CAJ | 학술논문

土的抗剪强度与其剪切破坏面上的正应力一般呈线性关系，反映了土的剪切强度本质特性。常用的强度准则有Mohr–Coulomb准则、Drucker–Prager屈服准则、Matsuoka–Nakai准则，分别对应于与大主应力呈45°+?/2的剪切破坏面、八面体面和空间滑动面（SMP）上的剪应力比为常数的关系。本文提出了一种由k3σ1，k3σ2，k3σ3确定土单元大、中、小主应力轴交点的空间滑动面，称为3σ空间滑动面；建立了3σ空间滑动面剪应力比为常数的准则，称为3σ空间滑动面强度准则，该准则在应力空间描述的强度破坏面为π平面上呈曲边三角形形态的光滑锥面。进行了Mohr–Coulomb强度准则、Drucker–Prager强度准则、Matsuoka–Nakai强度准则与Lade–Duncan强度准则、3σ空间滑动面强度准则在应力空间描述强度破坏面的比较分析，以及不同π平面上Lade–Duncan准则和3σ空间滑动面强度准则随b值的变化规律。结果表明Lade–Duncan强度准则与3σ空间滑动面强度准则近似一致，从而揭示了Lade–Duncan强度准则的物理本质基础：Lade–Duncan强度准则实质上近似服从土破坏时3σ空间滑动面上剪应力与正应力呈线性变化的规律。即Lade–Duncan强度准则描述土单元剪切破坏时的空间滑动面近似为3σ空间滑动面。根据4种原状黄土固结排水条件下的真三轴压缩试验结果，验证了3σ空间滑动面强度准则的合理性与可靠性。
토적항전강도여기전절파배면상적정응력일반정선성관계，반영료토적전절강도본질특성。상용적강도준칙유Mohr–Coulomb준칙、Drucker–Prager굴복준칙、Matsuoka–Nakai준칙，분별대응우여대주응력정45°+?/2적전절파배면、팔면체면화공간활동면（SMP）상적전응력비위상수적관계。본문제출료일충유k3σ1，k3σ2，k3σ3학정토단원대、중、소주응력축교점적공간활동면，칭위3σ공간활동면；건립료3σ공간활동면전응력비위상수적준칙，칭위3σ공간활동면강도준칙，해준칙재응력공간묘술적강도파배면위π평면상정곡변삼각형형태적광활추면。진행료Mohr–Coulomb강도준칙、Drucker–Prager강도준칙、Matsuoka–Nakai강도준칙여Lade–Duncan강도준칙、3σ공간활동면강도준칙재응력공간묘술강도파배면적비교분석，이급불동π평면상Lade–Duncan준칙화3σ공간활동면강도준칙수b치적변화규률。결과표명Lade–Duncan강도준칙여3σ공간활동면강도준칙근사일치，종이게시료Lade–Duncan강도준칙적물리본질기출：Lade–Duncan강도준칙실질상근사복종토파배시3σ공간활동면상전응력여정응력정선성변화적규률。즉Lade–Duncan강도준칙묘술토단원전절파배시적공간활동면근사위3σ공간활동면。근거4충원상황토고결배수조건하적진삼축압축시험결과，험증료3σ공간활동면강도준칙적합이성여가고성。
The linear relation between shear strength and normal stress of failure plane shows the essential property of soil shear strength. The Mohr–Coulomb criterion, Drucker–Prager yield criterion and Matsuoka–Nakai criterion respectively respond to the linear relationship between shear stress and normal stress on different shear failure planes including shear failure plane with the angle of 45°+?/2relating to the plane of the main principal stress, the octahedral plane in the principal stress space of soil element and the spatially mobilized plane named alsoσ spatially mobilized plane. In this paper, new3σ spatially mobilized plane is proposed using three pointsk3σ1,k3σ2,k3σ3in the soil element in the principal stress axes, named as the3σ spatially mobilized plane. Furthermore, the new strength criterion is also proposed using the shear stress ratio on the3σspatial mobilization plane being constant. The strength failure surface depicted in the principal stress space by this criterion is a smooth cone surface with the curved triangle shape onπ plane. The strength failure surfaces of Mohr–Coulomb criterion, Drucker–Prager yield criterion, Matsuoka–Nakai criterion, Lade-Duncan criterion and3σ spatially mobilized plane criterion described in the stress space as well as the change laws of Lade-Duncan criterion and3σ spatially mobilized plane criterion with parameterb on differentπ planes are comparatively analyzed. It is shown that the Lade-Duncan criterion and3σ spatially mobilized plane strength criterion are approximate, which reveals the physical essence of Lade-Duncan strength criterion, that is, the former approximately obeys the linear relationship between shear stress and normal stress on 3σ spatially mobilized plane at failure of soils. The Lade-Duncan criterion describing the shear failure of soil element is approximately the3σ spatially mobilized plane. By comparing the strength criterion with the measured strength of true triaxial tests on four kinds of intact loess under consolidation and drainage, the laws of loess can be described by means of the3σ spatial mobilization plane strength criterion under the complex stress condition, and the rationality and reliability of the proposed strength criterion are verified by its consistency with the experimental values.