Serving professionals in engineering, environmental, and groundwater geology
since 1957

MONTHLY DINNER MEETING

Date: Tuesday, January 11, 2005
Location: Steven’s Steak House, 5332 Stevens Place, Commerce, California
Time: 6:00 p.m.-Social Hour; 7:00 p.m.-Dinner; 7:45 p.m.-Presentation

Cost: $25 per person with reservations, $30 at the door, $12 for students with a valid Student ID
Reservations: Call (949) 253-5924 ex 564, or email Brian Villalobos,
By noon, Monday, January 10, 2005

PRESENTERS: Mark McLarty and Jeffrey Geraci
TOPIC: “Stabilization of a Southern California Coastal Bluff Using Ultrafine Cement Grout and Cement-Treated Soil”

ABSTRACT

Erosion processes are continually at work in ocean bluff areas, often threatening adjacent structures and property. Many local planning and regulatory agencies have rejected typical mitigation measures that rely on reinforced concrete and unsightly earthworks. The property in this case study is situated at the top of just such a bluff. An unattended irrigation system positioned at the rear of the property locally saturated clean, sandy terrace deposits, causing a prominent slope failure. Approximately 12m of marine terrace deposits locally cap resistant metamorphic bedrock, forming the remaining portion of the 40-m sea cliff. Terrace deposits consist of medium sand with less than 5 percent passing the #200 sieve. These materials are typically uncemented, and when exposed in steep slopes, have a tendency to run. Mitigation measures involved ground improvement within undisturbed terrace soils, and reconstruction of the former slope face with cement treated soil (CTS). Permeation grouting methods were used to stabilize surrounding terrace sands to allow for steep, near-vertical backcuts on the order of 6m to 8m high. Initial design considerations were based on laboratory studies of several grout and CTS mix designs. Treatment of the outer portion of the terrace deposits to a depth of 4.5m was initially accomplished with sodium silicate grout. Interior portions of the terrace deposit were treated with ultrafine cement grout, mixed at a 4:1 ratio. Sleeve port pipes were used to isolate discrete treatment intervals. Excavation of the backcuts for the grading phase revealed a thoroughly cemented profile. All grading was performed by hand, and required the use of air-spades to dig through the grouted sands. These excavations revealed a uniformly cemented earth mass with sufficient strength to safely allow the near vertical excavations required for construction of the CTS slope repair. The keyway for the repair was established on a nearly level excavation on relatively unweathered bedrock. Slope reconstruction involved incremental construction of a compacted CTS berm at the face of the slope, followed by filling of the area between the berm and the backcut with sand-cement slurry. Seepage encountered during construction was mitigated by a system of drilled horizontal drains, and typical excavation backdrains. The combined repair scheme, consisting of soil cement replacement and permeation-grouted earth mass has resulted in a reconstructed slope configuration that has a factor of safety in excess of 1.5.

BIO

Mark McLarty:
Mark McLarty is a Principal Engineering Geologist with AMEC Earth & Environmental, Inc.’s Anaheim, California office. He received a BS degree in Geology from California State University, Los Angeles in 1973. Mark has managed and consulted for numerous projects throughout his career, including fault and seismic evaluations, landslide and slope stability studies, dam embankment and other hydrologic projects, groundwater projects, and litigation support. His experience has allowed him to work with a number of public agencies and private design firms.

Jeff Geraci:
Jeff Geraci has been with Moore & Taber since 1990. He is an engineering geologist, and currently works as a Project Manager for geotechnical construction services. He has designed and managed numerous remedial grouting and ground improvement projects. He designed and maintains the Moore & Taber website (mooreandtaber.com), and publishes the company newsletter “Geotechnical Constructors Journal”. Jeff is a member of the ASCE Grouting Committee, and has recently been appointed to AEG’s Website Design Working Group. He is also a member of the ACI Committee 552 “Cement Grouting”. He also serves as Webmaster/Editor for the Los Angeles Chapter, ASCE Forensic Engineering Technical Group (asceforensics.org).