"1. Overview of construction method The micro pile is a slim foundation component that transfers axial loads (both compressive and tensile) from a structure into deeper and better bearing layers of foundation soil. In principle is especially suitable in cases of foundation of work in con-struction ally confined spaces, reconstruction of works and their foundations, underpinning of existing foundations or securing driving of underound works. The micro pile consists of three components : a head, which takes over the load of the building construction, a shaft that normally penetrates soft layers and a root fixed by grouting into the load on it. 2. Construction sequence Installation process in accordance with the requirements of the “NBN EN 14199 : Micro-piles” standard 1) Placement of the first section of the steel drill casing equipped with the drill bit fixed on a rod. Start of the boring process under fluid flushed inside the drill casing. 2) Coupling of the additional casing segments and continued boring under supporting drilling fluid until the required depth has been reached. 3) After reaching the design depth, replacement of the drilling fluid by the primary grout Injection of cement grout under pressure. The micropile is formed by single stage grouting under the so-called “unitary and global” grouting under low pressure or I.G.U. mode (« Injection Global et Unitair ») or the micropile is formed by multi-step grouting under the so called “repetitive and selective” grouting under high pressure or I.R.S. mode (“Injection Repetitive et Selective”).
"1. Overview of construction method Jet grouting is a method of soil stabilization which involves the injection of a stabilizing fluid into the subsoil (or the soil under treatment) under high pressure under high velocity. The injection process involves a certain amount of site preparation as well as injection equipment. The soil stabilization by jet grouting is occurs due to the hardening of grouted fluid within the soil. These hardened bodies forms like cemented columns which are grouted in numerous numbers as per requirement, thus stabilizing the soil. These columns are called as jet columns or jet grouted 2. Jet Grouting Procedure Initially, the area where the soil has to be treated is chosen and a hole is drilled to the required depth. The depth depends upon how deep the weak subsoil exist. The hole drilled may be small of approximately 10 to 20 cm, Drilling can be done by rotating drilling system under high pressure to the desired depth. The next step is to place the equipment over the drill hole to conduct the injection process. The equipment consists of a jet grouting string of almost 7 to 10 cm diameter. At the end of this string, it possesses a nozzle in in order have an injection at a higher velocity. The nozzle is small of diameter ranging from 1mm to 10mm. Now at the start, the string is raised and rotated slowly to seal the whole column surface with soil and the fluid system that has to be injected. Now the main jetting starts. As it progresses the fluid is injected(through a rotary motion) and the string is raised Now between the process, a part of mud within the pit created and the fluid mix rises to the top, which is called as spoil. This gives an indication that the bottom is fully sealed with the grout and soil mix. The raising of the string is done in between the process at a distance of 40 to 100mm depending upon the depth of treatment. For each raising, a rotation is performed. There are certain systems in which raising is a continuous process along with the rotation of the string. The speed of rotation of the equipment is kept constant irrespective of the method chosen, which will help in giving us a properly refined grouting column. Which are classified based on the number of the fluids injected into the subsoil. The fluids are: • Grout i.e. Water + Cement for single fluid • Air + Grout for double fluid • Water, air and grout for triple fluid Based on the number of fluids employed the jet grouting strings are made up of different pipe types as shown in fig.3. Fig.3: Jet grouting Systems for (a) Single fluid (b) Double fluid (c) Triple Fluid 1) Single Fluid Jet Grouting System In the case of a single fluid system, the W-C grout is injected into the ground through one or more nozzles. Here the soil remolding and subsequent cementation are done by the same fluid. The functions of removing the excess spoil and the binding action are all conducted by a single fluid. This system has a limitation of losing a high amount of kinetic energy. This is because of high friction existing that a single fluid finds it difficult to manage alone. 2) Double Fluid Jet Grouting System In double fluid system of jet grouting, the soil disaggregation and cementation are carried out by a single fluid the water-cement grout, but the difference is that the jet of grout is sent to an area of air that enhances the effectiveness of reducing the energy loss. For this, a more suitable air jet is provided through a coaxial annual nozzle place around the grouting nozzle. Here the excess soil is removed by the action of the air-lift. 3) Triple Fluid Jet Grouting System Here the soil remolding and cementation are clearly separated. The soil loosening is done by a high-velocity water jet and air. The water jet provided with the help of coaxial air jet, supplied by an annular nozzle similar to the one used for the double system. The water-cement grout is then taken from a separate nozzle that is placed on the lower part of the monitor or nozzle. The purpose of grout is in cementing the soil previously remolded by the water jet . Due to this reason the grout is delivered at a lower velocity. 3. Applications of Jet Grouting Jet grouting finds is a method of ground improvement and finds applications in the following: 1) For construction of horizontal barriers 2) Control of groundwater Jet columns can act as horizontal barriers to control the ground water around dams or areas of contaminated ground. This also decreases the soil permeability. 3) Underpinning Jet grouting can be employed as a method to stabilize foundation systems mainly shallow ones. The procedure involves drilling through the nearby foundation and making a stable bed underneath the footing for better load distribution. 4) Tunneling Jet grouting stabilizes the local area under tunnel construction so that heavy equipment required for tunneling can be used without destabilizing the nearby areas. 5) Support for excavation Advantages of Jet Grouting Jet grouting provides with the following advantages when implemented which are the root causes behind its success: ▫ Large cemented material column creation without causing huge ground disturbances (subsoil) ▫ Columns form continuous elements forming in different shapes thus improving the mechanical properties and decreasing porosity. ▫ Improvement in construction process thus emerging out with a better design philosophy It's attractive nature in terms of confined space working and under difficult site conditions
"1. Overview of construction method The main purpose of the Earth Anchor method is to excavate the back of an earth retaining wall in a cylindrical shape and install an anchor to support the surrounding ground. The function of an anchor is to anchor a structure to the ground through tension members, and there are similarities with piles in terms of support mechanisms. However, in the case of anchors, they are usually fixed by applying design is simple. Completely different from drawn piles, anchors are composed of the following three components in the force transmission path. 1) Anchor Head The force in the structure is a simple tensile force, which is intended to be transmitted to the tensile part without difficulty. It is composed of the fixing(fixing) hardware of the tensile member, an acupressure plate, and a placenta area, and serves to and adjust distribute the concentrated force of the anchor the direction to fix it. do. 2) Tensile part It is a part for transmitting the tensile force from the head of the anchor to the anchor body provided in the ground. It is usually made of PC steel wire as the main material, and the free field is insulated from the ground or structure by sheaths and caissons and has a structure that can expand and contract freely. 3) Anchor body It is a part of a tensile material that is prepared to transmit tensile force to the ground according to the frictional resistance with the ground, and in most cases, it is composed of a cement-based compound. PERMANENT ANCHOR Type of Anchor Ground anchor can be categorizedby service period, supporting method, installation angle or injection, pressing method of grout material. Depending on the service period, anchor sare divided into temporary anchor and permanent anchor. Temporary anchor is widely used to tempororary support soil-cement blocks or ground, while permanent anchor is for stabilization of slopes or prevention of roll-over and damage of permanent structures. Depending on the support method of ground, it can be di vided into frictional type anchor, pressure type anch or and complex type anchor. Frictional type anchor is supported by friction between grout and ground, and thus further categorized into tensioning anchor and pressing anchor, by the way the load is applied on the grout. Based on the load distribution, it can be divided to load-centric type anchor and load-distributing type anchor. 2. Use (Application) of Earth Anchor Construction method 1) Drilling 2) Manufacturing and installation of ANCHOR main body A. ANCHOR: PC steel wire ∅12.7mm B. Length: In accordance with design requirements C. PC steel wire uses Design standard products and sufficient manufacturing facilities are secured. D. PC steel wire is cut accurately and finished cleanly, and is manufactured to the size and specifications specified in the design. E. Assembly is in accordance with the design, and rust and foreign substances attached to the strand must be removed. F. When inserting a tension member, the excavation hole is completely cleaned and then inserted deep into the anchorage site. G. When inserting the tension member, insert it slowly to prevent the cavity wall from collapsing. H. The tension member must be securely fixed so that its position does not move during grouting, and must be located in the center of the hole. I. The installation angle of the anchor is (30 degrees) and the free anchorage is in accordance with the design. J. The anchor method follows site specifications, but as a standard, ϕ12.7 (4 strands) strands are used, and the allowable tensile force and maximum tensile force of each strand are as follows. K. Cover the free area with an industrial water tent hose to prevent grout. Type Allowable tension stress Maximum Tensile Stress Remark ⌽12.7 11.2 t 18.7 t 3) Grouting A. Grouting starts at the end of the ball and allows the groundwater and air inside the hole to be discharged to the outside. B. During the first injection, limit the injection pressure to prevent destruction of the base ground. C. The Grout Hose uses a material that can withstand a maximum pressure of 20 Bar, and its size is ∅13mm. D. During the second injection, a free field is maintained. E. After grouting, do not apply tension or impact to the anchor body until the required strength is achieved. F. After curing is completed, conduct a tensile test to check whether the tensile force of the anchorage is secured as designed G. If the test result fails, re-construction is carried out, and if the test results pass, the tension member, which is a PC steel wire, is fixed to the bracket. 4) Curing A. In principle, curing is done for 7 days (curing period can be shortened when using quick-curing agent), and when installing beams and strips, care must be taken with underground water and strands. 5) Tensile work A. Once the acupressure plate installation is complete, the cone is assembled and tensioning work is performed. B. When performing tensioning, check the state of the cylinder of the tensioner and the amount of stretching of the steel wire, and then tension and settle until the pressure reaches about 120% of the design load. C. For several anchors that are installed for the first time and anchors in location where the construction has changed, a tensile est must be performed under the direction of the supervisor to measure the elongation of the anchors to ensure safety. D. When the anchor is tense, workers are prohibited from accessing the back of the jack for safety reasons. E. Secure and install an extra length for tension, and do not cut the extra length in preparation for re-tensioning. F. Continue repeating until the Desing requirement tension of tension is achieved. G. When the lower anchor is tensioned, the upper anchor must be tensioned to compensate for the relaxation of the tension of the upper anchor. H. This is done only when it is necessary to know the ultimate pulling force in advance to check whether the assumptions such as soil constants used in the design of the anchor body are valid or not. I. The tensile test is conducted on equivalent conditions to the anchor actually provided or on a previously constructed anchor. J. The planned maximum load is 95% of the tensile member's yield strength or 80% of the crushing strength, whichever is smaller. K. If the PC strand comes out during the test, it is considered the limit load.