1. TECHNICAL FIELD OF THE INVENTION

The present invention generally relates to a method for stabilizing soil, in particular to an anchor system having a bore with a bulging end to increase stability of unstable grounds.

2. BACKGROUND OF THE INVENTION

It is well known that ground anchor has been used for centuries to stabilize unstable grounds such as hill slopes, river banks and terrains. Basically the ground anchor is planted deep into a hard and stable soil structure and is connected to a reinforcement or retaining wall on the ground surface by a tie rod. The ground anchor provides the required stabilizing force that is transmitted to the soil at a suitable distance behind the reinforcement or retaining wall on the ground surface like those found along highways and hill slope either to contain the earth prevent landslides or as a reinforcement for landslide prone slopes.

To reinforce such soil, a study on the soil density and consistency are made so as to determine the required depth and the type of anchor which must be planted into the soil. Depending on the type of soil, the choice of anchor is significantly important especially if the anchor is to be permanently installed to withstand varying and increasing load for many years. Another factor of concern is the grouting material and process. The choice of grouting material is also another important factor as it has to suit the chosen anchor system in order for the system to perform well for many years.

There is already a practice of a soil reinforcement using an expandable anchor planted into the ground. A hole is dug in the ground to be reinforced and the anchor is planted into the ground through the hole. The anchor is then expanded to lock against the soil adjacent and the hole is grouted to complete the anchorage. The disadvantage of this

SUBSTITUTE SHEET type of anchor system is the frequent failure due to the expandable anchor bursting and damaging the soil structure around it making the surrounding soil weak that will lead to malfunctioning of the anchor system.

There is another practice of using an anchor in conjunction with a hole having a bulging end. However, this is mainly used for anchoring vertical column meant for increasing load bearing capacity. The bulging end is used to increase load bearing area to increase the load bearing capacity of the column. This type of anchor system has a considerably high not only compressive loading but also tensile loading capacity. This property has not been fully utilized in soil engineering work such as soil stabilization and erosion control.

Therefore, the present invention seeks to provide a method for stabilizing soil in an attempt of overcoming the shortcoming of the above practice. The present invention is especially important, though not specifically for stabilizing soil in hill slope, river bank and terrain for preventing land movement that may lead to landslide.

3. OBJECT OF THE INVENTION

It is therefore a primary object of present invention to provide a method for stabilizing soil which is efficiently applicable for all types of soil, thus is economical.

This and other object of the present invention is accomplish by providing, A method for stabilizing unstable grounds having a predetermined soil density and consistency, said method comprising the steps of:

forming a hole (1) to a predetermined depth in ground to be reinforced;

said hole having a mouth (12);

installing an anchor (2) in said hole (1);

said anchor (2) having at least one anchor arm (24), said

SUBSTITUTE SHEET anchor arm (24) being locked by a locking pin (26) in close position in normal condition;

installing a capping plate (15) to cover said mouth (11) of said hole

(1);

releasing said locking pin (26) to expand said anchor (2); and grouting said hole (1) with a grouting material,

characterised by

said hole (1) being provided with a bulging end (11) at inner side to accommodate said anchor arm (24) when expanded.

4. SUMMARY OF THE INVENTION

The present invention relates to a method for stabilizing unstable grounds having a predetermined soil density and consistency. In the broadest aspect of the present invention, the method comprises forming a hole (1) to a predetermined depth in ground to be reinforced, preparing a bulging end (11), inserting a specific type of anchor and grouting the hole (1). Before boring process, calculation is carried out to determine the depth of the hole required to obtain the needed strength depending on the soil condition and hardness. The hole (1) is then formed using eccentric reamer drill or any other suitable equipment. At the end of the hole (1), a bulging end (11) is formed using the same eccentric reamer. The hole (1) has a mouth (12) adapted for giving access for installing an anchor (2) and a bulging end (11) adapted for receiving the expanded anchor arm (24). The anchor (2) is of the V-arm flip anchor having an anchor arm (24) kept in close position under normal condition by a locking pin (26). The anchor (2) is installed in the hole (1) by inserting through the hole (1) until it reaches the bulging end (11) at a predetermined depth. The locking pin (26) is then release by pulling a cord (not shown) to unlock the locking pin (26). This will free the anchor arm (23) and set the anchor arm (24) expanded to lock with the adjacent ground of the bulging end (11). After this grouting may be applied and

SUBSTITUTE SHEET later having the mouth (12) of the hole (1) closed with a capping plate (15).

5. BRIEF DESCRIPTION OF THE DRAWINGS

There are shown by way of examples the drawings of preferred embodiment of the present invention,

FIG. 1 showing the hole for anchor apparatus according to one embodiment of the present invention.

FIG. 2 showing the V-arm flip type anchor used in the present invention.

FIG. 3 showing the V-arm flip type anchor installed in the hole.

. DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to FIG. 1 showing the hole for the anchor apparatus according to one embodiment of the present invention. Along hill slope, river banks or terrain where reinforcement is to be installed, a hole (1) having a bulging end (11) and a mouth (12) is drilled to the predetermined depth using drilling hammer or any other suitable method. The predetermined depth is calculated depending on the hardness, density and consistency of the soil. Upon reaching the required depth a bulging end (11) is prepared using an eccentric reamer.

Referring now to FIG. 2 showing the V-arm flip type anchor used in the present invention. The anchor (2) comprises of an anchor body (21) having an anchor head (22) at one end and an anchor tail (23) at another end. The anchor body (21) is provided with a pair of anchor arms (24) adapted to engage the anchor (2) to adjacent soil. In its original position the pair of anchor arms (24)arms is kept in a closed

SUBSTITUTE SHEET position by a locking pin (26) with ends resting within a burrow (28) on each arm (24). The locking pin (26) is provided a release means for releasing the locking pin (26) and thus engaging the anchor (2) to adjacent soil. Any release means may be employed but in the present case a simple loop is provided so that a wire rope may be fastened to the loop before driving the anchor (2). Preferably, the dimension of the anchor head (22) is 99 mm across in closed position and having a length of 300 mm.

Due to the structure of this type of soil for example rocks, gravels or the like, drilling of the hole (1) is done using an eccentric reamer type of rotary drilling hammer (3) as in FIG. 3 like the ODEX' eccentric reamer. This type of eccentric reamer is able to drill a hole and create a bulging end or bulb end at the end of the hole (1). The drilling is done using preferably a pilot bit (31) having a diameter of 10 mm. The resultant diameter of the hole is preferably 125 mm. The hole is for a predetermined depth, preferably extending 3 meters beyond the passive zone of the soil structure.

Referring now to FIG. 3 showing the V-arm flip type anchor installed in the hole. To install the anchor (2) is driven into the hole (1) using a reinforcement bar attached to its tail (23). It was noted that most failures of anchorage is attributed to the loss of this anchorage friction with potential effect of sliding surfaces commonly known as the active zone. Upon reaching the bulging end (11) of the hole (1), the locking pin (26) is released from the burrow (28) and opens up thus engaging adjacent soil. The hole (1) is now ready for grouting. The dimension of the anchor (2) in this open position is preferably 265 mm across and with a length of 300 mm.

For soil with SPT greater than 30 blows, the grouting material is filled through a grouting hose (not shown) until the material overflows by emerging from the orifice (not shown) of the plate (15). The capping

SUBSTITUTE SHEET plate (15) is tightened at least 28 days after the filling of the grouting material. For soil with SPT less than 30 blows, the grouting material is filled at least 2 meters from the bulging end (11). After 14 to 28 days, the required tension is applied followed by completely filling up the hole (1) until the material overflows by emerging from the orifice (not shown) of the capping plate (15). The capping plate (15) is preferably having a dimension of 0.6 m to 0.8 m square. In both cases the grouting hose (not shown) is pulled out and the grouting material debris is cleaned and the anchor head (22) is sealed with concrete.

While the preferred embodiment of present invention has been described, it should be noted that various changes, adaptations and modifications may be made thereto. It should be understood, therefore, that the invention is not limited to details of the illustrated invention shown in the figures and that variations in such minor details will be apparent to one skilled in the art.

SUBSTITUTE SHEET