According to Biot's (1956a, b) model, the presence of water plays an important role in the propagation of seismic waves in at least three different ways: (1) in an infinite medium, water saturation induces an attenuation that can be accounted for by a complex formulation of wave velocities, as in viscoelastic media; (2) at the boundaries of the saturated medium, pore pressure and water flux determine specific continuity conditions; and (3) there is a second compressional wave, called the P2 wave. In this paper, we discuss the latter two effects. Biot's model is presented first, with homogenization theory used to provide the numerical values of the different coefficients used in the model. In an infinite medium, the model is of practical interest when the frequency ƒ is about the same order of magnitude as a characteristic frequency noted ƒc, which depends on the properties of the constituents. This limits the application of Biot's model to a few particular fields in geophysics. In a layered medium, Biot's model has a wider scope in that it provides a tool for modeling fluid-solid interaction at the boundaries of the saturated medium. This is illustrated in our paper for the case of a very permeable water-saturated surface layer over an elastic half-space. Two examples are given; in the first example (rigid sands) we discuss the physics of the strongly attenuated P2 wave predicted by Biot, the amplitude of which becomes significant when the ƒ/ƒc ratio is about equal to or greater than 0.1. In the second example (soft unconsolidated sediments) the P2 wave is negligible, but the calculation of the complete wave field is required when the ƒ/ƒc ratio is about 0.01. There is no adequate equivalent single phase model that gives a correct estimation of the amplitude of the ground motion. In this case, we argue that the P2 wave is not important in itself, but Biot's model allows the description of the fluid-solid interaction at the water table; continuity of effective stress and pore pressure can be explicitly formulated.

Seismic wave propagation in a very permeable water‐saturated surface layer

Eight records of seismic-induced pore-water pressure and corresponding acceleration records were gathered from aftershocks of the 25 to 27 May 1980, Mammoth Lakes, California, earthquake sequence. The records were obtained from lakeshore sediments at Convict Lake that had undergone liquefaction and subsequent lateral-spreading failure. The pore-pressure records showed several similarities to corresponding strong-motion acceleration records. The pore-pressure traces show clear P - and S -wave phases and are in phase with corresponding P -wave components of the acceleration records. S -wave components of pore-pressure records appear most similar in waveform to one or the other of the corresponding horizontal acceleration components. Although the P -wave portions of pore pressure are in phase with their acceleration counterparts, the amplitudes are not related by a strictly proportional factor. S -wave portions of the porepressure records show a phase lag compared to the S wave of the respective acceleration trace. In most cases, the frequency of the pore-pressure S -wave components are also about 5 Hz lower in frequency than the acceleration S waves.

Seismic-induced pore-water pressure records from the Mammoth Lakes, California, earthquake sequence of 25 to 27 May 1980

/pdf/analysis-of-rigid-retaining-walls-during-earthquakes-h4ntjyysw7.pdf

Analysis of Rigid Retaining Walls During Earthquakes

PROBLEM TO BE SOLVED: To provide a method for constructing an underground wall, capable of efficiently forming the underground wall in a cavity part existing underground.SOLUTION: A pipe body 9 and a bag body 7 are inserted into a drilling hole 3. Then, a filler is sent into the bag body 7 by pressure via the pipe body 9. The bag body 7 is expanded by the filler inside the cavity part 5. For example, the bag body 7 is expanded into a diameter larger than that of the drilling hole 3. For example, the filler is a grout material. In this case, it is preferable that adjoining bag bodies 7 are made to come into tight contact with each other. Moreover, it is preferable that the bag body 7 and the inside surface of the cavity part 5 are made to come into tight contact with each other. Thereby, an underground wall 10 having a high closing characteristic to the cavity part 5 can be constructed.

Underground wall and method for constructing the underground wall

PURPOSE:To safely construct a reclamation layer by the combined use of properly treated wastes and ready-mixed concrete as reclamation materials. CONSTITUTION:A ready-mixed concrete A is obtained by mixing cement with inorganic wastes such as cinders, sludges, mineral slags, etc., and cubic compressed solids B are obtained from waste plastics, waste rubbers, etc. Pressed wastes C are also obtained from waste metals, waste glass, waste ceramics, etc., for reclamation. In the case of underground spaces which workers are hard to enter, the solids B are arranged into a matrix form at a given interval and concrete A is placed to a laminate layer. Also, the wastes C and the concrete A may be compressed together to form a laminate layer. The reclamation layer having high strength and high uniformity can thus be safely constructed.

Reclamation work for waste pit

Record of Lateral Pressure Taken During Earthquake

PURPOSE:To drive on-site concrete piles without slime by a method in which when an on-site concrere pile is driven, slime which deposits on the bottom of pit is solidified with a specific hydro-reaction type chemical liquid to give it a strength similar to or higher than the ground. CONSTITUTION:A hydro-reaction type chemical liquid composed mainly of an isocyanate or an isocyanate-dominated compound is confined in a slime 2 staying on the bottom B of a pit for an on-site concrete pile, and broken by the pressure of a given height of placed concrete 6. Or, capsules whose dissolving time is adjusted to the placing time of the concrete are set. By this, the isocyanate (compound) reacts with water in the slime 2 to solidify the slime 2, whereby giving a strength similar to or higher than the ground to the slime 2. Thus, waiting time for the settlement of the slime 2 and repeated removing operation for the slime 2 by a bucket or vacuum device can be lessened and therefore the efficiency of operation can be raised.

Solidifying treatment work on slime in on-site concrete pile

Method of construction of shielding wall of large-sized underground cavity

PURPOSE:To enlarge a workable opening by using the processes, setting of waling on a sheathing wall, circumferential arranging of shelf piles, laying of a steel ring, setting of baggy parts, and charging of pressure liquid into each small chamber CONSTITUTION:A pit 1 of a square cross section is formed by excavation, and walings 3 are provided endlessly to a bracket 4 of a sheathing wall 2 and also in several places in the vertical direction of the pit 1 Then, large numbers of shelf piles 5 are set in the circumferential position, brackets 6 are attached to several places of the outside faces in the face of the brackets 4, and a supporting part 7 is placed between both Furthermore, a steel ring 8 is laid, a baggy part 9 is set, and a liquid is charged under pressure through an injection tube 11 into each of small chambers 9a in such a way as to press the waling 3 outwards at the ring 8 as a reaction supporting point for sheathing work

Ikuta Yuukou

Papers

Record of Lateral Pressure Taken During Earthquake

Solidifying treatment work on slime in on-site concrete pile

Method of construction of shielding wall of large-sized underground cavity

Cut beam work

Building of shielded wall in underground hollow