Non-Homogeneous Reinforced Earth Fill for Riverbank Stabilization

The paper presents a study of backfill material for the reinforced earth used as riverbank restoration, based on two cases of stabilization with reinforced earth using geogrid type TENSAR reinforcements. The two cases are located one on Blue River in Kansas City, Missouri and the other on Delaware River in Kansas, respectively. Both projects were designed to restore the damaged riverbank due to slope failures in order to protect existing public utilities (water lines) and public roadways close to the failed riverbank, with limited space for excavation or setback the riverbank slope. Geotechnical investigation indicated very low soil strength parameters of the riverbank material being one of the principal causes of the slope instability. The failures occurred during the river rapid drawdown from the top of the riverbank to the normal river stage. The most economical repair alternative was to reconstruct the riverbank to an acceptable stable slope by reinforcing it with geogrid. Due to space restriction and limited funds the reinforcements were placed within 1-foot thick layer of granular material between 3 feet thick layers of cohesive material obtained from riverbank excavation. A sand layer placed behind the reinforced earth mass provides the adequate drainage of the stabilized earth. The horizontal sand layers reduce the length of the reinforcements, preventing additional damages of the adjacent public roads, and consequently the excavation volume and project cost. The horizontal sand layers around the reinforcements and the drainage sand layer behind the reinforced earth mass provided proper drainage of the reinforced earth mass and increased the stability of the riverbank to acceptable level for the case of sudden drawdown of the river stage. The paper presents the subsoil investigation, design analyses, construction aspects and the stabilized riverbank behavior after repair

Selection of Most Appropriate Procedures for Seismic Evaluation of Levees Based on Case Histories

The current methodology for embankment dams evaluation is not appropriate for levees of low heights, which have little effect on the stress state of the foundation soil and, therefore, on its response to the seismic action. In many cases the liquefaction potential of the alluvial deposits is not affected by the levee presence, although is the main factor in levee degradation. Lateral spreading of liquefiable foundation is the main cause of small levee cracking and settlement induced by earthquakes. On the other part, the procedures recommended for evaluation of lateral spreading are not directly applicable to the analysis of levees. In this paper both categories of procedures (for dams and for free field affected by lateral spreading) are applied comparatively for evaluation of a case history. This paper summarizes results of different procedures on a case history, where a California levee was severely damaged during Loma Prieta earthquake. Recommendations are made for the analysis of various categories of levees

Geotechnical Risk Analysis of the Local Flood Control Projects on the Kansas River in Topeka, Kansas

The paper presents the results of the geotechnical evaluation of the existing conditions of the local flood protection of Topeka, the state capital of Kansas. The existing levee system constructed by the U.S. Army Corps of Engineers consists of 6 levees units along the north and south bank of the Kansas River and tributaries, Soldier Creek and Shunganunga Creek. The geotechnical evaluation of the existing conditions of the levee system was based on all available geotechnical data and on the past performance of the system. The critical reaches of each levee unit were identified based on the geotechnical conditions and levee geometry. The geotechnical levee system response to river stage loading was evaluated. Geotechnical information included subsurface investigation performed for the design and construction of the levee, geotechnical information obtained for subsequent levee modification, and cone penetrometer tests and laboratory testing performed on selected samples collected from additional borings drilled in areas considered critical or known to experience excessive underseepage during previous flooding events. Uncertainty analyses were performed to define the existing condition of the Topeka Levee System. The system response was determined by evaluating the foundation and embankment materials and assigning values for the probability moments of the random variables considered in the analyses. The performance functions considered for the risk analyses were slope stability and underseepage piping stability. The internal erosion due to seepage through the embankment was not considered, the levee embankments being constructed of cohesive fill. A set of conditional-probability-of-failure versus floodwater-elevation graphs were developed as related to underseepage piping stability and slope stability for the long-term seepage. Reliability analysis was performed using Taylor’s Series Method. In the Taylor method, random variables were quantified by their expected mean values, standard deviations, and correlation coefficients

General Report - Session 3

This General Report summarizes the 84 papers accepted for the Session 3 focused on: - 3a. Case Histories on Failure and Remediation of Slopes, Dams, Embankments and Landfills (53 papers), - 3b. Case Histories on Failure and Remediation of Retaining Structures, Slurry Walls, and Deep Excavations, Dewatering, Stability (27 papers), - 3c. Improving the Stability and Maintenance of Monuments (4 papers). The papers originate from 26 countries (11 European countries, 3 American countries, 11 Asian countries and 1 African country). The papers cover a number of relevant topics divided into three different sub - sessions. As for the two papers included in Session 3c, only one deals with maintenance and retrofit of historical monuments. Indeed paper 3.03c is more pertinent to session 3b. On the other hand some papers included in Session 3a could also be considered in Session 3b and vice versa

Repair of Scour Holes and Levees After the 1993 Flood

The record high water during the summer of 1993 significantly impacted the flood control levee structures in the U.S. Army Corps of Engineers, Kansas City District. Scour holes in the levees and their foundations reached bedrock, up to 75 feet deep in some places, and extended up to 2,000 feet landward of the landside toe on lengths reaching 2,100 feet along selected levee embankments. Different methods used by the Corps of Engineers to repair the scoured levee embankment and foundation soils, their hydraulic impact on river stages, and the efficiency of different methods are presented. The methods discussed consist of: (1) backfill of the riverside scour holes; (2) backfill of the scour hole and reconstruction of the levee embankment to the original centerline; (3) realignment of levees landward of the scour boles; and (4) a grouted cut-off wall in a rockfill embankment and construction of a ring levee around the landside scour hole. The efficiency of different methods was evaluated by observation of the levee system during subsequent flood events