基于吸力量测确定膨胀土活动带和裂隙深度

采用M itchell公式和裂隙扩展深度方程两种吸力法确定安康地区膨胀土大气影响深度和裂隙开展深度。其一通过对安康地区两处天然边坡开挖观测井,利用张力计进行不同深度处吸力值的现场量测,根据M itchell提出公式计算大气影响深度;其二根据非饱和土抗拉强度公式,建立膨胀土裂隙扩展深度方程,利用基质吸力量测结果求其理论解。结果表明,安康地区膨胀土吸力变化曲线随深度增加变幅减小,呈“波浪式”推移。M itchell公式确定安康地区膨胀土的大气影响深度为3.35m以内,裂隙深度方程确定裂隙开展深度为3.06³.14m。利用M itchell公式计算大气影响深度与膨胀土断裂理论公式确定的裂隙开展深度结果接近。

DEPTH IDENTIFICATION OF THE ACTIVE AND CRACKING ZONES IN EXPANSIVE SOILS FROM IN-SITU SUCTION MEASUREMENT

In order to assess the active zone depth and the cracking zone depth of expansive soil below ground surface,Mithchell formulation and crack expansion equation are used.Through excavating observation wells in two inartificial slopes in Ankang area,the suction values at different depths were measured by tensiometer.According to the Mithchell formulation,the active zone depth is calculated.According to the theory of tensile strength of unsaturated soil,the equation of crack expansion is formulated.The theoretical solution is obtained through calculation from the results of suction measurement.The results indicate that the suction curves of expansive soil do not change significantly with the increase of depth.The curves undulate with depth.The active zone depth of expansive soil is found to be between 3.17 m and 3.32 m.The crack depth is found to be between 3.06 m and 3.14 m.Therefore,the results of the two methods are close.