Changelog

v0.6.0 — 2026-07-15 (Mononobe-Okabe Rewrite: Exact Mechanics + Four-Figure Report)

• Correctness fixes (all M-O coefficient users): the Coulomb / M-O sin-form denominators now use sin²β per Das Eq. 16.26 / 16.38 (the old sinβ overestimated K_a, K_p, K_ae by 1/sinβ for battered walls; exact at β = 90°); Coulomb K_p now uses sin(β+α) (was sin(β−α)); the seismic thrust carries the (1−k_v) factor per Kramer Eq. 11.7. Both webapp/calculators and the geostructpy library are fixed; the Theory page formulas updated to match.
• New mechanics: exact Zarrabi-Kashani (1979) critical failure-plane angle α_AE (replaces the 45°−φ/2+θ/2 approximation); seismic passive K_pe (Kramer Eq. 11.10, evaluated at the true inertia angle); Seed–Whitman resultant height z̄ with the static part at its distribution centroid and ΔP_ae at 0.6H; wall-normal force components P_h, P_v and overturning moment; Seed–Whitman ¾k_h approximation check.
• Validity guards: hard check φ − α − θ ≥ 0 with the limiting coefficient k_h,lim = (1−k_v)tan(φ−α) and a clamped limiting-state report instead of a crash; domain guards for β ≤ δ, α+β ≥ 180°, β−δ−θ ≤ 0, k_v ≥ 1, and root-degeneracy in K_p/K_pe — invalid inputs now return a readable message instead of an HTTP 500.
• c′-φ′ backfill (Das §16.10): tension-crack depth and closure term now carry the (1−k_v) factor so the closed form is the exact integral of the reported pressure profile; the static thrust receives the same correction so ΔP_ae and z̄ compare like with like; full-height tension is clamped to zero thrust with a warning.
• Independent QA in every report: the critical wedge's pseudo-static force polygon (W, k_hW, k_vW, R, P_ae) is solved from equilibrium independently of the K_ae formula and must close — the report prints the agreement (Δ ≈ 0.000%).
• New report UI: validity banner, six key-result stat tiles, and a 2×2 figure grid — Fig. 1 cross-section with exact wedge + corrected pressure diagrams, Fig. 2 closed force polygon, Fig. 3 K_ae–k_h sensitivity (φ±5° family, Seed–Whitman line, design point, k_h,lim), Fig. 4 pressure distribution with increment band; numbered calculation sheet with pressure-ordinate table and design summary.
• Verification: new tests/qaqc_mononobe_okabe harness — closed forms checked against an independent brute-force trial-wedge search (critical angle, max thrust, polygon closure to machine precision), static Coulomb limits, and end-to-end report scenarios.

v0.5.0 — 2026-04-08 (Braced Cut + Bowles Citations)

• New module: /braced-cut — basic braced excavation analysis using the Peck (1969) apparent earth-pressure envelope. Three soil cases: sand (rectangular envelope), soft / medium clay (trapezoidal with Peck reduction factor m = 0.4 when N_s > 6), and stiff clay. Per-strut design force and Bjerrum & Eide (1956) bottom-heave check for clay. Per Das & Sivakugan Ch. 19 (§19.3 envelope p. 820, §19.5 design p. 823, §19.7 bottom heave p. 835) and Bowles 5e Ch. 14.
• Slope stability citations: integrated Bowles (1996, 5e) Ch. 2 references throughout the per-layer report and top callout. Each formula row now lists Bowles equation numbers alongside Das & Sivakugan: w → Bowles §2-2 Eq. 2-3; e₀ → §2-3 Eq. 2-10; γ_d → Eq. 2-9; γ_sat → Eq. 2-11; K₀ → Bowles §2-8 Eq. 2-18a, p. 39 (Jaky simplified) plus Eq. 2-19 sloping ground / Eq. 2-23 OCR adjustment / Eq. 2-22 from Poisson's ratio; dilatancy → §2-11.3 cohesionless soils; S_s → §2-10 Consolidation Principles, p. 56. Top callout adds full Table 2-8 E_s ranges (very soft clay 2–15 MPa through dense sand+gravel 100–200 MPa) and Table 2-7 Poisson's ratio ranges.
• Theory page: Bowles 5e added as the third Primary Textbook with full chapter map (Ch. 2 properties, §2-8 K₀ p. 39, §2-10 consolidation p. 56, §2-11 shear p. 90, §2-14 elastic p. 121 with Tables 2-7/2-8, plus Ch. 4/11/12/13/14/16-18 cross-references).
• Nav: "Braced Cut" link added to the top bar. Total routes now 19 (was 18).

v0.4.0 — 2026-04-07 (Bundled QAQC Sprint II)

• New module: /sheet-pile — cantilever sheet pile in sand per Das & Sivakugan §18.4 (pp. 758–764). Solves the Das Eq. 18.17 quartic for required embedment depth, computes maximum moment, and reports required section modulus.
• New module: /anchor — deadman anchor holding capacity for plates in sand (Ovesen-Stromann, Das §18.19, p. 804) and clay (Mackenzie / Tschebotarioff, Das §18.20, p. 811).
• Retaining wall: added front soil depth input (y) with optional passive-resistance credit toggle. Updated the wall cross-section plot to draw front soil fill, passive-pressure triangle, and P_p arrow. Default behavior (y = 0, passive off) is unchanged. Ref: Das §16.11 (p. 676), §17.4 (p. 699).
• Mononobe-Okabe: new textbook-style two-panel plot (wall cross-section with static + seismic pressure triangles & force arrows, plus a trial failure-wedge polygon with W, k_hW, P_ae, R vectors) styled after Das Fig. 16.23 (p. 668) and Kramer (1996) Fig. 11.1. Added optional c'-φ' backfill case per Das §16.10 (p. 672) with disclaimer when outside the vertical-back / horizontal-surface range.
• Terzaghi: automated groundwater-table Cases I-III per Das §6.5 Fig. 6.5 (pp. 217–219). New inputs for γ_sat and water-table depth; case-aware γ_q / γ_ny substitution with Case I/II/III detection and reporting.
• Bored pile: added transverse shear check per ACI 318-19 §22.5.5.1 (V_c), §22.5.10.5.3 (V_s), §21.2 (φ = 0.75), and R10.7.1 (circular-section equivalent width). New inputs for V_u, tie pitch, and tie diameter. Skipped gracefully when V_u = 0.
• Slope stability: per-layer formula report now includes a new Reference column with specific Das & Sivakugan 9th SI section numbers (§2.5, §2.6, §16.2 p. 640, §9.12 p. 382) and the Bolton (1986) Géotechnique 36(1) source for the dilatancy formula, plus an honest note that Poulos & Davis (1980) doesn't cover weight-volume relationships directly. Also added a data_source field on imported layers that tracks "SPT → Polish Code PN-59/B-03020 <table>" vs. "User-entered (measured / lab)".
• Nav: added Sheet Pile and Anchor links to the top bar. Theory page gained new sections 7.1 (Cantilever in Sand) and 8.1–8.2 (Deadman anchors in sand / clay).
• Integration: bundled the Das & Sivakugan (2019, 9th SI) and Poulos & Davis (1980) textbook citations across every calculator's tooltips and reference boxes with verified page numbers where possible.

v0.3.1 — 2026-04-07 (QAQC Reference Pass)

• New: reusable qa-note tooltip component (small blue "i" badge) and per-page ref-box bibliography on every calculator.
• Added 35 inline thumbnotes and 110 reference-box citations across 9 calculator pages.
• Theory page: expanded the References section into 7 categories with 46 entries.
• Cleanup: removed redundant PGA field from Mononobe-Okabe (k_h/k_v now effective coefficients per AASHTO §11.6.5.2). Made stability's q_all optional (skip bearing check when 0). Added rock-socket toggle to bored pile.

v0.2.1 — 2026-04-02

• New: Micropile design module (NSCP 2015, AISC 14th Edition, ACI 318-14/19)
• Slenderness check, soil compression/tension capacity, lateral embedment depth
• Concrete flexural & axial P-M interaction diagram
• Concrete shear capacity check
• Rebar library (#6 through #18) with automatic properties

v0.2.0 — 2026-04-02

• New: Lightweight Flask web application (Railway-ready deployment)
• New: Terzaghi (1943) bearing capacity calculator with interactive factor plots
• New: Meyerhof (1963) bearing capacity calculator with shape, depth, and inclination factors
• New: Mononobe-Okabe seismic earth pressure calculator with pressure distribution plots
• New: Retaining wall stability analysis (sliding, overturning, eccentricity checks)
• New: Theory & Technical Notes page aligned with AIT CE75.05 lecture content
• New: Print report button on all calculator pages
• New: Disclaimer notice for APEC Consultancy team use
• Improved: Unified navigation and consistent UI across all modules
• Improved: MathJax rendering for step-by-step equation output

v0.1.0 — 2024

• Initial release of geostructpy Python package
• Mononobe-Okabe seismic earth pressure class (geostructpy/monobe-okabe.py)
• Standalone Meyerhof bearing capacity factor visualization (HTML/Plotly)
• Standalone Mononobe-Okabe calculator (HTML/Vue.js)
• Shallow foundation ULS module with Terzaghi and Meyerhof factors
• Retaining wall sliding safety calculation