1.2 Terzaghi (1943) Bearing Capacity Equation

For a general shear failure of a shallow foundation:

\[ q_u = c'N_cS_c + qN_q + \tfrac{1}{2}\gamma B N_\gamma S_\gamma \]

Where:

• \(q_u\) = ultimate bearing capacity (kPa)
• \(c'\) = effective cohesion (kPa)
• \(q = \gamma D_f\) = surcharge pressure at foundation level (kPa)
• \(\gamma\) = unit weight of soil (kN/m³)
• \(B\) = width of foundation (m)
• \(N_c, N_q, N_\gamma\) = bearing capacity factors (functions of \(\phi'\))

Shape Factors:

Foundation Type	\(S_c\)	\(S_\gamma\)
Strip	1.0	1.0
Square	1.3	0.8
Circular	1.3	0.6

1.3 Meyerhof (1963) Bearing Capacity Equation

Improved Terzaghi's equation with shape, depth, and inclination factors:

\[ q_u = c'N_cF_{cs}F_{cd}F_{ci} + qN_qF_{qs}F_{qd}F_{qi} + \tfrac{1}{2}\gamma BN_\gamma F_{\gamma s}F_{\gamma d}F_{\gamma i} \]

Shape Factors (De Beer, 1970)

\[ F_{cs} = 1 + \frac{B}{L}\frac{N_q}{N_c}, \quad F_{qs} = 1 + \frac{B}{L}\tan\phi', \quad F_{\gamma s} = 1 - 0.4\frac{B}{L} \]

Depth Factors (Hansen, 1970)

For \(D_f/B \leq 1\):

\[ F_{qd} = 1 + 2\tan\phi'(1-\sin\phi')^2 \frac{D_f}{B} \]

For \(D_f/B > 1\):

\[ F_{qd} = 1 + 2\tan\phi'(1-\sin\phi')^2 \arctan\left(\frac{D_f}{B}\right) \] \[ F_{cd} = F_{qd} - \frac{1-F_{qd}}{N_q\tan\phi'}, \quad F_{\gamma d} = 1 \]

Load Inclination Factors

\[ F_{ci} = F_{qi} = \left(1 - \frac{\theta}{90^\circ}\right)^2, \quad F_{\gamma i} = \left(1 - \frac{\theta}{\phi'}\right)^2 \]

1.4 Drained vs. Undrained Analysis

• Saturated Fine Materials (Clay): Use undrained shear strength (\(c_u\), \(\phi = 0\)). The \(N_\gamma\) term drops out.
• Saturated Coarse Materials (Sand/Gravel): Use effective shear strength (\(c'=0\), \(\phi'\)). The \(N_c\) term drops out.

2.1 Ultimate Limit State (ULS)

The maximum load-carrying capacity of the foundation. Using the LRFD approach:

\[ R_{dg} \geq E_d \]

Where \(R_{dg} = \phi_g \times R_{ug}\) is the design geotechnical strength, \(\phi_g\) is the reduction factor (0.4 to 0.8), and \(E_d\) is the factored design load.

2.2 Serviceability Limit State (SLS)

Settlement and angular distortion criteria:

\[ \rho_{max} \leq \rho_{all}, \quad \theta_{max} \leq \theta_{all} \]

Common allowable angular distortion for tall buildings: \(\theta_{all} = 1/500 = 0.002\).

2.3 Settlement Components

\[ S_{TF} = S_e + S_c + S_s \]

• \(S_e\) = Immediate (elastic) settlement
• \(S_c\) = Primary consolidation settlement
• \(S_s\) = Secondary consolidation (creep)

Immediate Settlement (Bowles, 1987)

\[ S_{e} = q_o(\alpha B') \frac{1-\mu_s^2}{E_s} I_s I_f \]

Primary Consolidation

Normally consolidated:

\[ S_c = \frac{C_c H_c}{1+e_o} \log\frac{\sigma'_{vo} + \Delta\sigma}{\sigma'_{vo}} \]

Overconsolidated:

\[ S_c = \frac{C_s H_c}{1+e_o} \log\frac{\sigma'_{vo} + \Delta\sigma}{\sigma'_{vo}} \]

3.1 Static Earth Pressure Coefficients (Coulomb)

Active:

\[ K_a = \frac{\sin^2(\beta + \phi)}{\sin\beta\sin(\beta - \delta)\left[1 + \sqrt{\frac{\sin(\phi+\delta)\sin(\phi-\alpha)}{\sin(\beta-\delta)\sin(\beta+\alpha)}}\right]^2} \]

Passive:

\[ K_p = \frac{\sin^2(\beta - \phi)}{\sin\beta\sin(\beta + \delta)\left[1 - \sqrt{\frac{\sin(\phi+\delta)\sin(\phi+\alpha)}{\sin(\beta+\delta)\sin(\beta+\alpha)}}\right]^2} \]

3.2 Seismic Active Earth Pressure (Mononobe-Okabe)

Extends Coulomb's theory with pseudo-static seismic forces:

\[ K_{ae} = \frac{\sin^2(\beta + \phi - \theta)}{\cos\theta\sin\beta\sin(\beta - \delta - \theta)\left[1 + \sqrt{\frac{\sin(\phi+\delta)\sin(\phi-\alpha-\theta)}{\sin(\beta-\delta-\theta)\sin(\beta+\alpha)}}\right]^2} \]

Seismic inclination angle:

\[ \theta = \arctan\left(\frac{k_h}{1 - k_v}\right) \]

3.3 At-Rest Earth Pressure

\[ K_0 = 1 - \sin\phi \]

Known as Jaky's formula (1944). Used for normally consolidated soils.

3.4 Earth Pressure Parameters

Symbol	Description
\(\phi\)	Angle of internal friction of backfill soil
\(\beta\)	Angle of wall face from horizontal
\(\delta\)	Wall-soil friction angle
\(\alpha\)	Angle of backfill slope from horizontal
\(k_h, k_v\)	Horizontal and vertical seismic coefficients
\(\theta\)	Seismic inclination angle

4.1 Rankine Earth Pressure

\[ K_a = \frac{1 - \sin\phi}{1 + \sin\phi}, \quad K_p = \frac{1 + \sin\phi}{1 - \sin\phi} \] \[ P_a = \tfrac{1}{2}\gamma H^2 K_a \quad \text{(acting at } H/3 \text{ from base)} \]

4.2 Sliding Safety Factor

\[ FS_{sliding} = \frac{\mu W + cB + P_p}{P_a} \geq 1.5 \]

4.3 Overturning Safety Factor

\[ FS_{overturning} = \frac{\sum M_{resisting}}{\sum M_{overturning}} \geq 2.0 \]

4.4 Eccentricity Check

\[ e = \frac{B}{2} - \frac{M_R - M_O}{W} \leq \frac{B}{6} \]

Base pressure distribution:

\[ q_{max,min} = \frac{W}{B}\left(1 \pm \frac{6e}{B}\right) \]

5.1 Standard Penetration Test (SPT)

The SPT measures the number of blows (N) required to drive a split-spoon sampler 300 mm into the soil using a 63.5 kg hammer falling 760 mm.

Soil Classification by SPT N-value

N-value	Sand	Clay
0 – 4	Very Loose	Very Soft
4 – 10	Loose	Soft
10 – 30	Medium Dense	Medium Stiff
30 – 50	Dense	Stiff
> 50	Very Dense	Very Stiff / Hard

5.2 SPT N₆₀ Correction

The field N-value is corrected to a standard 60% energy ratio:

\[ N_{60} = \frac{E_m \cdot C_B \cdot C_S \cdot C_R}{0.60} \cdot N \]

Where:

• \(E_m\) = hammer energy ratio (typically 0.45 for donut, 0.60 for safety hammer)
• \(C_B\) = borehole diameter correction (1.0 for 65–115 mm, 1.05 for 150 mm, 1.15 for 200 mm)
• \(C_S\) = sampler correction (1.0 for standard, 1.2 for non-liner)
• \(C_R\) = rod length correction (0.75 for 3–4 m, 0.85 for 4–6 m, 0.95 for 6–10 m, 1.0 for >10 m)

Overburden Correction (N_1,60)

\[ (N_1)_{60} = C_N \cdot N_{60} \] \[ C_N = \sqrt{\frac{P_a}{\sigma'_{vo}}} \leq 2.0 \]

Where \(P_a\) = atmospheric pressure (~100 kPa) and \(\sigma'_{vo}\) = effective overburden pressure.

5.3 Unconfined Compressive Strength (UCS)

The UCS test measures the maximum axial compressive stress a cylindrical rock or soil specimen can sustain without lateral confinement:

\[ q_u = \frac{P_{max}}{A} \]

Rock Classification by UCS

UCS (MPa)	Classification
< 1	Very Weak Rock
1 – 5	Weak Rock
5 – 25	Medium Strong Rock
25 – 50	Strong Rock
50 – 100	Very Strong Rock
> 100	Extremely Strong Rock

Undrained shear strength from UCS: \( c_u = q_u / 2 \)

5.4 SPT Correlations

Friction Angle (Peck, Hanson & Thornburn)

\[ \phi' \approx 27.1 + 0.3 N_{60} - 0.00054 N_{60}^2 \quad \text{(for sands)} \]

Undrained Shear Strength (Terzaghi & Peck)

\[ c_u \approx 6.25 N_{60} \quad \text{(kPa, for clays)} \]

Elastic Modulus

Sand (Schmertmann, 1970): \( E_s \approx 500(N_{60} + 15) \) kPa

Clay: \( E_s \approx 600 c_u \) to \( 1500 c_u \) kPa

6.1 Mohr-Coulomb Constitutive Model

The Mohr-Coulomb failure criterion defines shear strength as:

\[ \tau_f = c' + \sigma'_n \tan\phi' \]

In principal stress space:

\[ \sigma_1 = \sigma_3 \tan^2\left(45 + \frac{\phi'}{2}\right) + 2c'\tan\left(45 + \frac{\phi'}{2}\right) \]

Required model parameters:

• Elastic Modulus, \(E\) (kN/m²)
• Poisson's Ratio, \(\nu\)
• Cohesion, \(c\) (kN/m²)
• Friction Angle, \(\phi\) (degrees)
• Dilatancy Angle, \(\psi\) (degrees)
• Unit Weight, \(\gamma\) (kN/m³)

6.2 Midas GTS NX Material Input

The Mohr-Coulomb model in Midas GTS NX requires parameters across three tabs:

General Tab

• Elastic Modulus, E — from lab tests or SPT correlation
• Poisson's Ratio, ν — typically 0.2–0.3 for soils, 0.25–0.35 for rock
• Unit Weight, γ — from lab measurements
• Ko = 1 − sin(φ) — Jaky's formula for normally consolidated soils

Porous Tab

• Saturated Unit Weight = (G_s + e) / (1 + e) × γ_w
• Initial Void Ratio, e₀ = G_s × w (for saturated soil)
• Permeability, k — isotropic for most analyses

Non-Linear Tab

• Cohesion, C — same as General tab
• Frictional Angle, φ — same as General tab
• Dilatancy Angle, ψ — typically φ − 30 for φ > 30, else 0

6.3 Derived Soil Parameters

Dry Unit Weight

\[ \gamma_d = \frac{\gamma}{1 + w} \]

Saturated Unit Weight

\[ \gamma_{sat} = \frac{G_s + e}{1 + e} \gamma_w \]

Effective Unit Weight

\[ \gamma' = \gamma_{sat} - \gamma_w \]

Void Ratio (from moisture content, saturated)

\[ e = G_s \cdot w \quad \text{(for } S_r = 1 \text{)} \]

Specific Storativity

\[ S_s \approx \frac{\gamma_w}{E} \]

7.1 Cantilever Sheet Pile in Sand

Closed-form embedment analysis per Das & Sivakugan (2019, 9th SI) §18.4 "Cantilever Sheet Piling Penetrating Sandy Soil" (pp. 758–764). The wall is treated as rigid and the soil as homogeneous sand above and below the dredge line.

Pressure Distribution (Das Fig. 18.11)

Active pressure above the dredge line:

\[ \sigma_1' = K_a \gamma (L_1 + h_q) \quad \text{(at water table)} \] \[ \sigma_2' = \sigma_1' + K_a \gamma' L_2 \quad \text{(at dredge line)} \]

Below the dredge line, net pressure is the passive-minus-active difference. The depth to the point of zero net pressure (Das Eq. 18.11):

\[ L_3 = \frac{\sigma_2'}{(K_p - K_a)\gamma'} \]

Embedment (Das Eq. 18.17)

\[ D^4 + A_1 D^3 - A_2 D^2 - A_3 D - A_4 = 0 \]

Solved numerically for the smallest positive real root. Das recommends a 20–30% safety factor on the theoretical embedment (p. 762).

Design Moment & Section Modulus (Das Eq. 18.19–18.22)

\[ z' = \sqrt{\frac{2P}{(K_p - K_a)\gamma'}} \quad \text{(depth of zero shear)} \] \[ M_{max} = P(z' + \bar{z}) - \tfrac{1}{6}(K_p - K_a)\gamma' z'^3 \] \[ S_{req} = \frac{M_{max}}{\sigma_{allow}} \]

Scope in this build: cantilever walls only; homogeneous sand; anchored walls (§18.9–18.12) and sheet piles in clay (§18.6, §18.16) are deferred.

8.1 Deadman Anchor in Sand (Ovesen-Stromann)

Per Das & Sivakugan (2019, 9th SI) §18.19 Holding Capacity of Anchor Plates in Sand, p. 804, Fig. 18.29:

\[ P_u = B \cdot h \cdot \gamma H (K_p - K_a) \cdot R_f \]

where B and h are plate width and height, H is the depth to plate centroid, and R_f is the shape/overburden factor from Das Fig. 18.29 (interpolated from knots at H/h = 1, 2, 3, 4, 5 giving R_f = 1.00, 1.40, 1.75, 2.00, 2.20).

Typical factor of safety FS = 2.0 per Das p. 804.

Original reference: Ovesen, N.K. & Stromann, H. (1972). Design method for vertical anchor slabs in sand. Proc. ASCE Specialty Conf. on Performance of Earth and Earth-Supported Structures, Purdue University, 1481–1500.

8.2 Deadman Anchor in Clay (Mackenzie / Tschebotarioff)

Per Das & Sivakugan (2019, 9th SI) §18.20 Holding Capacity of Anchor Plates in Clay, p. 811:

\[ P_u = B \cdot h \cdot N_c \cdot c_u \cdot R_f \]

with N_c = 9 and R_f transitioning from 0.5 at H/h = 1 to 1.0 at H/h ≥ 3 (deep anchor limit). The 9c_u bearing capacity factor reflects the full passive plus active sum for the undrained (φ = 0) case.

Originals: Mackenzie (1955) M.Sc. thesis, Princeton University; Tschebotarioff, G.P. (1973) Foundations, Retaining and Earth Structures, 2nd Ed., McGraw-Hill.

References

Consolidated bibliography for all GeoStructPy calculators. Each per-calculator page also has a focused references box at the bottom citing only the sources used by that module.

Primary Textbooks (used throughout)

1. Das, B.M. & Sivakugan, N. (2019). Principles of Foundation Engineering, 9th Edition, SI. Cengage Learning. Provides chapter-by-chapter coverage of every shallow- and deep-foundation calculation in this app:
   • Ch. 2 — Geotechnical properties of soil (weight–volume, shear strength)
   • Ch. 3 — Subsoil exploration, SPT (§3.15), CPT (§3.21), boring logs (§3.27)
   • Ch. 6 — Shallow foundations: ultimate bearing capacity (Terzaghi §6.3, water table §6.5, general equation §6.6, eccentricity §6.10–6.13)
   • Ch. 7 — Special bearing-capacity cases incl. seismic (§7.10), rock (§7.11)
   • Ch. 8 — Vertical stress increase (Boussinesq, Westergaard §8.12)
   • Ch. 11 — LRFD design philosophy
   • Ch. 12 — Pile foundations (β §12.13, α §12.14, rock tip §12.16, lateral §12.19, negative skin friction §12.23)
   • Ch. 13 — Drilled-shaft foundations (§13.5–13.13)
   • Ch. 14 — Piled rafts (Poulos–Davis–Randolph method §14.3)
   • Ch. 16 — Lateral earth pressure (Rankine §16.3, Coulomb §16.7, surcharge §16.8, seismic M-O §16.9)
   • Ch. 17 — Retaining walls (stability §17.4, overturning §17.5, sliding §17.6, bearing §17.7)
   • Ch. 18 — Sheet-pile walls and anchors (§18.3 cantilever, §18.9 anchored, §18.18 deadman holding capacity)
2. Poulos, H.G. & Davis, E.H. (1980). Pile Foundation Analysis and Design. John Wiley & Sons. The classic monograph on pile–soil interaction. Covers axial capacity of single piles, elastic-theory settlement, group effects, negative skin friction, lateral loading on single piles and groups, piled rafts, and dynamic effects. Used as the primary reference for the bored-pile and micropile modules.
3. Bowles, J.E. (1996). Foundation Analysis and Design, 5th Edition. McGraw-Hill. Comprehensive practitioner-oriented reference. Used to cross-validate the slope-stability calculator's parameter ranges and weight–volume / K₀ / shear-strength formulas:
   • Ch. 2 — Geotechnical and Index Properties: §2-2/2-3 weight–volume relationships (Eq. 2-1 to 2-11)
   • §2-8 — In Situ Stresses and K₀ Conditions (p. 39): Eq. 2-17 (def.), Eq. 2-18a Jaky K₀ = 1 − sinφ\', Eq. 2-19 sloping ground, Eq. 2-22 from Poisson's ratio, Eq. 2-23 OCR adjustment
   • §2-9 — Soil Water; Soil Hydraulics (p. 46)
   • §2-10 — Consolidation Principles (p. 56) — reference for the S_s = γ_w/E shortcut used in Midas/PLAXIS input
   • §2-11 — Shear Strength (p. 90): Eq. 2-52 s = c + σtanφ; UU / CU / CD test conditions; §2-11.3 cohesionless soils
   • §2-14 — Elastic Properties of Soil (p. 121): Hooke's law, Table 2-7 Poisson's ratio ranges, Table 2-8 E_s ranges
   • Ch. 4 — Bearing Capacity (esp. §4-7 water-table effect, §4-9 footings on slopes)
   • Ch. 11 — Lateral Earth Pressure (theory of plasticity / theory of elasticity)
   • Ch. 12 — Cantilever Retaining Walls (alternative reference to Das Ch. 17)
   • Ch. 13 — Sheet-pile Walls (cantilever and anchored)
   • Ch. 14 — Walls for Excavations (braced cuts)
   • Ch. 16–18 — Single piles, dynamic capacity, pile groups (cross-reference to Poulos & Davis)

Foundation Analysis & Bearing Capacity

1. Terzaghi, K. (1943). Theoretical Soil Mechanics. John Wiley & Sons.
2. Terzaghi, K. & Peck, R.B. (1967). Soil Mechanics in Engineering Practice (2nd ed.). Wiley.
3. Meyerhof, G.G. (1963). Some recent research on the bearing capacity of foundations. Canadian Geotechnical Journal, 1(1), 16–26.
4. Hansen, J.B. (1970). A revised and extended formula for bearing capacity. Bulletin No. 28, Danish Geotechnical Institute.
5. De Beer, E.E. (1970). Experimental determination of the shape factors and the bearing capacity factors of sand. Géotechnique, 20(4), 387–411.
6. Vesic, A.S. (1973). Analysis of ultimate loads of shallow foundations. J. Soil Mech. Found. Div., ASCE, 99(SM1), 45–73.
7. Bowles, J.E. (1996). Foundation Analysis and Design (5th ed.). McGraw-Hill.
8. Bowles, J.E. (1987). Elastic foundation settlements on sand deposits. J. Geotech. Eng., ASCE, 113(8), 846–860.
9. Das, B.M. & Sivakugan, N. (2017). Principles of Foundation Engineering (9th ed.). Cengage.
10. Poulos, H.G. (2017). Tall Building Foundation Design. CRC Press.

Earth Pressure & Retaining Walls

11. Coulomb, C.A. (1776). Essai sur une application des règles de maximis et minimis à quelques problèmes de statique. Mém. Acad. Roy. Sci.
12. Rankine, W.J.M. (1857). On the stability of loose earth. Phil. Trans. Royal Society of London, 147.
13. Jaky, J. (1944). The coefficient of earth pressure at rest. J. Soc. Hungarian Architects and Engineers, 78(22), 355–358.
14. Mononobe, N. & Matsuo, H. (1929). On the determination of earth pressures during earthquakes. Proc. World Engineering Conference, Tokyo, 9, 177–185.
15. Okabe, S. (1926). General theory of earth pressures. J. Japan Society of Civil Engineers, 12(1).
16. Seed, H.B. & Whitman, R.V. (1970). Design of earth retaining structures for dynamic loads. ASCE Specialty Conf. on Lateral Stresses in the Ground and Design of Earth Retaining Structures, 103–147.
17. Kramer, S.L. (1996). Geotechnical Earthquake Engineering. Prentice Hall.

Site Investigation & Soil Parameters

18. Skempton, A.W. (1986). Standard penetration test procedures and the effects in sands of overburden pressure, relative density, particle size, ageing and overconsolidation. Géotechnique, 36(3), 425–447.
19. Stroud, M.A. (1974). The standard penetration test in insensitive clays and soft rocks. Proc. Eur. Symp. Penetration Testing, Stockholm, 2.2, 367–375.
20. Schmertmann, J.H. (1970). Static cone to compute static settlement over sand. J. Soil Mech. Found. Div., ASCE, 96(SM3), 1011–1043.
21. Peck, R.B., Hanson, W.E. & Thornburn, T.H. (1974). Foundation Engineering (2nd ed.). Wiley.
22. Bolton, M.D. (1986). The strength and dilatancy of sands. Géotechnique, 36(1), 65–78.
23. PN-59/B-03020 (1959). Posadowienie bezpośrednie budowli — Obliczenia statyczne i projektowe. Polish Standard for SPT-derived soil parameters.

Constitutive Models & Slope Stability

24. Mohr, O. (1900). Welche Umstände bedingen die Elastizitätsgrenze und den Bruch eines Materials? Zeitschrift VDI, 44.
25. Hoek, E. & Brown, E.T. (1997). Practical estimates of rock mass strength. Int. J. Rock Mech. & Min. Sci., 34(8), 1165–1186.
26. Midas IT (2023). Midas GTS NX User Manual — Material Models. Midas Information Technology.
27. Plaxis (Bentley Systems, 2023). PLAXIS Material Models Manual — Interface reduction factor R_inter.

Pile Foundations

28. Reese, L.C. & O'Neill, M.W. (1988). Drilled Shafts: Construction Procedures and Design Methods. FHWA-HI-88-042.
29. Tomlinson, M.J. (1971). Some effects of pile driving on skin friction. Proc. ICE Conf. on Behaviour of Piles, London.
30. Burland, J.B. (1973). Shaft friction of piles in clay — a simple fundamental approach. Ground Engineering, 6(3), 30–42.
31. FHWA (2010). Drilled Shafts: Construction Procedures and LRFD Design Methods, FHWA-NHI-10-016 (Brown, Turner & Castelli).
32. FHWA (2005). Micropile Design and Construction Guidelines, FHWA-NHI-05-039 (Sabatini et al.).
33. Bruce, D.A. & Juran, I. (2000). Drilled and Grouted Micropiles — State-of-Practice Review, FHWA-RD-96-016/019.

Codes & Standards

34. ACI Committee 318 (2019). Building Code Requirements for Structural Concrete (ACI 318-19). American Concrete Institute.
35. ACI Committee SP-17 (2014). The Reinforced Concrete Design Handbook — Chapter 2: Cantilever Retaining Walls. ACI.
36. AASHTO (2020). LRFD Bridge Design Specifications (9th ed.).
37. AISC (2010). Steel Construction Manual, 14th ed. American Institute of Steel Construction.
38. NSCP (2015). National Structural Code of the Philippines (7th ed.). ASEP.
39. Eurocode 7 (EN 1997-1:2004). Geotechnical design — General rules. CEN.
40. Eurocode 8 Part 5 (EN 1998-5:2004). Foundations, retaining structures and geotechnical aspects. CEN.
41. NAVFAC (1986). Design Manual 7.02 — Foundations and Earth Structures. Naval Facilities Engineering Command.
42. ASTM D1586 / D1586M-18. Standard Test Method for Standard Penetration Test (SPT) and Split-Barrel Sampling of Soils.
43. ASTM D2166 / D2166M-16. Standard Test Method for Unconfined Compressive Strength of Cohesive Soil.
44. ASTM D7012-14. Standard Test Methods for Compressive Strength and Elastic Moduli of Intact Rock Core Specimens.
45. ISRM (1981). Rock Characterization, Testing and Monitoring — ISRM Suggested Methods. Pergamon Press.

Lecture Notes

46. Chao, G. (2019). CE75.05 Geotechnical Engineering — Lecture Notes. Asian Institute of Technology, Thailand.