# A Method to Estimate Dynamic Pore Water Pressure Growth of Saturated Sand-Gravel Materials
## 6 Conclusions  
This paper investigated the different factors that influence liquefaction using the large-scale dynamic triaxial test on a sand-gravel material from the Xinjiang valley, China. The liquefaction characteristics of saturated sand-gravel materials are similar to those of sand. Our proposed pore water pressure growth model can be universally applied to both sand-gravel materials and sandy materials. We propose an evaluation method for the number of cycles required to reach liquefaction, which is the key parameter in the pore water pressure growth model. The main conclusions of this paper are as follows:  
1. Dislocation and slip occur between the grains of the saturated sand-gravel material under cyclic loading. This causes both reversible and irreversible two-part volume strains, causing an increase in the periodic fluctuation of the dynamic pore water pressure. The increase in the dynamic pore water pressure is more obvious and the amplitude is larger due to the large pores between the sand-gravel materials. The dense saturated sand-gravel material with its large consolidation stress ratio shows a small volume shrinkage and a large volume expansion, where dilatancy can inhibit the increase in the pore water pressure in the sand-gravel. 2. During cyclic loading, volume expansion or shrinkage occurs alternately in the saturated sand-gravel material. The mean effective stress of the sand-gravel material decreases, causing the dynamic shear modulus of the material to decrease and the dynamic strain of the material to increase under the same dynamic stress conditions. 3. Even if the relative density of the sand-gravel material reaches 90%, there is still the possibility of liquefaction under dynamic loading. Earth-rock dams that are built on sand-gravel overburdens and earth-rock dams filled with sand-gravel materials in earthquake-prone areas should use our proposed analysis and evaluation method to investigate the possibility of sand-gravel liquefaction. We used test data and considered the influence of relative density to modify the existing empirical formula and provide an evaluation method for the number of cycles required to reach liquefaction. We propose a pore water pressure growth model that is suitable for both sand-gravel and sandy materials. Comparisons and validations demonstrated that the proposed model accurately describes the three types of pore water pressure growth processes during liquefaction. The pore pressure growth model proposed in this paper can be used to analyze the liquefaction resistance of the dam foundations and dam structure of high earth-rock dams and high sand-gravel dams located on deep overburdens. Methodology, S.C. and B.S. ; Writing--original draft, J.C.; Writing--review & editing, Z.F. All authors have read and agreed to the published version of the manuscript. Figure 13: Verification of the pore water pressure model proposed in this paper. * _[PERSON] et al. (2006)_ [PERSON]; [PERSON]; [PERSON]; [PERSON] Study of dynamic pore water pressure and axial strain in saturated sand-gravel composites. _Rock Soil Mech._**2006**, _27_, 925-928. [CrossRef]
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