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西安地裂缝是近年陆续出现的一种张拉裂缝,它的方位通常呈东北向。由于工业及民用过量地采取承压水,增大了承压水层土粒间的有效压力,引起土层的固结沉降,在沉降过大及不均匀沉降的影响下,使地面产生了这种张拉裂缝。由粘性土的极限平衡理论证明并导出裂缝的极限垂直深度 Z_0为:Z_0=(2c)/(γ)tg(45°+((?))/(2))K、太沙基得出相似的计算公式为:Z_0=(2.67c)/(γ)tg(45°+■)/(2))这里 c■分别为内聚力、容重、及内摩擦角房屋基础避让裂缝的安全距离 L_(?)按规范 TJ7-74建议并进行适当修正后的计算公式为:对条形基础:L_b=Z_0+3.5B+(D)/(tgα)对矩基形础:L_b=Z_0+2.5B+(D)/(tgα)这里 B 为基础埋深,α≤45°的土的稳定坡角,D 为基础埋置深度,其他符号同前。考虑现场施工等影响,上述安全避让距离的计算值尚须乘一系数 K 值,K 取1.2～1.4。
Xi’an ground fissure is a kind of tensile crack which has appeared one after another in recent years. Its orientation is usually northeast. Due to the excessive use of confined water by industrial and civil use, the effective pressure between the soil particles in the confined water layer is increased, resulting in the consolidation and settlement of the soil layer. Under the influence of excessive settlement and uneven settlement, the ground produces such a result. Tension cracks. The ultimate vertical depth Z_0 of the crack is proved by the limit equilibrium theory of the clay soil and is derived from: Z_0=(2c)/(γ)tg(45°+((?))/(2))K. The calculation formula is: Z_0 = (2.67c)/(γ)tg (45°+■)/(2)) where c ■ is the safety distance L_ (?) of the cohesive force, bulk density, and internal friction angle of the building foundation. ) According to the specification TJ7-74 recommendations and the appropriate calculation formula is: for the strip basis: L_b=Z_0+3.5B+(D)/(tgα) on the basis of the moment base: L_b=Z_0+2.5B+(D) /(tgα) where B is the buried depth, the stable slope angle of soil with α ≤ 45°, and D is the basic buried depth. Other symbols are the same as above. Considering the impact of on-site construction, the calculated value of the safe avoidance distance must still be multiplied by a factor K value, with K taken from 1.2 to 1.4.