土体变形因素,实现了从应力历史推广到应力状态的广义情况,为定量描述不同孔隙结构土体双应力状态下的持水特性、渗透特性和强度特性提供了一条途径。     

Mechanisms of soil vulnerability to compaction of homogenized and recompacted Ultisols

Soil compaction is a main cause of soil degradation in the world and the information of soil compaction in subtropical China is limited. Three main Ultisols (quaternary red clay, sandstone and granite) in subtropical China were homogenized to pass through 2 mm sieve and recompacted into soil cores at two bulk densities (1.25 and 1.45 g cm⁻³). The soil cores were equilibrated at different matric potential values (−3, −6 and −30 kPa) before subjected to multi-step compaction tests. Objectives of this study were to determine how different initial soil conditions and loading time intervals influence pre-compression stress and to evaluate an easy measure to determine soil vulnerability to compaction. It became evident that the soil strength indicator, pre-compression stress, was affected by soil texture, initial soil bulk density and matric potential. The coarser the soil texture, the lower the bulk density and the higher the matric potential, the lower was the pre-compression stress. The pre-compression stress decreased exponentially with increasing initial soil water content. Soil water content and air permeability decreased after compaction. The amount of water loss was affected not only by soil texture, bulk density and initial water content but also by loading time interval. These results indicate soil pore structure and hydraulic conductivity changed during compactions. The applied stress corresponding to the highest changes of pore water pressure during compaction had a significant linear relationship with the pre-compression stress (R=0.88, P<0.001). The correlation was ascribed to that the changes in pore water pressure describe the dynamics of the interactive effects of soil pore characters and soil water movement during compaction. The results suggested the evaluation of soil vulnerability to compaction have to consider the initial soil condition and an easy method to measure the changes in pore water pressure can be applied to compare soil strength and soil vulnerability to compaction.     

紫花苜蓿和马唐根的生物力学性能及相关因素的试验研究

选择固土护坡植物时，植物根的抗拉强度是一项重要的力学指标。对豆科的紫花苜蓿和禾本科的马唐根的抗拉力和纤维素含量的研究表明，根的抗拉强度和纤维素含量均与直径呈显著的负相关关系，根的抗拉强度与纤维素含量呈正相关关系，表明“木本植物根的抗拉强度、直径和纤维素含量关系”的研究结论在这两种草本植物上也同样适用。对紫花苜蓿和马唐根的抗拉强度与其“木质素/纤维素”之间关系的研究表明，两者呈负相关关系，证实纤维素含量对于维持根抗拉强度的作用大于木质素含量。研究发现，豆科紫花苜蓿根的应力-应变为对数函数关系，不符合胡克定律，马唐根的应力-应变关系的本构方程基本遵从胡克定律。直径愈小，紫花苜蓿和马唐根的应力—应变关系对应变率敏感程度愈高，根的极限延伸率愈大。另外，根的抗拉力和直径测试设备的改进，实验结果更准确可靠。这方面研究对揭示植物根系提高土壤抗冲击性和抗剪强度机理，更好地进行水土保持植物的选择和优化组合具有重要意义。     

Zusammenhang zwischen hydraulischer und mechanischer Bodenstabilität in Abhängigkeit von der Belastungsdauer

Interaction between mechanically and hydraulically affected soil strength depending on time of loading Soil‐deformation analysis often only considers the direct effects of mechanical stress on changes in void ratio or pore functions while the interaction between hydraulic and mechanical processes is seldomly mentioned. Thus, we analyzed the effect of mechanical stress and time of soil settlement on changes in soil strength and the corresponding interactions between stress‐dependent changes in pore water pressure on precompression stress for a clayey silt. Disturbed samples with a bulk density of 1.4 g cm^–3 and a water content of 25 g (100 g)^–1 were compressed for four time steps (10–240 min) at eight stresses (20–400 kPa) with four replications. During the experiments, the changes of pore water pressure and void ratio were registered. With increasing time of stress application, we determined an increased soil strain. The higher the stress‐application time, the smaller gets the void ratio and the precompression stress value. Parallel to these variations in settlement, we also found changes in the pore‐water‐pressure values. This is a consequence of decreasing pore diameter while the water saturation increases. Thus, the proportion of neutral stresses on total stress increases which coincides with a change of water suction (= unsaturated) conditions up to even positive pore‐water‐pressure values (from less negative to positive pore water pressure values). From our experiments, we can conclude that the changes in pore‐water‐pressure values already occur at normal stress values smaller than the precompression stress. This underlines the increasing sensitivity of soil deformation processes close to the internal soil strength. The results support the idea, that in order to quantify the mechanical strength of structured unsaturated soils, we always have to determine the changes in pore‐water‐pressure values, too.     

Variation of the critical-state boundaries of an agricultural soil

The critical-state theory can be applied profitably to analyse the mechanical behaviour of agricultural soil. Critical-state parameters and other soil properties are affected by the microstructure and unsaturated nature of agricultural soils. We determined the critical-state boundaries of an agricultural soil in both saturated and unsaturated triaxial tests and examined the effects of matric suction and initial structure on critical-state boundaries. On the compression plane, the presence of air and matric suction in the pores of unsaturated soil significantly affected critical-state boundaries by increasing compressibility, λ On the deviatoric stress-mean net stress plane, the strength increased with matric suction. On this plane, the critical-state lines for the unsaturated tests had non-zero intercepts. For a given soil structure, the frictional parameter M remained fairly constant with matric suction change. However, a change in the initial microstructure resulted in a change in M, causing the position of the critical-state line to ‘pivot’ in state space.     

非饱和土双应力变量广义土水特征曲线模型验证

利用基于轴平移技术的Geo-Expert高级型应力相关土-水特征曲线压力板仪研究不同覆土压力(0、40、100、200 k Pa)对南阳膨胀土土水特征曲线(soil-water characteristic curve,SWCC)的影响;并对提出的考虑土体变形及多孔隙分布形态的双应力变量广义SWCC表征方程进行如下试验验证:1)不同覆土压力下微多孔隙分布形态的南阳膨胀土侧限固结试验及脱湿试验SWCC验证;2)零净法向应力状态双孔隙尺度硅藻土双峰SWCC试验验证;3)不同净围压状态下单孔隙尺度韩国残积土SWCC试验验证;4)多应力路径下法国Bapaume黄土,不同初始干密度下日本Edosaki砂土在脱湿-吸湿过程SWCC试验验证;并比较分析新方程与van Genuchten方程及Fredlund等方程的差异性。结果表明:1)覆土压力会显著改变膨胀土结构及孔隙通道,进而改变SWCC边界效应区、过渡区形态;也改变了双重孔隙尺度土壤的进气值;第1个波峰SWCC进气值均在1 k Pa左右;相比于零覆土压力试样,40、100、200 k Pa覆土压力试样第2个波峰SWCC进气值分别高4.74、17.58、67.23 k Pa;2)未考虑净法向应力影响的单应力状态多峰SWCC、考虑侧限双应力状态多峰SWCC、各向同性净法向应力单峰SWCC、不同脱湿-吸湿路径SWCC及不同初始干密度的SWCC试验拟合曲线均表明,双应力广义SWCC具有包容复杂影响因素的能力;3)新方程能够利用至少3个土-水数据即可拟合出具有较高的精度的整条SWCC。研究为定量描述土壤的持水、渗透及强度特性提供参考。     

基于土-水特征曲线的植物边坡抗剪强度研究

土-水特征曲线通常用于估计非饱和土壤的抗剪强度,但是由于植物根系的吸水作用和加筋效应,使得植物边坡的抗剪强度不能直接利用基于基质吸力的非饱和土抗剪强度计算公式进行计算。以裸露边坡和植被边坡为研究对象,采用张力计现场测试和室内剪切试验相结合的方法,拟合水土特征曲线关系。结果表明:(1)植物根系的植入有效地提高了边坡土体的进气值,较素土进气吸力值增幅41.10%。在同等含水率条件下,植物边坡基质吸力明显大于素土边坡,提高了边坡土体的持水能力。(2)边坡红黏土基质吸力与含水率的关系符合V-G模型,利用最小二乘法得到模型参数。(3)随着体积含水率的增大,带根土与素土的抗剪强度参数值变化趋势大致相同,均呈现先增大后减小的趋势,但带根土的变化参数大,当含水率21.29%时,带根土黏聚力相较于素土增加了4.86 kPa,增幅18.55%,而内摩擦角对根系存在的敏感程度不如黏聚力。(4)随着土壤基质吸力不断增大,植被边坡与素土边坡的抗剪强度力学参数变化趋势大体相同,当土基质吸力为60～90 kPa土体的黏聚力提高最为明显,但植被边坡由于植物根系的存在,土体内基质吸力对边坡土体的抗剪强度提高幅度更大,黏聚力与内摩擦角最大增长幅度分别为37.34%和40.30%。通过建立土-水特征曲线参数与植物边坡抗剪强度的关系,可计算不同含水率或基质吸力条件下植物边坡的抗剪强度,为进一步分析工程实际中植物边坡的稳定性提供理论依据。     

非饱和砂质黏性紫色土崩解特性及MICP加固试验

砂质黏性紫色土遇水极易崩解是导致西南山区土壤侵蚀流失等水土灾害的重要原因,为揭示其崩解规律和机制,改善土体的崩解性,采用自制崩解测量仪对不同初始干密度、含水率及颗粒级配条件下的紫色土进行浸水崩解试验,并从非饱和有效应力角度分析了其崩解演化机制,在此基础上,通过扫描电镜（Scanning Electron Microscope,SEM）探讨利用微生物诱导碳酸钙沉积（Microbial Induced Calcite Precipitation,MICP）加固技术对紫色土崩解性的改善效果。结果表明：1）紫色土浸水崩解全过程包含排气吸水期、平衡期、崩解发展期、崩解残余期4个阶段;2）崩解率与平均崩解速率随初始干密度及含水率的增大而减小,且细颗粒含量越高,平均崩解速率越大;3）紫色土浸水后非饱和有效应力的衰减过程受初始饱和度的影响较大,平均崩解速率随初始饱和度的增大呈指数函数衰减;4）MICP加固土的崩解率和平均崩解速率相较于素土分别下降了73～97个百分点和84%～99%,固化沉积的碳酸钙晶体使土体结构中的微裂隙与大孔隙大幅减少,形成较为致密的孔隙结构,大幅增强了粒间胶结强度,使土体抗崩解性能明显提升。MICP技术可以作为西南山区紫色土水土灾害防治的有效措施。     

The strength of unsaturated mixtures of sand and kaolin and the concept of effective stress

Pastes containing sand and 0, 5, 20 and 80 g kaolin kg^?1 mixture were equilibrated at matric potentials of – 2, – 10, – 100 and – 1000 kN m^?2 or allowed to air-dry. The strength of cylindrical samples was determined in unconfined compression and by the indirect tensile strength test. Measured strengths are explained using the Coulomb-Mohr theory and the concept of effective stress. At pore water tensions greater than 10 kN m^?2 effective stress was the dominant factor in determining compressive and tensile strength. The contrast between this behaviour and that of friable topsoils is discussed.     

紫色土坡耕地埂坎裂隙发育对土壤入渗的影响

为揭示埂坎裂隙发育程度对土壤入渗性能的影响,该研究选取了3种裂隙发育程度（重度发育、中度发育、轻度发育）的埂坎为研究对象,利用双环入渗试验揭示裂隙发育的埂坎土壤入渗规律并采用入渗模型进行模拟。结果表明：1）不同裂隙发育程度下,埂坎土壤入渗率变化趋势均为先迅速下降后逐渐趋于稳定。有裂隙埂坎各时段的入渗率均大于对照组无裂隙埂坎,但其差值均随入渗时间的增加而减小;2）随着埂坎裂隙发育程度的增加,土壤初始入渗率、平均入渗率、稳定入渗率和累积入渗量均增大,其中初始入渗率的增幅最高（98.72%）;3）控制初始含水率条件下,裂隙深度和面积-周长比仍与初始入渗率、平均入渗率及120 min累积入渗量呈显著正相关（P＜0.05）,裂隙面密度仅与平均入渗率呈显著正相关（P＜0.05）;4）Kostiakov模型和Mezencev模型对不同裂隙发育程度下埂坎入渗过程拟合效果较好（R2为0.84～0.99）,但Kostiakov模型只有在一定时间范围条件下才能有效描述裂隙埂坎入渗过程。研究结果可为紫色土区坡耕地埂坎的建设、维护管理和合理利用及水土保持提供参考。     

土壤基质吸力与土壤微生物活性关系的研究

研究了土壤微生物活性与土壤基膜吸力的关系，将土壤发泡点，即土壤导气率由0突变为非0时的基质吸力，与微生物的最高呼吸活性相联系，试图证明土壤微生物的最高活性发生于略高于土壤发泡点的基模吸力。对粗沙土、细沙土和砂壤土三种轻质地土壤的测定表明，土壤微生物的最高呼吸活性发生在略高于土壤发泡吸力的基质吸力。土壤基模吸力较小时微生物活性到达最高值的速度较慢，土壤基模吸力在发泡点附近时，微生物活性到达最高值的速度较快。     

SOME EFFECTS SUB-SURFACE DRAINAGE AND PLOUGHING ON THE STRUCTURE and COMPACTABILITY A CLAY SOIL

In a field experiment to determine the direct and indirect effect on soil structure, of sub-surface piped drainage as compared with natural surface drainage only, in ploughed and unploughed soil, a factorial systematic design with four replicated blocks was used. Structural changes were monitored during 8 months of natural rain and finally irrigation, by measuring surface heights and soil strength (penetration resistance) in relation to moisture content and matric suction, at plough sole depth (27 cm). A compaction test using a tractor with differentially loaded wheels, was applied at various times after irrigation, measuring the resulting wheel sinkage and wet density of the soil. The effects of the drainage treatments were found to be temporary, except a ‘crusting’ effect during the drying of the unploughed surface drained soil. The ploughed soil with sub-surface drainage showed greater frost heave than the undrained soil. The soil strength at 7.5-22.5 cm. depth was linearly related to the matric suction within the range of –3 to 20 cm-water. The compaction data for the unploughed soil suggested relationships between matric suction, sinkage, and wet density, but complicated interactions prevented any general conclusion. In the ploughed soil, compaction data established the beneficial effects of subsurface drainage in reducing damage from tractor traffic, decreasing wheel sinkage and reducing compaction both below and 16 cm from the track edge. A rise in matric suction of 10 cm-water, in the range 2-24 cm-water was, on the average, as effective in reducing rutting as a wheel load reduction of 670 kg (0.54 kg/cm² reduction of tyre inflation pressure). It was concluded that for clay soils having a temporary excess moisture, draining the water table to below 50-60 cm depth should be recommended as a precautionary measure to minimize structural damage.     

不同盆栽基质水分特征曲线的对比分析与模拟

现有关于盆栽控水模拟土壤干旱条件的试验中多采用含水率作为水分胁迫阈值,然而由于基质配比不同导致含水率相同的基质的水分状况也不尽相同,这导致各研究间结果难以对比和参考。为快速获取盆栽基质水分特征曲线,建立基质水分特征曲线预测模型。该研究以盆栽控水试验常用的泥炭土、蛭石和珍珠岩为基质材料,测定了不同配比基质的水分特征曲线,通过不同方法（多元回归模型、人工神经网络）建立了其预测模型。结果表明,人工神经网络模型对基质水分特征曲线的预测精度高于多元回归;相较于人工神经网络,多元回归模型的稳定性更高。综合考虑模型的精度和稳定性,多元回归模型是预测作物盆栽基质水分特征曲线的最佳模型。该模型为基质水分特征曲线快速获取以及相关作物干旱胁迫研究间的对比提供了方法和依据。     

The response of Aporrectodea rosea and Aporrectodea trapezoides (Oligochaeta: Lubricidae) to moisture gradients in three soil types in the laboratory

The question of whether the response of earthworms to soil moisture is governed by their reaction to soil wetness (moisture content) or to soil water energy (matric suction) was examined in two species of earthworm using moisture gradients in three contrasting soil types with clay contents varying from 4 to 39%. Gravimetric moisture gradients ranging over 5–30% were established in horizontal cores comprising 12 or 14 sections containing loosely packed soil. Earthworms were introduced to each section at the beginning of each experiment. The earthworms moved from sections containing dry soil into adjacent sections containing moister soil. Clear effects were evident after 6 h but these became more obvious after 96 h. For the earthworm Aporrectodea rosea, the threshold soil mositure level at which earthworms were induced to move away from dry soil was a matric suction of about 300 kPa (pF 3.4) and was independent of soil type. In contrast, for A. trapezoides, the threshold soil moisture varied with soil type (sandy loam 15 kPa, loam 25 kPa, clay 300 kPa). We conclude that, for the earthworm A. rosea, matric suction and not water content of soil provided the cue by which the earthworm recognized dry soil. For A. trapezoides, there was an interaction between matric suction and soil type in which the response of A. trapezoides to soil moisture varied with soil texture and the threshold for avoidance of dry soil ranged from a matric suction of 300 kPa (20% w/w) in clay to 15 kPa (10% w/w) in sandy loam.     

侵蚀坡耕地土壤强度变化特征

Undisturbed soil cores were taken from different slope positions （upslope, backslope and footslope） and soil depths （0-15, 20-35 and 100-115 cm） in a soil catena derived from Quaternary red clay to determine the spatial changes in soil strength along the eroded slope and to ewluate an indicator to determine soil strength during compaction. Precompression stress, as an indicator of soil strength, significantly increased from topsoil layer to subsoil layer （P 〈0.05） and was affected by slope position. In the subsoil layer （20-35 cm）, the precompression stress at the footslope position was significantly greater than at the backslope and upslope positions （P 〈0.05）, while there were no significant differences at 0-15 and 100-115 cm. Precompression stress followed the spatial wriation of soil clay content with soil depth and had a significant linear relationship with soil porosity （r^2 = 0.40, P 〈 0.01）. Also, soil cohesion increased with increasing soil clay content. The precompression stress was significantly related to the applied stress corresponding to the highest change of pore water pressure （r^2 = 0.69, P 〈 0.01）. These results suggested that soil strength induced by soil erosion and soil management wried spatially along the slope and the maximum change in pore water pressure during compaction could be an easy indicator to describe soil strength.     

Zur Bedeutung des Aggregierungsgrades für die Spannungsverteilung in strukturierten Böden

The effect of soil aggregation on stress distribution in structured soils The mechanical compressibility of arable soils can be described by preconsolidation load value and by the shear resistance parameters of the bulk soil and single aggregates. In order to quantify the effective stress equation must be also known the hydraulic properties of the soil in dependence of the intensity, kind, and number of loading events. The soil reacts as a rigid body at very fast wheeling speed inclusive a very pronounced stress attenuation in the top soil while stresses will be distributed in the soil threedimensionally to deeper depths at slower speed. These variations can be explained by the mechanical as well as by the hydraulic parameters of the bulk soil and single aggregates. Thus, the pore water pressure value of the bulk soil as a parameter of the effective stress equation further depends on the hydraulic properties of the inter- and intraaggregate pore system and continuity. As can be derived from the results the pore water pressure values are identical irrespective of the predessication for clayey polyhedres at high load while in coarse textured prisms the pore water pressure value depends on load and predryness. The consequences for soil strength under dynamic loading are shortly discussed.     

Shrinkage properties of differently managed clay soils in Finland

Soil cracking is a well-known phenomenon, also seen in clay soils in the boreal climatic zone. This study was carried out to quantify soil shrinkage properties in six differently managed clay soils in Finland (Vertic Cambisols, 51% clay). Cylinder samples (100 cm³) were taken in spring from two depths (0–5 and 5–10 cm), then saturated with water and dried as a function of applied suction. The heights of the sample were measured after each drying step and the volume of soil was calculated assuming isotropic shrinkage. The volume loss by shrinkage at a suction of −50 kPa was 1.6–3.8% and the total shrinkage was 5.2–10.5% of the total soil volume, respectively. All shrinkage curves showed structural shrinkage which occurred in the matric potential range from saturation to around −6 kPa. The shrinkage curves were characterized by minor proportional and wide residual shrinkage zones. Eight of twelve sites showed a steeper shrinkage in the proportional shrinkage zone than the theoretical 1:1 line. Large slope values, up to 3.0, reflect the collapse of inter-aggregate pore space due to shrinkage pressure. The results indicate significant particle rearrangement and structural changes, e.g. structural collapse and changes in inter-aggregate pore space due to shrinkage pressure. Continuous water saturation and variable periods of freezing between spring and autumn are mostly responsible for soil weakness against increasing effective stress as soil dries. It is presumed that shrinkage behaviour will change substantially with increases in drying and wetting cycles.     

Soybean seedling root growth as influenced by soil texture,matric suction and bulk density

Abstract

Laboratory experiments were conducted under controlled conditions to determine the effect of five matric suctions (0.05, 0.10, 0.30, 1.00 and 3.00 bars) and three bulk densities (1.10, 1.30 and 1.50 g.cm^?3) on the moisture content, penetrometer resistance and soybean (Glycine max L.) root growth in six different soil textural groups (sand, silt, clay and their combinations).

The different textural groups were compacted in PVC pipes 4.4 cm ID and 10 cm long and placed in pressure cells to obtain the desired matric suction. After equilibrium five pregerminated soybean seedlings were fixed on the soil surface. At the end of 48 hours root elongation was measured.

There was an increase in root growth in all the textural groups at all the bulk densities when the matric suction was increased from 0.05 to 0.30 bar. There was however a gradual decrease in root growth as the matric suction increased from 0.30 to 3.0 bars. The reduction in root growth at low and high matric suctions was related to moisture content, change in soil resistance and redox status of the soil system.

The measured penetrometer resistance values were directly related to the level of compaction, soil matric suction and also were dependent upon the texture. Close relationships were recorded between redox potentials and soil matric suction.     

基于CT技术的原状黄土细观结构动态演化特征

非饱和原状黄土具有典型的结构性,结构性对其强度、变形等特征产生重要影响,但结构性对其屈服特性的影响却鲜有报道。为研究结构性对非饱和原状黄土在各向等压加载过程中的屈服特征影响规律,以非饱和土多功能三轴仪为研究工具,对4个非饱和原状黄土试样进行控制吸力的各向等压加载试验。借助CT(computerized tomography)技术,对变形和排水稳定后黄土试样进行实时动态扫描,将加载过程中的宏观力学指标与细观扫描数据联系,以明晰原状黄土加载过程中的结构演化规律。结果表明:原状黄土屈服前,CT数ME增长缓慢,说明结构性起到了抵御外部荷载的作用;当试样屈服后,ME呈线性增长趋势,试样进入塑性硬化阶段,结构性的作用明显降低。吸力增大时,原状黄土结构性对其力学变形特征影响较小;而吸力减小时,土颗粒之间水膜润滑作用明显,结构性对于抵抗外部荷载的作用增强。施加净平均应力后的原状黄土,其内部的孔洞和孔隙会减小,但不会完全闭合,这与新形成的结构能抵御外部荷载有关。研究结果可为进一步建立原状黄土结构性本构模型提供借鉴。     

紫色土埂坎根-土复合体土水特性与抗剪强度

研究根-土复合体土-水特征曲线与抗剪强度的关系,可为紫色土埂坎根-土复合体强化机理的揭示与埂坎稳定性的维持提供科学依据。选取三峡库区典型紫色土坡耕地埂坎草本植物根—土复合体为研究对象,结合Hyprop2土壤水分特征曲线测量仪、滤纸法与直剪试验,拟合土-水特征曲线,揭示基质吸力对根-土复合体抗剪强度的影响。结果表明:(1)根-土复合体土-水特征曲线明显分为边界效应区、过渡区与非饱和残余区,3种常用模型(B-C、VG、F-X)中F-X模型拟合该曲线效果最好,根-土复合体饱和含水率、进气吸力、残余区含水率以及相同体积含水率下的基质吸力均高于素土。(2)随着体积含水率降低,根-土复合体黏聚力先增大后减小,试验范围内黏聚力最大值51.25 kPa出现在体积含水率约23%时,内摩擦角则线性增大。相同体积含水率下,根-土复合体黏聚力较素土最大增加50%,内摩擦角提升不大。(3)基质吸力对根-土复合体抗剪强度的增强作用具有阶段性特征,各阶段临界吸力值与土-水特征曲线一致,过渡区(基质吸力为3~500 kPa)土体抗剪强度提高明显,进入非饱和残余区后(基质吸力>500 kPa)由于黏聚力下降,土体抗剪强度增速减慢,根-土复合体抗剪强度随基质吸力增大而提升的幅度大于素土。通过建立埂坎根-土复合体土-水特征曲线和抗剪强度的关系,可估测实际工况下的埂坎土体抗剪强度,进而为坡耕地埂坎的建设、维护管理以及坡耕地侵蚀阻控提供理论依据。