(9) Bearing stratum: very dense, RQD of 40, and the average strength of 10.65 MPa
The soil layers surrounding the piles were residual soil with thickness of 5 m, weathered diorite with average thickness of 4 m, highly weather diorite with average thickness of 1.7 m, and bearing stratum.
This is highly becasue the bearing stratum is diorite, which leads to a small settlement decrease after base grouting.
Soil layers Depth (m) Average [GAMMMA] N value (kN/[m.sup.3]) Miscellaneous fill 2.61 5 19.0 Silty clay 3 7 18.9 Gravel 3.5 21 20.0 Silty clay 3.5 21 19.3 Gravel 5.5 22 20.0 Residual soil 5 23 18.0 Weathered diorite 4 41 18.5 Highly weathered diorite 1.7 43 25.5 Bearing stratum N/A >50 28.8 Soil layers C (kPa) [phi]' Fak (kPa) ([degrees]) Miscellaneous fill 5.0 10.0 -- Silty clay 16.6 19.7 150 Gravel 5.0 30.0 260 Silty clay 18.2 16.8 200 Gravel 8.0 30.0 280 Residual soil 5.0 28.0 200 Weathered diorite 10.0 30.0 240 Highly weathered diorite 12.0 48.0 450 Bearing stratum 12.0 54.0 2000 TABLE 2: Information of tested piles.
In terms of engineering design, it is advisable to identify the optimal branch quantity for the particular bearing stratum; under the terms articulated in this paper, the optimum number of branches was 1 to 3.
Considering geological engineering conditions and loading requirements, it is advisable to identify an optimum branch quantity for the specific bearing stratum; in this case, the optimum branch quantity was 1 to 3.
It is well known that the load for the bearing stratum is transmitted progressively (during the loading process stage when the load magnitude vary from 0 till its final magnitude F), at first through the shaft and only after the tip is "employed", then load is transmitted via the shaft and the tip.
The classical patterns of the pile bearing stratum failure, proposed by the different researches which were summarized by Vesic (1967), are shown in Fig.
For this reason the patterns of pile bearing stratum failure has to be chosen very accurately.
Hence, causing crushed hydraulic support on the working face when only one bearing stratum exists in the overlying strata is easy.
Figure 7 shows that the range of rock mass (2) above the single bearing stratum in Figure 7(b) was substantially larger than that above the two bearing strata in Figure 7(a).
(1) Under the load transmission in loose water-bearing strata, causing a large-scaled roof subsidence in the overlying strata when a single bearing stratum exists is easy, thereby inducing pressing frame accident.