EWB-NY Cambodia Water Project

10.16.2006

First Site Visit: Preliminary Gameplan

Project Description:

A concrete weir structure will be constructed in Cambodia to replace a centuries-old earthen dam that failed in the year 2000. The new concrete dam will abut against the intact portions of the existing earthen dam.

Existing Site Conditions:

Soil ranges from Sand, to clayey sand, to sandy clay. Water table at approx. 1.5 feet below ground surface.
No other soil data exists.

Potential Soil Issues:

Bearing capacity
Shear failure
Settlement
Seepage
Slope Stability
Corrosivity

Design Approach:

The new weir is a concrete counterfort wall constructed on spread footings. We propose over-excavating to remove much of the sandy soil. Then pour a cut-off wall deep below footing to confine seepage flow and minimize effects of seepage to reasonable calculated level.

Seepage analysis shall be performed using the method of flow nets to solve Laplace's continuity equation.

On-Site Soil Testing:

We propose a series of soil tests to be conducted on site in early November. Testing must be highly portable, reliable, and inexpensive. The site is remote, and equipment has to be carried in on the back of a motorcycle.

IN-SITU TESTING:
· Piezometric head --> DRIVE POINT PIEZOMETER
· Porosity (conductivity) --> OPEN END TEST?
· Undrained shear strength (Cu) --> VANE SHEAR TEST (ASTM D4648-05)
· Specific gravity --> sand cone density apparatus (ASTM D1556), or rubber-balloon (ASTM D2167)
· Moisture content --> SPEEDY MOISTURE TEST (CALCIUM CARBIDE REAGENT TEST) (ASTM D4944-04)
· Consolidation --> RECOMMEND COMPACTION PROCEDURES AND DRAINAGE/FILTER LAYER TO MINIMIZE CONSOLIDATION EFFECTS
· Liquid and plastic limits --> STATIC CONE PENETROMETER
· Peak angle of friction (non-cohesive soil/sand) --> CORRELATED TO RELATIVE DENSITY and STATIC CONE BEARING RESISTANCE
· Grain size analysis --> SIEV ANALYSIS
· Soil corrosivity --> SOIL RESISTIVITY MEASUREMENT (ASTM G187) and pH MEASUREMENT
· Organic content --> VISUAL INSPECTION

LAB TESTING:
· Unconfined compression test (Rock) --> NO ROCK CORINGS (assume bedrock is deep, design spread footings to bear on soil)
· Poisson's ratio --> NOT REQUIRED
· Modulus --> NOT REQUIRED

9.06.2006

Water Gate Concept

The preliminary concept for the new water gate structure (dam) at Balang Commune was developed by Mr. Yinn Sovann at the Ministry of Hydrology and Meteorology. We'll have to do some work to verify it's robustness and sustainability, and to ensure it addresses the needs of the community in a comprehensive manner.