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液化筛查计算器

EN 1998-5 §F + EN 1997-1 简化液化评估：Seed & Idriss法、逐层CSR/CRR/FoS（至20m深度）、石原式沉降估算、减灾建议。

地震输入
土体剖面
液化结果
最不利安全系数
可液化层
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可能液化（1.0 ≤ FoS < 1.25）
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沉降计算 → 浅基础承载力 → 桩基承载力 →

Standards compliance

FAQ
EN 1998-5 §F提供了基于Seed & Idriss (1971)简化方法的地震液化评估信息性程序。
CSR = 0.65 × (a_max/g) × (σ_v/σ′_v) × r_d。代表地震引起的标准化循环剪应力需求。
CRR = CRR₇.₅ × MSF × Kσ。CRR₇.₅基于(N₁)₆₀,cs（Youd et al. 2001）。MSF和Kσ校正震级和上覆压力。
(N₁)₆₀,cs是标准化为60%能量比的SPT击数，经上覆压力校正（CN）和FC≥35%细粒含量校正（Idriss & Boulanger 2008）。
根据石原·吉峰 (1992)：FoS < 1.0的层按比例贡献。请咨询合格岩土工程师。
对高或中等敏感性（FoS < 1.25）的重要结构（等级III/IV）。方法：碎石桩、注浆、桩基。

Methodology

1. Cyclic Stress Ratio (CSR): CSR = 0.65 × (a_max/g) × (σ_v/σ′_v) × r_d. The 0.65 factor accounts for the number of equivalent uniform cycles. r_d is the stress reduction coefficient from Liao & Whitman (1986).

2. Corrected SPT Blow Count (N₁)₆₀,cs: The SPT N-value is first corrected to 60% energy ratio (N₆₀), then normalized for overburden (CN), and finally adjusted for fines content (FC) using Idriss & Boulanger (2008): for FC ≥ 35%, a fines correction ΔN = 5.6×exp(0.06·FC − 0.22) is added.

3. Cyclic Resistance Ratio (CRR): CRR₇.₅ is derived from (N₁)₆₀,cs using the Youd et al. (2001) clean-sand correlation. MSF scales CRR to the design magnitude (Seed & Idriss 1979, Idriss 1995). Kσ corrects for effective overburden stress (Harder & Boulanger 2006).

4. Factor of Safety: FoS = CRR / CSR. FoS > 1.25 → non-liquefiable. 1.0 ≤ FoS ≤ 1.25 → potentially liquefiable. FoS < 1.0 → liquefiable.

5. Post-Liquefaction Settlement: Volumetric strain ε_v is estimated from Ishihara & Yoshimine (1992) using the FoS and relative density Dr (inferred from (N₁)₆₀,cs). The settlement is S = ε_v × H_layer.