Soil nail walls' design principles and analyses by using snap-2, snailz, plaxis, slide programs

Construction operations like highways, bridges and buildings have been developed in recent years in our country. Soil nail walls have a very important role to build these kinds constructions. Especially, the cities that have many vehicles because of raising population need parking lots. So, the buildings need to be constructed with parking lots toward to underground. In the content of this thesis, soil nail walls and construction stages have been defined. Firstly, the soil is excavated and reinforcements are drilled or driven to the soil. The grout is injected to soil hole. The reinforcement is covered with grout. Grout helps to protect reinforcements from corrosion. After grout is executed, wire mesh is placed on soil surface and grouted. Grout, reinforcements, wire meshes, centralizers, grout pipes, drainage strips, waler bars, plates, nuts are materials that are needed to construct a soil nail wall. Advantages and disadvantages of soil nail walls are also mentioned in this thesis. The advantages of soil nail walls are evaluated in detail as three parts which are construction, performance and cost. Large amounts of groundwater and utilities behind the wall can create disadvantageous situations for soil nail walls. Suitable and unsuitable soil conditions are evaluated for soil nail walls. Soil nail walls can be constructed for unsuitable soil types, but soil nail wall systems can be more expensive to design and construct when compared other wall types. Soil nail wall system is compared with other wall system like anchorage wall system and reinforced wall system. Some factors affecting costs and construction schedule for soil nail walls are mentioned. Design methods are evaluated for soil nail wall systems and FHWA (Federal Highway Administration) design method is explained in detail with service load design approach. Soil nail wall design stages are evaluated. While soil nail wall is being designed, utilities and other underground structures must be considered by designer. The other buildings, roads and any kind of additional loads also must be considered by designer to design soil nail walls. Wall heights, face batters, lengths; soil nails' angles, lengths; horizontal and vertical soil nail distances; nail distribution on wall are designed by design engineer. Soil nail load working mechanism is explained step by step to understand load distribution at nails when excavation process is occurred. Two limit situations must be considered to design soil nail walls which are strength limit states and service limit states. Strength limit state analyzes to collapse or failure modes which are external failure modes, internal failure modes and facing failure modes. Service limit state analyzes wall deformations. External failure modes include global stability failure, sliding stability failure, bearing capacity failure. Internal failure modes include nail-soil pullout failure, bar-grout pullout failure, nail tensile failure. Facing failure modes include facing flexure failure, facing punching shear failure, headed-stud failure which it occurs only for permanent walls. All failure modes must be checked by designer engineer when soil nail walls are designed. Soil nail wall and soil behind the wall tend to deform outward during or after soil nail wall is constructed. Maximum horizontal displacements occur at top of the wall. Some factors effecting displacements are mentioned in this thesis. FHWA has approach to calculate how much soil nail wall has horizontal or vertical displacement in a project. Snap-2, Snailzwin, Plaxis and Slide are programs that can be used for soil nail wall analysis. All of these programs' solution approaches and methods have been examined and given information about them in this thesis. Global stability failure, sliding stability failure, bearing capacity failure analyses are indicated for Snap-2 program. Bishop Method is mentioned which Snap-2 uses to analyze global stability failure. Global stability failure analysis is explained for Snailz, Plaxis and Slide programs and displacements can be calculated by Plaxis program. Snailz can calculate global stability of soil nail walls. The program uses bilinear wedge analysis method. Soil behind the wall is divided two wedges. All horizontal and vertical forces like surcharge loads, wedge weights, earthquakes loads, nail forces are considered for each wedge. Plaxis uses finite element method to analyze global stability factor of safety and displacements. It has eight material models. Mohr-Coulomb and Hardening soil model are the most commonly used material models. Slide is same like Snap-2. Slide uses Bishop Method to analyze global stability factor of safety. It has also eight different solution methods like Janbu, Corrected Janbu, Spencer, Ordinary etc. In the content of this thesis, BJK Fulya facility project containing cross section of soil nail walls is evaluated. General information about project and cross section are given to show used material for soil nail wall and to analyze with FHWA design method and other computer programs. Soil nail wall cross section is analyzed with FHWA design method and found nail tensile capacity, facing capacity and pullout capacity. External failure modes also are analyzed with same method and found global stability, sliding stability and bearing capacity factor of safety values. The results are compared FHWA's limit factor of safety values. Global stability, sliding stability and bearing capacity factor of safety values are found using Snap-2 program and results are compared with FHWA's factor of safety values. Global stability factor of safety values are found using Snap-2, Snailzwin, Plaxis and Slide programs. The results are compared with each others. Using Plaxis program, applied loads to each soil nail are calculated. Also, soil nail wall displacement graph is created and displacements are calculated. As a result, factor of safety values of global stability given by programs are close each others. Only Snap-2 couldn't give any result for cross section of BJK Fulya Project. Program cannot calculate if top soil nail is shorter than under soil nails. In this situation, program assumes that all nails used in project are same length and gives low factor of safety result. Also, Snap-2 uses lowest friction angle calculating sliding stability and bearing capacity factor of safety values. In this situation, founded results do not give realistic values. In BJK Fulya Project, sliding stability and bearing capacity factor of safety values are found lower because Snap-2 has taken lowest friction angle value in soil layers. However, it should take friction angle value from soil layer which is located at toe of soil nail wall. The global stability results are found 1.18, 2.03 and 1.43 by using Snailz, Plaxis and Slide software programs, respectively. Snap-2 cannot give any results because shorter nails are used at top of the wall in BJK Fulya Project. Snailz software result is 1.18 and this is not higher than FHWA's recommendation value 1.35 for global stability. If global stability result is found lower than FHWA's recommendation value in calculation, nail lengths or reinforcements' diameter should be extended or reinforcements' yield strength should be chosen higher value. Plaxis gives displacement results and 53 mm is obtained result for BJK Fulya Project. This result is higher than inclinometer measurement getting from field. Snap-2, Snailz and Slide cannot give displacement results. Plaxis also calculates tension forces at soil nails separately. FHWA Method cannot calculate too many critical slip surfaces for global stability value because it needs too much calculation. Computer software should be used to obtain global stability results. Long nails should be chosen at top of the soil nail walls because maximum displacements occur at that point.