4704 HARBOR LN 2018-01-02 MF Import

' Geotechnical Engineering Evaluation Anderson Landslide Repairs 4704 Harbor lane Everett, Washington September 15, 2009 I NGA File No. 816909 Page 19 tic -back rod within the length of the no-load zone. A sand cement grout should not be allowed in the performance test anchors, as it will impact the lest results. Soil Design Values: We have not advanced any explorations in the areas where the anchors are planned. Therefore, the design strengths for anchor adhesion are difficult to estimate. If silts are encountered, creep will become an important factor in the design loads. For use in design of the performance anchors, we estimate an allowable grout to soil adhesion of 2,000 pounds per linear foot (pit) for minimum 4-inch diameter grouted anchors. This value is presented for planning purposes only and should be confirmed or modified using the data obtained from the performance testing prior to production tie -back installation. Tic -back Installation and Testing: The contractor should be responsible for using equipment suiteC :or the site conditions. We do not recommend the use of open hole methods for the purpose of installing the tic -backs. Secondary grouting to increase soil adhesion may be used; however, if secondary grouting is used, the anchors should be tested using the methods outlined for the performance testing. Five percent of the anchors, but a minimum of two, should be perfonnance tested to 200 percent of the anchor design capacity. 'file perfonnance tests should consist of cyclic loading in increments of 25 percent of the design load, as outlined in the Federal Highways Administration (FHA) report No. -'HWA/ItD-82/047. Final soil adhesion design values will be based on these tests. The test location should be detennined in the field, based on soil conditions observed during excavation. All production tie -backs should be proof -tested to at least 130 percent of design capacity. The tic -back testing program should be reviewed and monitored by NGA. Slope Improvements and Drainage After the wall has been successfully installed, the portion of the slope below the wall should be further investigated and slope improvements perforated to lessen the potential for future erosion and sliding below the wall. These conditions, if not addressed, could lead to future slides and may eventually undennine the wall. These improvements should include removing the vegetative cover and slide debris directly below the wall to a depth of four to six feet, benching the slope below the wall to a gentle inclination, placing rock NELSON GEOTECHNICAL ASSOCIATES, INC. 2S